Module 5 - Heredity Biology Notes PDF

MODULE 5 - HEREDITY IQ1: 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 t...

MODULE 5 - HEREDITY IQ1: 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 – plants: asexual and sexual reproduction – fungi: budding, spores – bacteria: binary fission – protists: binary fission, budding Reproduction is the process of creating offspring. Fertilisation is the successful fusion of gametes (sex cells) to form a zygote ➔ Haploid = half the number of chromosomes ➔ Diploid = full number of chromosomes SEXUAL ASEXUAL ➔ Sexual reproduction requires two ➔ Asexual reproduction is the fusion of a gamete to organisms/genders; male and female sex cell produce an offspring without sex and only ➔ A haploid (n) gamete from each parent combines requires one organism/gender to produce genetically unique diploid (2n) ➔ A parent cell replicates and divides, generating offspring offspring that are genetically identical/clones ANIMALS : advantages of external and internal fertilisation TYPE OF FERTILISATION DESCRIPTION ADVANTAGES INTERNAL FERTILISATION ➔ Haploid (n) male and female gametes ➔ Less gametes have to be produced unite to produce genetically unique ➔ Higher chance of fertilisation diploid (2n) offspring ➔ Protected from disease, predation and ➔ Sperm and egg unite within the external conditions female body to fertilise ➔ Development of the zygote occurs inside the female body ➔ Occurs in terrestrial and aquatic environments EXTERNAL FERTILISATION ➔ Parents discharge their gametes ➔ Produces more offspring outside the body ➔ Female can continue to reproduce ➔ Development of offspring occurs without pause outside the body ➔ Parents don't expend energy for ➔ Occurs in terrestrial and aquatic gestation environments ➔ Offspring can be spread widely = less competition PLANTS : asexual and sexual reproduction The majority of plants are seed-producing plants; used by gymnosperms (eg. pine trees) and angiosperms (flowering plants) to reproduce sexually. All groups in the plant kingdom reproduce sexually BUT some plants can also reproduce asexually with the assistance of humans using various gardening techniques such as cuttings and grafting or the use of biotechnology approaches (eg. tissue cell propagation) Flowers, specifically, are important in the sexual reproduction of plants. They produce male sex cells (pollen grains) and female sex cells (ovum - contained in the ovules). These must meet for reproduction to begin = pollination. FUNGI : budding, spores Fungi belong to the Eukarya domain and are unicellular OR multicellular, heterotrophic organisms. They produce both asexually and sexually but their primary mode of reproduction is asexual. ➔ Yeast reproduces asexually ➔ Budding is the formation of abud on the side of a cell, followed by a nuclear division to provide each cell with a genetically identical nucleus. After the bud is nearly as large as the parent, cytokinesis occurs; this is the separation of the cytoplasm to form two separate cells. ➔ It is slower and more complex than binary fission ➔ When fungi reproduces sexually, two fungi temporarily fuse to create a diploid structure and produce spores by meiosis and so the spores contain genetic material from 2 parent cells ➔ The mushroom seen in many species of multicellular fungi is actually a reproductive structure or fruiting body that releases spores into the environment. They release a huge number of light spores that are easily dispersed by wind, water, animals or even humans. ➔ The hyphae reaches deep into a material and releases enzymes which break down living material in order to absorb nutrients. BACTERIA : binary fission Bacteria are unicellular prokaryotic organisms and reproduce asexually through the process of binary fission. Binary fission typically results in the formation of two daughter cells that are genetically identical to the parent organism. 1. Cell elongates by building more cell wall 2. Bacterial genome replicates and remains attached to the membrane. At the same time, any plasmid present (small circular DNA) replicate 3. Duplicated DNA begins to separate, moving towards the poles as the cell elongates more. 4. Cleavage furrow begins to form and cell wall forms in cleavage furrow 5. Two identical daughter cells are produced PROTISTS : binary fission, budding analyse the features of fertilisation, implantation and hormonal control of pregnancy and birth in mammals Mammals are a class of organisms that reproduce sexually using internal fertilisation. FERTILISATION = the successful fusion of gametes MAMMAL DESCRIPTION PLACENTAL ➔ The embryo grows inside the uterus (viviparous), and a placenta allows nutrients and oxygen to be supplied and wastes to be removed via the mother’s blood ➔ The fetus is directly connected to the mother ➔ Pregnancy tends to be longer and offspring are more developed when born ➔ Examples of placental mammals include: humans, dogs, cats, giraffes and whales. MARSUPIALS ➔ Marsupials have viviparous births and also have placentas to support internal embryonic development ➔ They give birth to tiny, partially developed babies that continue to develop after birth; typically within the mothers pouch ➔ The baby, called a “joey”, has to climb out of the reproductive tracts and into the pouch. Here, is it protected, nourished and develops ➔ Examples of marsupials include: kangaroos, wombats and possums. MONOTREMES ➔ Monotremes lay soft-shelled eggs (oviparous births) from which a very small puggle (baby) emerges and continues to grow and be nourished by the mother’s milk ➔ They have cloacas rather than vaginas ➔ The underdeveloped baby emerges from the egg and will suckle for lactation IN MALES The reproductive system of males consists of: ➔ Paired testicles ➔ Scrotum (produces and stores mature sperm continuously) ➔ Seminiferous tubules (sperm cells form) ➔ Epididymis (stores sperm cells) ➔ Cowper's gland, prostate and seminal vesicle (produces secretions of seminal fluid) ➔ Vas deferens leads from the testicles to the urethra ➔ Hormones (LH and testosterone) The penis must become erect when ready for copulation. An erection is an increase in blood flow into the columns of spongy tissue located on the shaft of the penis in order for it to become rigid and allow for internal fertilisation. HORMONES INVOLVED DESCRIPTION TESTOSTERONE ➔ Testosterone is responsible for normal secondary sex characteristic development, libido or sex drive and normal erections. ➔ It triggers the production of sperm LUTEINISING ➔ LH is released into the bloodstream and acts ONLY on the testicles to encourage HORMONE spermatogenesis within the seminiferous tubules (action of FSH) and testosterone production by neighbouring Leydig cells (action of LH) between the seminiferous tubules ➔ Essentially, LH stimulates the production of another hormone, testosterone IN FEMALES The reproductive system of females consists of: ➔ A uterus that allows the implantation of a fertilised egg in the endometrium -- there, it will grow and develop until birth ➔ Paired ovaries containing egg cells that will mature monthly during ovulation ➔ Paired fallopian tubes which connect to the uterus. Each tube has fimbriae ➔ Cervix connecting the uterus and vagina ➔ A set number of follicles (eggs on standby in the ovary that need to be activated) ➔ Vagina IMPLANTATION = zygote is attached to reproductive tract After fertilisation, the zygote grows by cell division (mitosis) as it travels down the fallopian tube towards the uterus. After about one week, the clumped cells (called a blastocyst) reach the uterus. The blastocyst attaches to the lining of the uterus and, thus, causes implantation. Once the blastocyst has been implanted into the uterine wall, the embryo begins releasing hormones such as hCG to sustain the corpus luteum THE MENSTRUAL AND OVARIAN CYCLES ★ The Ovarian Cycle The ovarian cycle refers to the monthly cycle of egg development in the ovary with follicular phase, ovulation and the luteal phase regulated by hormones. Essentially, it is a follicle turning into an ova. There are three main phases: 1. Follicular phase: A follicle takes between 10-21 days to develop in the ovary ➔ (FIRST HALF) During this time, one follicle fully matures. This follicle releases oestrogen which stimulates the endometrium to thicken. In the middle of the cycle, an egg bursts out of the follicle 2. Ovulation: a functional ovum is released from the ovary ➔ Ovulation is part of the menstrual cycle where the ovary releases a ripe egg, an ovum 3. Luteal phase: the ruptured follicle develops from into the corpus luteum which secretes hormones to prepare the endometrium of the uterus for pregnancy. If pregnancy does not occur, the corpus luteum breaks down for the start of a new cycle ➔ (SECOND HALF) The remnants of the burst follicle form the corpus luteum, which releases progesterone and oestrogen. These hormones cause the endometrium to thicken and stabilise. At the end of this cycle, the corpus luteum disintegrates which causes a decrease in progesterone and oestrogen, stopping the release of FSH and LH and triggering ovulation ★ The Menstrual Cycle The menstrual cycle refers to the cyclical preparation of the endometrium of the uterus for pregnancy in females with discharge of blood and tissue through the cervix if implantation does not occur. Essentially, the old ovum eggs need to be replaced and are done through the shedding of the endometrium. A puberty gonadotropin releasing hormone (GnRH) from the hypothalamus stimulates the release of follicle stimulating hormone (FSH) and luteinising hormone (LH) from the anterior pituitary gland. FSH and LH stimulate the ovary to become active and, with oestrogen and progesterone from the ovary, they regulate the menstrual cycle. ➔ It is usually between 25 and 35 days in length, averaging 28 days. This is the full cycle of the menstruation and ovarian process: During the first 7 days of the menstrual cycle, a few follicles begin to grow and secrete oestrogen hormones into the bloodstream to prepare the lining of the uterus for pregnancy. Around day 7, all follicles stop growing EXCEPT ONE which continues to grow and nourish the developing egg inside. On day 12, the follicle secretes large amounts of oestrogen into the blood. As it reaches the hypothalamus and the pituitary gland in the brain, the anterior releases mass amounts of LH into the blood. On day 14, the LH causes the follicle to undergo a sudden growth spurt. Before ovulation, the egg detaches from the inside of the follicle and releases chemicals that cause one of the fallopian tubes to move closer and surround the follicle. The follicle swells up until it bursts and ejects the egg and fluid into the abdominal cavity. In response, the fimbriae sweep across the ovulation site and pick up the egg, transporting it further into the fallopian tube. Once inside, the muscular contractions gently push the egg towards the uterus. After ovulation, the egg lives for 12-24 hours, so it must be fertilised with a male sperm during this time for a woman to become pregnant. If the egg is not fertilised at this time, it dissolves away and is shed, along with the uterine lining, during menstruation. This cycle is then repeated. HORMONAL CONTROL = Hormones involved -- How? What? Why? HORMONES INVOLVED DESCRIPTION OESTROGEN ➔ Oestrogen repairs and thickens the uterine lining and prepares the endometrium for the implantation of a zygote ➔ At 1 month, the oestrogen levels begin to consistently increase due to the need to develop thicker walls to support the zygote during pregnancy. At 9 months, oestrogen decreases dramatically to 0 because it is no longer produced and dissolves for an easier delivery; birth is unable to occur if uterine lining is too thick PROGESTERONE ➔ Progesterone maintains the endometrium lining and supports the pregnancy (pregnancy can be lost is progesterone is too low) ➔ At month 1, the progesterone levels consistently rise until month 9 at delivery, to which they dramatically drop to 0 as it is no longer produced. It is no longer produced due to the endometrium no longer requiring the maintenance of the thick uterine lining. GONADOTROPIN The gonadotropin-releasing hormone (GnRH) is produced by the hypothalamus of the brain RELEASING HORMONE and triggers the anterior pituitary gland to release two important hormones FOLLICLE-STIMULATING ➔ FSH stimulates the growth of follicles to grow and mature the ovum in the ovary so it HORMONE (FSH) may be ready for fertilisation (only involved in the ovarian cycle, not pregnancy) ➔ High concentrations of LH cause the egg to burst out of the mature follicle (ovulation) LUTEINISING and cause the remnants of the burst follicle to form in the corpus luteum HORMONE ➔ It induces ovulation production of oestrogen (not involved during pregnancy) HUMAN CHORIONIC ➔ It is an embryonic hormone produced by some of the cells in the blastocyst/embryo GONADOTROPIN (hCG) when it implants in the endometrium. ➔ hCG maintains the corpus luteum in the mother, stimulating it to continue to produce oestrogen and progesterone and preventing the shedding of the endometrium → it stops the corpus luteum from deactivating and stops the producing of FSH/LH When hCG ↑, FSH & LH ↓ When hCG ↑, progesterone and oestrogen also ↑ PREGNANCY AND BIRTH IN THE HANDS OF HORMONES ★ 1ST TRIMESTER The embryonic hormone hCG rises rapidly to maintain the corpus luteum, allowing it to continue secreting progesterone. This ensures the uterine lining remains receptive to an embryo. The oestrogen and progesterone interact with the hypothalamus and anterior pituitary gland, causing a decrease in the production of LH, GnRH and FSH and preventing menstruation or ovulation from occurring High levels of progesterone stimulate change in the mothers body. These changes include: ➔ Enlargement of the uterus ➔ Formation of mucous plug to seal the cervix ➔ Growth of the maternal parts of the placenta ➔ Breast growth ★ 2ND TRIMESTER High levels of oestrogen and progesterone are vital to continue maintaining the pregnancy. However, the production of embryonic hCG declines and the corpus luteum deteriorates, stopping it from producing these hormones. The placenta takes over the role of producing oestrogen and progesterone ★ 3RD TRIMESTER Towards the end of this trimester, increased oestrogen is released. This induces receptors to form on the uterus wall that can bind with the hormone, oxytocin. Oxytocin is critical to triggering and maintaining labour by causing muscular contraction which push the baby to the cervix and vaginal opening  IQ2: 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 – DNA replication using the Watson and Crick DNA model, including nucleotide composition, pairing and bonding MITOSIS AND MEIOSIS ★ MITOSIS Mitosis, a type of cell division, is explicitly used for identical cells for growth and repair where diploid makes diploid: a full set of chromosomes makes another full set of chromosomes (NOT REPRODUCTION) ➔ Cell division is the process by which a multicellular organism grows, repairs, maintains and reproduces itself ➔ Mitosis itself is a process of division of the nucleus and cytokinesis is the division of the cytoplasm STAGE DESCRIPTION INTERPHASE This is where DNA replication occurs. ➔ Each single stranded chromatid has its DNA duplicated, which forms a genetically identical sister chromatid; this now becomes double stranded DNA PROPHASE During prophase, the chromosomes coil up and they appear as their classic “X” shape under a microscope. During this phase, the nuclear membrane dissolves in the cytoplasm and the centrioles begin to move and align up at opposite ends of the cell’s equator METAPHASE During metaphase, the chromosomes line up above each other along the poles of the cells. The spindle fibres which are attached to the centrioles will now have access to attach to the chromosomes centromeres RANDOMLY ➔ Essentially, they line up against the equator of the cell and a network of spindle fibres appear and extend to each chromosome ANAPHASE During anaphase, the chromatids that are attached to centrioles via spindle fibres are being pulled towards opposite ends of the somatic cell. The cell membrane is also starting to alter its shape for cell division. TELOPHASE During telophase, the spindle fibres disappear and a new nuclear membrane begins to form around the two sets of chromosomes CYTOKINESIS During cytokinesis, the cytoplasm of a single eukaryotic cell divides into two daughter cells, each with an identical and equal amount of genetic material as the original parent cell. These cells are now capable of entering interphase and undergo mitosis when required.  ★ MEIOSIS https://www.youtube.com/watch?v=iCL6d0OwKt8 Meiosis is a special type of cell division that creates gametes (eggs and sperm) and only occurs in the reproductive organs of organisms that reproduce sexually. Meiosis results in haploid cells by two rounds of cell division (I & II). USED IN REPRODUCTION MEIOSIS I: STAGE DESCRIPTION INTERPHASE I DNA replication occurs here. Each chromatid has its DNA replicated, forming another genetically identical sister chromatid. ➔ The number of chromosomes have not changed before and after interphase PROPHASE I During prophase, the chromosomes coil up and the nuclear membrane dissolves in the cytoplasm. The centrosomes begin to move and align up at opposite ends of the cell’s equator ➔ Homologous chromosomes will line up side-by-side across the equator cell for crossing over ➔ During crossing over, the double stranded homologous chromosome pairs (one paternal and one maternal) exchange their genetic material. This creates new allele combinations that are different from their parents METAPHASE I As the nuclear membrane dissolves, the spindle fibres attached to the centrosome can bind with the chromosome at the centromeres. This process is random ANAPHASE I The spindle fibres move the chromosomes in each homologous pair to different sides of the cell membrane TELOPHASE I The coiled chromatids of each chromosome start to uncoil. The spindle fibres begin to break down and a new nuclear membrane is created to enclose the chromosomes. Since each chromosome of the homologous pair is now in different cells, there are no longer homologous pairs in each of the haploid cells. MEIOSIS II: “mitosis for haploid cells." STAGE DESCRIPTION PROPHASE II Chromosomes coil and the nuclear membrane breaks down. The centrioles move apart, the spindle fibres form and begin to capture chromosomes from the centromeres ➔ The two sister chromatids of each chromosome are captured by the fibres from opposite centrioles METAPHASE II The chromosomes line up along the equator of the cell. ANAPHASE II The sister chromatids separate and are pulled towards opposite ends of the cell by the spindle fibres TELOPHASE II The nuclear membrane forms around each set of chromosomes and they begin to uncoil. Cytokinesis then splits the chromosome sets into new cells, forming the final products of meiosis: four haploid cells in which each chromosome has just one chromatid Four haploid gametes from the splitting of each of the two haploid cells; each of the gametes inherits one allele of every gene. This is because each of the double-stranded chromosomes that contain two alleles for different genes have separated during Anaphase II. ➔ The four gametes are either sperm or egg cells. ➔ The gamete can fuse with its opposite kind to form a diploid cell so that the zygote will have two alleles for a given gene. DNA REPLICATION DNA is the genetic material that an organism inherits from its parents, shaped as a double-helix. It is double stranded and has a sugar-phosphate backbone, as well as a nitrogenous base that only bonds in specific pairs: A → T & C → G. This is a “nucleotide” DNA replication is the process by which the double stranded DNA molecule is 'unzipped' by enzymes, and free nucleotides bind to each of the exposed backbones to create two identical DNA molecules. It is essential prior to cell division. ★ PHASE ONE: INITIATION 1. An enzyme called helicase causes the DNA to progressively unwind 2. After the DNA unzips, helicase destroys the hydrogen bonds between the complementary base pairing, exposing each nucleotide base ★ PHASE TWO: ELONGATION 3. Primase adds RNA primer for synthesis to be initiated. DNA polymerase adds free floating DNA nucleotides and inserts them with their complementary base 4. DNA polymerase corrects base pairing errors by splicing out the incorrect base and replacing it with the correct one ★ PHASE 3: TERMINATION 5. Ligase seals the two strands together and the strands recoil back into a double helix assess the effect of the cell replication processes on the continuity of species DNA REPLICATION ➔ DNA is the fundamental hereditary unit, which directs all processes in a cell. Reproduction of cells is dependent upon DNA replication, as the creation of new cells requires more DNA to be produced ➔ By copying the genetic material of a cell, replication ensures that information important for life is transferred down through the generations. ➔ If DNA were not replicated before mitosis and meiosis, cell division would halve the amount of DNA, and resulting cells would die due to inadequate amounts of genetic information. MEIOSIS ➔ Gametes are the end product of meiosis - haploid cells with half the number of requisite chromosomes to make a fully functional cell. ➔ The combination of gametes during sexual reproduction creates variation from both parents ➔ Processes of crossing over, independent assortment and random segregation allow for combinations of different alleles, increasing variation in offspring and the wider population ➔ Genetic diversity (introduced by meiosis and sexual reproduction) is very important for the continuity of species, as mutation and variation are essential factors for survival and evolution MITOSIS ➔ Mitosis is essential for development and growth of organisms as it increases the number of cells in an organism, allowing for development of a multicellular body. ➔ Mitosis allows for old cells to be replaced, ensuring that tissues continue to function effectively and efficiently ➔ Allows us to develop to maturity when we can pass our genetic information onto offspring through sexual reproduction  IQ3: How can the genetic similarities and differences within and between species be compared? model the process of polypeptide synthesis, including: Polypeptide synthesis is the biological production of peptides, which are organic compounds in which multiple amino acids are linked via peptide bonds. They are the building blocks of proteins, which are essential to cell function TRANSCRIPTION AND TRANSLATION DNA → mRNA → tRNA + Ribosome + MRNA → Polypeptide → Protein (Transcription) (Modification) (Translation) (Folding) ★ TRANSCRIPTION Transcription is the process by which a complementary copy (mRNA) of a DNA gene is made in the nucleus. STEP ONE: RNA polymerase attaches itself to the DNA strand and breaks the hydrogen bonds that bind to the nitrogenous bases. This results in the unwinding of a section of the DNA double helix (initiation) STEP TWO: The section of DNA is unwound to allow free ribonucleoside triphosphate molecules to perform complementary base pairing with the template strand of the DNA. A → T & G → C STEP THREE: RNA polymerase moves downstream of the DNA (from 3′ to 5′) as more nitrogenous bases on the template strand are being paired with ribonucleoside triphosphate (elongation). As RNA polymerase moves downstream of the DNA, the enzyme rewinds the DNA behind it to reform the double helix. STEP FOUR: The propagation stage of transcription stops when the RNA polymerase arrives at a termination sequence. Here, the enzyme releases the chain of ribonucleoside triphosphate from the complex, creating an mRNA strand that has identical genetic information as the coding strand of the DNA (only difference is that uracil is present rather than thymine) as it is formed via complementary base pairing using the template DNA strand. ★ TRANSLATION Translation is the process whereby mRNA information is used to create a polypeptide chain and specify its amino acid sequence. STEP ONE: The mRNA migrates out of the cell nucleus and into the cell’s cytoplasm via the nuclear membrane pore. STEP TWO: A small ribosomal unit attached to the mRNA STEP THREE: Following the small ribosomal unit, the large ribosomal unit attaches to the mRNA ➔ With the mRNA enclosed by the ribosome, it means that translation occurs within ribosomes. The rough endoplasmic reticulum (organelle) contains many ribosomes on its surface STEP FOUR: There are tRNA molecules found in the cytoplasm that have an anticodon. One anticodon is made up of three RNA nucleotides, each RNA nucleotide has a nitrogenous base – A, U, C or G. Each of these tRNA molecules can bind with a specific type of amino acid that is specific to its anticodon. STEP FIVE: The mRNA codon specifies the tRNA, carrying an amino acid, with the complementary anticodon to bind with itself. The ribosome reads the mRNA codons so that the tRNA molecules with the correct anticodon bind with the correct mRNA codon STEP SIX: As the next mRNA codon specifies the another tRNA to bind with it, the prior tRNA molecule will detach from the mRNA and ‘transfer’ its amino acid to the new tRNA molecule that enters the ribosome complex. STEP SEVEN: The elongation process of building the amino acid chain stops when the ribosome complex reads the mRNA stop codon (a sequence of three RNA nucleotides). STEP EIGHT: The ribosome complex separates into its small and large ribosomal subunits and mRNA separates into its individual nucleotides STEP NINE: The polypeptide chain coils up as the amino acids form hydrogen bonding with each other. This single polypeptide can be a protein IMPORTANCE OF mRNA AND tRNA ★ mRNA ➔ contains nitrogenous bases that are complementary to those nitrogenous bases found in the template strand or identical to nitrogenous base to those bases found in the DNA coding strand ➔ ensuring that the organisms’ genes code for the correct mRNA codons; allows the correct tRNA molecule with matching anticodons that correct the amino acid that corresponds to the mRNA codon to form the correct amino acid sequence for the polypeptide chain The correct gene will allow the correct mRNA, formed from a complementary base pair, to specify the correct tRNA carrying a specific amino acid to bind with the matching mRNA codon. This ensures that the right amino acids sequence of the resulting polypeptide chain and, hence, the correct protein to be created. ★ tRNA ➔ ensures that its anticodon specifies and binds to the correct amino acid. This will ensure that the resulting polypeptide chain will have the right amino acid sequence that allows the protein-folding process to occur correctly. FUNCTION AND IMPORTANCE OF POLYPEPTIDE SYNTHESIS Polypeptide synthesis is the process by which cells create polypeptides, which are chains of amino acids. These chains fold to form proteins, which perform numerous vital functions within the body. The process of polypeptide synthesis involves two key stages: transcription and translation. FUNCTION: 1. Gene expression: Polypeptide synthesis is how genetic information, stored in DNA, is converted into functional proteins. This process allows the cell to produce proteins based on specific instructions encoded in genes 2. Transcription: DNA is transcribed into messenger RNA (mRNA). mRNA serves as the template that carries genetic information from the DNA to the ribosomes, where protein synthesis occurs 3. Translation: The mRNA is translated into a polypeptide chain at the ribosome. tRNA molecules bring specific amino acids to the ribosome based on the codons (three-base sequences) in the mRNA. Amino acids are linked together in the correct order to form the polypeptide IMPORTANCE: 1. Protein Production: Proteins are essential for virtually all cellular functions, including enzymatic activity (enzymes), structure (collagen), transport (haemoglobin), and regulation (hormones like insulin). Without polypeptide synthesis, the cell would not be able to produce these critical molecules 2. Cellular Function and Structure: Proteins are necessary for maintaining cell structure, regulating biochemical reactions, facilitating communication between cells, and responding to environmental signals. Every living organism relies on proteins for survival, and polypeptide synthesis is the foundational process by which these proteins are made 3. Genetic Expression and Regulation: Polypeptide synthesis is a key mechanism by which cells control gene expression. The synthesis of proteins in response to specific signals allows cells to adapt to changing conditions PHENOTYPIC EXPRESSION Gene —> mRNA —> tRNA attached to amino acid —> Polypeptide chain —> Protein —> Codes for a characteristic Environmental factors include: ➔ The organism’s diet or availability of food/water: ➔ pH of soil ➔ Temperature of ambient environment Genotype + Environmental Factors = Phenotype investigate the structure and function of proteins in living things STRUCTURE OF PROTEINS STRUCTURE DESCRIPTION PRIMARY The primary structure is the specific linear sequence of amino acids that make up a polypeptide chain. SECONDARY Regular, repeated patterns of folding of the protein backbone. TERTIARY The overall folding of the entire polypeptide chain into a specific 3D shape. QUATERNARY Occurs when a protein is made up of two or more polypeptides. Quaternary structure describes the way in which the different polypeptide subunits are arranged together to form the overall structure of the protein. FUNCTION OF PROTEINS Proteins are essential in performing a wide variety of functions within organisms. Their diverse roles are crucial to maintaining cellular structure, driving biochemical reactions, and supporting the body's physiological processes. 1. Structural Support: Proteins like collagen provide strength and support to tissues like skin, hair, and bones. 2. Enzymes: Proteins act as enzymes that speed up biochemical reactions, such as digestion (e.g., amylase). 3. Transport: Proteins like haemoglobin transport molecules (e.g., oxygen) throughout the body. 4. Defence: Antibodies are proteins that help the immune system fight infections. 5. Signalling: Proteins (e.g., insulin) regulate biological processes and communication between cells. 6. Movement: Proteins like actin and myosin enable muscle contraction and cellular movement.  IQ4: 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 Genetics is a field of biology that looks at genes and the ways they are inherited. Homologous chromosomes contain the same genes in the same order. However, they may have slight variations in the alternative forms (alleles) of each gene. The alleles for a gene are typically represented by the same letter, in either uppercase or lowercase. The genotype of an individual is written as two letters. When a person has to identical alleles (eg. FF or ff), they are homozygous for that trait ➔ The allele that is expressed in a heterozygous genotype (capital) is said to be dominant ➔ The allele that is not expressed in a heterozygous genotype (lowercase) is said to be recessive When a person has two different alleles (eg. Ff), they are heterozygous model the formation of new combinations of genotypes produced during meiosis, including but not limited to: AUTOSOMAL, SEX LINKAGE, CODOMINANCE, INCOMPLETE DOMINANCE AND MULTIPLE ALLELES ★ AUTOSOMAL ★ SEX LINKAGE The gene is located on one of the Biological gender in humans is numbered, or non-sex, chromosomes; it detected by the sex chromosomes; has nothing to do with gender XX for a female and XY for a male. Hence, sex-linked conditions in humans typically relate to the genes on the X chromosome. Examples include: ➔ Red-green colourblindness ➔ Haemophilia ➔ Muscular dystrophy As males only have an allele on its X chromosome and not on its Y chromosome, males are more likely to express sex-linked traits than females. This is because males only need one allele that codes for colour-blindness and the male will have the recessive sex-linked trait. For females, both recessive alleles must be inherited in order for a female to have the recessive sex-linked trait. ★ CODOMINANCE ★ INCOMPLETE DOMINANCE The phenotype of heterozygotes The phenotype of heterozygotes appears as a blend of the involves both alleles being express; phenotypes of either type of homozygote. neither dominant over the other ➔ There is mix/blend ➔ Sharing/cooperating  ★ MULTIPLE ALLELES While each gene in an individual has only two alleles present, there can be more that two possible alleles that determine a particular gene, eg. rabbit fur colour and human blood groups; both have multiple alleles for a single gene. PEDIGREES AND PUNNETT SQUARES ★ PEDIGREE ★ PUNNETT SQUARE 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: SINGLE NUCLEOTIDE POLYMORPHISM (SNPs) Single nucleotide polymorphism is the most common type of genetic variation among people. Each SNP represents a difference in a single DNA building block, called a nucleotide. Types of SNPs include: ★ INSERTION a type of mutation that involves the addition of one or more nucleotides into a segment of DNA ★ DELETION a type of mutation that involves the loss of one or more nucleotides from a segment of DNA ★ SUBSTITUTION a type of mutation in which one nucleotide is replaced by a different nucleotide  IQ5: Can population genetic patterns be predicted with any accuracy? investigate the use of technologies to determine inheritance patterns in a population using, for example: DNA SEQUENCING AND PROFILING ★ GEL ELECTROPHORESIS a laboratory method used to separate mixtures of DNA, RNA, or proteins according to molecular size. In gel electrophoresis, the molecules to be separated are pushed by an electrical field through a gel that contains small pores. This is done to compare DNA between columns. ★ POLYMERASE CHAIN REACTION Artificial DNA replication, amplifies the amount of DNA PCR must be done before both sequencing and profiling 1. Denature → DNA double strand splits into 2 singles HEAT to 95°C 2. Annealing → Sticks to the primers to the 5” (5 prime) COOL to 55°C 3. Elongation → Polymerase builds from the primer 5” to 3” , two identical strands, synthesises DNA The same as DNA replication but heated and cooled investigate the use of data analysis from a large-scale collaborative project to identify trends, patterns and relationships, for example: USE OF POPULATION GENETICS IN CONSERVATION MANAGEMENT POPULATION GENETICS STUDIES USED TO DETERMINE INHERITANCE OF DISEASE/DISORDER POPULATION GENETICS RELATING TO HUMAN EVOLUTION