Yr 11 Exam Revision, Sem 2, Biology PDF

A gene is an inherited characteristic made of DNA. Ch 6 Genes Controls structures and function. Influences structure, physiology & behaviour A gene is codes for a protein (polymer) which is made from amino acids (monomer) 3 bases are called a codon and when they are read the pro...

A gene is an inherited characteristic made of DNA. Ch 6 Genes Controls structures and function. Influences structure, physiology & behaviour A gene is codes for a protein (polymer) which is made from amino acids (monomer) 3 bases are called a codon and when they are read the produce an amino acid. A chain of amino acids is a protein. Allele-variation of a gene. Different forms of the same gene. The genome is the total set of genetic DNA (base pairs) carried by an individual in a somatic cell. Can find out seq. tat code for proteins, cause disease etc.. Epigenetics is the study of mutations to gene expression that don’t involve altering DNA seq Chromosomes DNA is coiled in Eukaryotic cells to form chromosomes. Somatic (body) cells have 46 (Diploid- 2n). Have 2 sets of linear chromosomes. Gametes (sex cells) have 23 (Haploid- n). Have 1 set of linear chromosomes Vary is size depending on number of nucelotides. Chrom. number and size varies in diff. species & within same species. Autosomes are chromosomes 1-22. 22 PAIRS or 44 OVERALL. Sex chromosomes are pair 23. 46 homologous chromosomes arranged into pairs. 22 matched pairs and 1 odd pair (number 23)-X and Y ‘Sex’ chromosomes. XX Female, XY Male  Meiosis is the splitting of a cell to produce 4 cells Meiosis with ½ the number of chromosomes as the original. Body cells: 2n=46 (Diploid) Sex cells: n=23 (Haploid) Meiosis produces gametes (haploid cells) with ½ the genetic material of the original cell. When sperm (n) and ova (n) meet, fertilisation occurs and produces a zygote that is 2n. Meiosis produces random combinations of homologous pairs via independent assortment. Provides variation and occurs during metaphase 1 Meiosis can allow exchange of chriomatid segments between chromosomes. Known as crossing over. Provides variation & occurs during prophase 1 1. INTERPHASE: Chromosome duplicates IPMATPMAT + C Meiosis 2. PROPHASE 1: Chromosome becomes visible & double stranded. NM breaks down & crossing over occurs. Lie side by side (synapsis) & coil around but move away with a section remaining in contact (chiasmata). Crossing over occurs here. 3. METAPHASE 1: Homologous Chromosome/s line up in the centre. Spindle fibres attach to centromere 4. ANAPHASE 1: Chromatids don’t separate. Whole chromosome pulled to opposite ends of cell via spindle fibres. X shaped. Chrom. Number doubles-> E.g. diploid is 10, you now have 20! 5. TELOPHASE 1: Chromosome pulled to the opposite end & NM reforms. Cell divides via cytokinesis. 6. PROPHASE 2: Nuclear mem breaks down & chromosomes become visible. 7. METAPHASE 2: Pairs of chromatids line up along equator of cell. Spindle fibres form & attach to centromere. 8. ANAPHASE 2: Spindle fibres pull the chromatids apart and to opposite ends of the cell. 9. TELOPHASE 2: Nuclear membrane forms around chromosomes & Cytokinesis occurs. 4 haploid cells produced (½ the number of chromosomes) Ch 9 Genotypes & The genotype is the set of genes in our DNA which Phenotype control a particular trait. Dominant trait- trait that is expressed by individual (AA or Aa) Recessive trait is one that is masked by the dominant trait (aa) If a person has 2 identical alleles of a gene Homozygousà AA or aa Pure breed-> can only pass on ONE allele Homo dominant (AA) or Homo recessive (aa) If a person has 2 different alleles of a gene Heterozygousà Aa Will show dominant trait. CARRIER!!! A phenotype is the visible trait that is observed in regards to an organisms structure or function. Controlled by their genotype & environment. Eye colour, height, fruit colour  Co-dominance is where both alleles are expressed in the phenotype. Co-dominance Neither is recessive so both are expressed. Blood type is an autosomal trait Both alleles for a particular gene in a heterozygous individual contribute to the expression of that characteristic in the phenotype. Blood Type A=have A antigen on cell surface (IA) Blood type B=have B antigen on cell surface (IB) Blood type AB=have both A and B antigen on cell surface (IA and IB)-> CO-DOMINANT Blood type O=have neither antigen on cell surface. (ii) Dad is type A. Mum is type B. You have type A, B and O children. Parent genotypes?? Asexual In eukaryotes Asexual Reproduction is where one parent organism produces offspring that is genetically Ch 8 identical to it. Produces a daughter cell clone No gametes (sex cells) are involved BUDDING A “bud” breaks away or is taken away from the main organism and carried away to a new location where they settle and develop. Less competition E.g. Sea sponges FRAGMENTATION Parent organism can be divided into separate parts & each part can regenerate/re-grow into a new identical organism. Each part can survive. E.g. Starfish  Called Vegetative propagation Asexual in plants New plants formed are genetically identical from parent plant. CUTTINGS of roots or stem give rise to identical plants Cut a section of plant (root, leaf) from original and then grow elsewhere. It will grow into a new plant identical to the parent. Can lead to grafting, where a stem of one  Advantage of Sexual Reproduction Sexual reproduction involves the fusion of 2 haploid games (ova & sperm) to form a genetically unique zygote. 1 male and 1 female. Provides VARIATION- A condition in which members of that population differ in 1 or more traits. Advantages Disadvantages Inc. genetic diversity as mixing DNA to form offspring More time, energy & resources spent. Takes time to build Allows org. to adapt and change to the environment population. Imp. Disease resistance by allowing variation of Risk of transferrable diseases via sex alleles/genes. Mixing DNA from gametes reduces inheritance of genetic Risk of losing embryo to outside influences diseases Cloning Cloning involves getting DNA from one living organism and creating identical copies of it. Copied material/organism is called a clone & has identical genotype of parent. Reproductive cloning produces copies of whole animals. Also called adult cloning as the cell used comes from a fully developed adult tissue Therapeutic cloning produces embryonic stem cells for experiments aimed at creating tissues to replace injured/damaged/diseased tissues. Downsides? Economic and to animal? vSymbiosis is the relationship between two different species. Relationships in Where they can benefit, not be affected or harmed. 3 types: vMutualism is a relationship where both organisms benefit. Ecosystems. Neither is harmed. vBird picking fleas off a buffalo. Food for bird and less pests for buffalo. vPygmy possum feeding form nectar on natives and pollinating them as they move from one flower to the next. vAlgae can live inside jellyfish & clams, taking nutrients but also providing organic compounds via photosynthesis. vCommensalism is where 1 organism benefits & the other isn’t affected. vClown fish is protected from predators by the stinging cells of anemone but anemone is neither harmed or benefited. vRemora fish attaches to shark to “hitch a ride” but shark is unaffected.  Aboriginal & Torres Straight Islander people have a strong, spiritual connection to land. Aboriginal & Torres Aboriginal & Torres Straight Islander people Straight Island knowledge studied the adaptations of indigenous animals & how they reproduced to ensure survival. Their community practices ensure that the density & distribution of populations aren’t impacted negatively. Only take the fish/food NEEDED-> prevents overfishing/hunting & populations can recover Biopiracy- Use of traditional indigenous knowledge to develop resources without permission  Autosomal Dominant Pattern Expressed when one or more copies of dominant allele is present. Both males/females have it All affected individuals have at least 1 affected parent. Parents can give to either gender Appears in nearly every generation Disappears from pedigree, doesn’t come back Equal no. of sex affected Huntington’s disease, dwarfism, Alzheimer’s disease, familial breast E.g. hypercholesterolemia is LDLR gene. cancer High cholesterol. Has dominant (B) and recessive (b) allele.  Autosomal Recessive Pattern Expressed when 2 copies of recessive allele are present. Both males & females have it 2 unaffected parents can have affected child All the children of affected parents must have trait Trait can disappear from branch but reappear Equal number of affected males and females E.g. Albinism is a recessive trait (a). Pigment is missing from eyes, skin and hair. Thalassaemia, Tay-Sachs disease, Wilsons disease, Red hair colour, Osteogenesis  X linked dominant pattern Dominant gene carried on X chromosome and only 1 copy is needed to express phenotype. More affected females than males A male with the trait passes it onto all his daughters but no sons. Female with trait may pass it to both daughters and sons. Every affected person has at least 1 parent with the trait If the trait disappears from a branch of the pedigree, doesn’t reappear. Incontinentia pigmenti-death (IP2 gene on X chromosome) Vitamin D resistant rickets  Trait carried on X chromosome where 1 X linked recessive copy is required in males to express pattern phenotype or 2 copies in females. More males than females show trait All sons of a female with trait are affected. All daughters of male with trait will be carriers-can appear in sons None of the sons of a male with trait and an unaffected female will show the trait unless mum is a carrier Favism (RBC are destroyed with All children of 2 individuals with the trait agent contact). Missing enzyme (G6PD) on long arm. F=dominant, will also show trait f=recessive. Shown only in females with ff genotype. Colour blindness (red-green)- CBD gene on X chromosome.