Question

2.How is it possible for a trait to “skip generations” (i.e., one of your traits was also in one of your grandparents, but not in either of your parents) when every piece of DNA in you was also in one of your parents? How do meiosis and fertilization play a role in this phenomenon?

7. Why do Punnett squares not work for genes located on mitochondrial or chloroplast DNA?

Answer 1

2)recessive traits skips generations.

let the alleles be A- dominant and a-recessive

aa individuals show the trait but Aa and AA individuals show a normal phenotype.

if the genotype of one of the grandparent is aa and the other grandparent is AA.

aa grandparent produces a gamete via meiosis and AA grand parent produces A gamete via meiosis.

these gamete fuse ( via fertilization) to produce zygote, zygote has genotype Aa, has normal allele so Aa individual ( your parent) is phenotypically normal. genotype of one parent is Aa ( father), genotype of other parent is also Aa, maternal grand parents were also aa and AA so mother is Aa.

there two different alleles in both parents, alleles segregate during gamete formation, to form a and A gametes.

Aa * Aa

	A	a
A	AA ( normal)	Aa ( normal)
a	Aa (normal )	aa (shows the trait)

so it is possible to have aa progeny who shows the trait.( that is your phenotype)

so recessive traits can skip generations.

( Meiosis helps to segregate alleles: Two different alleles of a gene are located on homologous chromosomes, during prophase I homologous chromosomes pair up then during metaphase I paired homologous chromosomes align such that any one of the chromosome can be separated to daughter cells, so so daughter cells formed by meiosis I, has one chromosome from each pair, then during meiosis II sister chromatids are separated so that daughter cells formed by meiosis II contains only one allele for each gene)