Meiosis

Question 1

Chromosome?

Answer 1

A single long DNA molecule and have 100 or 1000 of genes with a sequence of nucleotides along the DNA molecule.

Location on a gene = locus.

22 autosomes and 1 sex
23 maternal and 23 paternal

Question 2

Homologs?

Answer 2

Individual chromosomes from each parent that look alike but have different versions - allele- of genes at the corresponding loci.

Question 3

Prophase 1 ?

Answer 3

Chromosomes have been duplicated and the sister chromatids are held together by cohesins.

Duplicated homologs pair up - synapsis- and crossing over occurs, by a synaptomental complex and becomes visible as chiasmata.

Segments are transfered between non-sister chromatids - a paternal is traded for a maternal part.

Question 4

Metaphase 1?

Answer 4

Pairs of homologs are positioned at the metaphase plate

Question 5

Anaphase 1?

Answer 5

Duplicated chromosomes of each homologs pair move to the poles, the sister chromatid remains attached by cohesin.

Question 6

Independent assortment?

Answer 6

Since the pair of homologs are positioned independently of the other pairs at metaphase 1, the first division results in each pair sorting its M and P homologs into daughter cells independently of every other pair.

Question 7

N=23?

Answer 7

Combination of P and M is 2^23 - 8.4 million possible combinations of chromosomes without crossing over.

Question 8

Crossing over?

Answer 8

Recombinant chromosomes that results in chromosomes with new combos of M and P alleles.

Question 9

Metaphase 2?

Answer 9

Combining DNA inherited from 2 parents into a single chromosome. Different possible arrangements of non-identical sister chromatids during this phase - increases the the number of genetic types of daughter cells that can result from meiosis.

Question 10

Random fertilization?

Answer 10

2^23 x 2^23 - 2n zygote

Question 11

Mutations?

Answer 11

Are the original source of different alleles