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UW-Madison BIOLOGY 101 - Meiosis and genetics

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Zoology 101: Animal Biology Last Lecture Outline Lecture 16 1. Finish up on cancer2. Meiosis3. Sexual ReproductionCurrent Lecture 1. Finish up of meiosis2. Genetics Finish up meiosis• Mistakes can happen during mitosis/meiosis• Nondisconjunction: homologous chromosomes in meiosis or sister chromatids is meiosis 2 don't separate from each other ◦ abnormal gametes (either 3 or 1 chromosomes)▪ Aneuploid gametes◦ n+1 sperm and and n egg = 2n+1 zygote → Trisomy. Trisomy 21: Down Syndrome ◦ As age increases in female, risk of down syndrome increases ◦ Human ogenisis (egg formation) in fetal ovary haults at the beginning of meiosis 1▪ during ovulation, meiosis resumes▪ as you age, eggs ignore metaphase checkpoint Genetics • From sexual reproduction and meiosis, gametes are variable but similar • Two Hypothesis' ◦ Blending ▪ From the two parents, offspring are intermediate ◦ Particulate ▪ Mendel and pea experiment; each parent has discrete units passed through generations ▪ Pea used as a model organism → many offspring are produced, can control matings • P generation: true breeding plants (homozygus for purple flowers) ◦ Homo dominate is purple; dominate allele; haploid gamete is P◦ Homo recessive is white; recessive allele; Haploid gamete is p • F1 generation is heterozygous (different alleles: Pp) ◦ Principle of segregation: Alleles separate from each other during meiosis; half have P half have p ◦ Punnett square- allows us to organize and predict the out come Gametes P pP PP Ppp Pp pp◦ Genotypic Ratio 1PP:2Pp: 1pp◦ Phenotypic ratio: 3 purple flowers to 1 white ◦ Phenotype is determined by genotype◦ Purple color= pigment → anthocyanin▪ P gene= wild type → dominant/normal (anthocyanin) ▪ p gene= mutant of anthocyanin gene, recessive ◦ In purple; all normal genes are homozygous → protein P ◦ F1: heterozygous; 1 chromosome has wild, 1 has mutant, meaning:▪ ½ gametes will have normal▪ ½ will have mutants▪ Normal cancels out mutants, doesn't matter mutant is present • Does inheritance influence the inheritance of other traits? ◦ Seed color: Y-yellow y-green ◦ Shape: R- round r- wrinkled ◦ Parent RRYY and rryy form RY and ry gametes ◦ Cross fertilization occurs ▪ Principle of independent assortment: random alignment of chromosomes in metaphase ▪ use every combination RY Ry rY ryRY RRYY RRYy RrYY RrYyRy RRYy RRyy RrYy RryyrY RrYY RrYy rrYY rrYyry RrYy Rryy rrYy rryy▪ 9-3-3-1 ratio• Human genetics: correlating genotype with phenotype ◦ ex. Cystic


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UW-Madison BIOLOGY 101 - Meiosis and genetics

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