9.2 meiosis and genetic variation

Question 1

mitosis

Answer 1

produces 2 daughter cells with same number of chromosomes as parent cell and as each other

Question 2

meiosis

Answer 2

produces 4 daughter cells each with half the number of chromosomes as parent cell

Question 3

haploid number of chromosomes

Answer 3

23

Question 4

diploid number of chromosomes

Answer 4

46

Question 5

process of meiosis

Answer 5

Interphase:cell copies chromosomes and organelles
Prophase 1 : chromosomes become dense and become visible. Homologous chromosomes pair together and crossing over takes place. Nuclear membrane breaks down, centrioles move to opposite poles of the cell and spindle fibres assemble into spindle apparatus
Metaphase 1: pairs of homologous chromosomes are lined up at random on the equator of spindle apparatus
Anaphase 1: spindle fibres shorten and homologous chromosomes move to opposite poles
Telophase 1: nuclear membranes reform and chromosomes become separate
Cytokinese: divides into two haploid cells

2. Second meiotic division-same occurs but with chromatids. 4 cells are formed containing 23 chromosomes.

Question 6

2 ways meiosis brings genetic variation

Answer 6

1. independent segregation of homologous chromosomes
2. new combinations of maternal and paternal alleles by crossing over

Question 7

gene

Answer 7

length of DNA that codes for a polypeptide

Question 8

locus

Answer 8

position of a gene on a chromosome or DNA molecule

Question 9

allele

Answer 9

one of different forms of particular gene

Question 10

homologous chromosomes

Answer 10

pair of chromosomes, one maternal and one paternal that have same gene loci

Question 11

independent segregation of homologous chromosomes

Answer 11

Homologous chromosome pairs line up at random
Combination of chromosomes of maternal and paternal origin that go into daughter cell at meiosis 1 is completely random

Question 12

independent assortment

Answer 12

each chromosome is inherited randomly and independent of other chromosomes

Question 13

crossing over

Answer 13

in meiosis 1, chromatids of each pair become twisted over one another

tensions are created and(normally equivalent( portions of chromatids break off

broken portions might then rejoin with the chromatid of the homologous partner(recombination)

new genetic combinations of maternal and paternal alleles are produced

Question 14

calc for possible no combinations of chromosomes for each daughter cell based on no chromosomes in an organism

Answer 14

2^n

n= number of pairs of homologous chromosomes

Question 15

calc for possible no combinations of chromosomes for each daughter cell from different parents

Answer 15

(2^n)^2

n= number of pairs of homologous chromosomes