Module 2—Meiosis & Sexual Life Cycles

Question 1

life cycle

Answer 1

generation to generation sequence of stages in the reproductive history of an organism, from conception to the production of its own offspring

Question 2

Alternation of ______ and ________ is common to all sexually reproducing organisms

Answer 2

meiosis and fertilization

Question 3

3 definitions of genetics

Answer 3

study of how traits are inherited

how genotype relates to phenotype

how information is transformed into living systems

Question 4

homologs

Answer 4

a pair of the same type of chromosome, one from each parent

Question 5

n

Answer 5

used to designate a set of chromosomes from a single parent

Question 6

n in humans =

Answer 6

23

Question 7

Even if DNA has been duplicated, we still call the cell diploid/2n because…

Answer 7

there are 2 sets of unique information

Question 8

diploid dominant life cycle

Answer 8

fertilization by two haploid gametes yields diploid zygote →

mitosis yields diploid adult →

meiosis yields haploid gametes

Question 9

alternation of generations life cycle

Answer 9

fertilization by two haploid gametes yields diploid zygote →

mitosis yields diploid sporophyte adult →

meiosis yields haploid spores →

mitosis yields haploid gametophyte adult →

mitosis yields haploid gametes

Question 10

sporophyte

Answer 10

diploid adult

Question 11

gametophyte

Answer 11

haploid adult

Question 12

haploid dominant life cycle

Answer 12

fertilization by two haploid gametes yields diploid zygote →

meiosis yields haploid cells →

mitosis yields haploid adult →

mitosis yields haploid gametes

Question 13

purpose of meiosis

Answer 13

create novel combinations of novel chromosomes

Question 14

drawbacks of asexual reproduction

Answer 14

mutation load

↓ genetic diversity means slow response to environmental change

Question 15

only ______ cells undergo meiosis

Answer 15

diploid

Question 16

events of prophase I (excluding those found in mitosis)

Answer 16

each chromosome pairs with its homolog, aligned gene by gene

crossing over occurs

microtubles attach to kinetochores of each homolog (the kinetochores of each sister chromatid joined and acting as one kinetochore)

homologs move toward metaphase plate

Question 17

homologous chromosomes move together & align together during…

Answer 17

meiosis I

Question 18

independent assortment

Answer 18

each pair of homologs lines up independent of the other pairs - any combination may end up in the daughter cells

Question 19

meiosis __ reduces the ploidy of the cells

Answer 19

meiosis I

Question 20

at telophase I, each half of the cell now has a _____ set of chromosomes, each composed of two…

Answer 20

haploid

non-identical sister chromatids

Question 21

most similar to mitosis

Answer 21

meiosis II

Question 22

what separates during meiosis II?

Answer 22

non-identical sister chromatids

Question 23

what separates during meiosis I?

Answer 23

homologs

Question 24

steps of crossing over

occurs when?

Answer 24

• occurs during prophase I
• homologs associate along their length
• DNA of maternal & paternal chromatids is broken
• synaptonemal complex is formed
• synapsis
• synaptonomal complex disassembles

Question 25

function of the synaptonemal complex

Answer 25

zipper like structure holding homologs together during crossing over

Question 26

synapsis

Answer 26

loose ends of DNA at the breaks are joined to the corresponding segments of nonsister DNA

Question 27

average crossing over events in human chromosomes

Answer 27

3

Question 28

crossing over produces…

protects cells from…

Answer 28

recombinant chromosomes

deleterious alleles

Question 29

3 mechanisms that produce genetic diversity

Answer 29

• Crossing over
• Independent assortment
• Random fertilization

Question 30

possible combinations during independent assortment

Answer 30

2ⁿ

>8 million in humans