Heredity PDF

Heredity 1. How does reproduction ensure the continuity of a species? explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:...

Heredity 1. How does reproduction ensure the continuity of a species? explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to: - animals: advantages of external and internal fertilisation Fertilisation ​- the fusion of male & female gametes to form a zygote Internal External Occurs by many land mammals Both male and females release the sex cells into Eg. reptiles, mammals & birds the surrounding environment (in water) Advantages Eg, Fish & amphibians - Increased possibility of the union of Advantages gametes (due to contained - Generally a large number of offspring environment) come out of this - Higher birth rate as the baby grows - More genetic variation inside - Easier to fertilise as they don’t need to - More selective of mates (internally) mate Disadvantages Disadvantages - Time must be spent trying to attain a - Fusion of gametes may not occur mate - Has to occur in water - Increased energy must be used to fuse - Decreased chance of gametes fertilisation/survival due to the possibility of them dying - plants: asexual and sexual reproduction Sexual Asexual - Involves fusion of genetic material - Offspring created is identical as it which is the combination of two comes from one parent - use of mitosis parents to form an offspring causing Types of asexual repro in plants high genetic variation - use of meiosis - Runners ​- side branches with clumps of - Process of Pollination​ - insects, birds or leaves and roots which grow on the wind carry pollen (male sex gamete) ground, the roots dig down and from a flower to another establish the plant as its own individual - The pollen attaches to the stigma plant, ie. Strawberries where the the fusion of the two - Bulbs ​- bulbs are underneath certain gametes causes a seed to grow where plants which allow buds to grow from the ovules once were > grows into a them and then flourish their own fruit individual plant eg. daffodil - Cutting ​- branch off a tree is cut and stripped down, then is planted again to grow as its own individual plant - fungi: budding, spores Fungi - eukaryotic organism (can be unicellular eg yeast, or multicellular eg. mushroom) - Can reproduce sexually or asexually depending on the environment  - When conditions are good they will reproduce asexually and grow rapidly, either through the use of ​spores​ (sex cells which are released to spread into the surrounding environment) or ​budding ​(fungus experiences a growth and then breaks off to form a new organism) - When conditions are bad, the fungi reproduces sexually through the spores from each fungus fusing with another fungi’s spores creating a new cell and growing a new fungi. This creates genetic variation due to the combination of the cells and also survival rate - bacteria: binary fission (ACSBL075) Bacteria is a single celled, prokaryotic organism eg. E-coli - Reproduce asexually through the use of ​Binary Fission - The bacterial cell makes another copy of its DNA before growing into twice it’s size - Cytoplasm divides and then there are two cell membranes ie. two bacterial cells - protists: binary fission, budding Protists are single celled organisms which don’t classify as a bacteria, fungi, plant or animal eg. Plasmodium (cause of malaria) - Reproduce through both binary fission and budding analyse the features of fertilisation, implantation and hormonal control of pregnancy and birth in mammals (ACSBL075) Mammals ​- classified as warmblooded, has a backbone, are able to produce milk and also has hair Fertilisation - Mammals reproduce sexually using internal fertilisation - through the fusion of male and female gametes (sperm and eggs) enabling the formation of a new organism 1. Ovary releases an egg (ovulation) about once a month in humans 2. The released egg travels to the fallopian tube via the oviduct 3. Sexual intercourse occurs and the male releases semen, which is comprised of sperm, directly into the vagina 4. The sperm swim from the vagina, through the cervix and uterus into the oviduct/fallopian tube 5. This is where the sperm fuses with the egg to create a zygote (new organism) 6. Zygote creates a strong membrane which prevents any other sperm fertilising the egg meaning that the remaining sperm will die out 7. The zygote travels down the oviduct to the uterus where it is implanted Implantation - Implantation ​is the attachment of the fertilised egg to the lining of the uterus. (it buries itself deeper to be overcome by the lining) - As an embryo forms (looks human like), the amniotic sac, umbilical cord and placenta develop - Amniotic sac contains the unborn baby and is filled with fluid - keeps the baby in optimal temperature and also provides safety from external factors - Placenta provides the oxygen and nutrients that a baby needs to survive whilst removing carbon dioxide and other waste. It is outside of the amniotic sac therefore there needs to be something to facilitate the nutrition/oxygen - The umbilical cord is the connection between the amniotic sac and the placenta (enables the survival of the baby)  - From implantation to birth, this period is known as pregnancy - Human pregnancy is about 9 months Hormonal Control of pregnancy and birth Pregnancy and birth can only occur with the help of hormones (chemical messengers) - Oestrogen ​- is caused by ​luteinising hormone​ (hormone which triggers ovulation) responsible for the development of female characteristics and also stimulates the female body to release an egg. It also aids blood flow and enables the growth and development of vital organs (eg. lungs and kidneys). It is later secreted in pregnancy to enable the production of progesterone - Progesterone​ - initially released by the ovaries and then later by the placenta. It stimulates the thickening of the uterine lining early in pregnancy. It gradually rises as pregnancy continues, this enables the placenta to keep working and also keeps the uterine relaxed. It additionally helps the mother’s immune system tolerate the growth of the child as it is seen as foreign in the body - Relaxin​ - loosens the uterine muscles to prepare the body for birth - Oxytocin ​- stimulates the production of milk and allows the uterine muscles to contract > allowing the body to go into labour and give birth evaluate the impact of scientific knowledge on the manipulation of plant and animal reproduction in agriculture (ACSBL074) Agriculture (farming) ​- growth of crops and animals for human needs - It provides us with the food and clothing which humans need to survive - Agriculture leads to having a good quality of life Selective breeding​ ​- creation of organisms with desirable traits, ie. a chicken with greater size or even a tomato which tastes better. Selective breeding can be done in 4 ways; Natural Breeding - Farmers place a male and female in the same enclosed environment and wait for them to breed naturally. The farmer is able to choose the characteristics as they choose which animals will be there, ie. size and speed - Very common and cheap, however takes a long time to occur Artificial Insemination - This is where sperm is taken from a male with certain desirable traits, and is inserted into the vagina of a female. Eg. sperm of a bull whose mother produces a lot of milk is inserted into the vagina of a cow who produces a lot of milk > this allows the offspring to produce a lot of milk as well Artificial Pollination - A person takes pollen from one flower and places it directly into another flower to produce a plant with desirable characteristics - Used to grow Kiwi fruit as an example Cloning - People create an identical copy of an organism by using genetic engineering techniques to do so - It is relatively new and isn’t that common in agriculture yet, however it may become prevalent in the future ​Impact of manipulating reproduction in agriculture Positive Negative - Increased sales of produce > generates - Reduce biodiversity - as the selective higher yield for farmers breeder reduces the gene pool of the - Trying to make foods more resistant to organism, this then may hinder the pests and disease - farmers spend less survival of an organism if something money on pesticides and then can were to occur. Eg a parasite killed off a spend more money on food production. breed of cattle Beneficial for the environment as well due to a decrease in pesticides and the chance the flow off will go to creeks and the ocean - scientific knowledge will also help us to predict possible outcomes from manipulation techniques. Not always precise but it helps to be prepared for any misalignment during the processes. 2. How important is it for genetic material to be replicated exactly? model the processes involved in cell replication, including but not limited to: - mitosis and meiosis (ACSBL075) Cell Replication​ - process by which cells replicate their genetic information by the process of dividing original cells Mitosis Meiosis -A type of cell division where a single - A type of cell division where one cell parent cell divides to form two identical divided into 4 ​non-identical ​daughter daughter cells cells - DNA is wrapped around proteins to - Different to the parent cell as they only form a substance - Chromatin (inside have one set of chromosomes the nucleus) - Only occurs in the gonads to create - Half of the chromatin comes from the variation in the gametes (sperm & ova) father and the other half comes from - At the end of Meiosis, there are 4 cells the mother with 23 chromosomes in each (all Mitotic Division process different) 1. Interphase - ​Replication of DNA (chromatin) to produce 2 copies of each. These copies are still joined at the middle - they shorten and thicken to the X shape of a chromosome  Meiosis Division Process Interphase ​- DNA is doubled to create two sister chromatids Meiosis I 1. Prophase I ​- chromosomes condense, nuclear membranes dissolve, they line up in any order (random segregation) and crossing over occurs, as the chromosomes line up in pairs with the chromosome given from the mother cell & father cell. 2. Metaphase I​ - spindles from centrioles 2. Prophase ​- Each chromosome has 2 connect to the centre of the strands called chromatids which are chromosomes met at the centre by a centromere. 3. Anaphase I ​- spindle fibres contract and These chromosomes are homologous as the homologous chromosomes move to there are two pairs for each the other side of the cell chromosome. and centrioles go to 4. Telophase I​ - spindle fibres dissolve and opposing ends of the cell the cell performs cytokinesis to make 3. Metaphase ​- Chromosomes line up two haploid daughter cells along the centre of the cell and the Interphase II ​- separation of sister chromatids centrioles release spindle fibres and (may not be identical due to crossing over in attach to pull apart the chromatids Prophase I 4. Anaphase ​- once the chromatids are Meiosis II separated, the centrioles contract until 1. Prophase II ​- chromosomes condense, they are at opposite ends of the cell nuclear membrane dissolves and 5. Telophase ​- spindle fibres dissolve and centrioles move to opposite ends of the a nuclear membrane regenerates and cell surrounds the two sides - Cytokinesis 2. Metaphase II​ - spindle fibres attach to occurs (division of the cytoplasm) to the chromatids and they are aligned form 2 identical daughter cells along the equator 3. Anaphase II​ - spindle fibres contract to separate the chromatids 4. Telophase II ​- cell membrane surrounds the cell and cytokinesis occurs to create 4 haploid cells Modeled Mitosis & Meiosis through the use of pipe cleaners, plasticine and string to represent the number, movement and genetic composition of chromosomes during cell division Advantages of Models Disadvantages of Models - Helps people understand and visualise - May not include all details (some complex concepts accuracy can be lost) - Cheap and easy to use/access models - Can give people an incorrect understanding of the process - DNA replication using the Watson and Crick DNA model, including nucleotide composition, pairing and bonding (ACSBL076, ACSBL077) DNA (deoxyribonucleic acid) ​- molecule which carries genetic information and contains all the information necessary for a molecule to function properly DNA Structure - Double helix structure and is made up of nucleotides - A ​nucleotide ​is composed of a sugar (pentagon), a phosphate (circle) and a nitrogenous base(A,T,G,C) - Nitrogenous base is always off the sugar, whereby the sugar and phosphate alternate to create the backbone - 4 different bases; ​Adenine​, ​Thymine​, ​Guanine​, & ​Cytosine - Adenine only pairs with Thymine and Guanine only pairs with Cytosine due to the ‘​Complementary Base-Pairing Rule​’ Watson & Crick DNA model - Published the model in 1950’s however they relied on the work of both Chargaff and Franklin - Their model made of steel created a 3D version/visual structure of the DNA structure, showing the Double-helix shape, nucleotides and also the hydrogen bonds (which connect the bases) - This enabled modern scientists understand how genes control cell processes and organism characteristics - Eg. used in medicine to make new and more effective medical treatments ie cancer DNA Replication - The process by which an existing DNA molecule is copied to produce 2 identical copies - Enzymes in the body such as ​Helicase​ (acts as a replication fork) cause the DNA to unwind/unzip (hydrogen bonds break) to form 2 single strands - DNA polymerase catalyses free nucleotides (ones which are in the cell) to pair to the strand according to the BP rule (ie A-T, G-C) as well as ensures that the right pair is there - This results in 2 identical copies of each DNA as they are recoiled back into the double-helix shape - This enables multiple copies of genes to occur, which is essential for cell replication  assess the effect of the cell replication processes on the continuity of species (ACSBL084) Mitosis - Mitosis is important as it creates new body cells (​somatic cells​) which are needed for growth, repair and maintenance. Mitosis ensures that an organism reaches an age where they can reproduce for themselves > reinforcing its necessity in the continuity of a species - Life creates in the zygote, without mitosis, the zygote would not be able to form into the adult organism - Helps in regenerating new tissue cells eg, blood cells, which are necessary for life - Maintains the equality of chromosomes in number and similarity in characteristics throughout all the cells. Meiosis - Allows for the continuity of a species as it allows organisms to reproduce with large amounts of variation. This enables a higher likelihood of survival as they can withstand greater impacts than those who are the same. - Plays a major role in ensuring the correct amount of chromosomes in an organism 3. Why is polypeptide synthesis important? construct appropriate representations to model and compare the forms in which DNA exists in eukaryotes and prokaryotes (ACSBL076) DNA ​contains all the information a cell needs to grow, replicate and survive. It’s structure is of a double helix & is made up of nucleotides (phosphate, sugar & bases), and hydrogen bonds. Prokaryotes Eukaryotes - A cell is prokaryotic if they have ​no - A cell is eukaryotic if they ​have ​a nucleus​ or ​no membrane bound nucleus ​and other ​membrane bound organelles organelles​, eg Endoplasmic reticulum, - Usually simple structures where the golgi body etc. DNA floats amongst the cytoplasm​ and - DNA is straight/linear​ (does not not in a nucleus reconnect with itself) and is found as - DNA is a ​circular shape​ and is known as chromatin in the ​nucleus of a cell a plasmid - Have more DNA than prokaryotes - Generally ​unicellular - Generally ​multicellular a​ nd have  - Eg. archaea & bacteria specialised cells - 50-100x bigger than prokaryotes - Eg. animals and plants model the process of polypeptide synthesis, including: (ACSBL079) Polypeptide Synthesis ​- refers to how polypeptides are made and has two stages; transcription & translation - transcription and translation Transcription ​- process by which the genetic information is copied from a section of DNA, onto an mRNA molecule - 1st process in polypeptide synthesis and first step in gene expression - It produces mRNA which are necessary for Translation (protein production) 1. Initiation​ - The gene unwinds and unzips, meaning there are 2 unpaired strands of bases. There is a place on the strand which is the promoter (start of transcription). RNA polymerase binds to the promoter and attaches free RNA nucleotides to the foundation as it passes by (due to complementary base pairing rule) however U’s replace T’s when pairing. It looks like A-U, C-G 2. Elongation ​- RNA polymerase moves along the template and places more bas strands 3. Termination​ - RNA polymerase encounters a codon which signals termination (stop codon). The new mRNA sequence may have some non-protein creating sequences and splicing occurs (removal of non-protein coding) and the coding regions are joined together (exons) 4. Once the gene is copied the mRNA is released and is moved into the cytoplasm of the cell A group of 3 bases on an mRNA molecule is known as a ​codon ​> eg. AGU (codes for an amino acid) Translation ​- process by which the copied genetic information on the mRNA is converted into a polypeptide, involves both tRNA & mRNA - mRNA strand is now in the cytoplasm and is attached to a ribosome  - tRNA is now used to transfer amino acids to the ribosome so they can be made into polypeptides 1. ​Initiation ​- once the start codon is identified, the tRNA is shown by the mRNA which codon they attach to using the anti-codon (opposite base triplet) - (eg. the anticodon (AAG) is paired with (UUC)) 2. Elongation ​- as the tRNA places the amino acid, the tRNA molecule is no longer needed and is released however the amino acid remains, so they form peptide bonds and as a result of this, a polypeptide chain 3. Termination - ​the polypeptide continues to grow until it reaches a stop codon, once this occurs, the protein folds into a unique shape for it’s desired function https://www.youtube.com/watch?v=oefAI2x2CQM&list=TLPQMjcwNDIwMjAlIehZwWHwUg&index= 2​ (for clarity if needed) - tRNA is comprised of an RNA molecule, 3 nitrogenous bases (anticodon) and also an amino acid - assessing the importance of mRNA and tRNA in transcription and translation (ACSBL079) Importance of mRNA Importance of tRNA - mRNA acts as a messenger as it copies - tRNA transports the correct amino and carries genetic information from acids to the ribosomes the DNA to the ribosomes - Without tRNA, there would be no way - Without mRNA, there would be no way for polypeptide synthesis to occur for genetic information to go to the ribosomes - analysing the function and importance of polypeptide synthesis (ACSBL080) Function of Proteins - Proteins are a major component of every cell and have many roles in bodily functions Structural Proteins​ - maintain cell shape and make connective tissues - Dietary intake of protein is important for the growth, repair and maintenance of tissue - Eg. Actin - found in muscle cells > allowing movement and muscle build up Enzymes​ - biological catalysts (living proteins which dictate the metabolic rate of an organism) - They act on a specific molecule to either break it down into something simple, or make something more complex, allowing efficiency and an easier way to survive - Eg. DNA Polymer​ase Messenger Proteins (hormones)​ - chemicals which are secreted into the blood to travel to target tissues where they cause a change in activity - They help regulate body processes - Eg. Insulin > regulates the blood glucose levels Storage & Transport Proteins​ - storage proteins bind to a certain substance to hold them in place & transport proteins bind to substances and carry them around the body (eg haemoglobin - carrying oxygen) Immunity Proteins​ - antibodies are proteins which react with antigens (foreign objects) to remove them from the body. Eg IgA Importance of Polypeptide Synthesis  - Proteins have vital functions eg, structural,enzymes etc, and are found in every cell and life couldn’t function without them - If protein synthesis didn’t exist, no proteins could be made - If protein synthesis didn’t work, the protein would have the incorrect structure for the function - Polypeptide synthesis forms products that are necessary to carry out replication, transcription and translation as well. - Eg, Enzymes - the function is determined whether the active site can bond to the substrate which it aims to. If the shape is wrong, then there is no function - assessing how genes and environment affect phenotypic expression (ACSBL081) Genome ​- an organism's complete set of genetic material (DNA) - (info for growth and survival) Genes ​- broken down sections of the DNA - coding for certain characteristics of a human (acts as a template for mRNA in polypeptide synthesis) Alleles​ - alternative forms of the same gene (eg. eye colour) Genotype​ - an organism's genetic makeup for a particular characteristic (eg. eye colour - blue (bb), brown (BB,Bb)) Phenotype ​- physical expression of the gene (eg. person with genotype bb has blue eyes) How environmental factors affect phenotype - At fertilisation, the zygote has the potential to grow into an adult with certain characteristics - ie. the phenotype is controlled by the genotype Nutrition ​- if a baby is properly nourished, it has the capability to grow into the predicted phenotype from the genotype however if the baby is malnourished, it may not grow to the full potential (the body isn’t gaining the nutrients required to survive and grow) Light Intensity ​- if a plant is grown in complete sunlight it should grow to the potential of the genotype and have the phenotype, however if it’s grown in darkness, it will not grow as desired - Both genes and the environment play a large role in the phenotype expression however it is responsible for each case. - Eg, genes are the most important in some characteristics - eye colour - Eg. environment is the most important - weight How gene factors affect phenotype Dominance of alleles​ - in organisms, alleles dictate the genotype of the organism, which then dictate the phenotype of the organism. If the gene is heterozygous, the allele which is dominant (capital letter) will be shown in the physical expression eg. brown eyes > blue eyes Co-dominance ​- both alleles are simultaneously expressed in the phenotype eg. Rune Cattle (patches of red and white), eg. Blood type - A & B blood type are shown together as AB investigate the structure and function of proteins in living things Protein ​- a molecule made of one or more polypeptide chains. These chains bond and fold to make a unique three dimensional structure - Protein is inherently important as our cells are made out of them and that we need protein to grow and repair bodies - Proteins are made of polypeptides, which are made of amino acids which are then made of carbon, oxygen, nitrogen and hydrogen - All ​proteins are made of polypeptides however​ ​polypeptides ​are NOT ​made of proteins  - The function of a protein depends entirely on its structure Structure of Proteins Amino Acids (CHONs) ​- 20 types of amino acids to choose from Polypeptides (chains of amino acids)​ - any amino acid can be placed in a random order > enables different polypeptides due to the different combinations of amino acids Proteins​ - proteins contain different numbers and combinations of proteins which then give a distinct structure and is important for the function of the protein Function of Proteins - Growth and maintenance of tissues - Controls biochemical reactions - enzymes (are proteins) - Proteins help form immunoglobulins, or antibodies, to fight infection. - Transport proteins carry substances throughout your bloodstream — into cells, out of cells or within cells. 4. How can the genetic similarities and differences within and between species be compared? conduct practical investigations to predict variations in the genotype of offspring by modelling meiosis, including the crossing over of homologous chromosomes, fertilisation and mutations (ACSBL084) Genetic Variation ​- a term used to describe the differences between the genomes (complete set of DNA) of individuals and the species. Also known as the differences in DNA of a group of organisms Random Segregation & Crossing over of homologous chromosomes in Meiosis - This is where one cell divides into 4 non-identical cells with only a haploid number of chromosomes (occurs in gonads for reproductive variation) - The pairs of chromosomes line up, however they are in a random order, meaning that the gene will be different and that different combinations of chromatids will end up in gametes - To ensure variety, the pairs cross over (they swap sections of their gene to have different chromosome make ups) - These haploid cells are now in the forms of gametes and are used in fertilisation Fertilisation - These gametes which have just gone through meiosis (already with Genetic variation), now fuse with either a maternal or paternal gamete which have gone through meiosis as well. They have different alleles and this contributes to the genotype/phenotype of the organism - It is highly unlikely that two gametes are the exact same and will lead to variation in the offspring Mutations - A mutation is a change in the base sequence of DNA - It can lead to a change in the genotype, as there is a change in the bases, this may change the codon and can lead to differing DNA sequences > change the phenotype - Eg, Sickle cell anaemia (affects how much oxygen the rbc can carry)  model the formation of new combinations of genotypes produced during meiosis, including but not limited to: - interpreting examples of autosomal, sex-linkage, co-dominance, incomplete dominance and multiple alleles (ACSBL085) Alleles​ - different forms of the same gene & are found on the same place in homologous chromosomes - If there was only 1 allele, every organism would end up with the same genotype and then the same phenotype (look the same) eg, Brown eyes - This is not a problem with sexual reproduction as there is meiosis and sexual reproduction (allows two copies for each chromosome) Dominant & Recessive Alleles Dominant ​- a genotype which is always expressed as the phenotype Recessive​ - a genotype which is expressed as the phenotype when there is no dominant allele Eg. the brown eye allele is dominant over the blue eyes, therefore brown allele will always show if it is present If the organism has two identical alleles, they have ​homozygous allele trait​ eg, BB -brown, bb -blue An offspring may have a ​heterozygous allele trait​ meaning they show the dominant gene however have the gene for recessive as well (eg, Brown eyes with the allele Bb - lowercase ‘b’ codes for blue) Autosome - ​any chromosome which is not a sex chromosome (eg. eye colour) (22 pairs of autosomes) Sex chromosome ​- any chromosome which codes for sexual characteristics eg. codes for breast development in women & penis development in males (only 1 pair of these) - These are referred to as the ​X ​& ​Y chromosomes - Males are XY (heterozygous) - Females are XX (homozygous) - They contain some characteristics for non sex genes as well Autosomal Inheritance - Refers to the patterns and expression of genes which are located in the autosomes - If the autosome is heterozygous, the dominant allele will be demonstrated through phenotype - If the autosome is homozygous, the allele will be shown as the phenotype - Eg, eye colour - the dominant allele will be shown over the recessive (brown > blue) Sex - Linkage - Since chromosomes come in pairs, there are two copies of each gene, except in sex-linked genes - There are more genes on the X chromosome than the Y, making it larger - As the male only has one copy of the X chromosome, the male will only show the gene portrayed, meaning it could be negative (eg, haemophilia), whereas a female may have the recessive and dominant genes (XX) and the dominant will show, however she will be a carrier Co-dominance - Refers to a situation where both alleles are expressed in the phenotype eg. Roan cattle (red and white patches of fur)  - Since they’re both co dominant, the alleles are capitals, eg, W - white, R - red, and can be placed in the punnett square meaning that RW is the patches of red & white Incomplete Dominance - The dominant allele is partially expressed, meaning it doesn’t dictate the phenotype of the organism eg. Snapdragon flower - The dominant allele allows some of the recessive to break through meaning that there is a blend in colour - Eg. Red genotype is RR, white is rr, so there is 100% chance of Rr - resulting in pink flowers Multiple Alleles - Three or more alternative forms of an allele that can create a variant number of phenotypes when they exist in different numbers. - constructing and interpreting information and data from pedigrees and Punnett squares Punnett Squares - These are a table which predict the possible genotype and phenotype of the offspring, produced by a male and female - EG. eye colour - Brown eyed father has genotype Bb and the blue eyed mother has bb - B b b Bb bb b Bb bb - 50% chance of brown, 50% chance of blue eyes - 1:1 ratio Pedigrees - A family tree which shows how organisms are related to one another & also show how characteristics are passed on over generations Importance of Pedigrees - Pedigrees are useful as they allow scientists to understand what is happening with the inheritance of a trait/disease  - They are used to figure out the inheritance pattern of a trait by seeing how often the trait is expressed in the phenotype - This allows geneticists to examine the genotype of individuals, and whether they’re carriers of the trait/will express it. - This is important with genetic disease, as the couple who are having a baby will be able to see the likelihood of the child developing a disease eg. cystic fibrosis - Can be used to see whether a person will have a disease later in life eg. Huntington’s disease collect, record and present data to represent frequencies of characteristics in a population, in order to identify trends, patterns, relationships and limitations in data, for example: - analysing single nucleotide polymorphism (SNP) Single Nucleotide Polymorphism (SNP) - Most common form of genetic variation amongst humans - It represents a change in a nucleotide (eg, cytosine replaces guanine in a certain stretch of data) - These occur once in every 1000 nucleotides, meaning there are around 4-5million SNPs in a person's genome - These usually act as biological markers helping scientists locate the whereabouts of genes - Most SNPs have no impact on health/development - These allow scientists to predict how a body will function with a certain drug or even determine how the body will act when surrounded by toxins - These can also track the inheritance of diseases amongst families - SNPs occur more frequently in non-coding regions rather than coding regions as a result of which they are mostly unnoticeable. 5. Can population genetic patterns be predicted with any accuracy? investigate the use of technologies to determine inheritance patterns in a population using, for example: (ACSBL064, ACSBL085) - DNA sequencing and profiling (ACSBL086) PCR (Polymerase Chain Reaction)  - A technique used to make large amounts of copies of a specific region of DNA, in vitro (test tube) - It is usually necessary to use PCR in cases of testing/analysing DNA - It is the scientists way of doing DNA replication (where DNA polymerase attaches free nucleotides to complementary bases on exposed strands), however occurs in a test tube and is only a specific section of DNA PCR Materials - DNA​ sample which is going to be copied in PCR eg, from a Crime scene - Going to need ​free nucleotides​ and also a ​heat stable DNA polymerase​ (catalyses DNA replication)as enzymes are affected by heat and pH - Primers​ are used to flank the target DNA region (act as a signal for DNA polymerase as they bind to each side of the region which is intended to copy) - Buffer ​is the liquid which prevents the sudden change of pH Steps in PCR - The mixture is placed in a thermal cycler, so it’s temperature can be heated & cooled in a controlled way (PCR uses temperature variation to control the replication process 1. Denaturing​ - the PCR mixture is heated up to 95 degrees and the DNA separates into two single strands which act as templates for the next step 2. Annealing​ - the PCR mixture is cooled to 55 degrees and allows the primers to bind to the template DNA sequences 3. Extension​ - reaction is heated to 72 degrees, the heat stable DNA polymerase is able to bind with the primers, move down the template and synthesise new DNA strands. Once the DNA region is copied, these 3 steps are repeated to continually make DNA copies Gel Electrophoresis Steps in GE 1. Preparing the set up ​- pouring a liquid agarose gel into a mould and inserting a well comb (to end up with a gel structure with holes at one end). Once the mould is set, it is placed into a gel box with a positive charge at one end and a negative charge at the other, it is then immersed into a buffer solution which can conduct electricity 2. DNA is loaded into the well​ - it can be sourced from a crime scene/patient through the use of a pipette. One well is added with a DNA ladder (common mix of prevalent genes). Make sure to record which is on each plane 3. Run the gel​ - power is turned on and the current runs through the gel. The DNA migrates through the gel towards the positive charge as DNA is negative (negatively charged phosphate in the nucleotides) 4. A dye is added to the DNA gel to be able to see the band of genes when the process is complete - The current provides the force to move through the gel and the gel acts as a filter due to the size of the DNA - This allows the DNA to be separated according to DNA size Applications of PCR and Gel Electrophoresis - Most applications use PCR to then load numerous DNA samples into the Gel Electrophoresis machine to visualise results of PCR. - DNA Sequencing​ - process of determining the base sequence of nucleotides (A,T,G,C).  It can be used for a single gene or the entire genome The PCR is used to amplify the DNA, then the Sanger reaction provides fluorescent fragments of each base by using chain-terminating nucleotides (terminate the connection of nucleotides with one another) which are then placed in the GE machine - DNA Profiling ​- process of analysing DNA variation for identification. Regions of DNA which vary between individuals are known as genetic markers > can be used to construct DNA profiles PCR is used to create short tandem repeats (a string of 2-5 nucleotides codons) which construct unique DNA profiles, this is then used with GE to determine the size of the DNA profile Applications of DNA Profiling - Parentage ​- every person has two copies of STR (chromosomes) due to the makeup. The person’s makeup should be present in the parents make up as well - Identification - Recombinant DNA ​- DNA which contains genes from two or more different sources. PCR is used to amplify another gene by inserting it into another DNA molecule. This is then placed on a GE and can then be determined to be successful or not - investigate the use of data analysis from a large-scale collaborative project to identify trends, patterns and relationships, for example: (ACSBL064, ACSBL073) - the use of population genetics data in conservation management Population Genetics​ - a field of study used to investigate the genetic differences within and between populations - In the Galapagos Islands (1982), there was extremely heavy rain causing cactuses to grow smaller seeds. This had a knock on effect for the species which feed off of these eg ​Cactus Finch - Due to the high genetic diversity of Cactus Finches, there are different and more noticeable traits like beak size. The smaller seeds meant that the birds with smaller beaks were able to access the seeds easier than the birds with larger beaks, meaning they would survive greater - If there was a lack of genetic diversity and most of the finches had large beaks, the species would have been significantly reduced and potentially eradicated due to this occurrence - It is proven that species with greater genetic diversity, are able to survive changes better - By analysing the conservation, scientists can discover; dominance, mutation rates and also aging - showing the importance of conservation management - population genetics studies used to determine the inheritance of a disease or disorder - Observation of interactions between genes can give ideas about what alleles might be dominant and whether disease causing alleles will show dominance or not. - Based on such ideas, whether a disease can be inherited or not can be determined. - A number of techniques in population genetics are used to measure allelic frequencies in a population, thus giving us an image of what number of alleles are being lost during evolution and what amounts are being transferred through gene flow. Analysing these data can give us a rough image of the probabilities of inheriting disorders within a population - population genetics relating to human evolution - Questions about human evolution are addressed through analysis of the fossil and archaeological records, combined with analyses of diversity in living human populations. - Higher genetic diversity in Africa has been said to indicate an origin in Africa, but in fact, the characteristic pattern of this diversity indicates only a larger number of ancestors, not greater time-depth, within Africa. - The oldest fossils showing modern human characteristics have been found in Africa and date to about 130,000 years ago. The oldest related modern human fossils outside of Africa appear in the Middle East, dating from about 90,000 years ago. - An alternative view is that humans have been evolving within a single evolutionary population, which, though structured, has been prevented from divergence into a new species within the last million years by gene flow. - Larger genetic distances between populations in sub saharan Africa and those in Europe or Asia generate ideas that people have migrated out of Africa and thus, the genetic variations in populations have split globally. - However, variable rates of genetic drift and gene flow between continental regions are a more likely explanation for observed geographic patterns of diversity. - The main point is that genetic diversity data can be interpreted to fit either model for modern human origins, and therefore have not resolved the debate.