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Unit 5 - Genetics, Meiosis: the process by which sex cells (gametes) are…

- - - - Use letters to represent alleles (dominant = upper case; recessive = lower case; codominant = superscript).
        (STEP 1)
      - Determine genotype and phenotype of parents (P generation).
        (STEP 2)
      - Draw Punnett grid - maternal gametes along the top, paternal gametes along the left.
        (STEP 4)
      - Determine genotype of paternal and maternal gametes (haploid, so consists of single allele).
        (STEP 3)
      - Complete Punnett grid and determine potential genotypes and phenotypes of F1 generation.
        (STEP 5)
- - - - Pairs of alleles are both expressed equally in phenotype of heterozygote (CBCW).
        
        Alleles represented by superscript (e.g. CB for blue coat, CW for white coat).
        
        Dominant alleles still uppercase and recessive alleles still lowercase.
  - - - Exception:
        Males have only 1 allele for each gene located on a sex chromosome, as these chromosomes aren’t paired (XY).
    - - If maternal and paternal alleles are the same, the offspring is said to be homozygous for that gene.
      - If the maternal and paternal alleles are different, the offspring is said to be heterozygous for that gene.
      - Males only have 1 allele for each gene located on a sex chromosome and are said to be hemizygous for that gene.
  - - - Females (XX) can be homozygous or heterozygous (carriers) for X-linked traits.
      - X-linked recessive conditions are more common in males, as they do not have another X chromosome to mask the recessive allele.
  - - - Autosomal dominant
        
        Both parents affected and offspring is unaffected
        
        parents are heterozygotes and offspring is homozygous recessive.
        
        All affected offspring have at least one affected parent
        
        homozygous dominant or heterozygous.
        
        Both parents unaffected and all offspring is unaffected
        
        homozygous recessive
      - X-linked dominant
        
        Daughters of affected father are also affected - daughters are heterozygous or homozygou
        
        Unaffected mother only has unaffected sons - mother is homozygous recessive.
        
        X-linked dominant traits appear more in females.
      - Autosomal recessive
        
        Both parents unaffected and all offspring is unaffected
        
        homozygous recessive.
        
        Both parents are affected and all offspring is affected
        
        parents are heterozygous carriers and offspring is homozygous recessive.
      - X- linked Recessive
        
        Affected mother only has affected sons - mother is homozygous recessive.
        
        Unaffected mother can have affected sons - mother is heterozygous carrier.
        
        X-linked recessive traits appear more in males.
    - - STEP 1:Determine whether the trait is dominant or recessive.
      - STEP 2:Determine if the chart shows an autosomal or sex-linked (usually X-linked) trait.
- - - - Colder Temperature: male offspring
      - Warmer Temperature: Female Offspring
      - Climate Change changes temperature of sand and disrupts sex ratio of turtles (produces more females)
        
        May lead to extinction if can't overcome environment change
    - - Wetter environment: more males
      - Drier Environment: more females
  - - - Acidic Flower (PH<4): blue color
      - Basic Flower (PH>7): Pink Color
      - Acidic flower (PH: 4-7): Purple color
  - - - Types
        
        Eumelanin(Black/Brown)
        
        Pheomelanin(Yellow, Red)
      - Temperature Effect on Melanin Pigments
        
        Low temperature --> less melanin pigment production
        
        Pigment production depends on amount of UV radiation absorbed
  - - - When the two yeast receptors bind together they form outgrowth and fuse together
        
        pheromone is recognised by specific receptors as cell binds with opposite mating type
        
        Mating of yeast can only occur between two haploid which is either a or α (alpha) type of mating.
        
        The mating type is determined by its locus which controls the sexual behavior of both haploid and diploid cell.
- - - - Traits determined by mitochondrial DNA are maternally inherited.
  - - - Both are also maternally inherited
- - - - Can become unlinked via recombination (crossing over during synapsis in meiosis I).
        
        *text
- - - - recombinant chromosomes.
        
        The result is new allele combinations on the chromosomes.
        
        These resulting chromosomes that contain genetic material from both homologues are called recombinant chromosomes.
        
        This process increases genetic diversity of potential offspring by creating new combinations in gametes.
- - - - Law of independent assortment: Pairs of alleles separate independently from one another during gamete formation.
      - Inheritance of one gene is independent to the inheritance of any other gene.
      - This is due to random orientation of homologous pairs in meiosis I.
      - During metaphase I, homologous chromosomes line up as bivalents at the equator.
      - The gametes can differ depending on whether they got maternal or paternal copies of chromosomes.
        
        Random assortment occurs for each homologous pair, so the number of possible gamete combinations are dependent on the number of homologous pairs n.
        
        ∴ Gamete combinations = 2n
        
        e.g. Humans have 46 chromosomes, n = 23. 223 = 8,388,608 different gametes by random orientation.
        
        Note: Independent assortment will not occur if 2 genes are linked (located on the same chromosome).