During meiosis I a the chromosome number is reduced by four

During _meiosis I: a) the chromosome number is reduced by four b) non-homologous chromosomes synapse C) dyads forms d) crossing over occurs e) all of the above In an organism with a diploid number of 12, how many tetrads are visible during meiosis I? a) 48 b) 24 c) 12 d) 6 e) 3 In Drosophila, a bristle mutation called singed is inherited as an X-linked recessive. If a female showing the singed phenotype is crossed with a wild type male, the offspring will be composed of phenotypically ____ flies. a) all wild types b) 1/2 singed males: 1/2 wild type females c) 1/2 wild type males: 1/2 singed females d) all singed e) 1/4 wild type males: 1/4 signed males: 1/4 wild type females: 1/4 signed females Homologous chromosomes are not necessarily identical in their: a) overall size b) placement of genes c) centromere placement d) alleles e) arm ratio In disease! exhibiting genetic anticipation: a) The disease is most severe in the first generation and decreases in severity in subsequent generations. b) The disease exhibits the same severity in all generations. c) The disease is milder in the first generation and increases in severity in subsequent generations. d) There is NO genetic component to the disease. Epistasis involves interaction between: a) different genes b) alleles at one gene locus

Solution

1)crossing over occurs

2)2n=12

so 2*12=24 chromatids

24/4=6 tetrads

3) xx(singed female) XY(wild male)

Gamates x X Y

Offsprings Xx (normal female) xY(SINGED male)

1/2 wild females 1/2 singed males

4)Homologous chromosomes are identical in their size,shape, gene except allele.