Lecture 6: Meiosis, Germ Cells and Fertilization

Question 1

Diploid

Answer 1

contains two sets of chromosomes, one from each parent

Question 2

Haploid

Answer 2

contains one set of chromosomes

Question 3

gametes

Answer 3

specialized reproductive cells; sperm or eggs generated through meiosis

Question 4

fertilization

Answer 4

haploid gametes fuse to form a diploid cell

Question 5

zygote

Answer 5

divides by mitosis to become a multicellular organism

Question 6

germline cells

Answer 6

gametes and their precursors

Question 7

somatic cells

Answer 7

form the rest of the body and leave no progeny

Question 8

In what two ways does meiosis create genetic diversity?

Answer 8

random segregation of homologs during meiosis

crossing over

Question 9

Are gametes haploid or diploid?

Answer 9

haploid

Question 10

What phase is chromosomes replicated?

Answer 10

S phase

Question 11

What are sister chromatids bound by

Answer 11

cohesion complexes

Question 12

What happens in meiosis I?

Answer 12

homologs pair, recombine and separate

Question 13

True or false? There is no further DNA replication in meiosis II

Answer 13

true

Question 14

What happens in meiosis II?

Answer 14

sister chromatids are divided to produce 4 daughter haploid cells

Question 15

What happens in prophase I?

Answer 15

homologs begin to pair

Question 16

What is a bivalent?

Answer 16

4 chromatid structure

Question 17

Where does crossing over occur in the bivalent?

Answer 17

the chiasma

Question 18

What are the five phases of prophase?

Answer 18

leptotene
zygotene
pachytene
diplotene
diakinesis

Question 19

What occurs in leptotene?

Answer 19

homologs begin to condense/pair

Question 20

What occurs in zygotene?

Answer 20

homologs pair and synaptonemal complexes form

Question 21

What occurs in pachytene?

Answer 21

synapsis is complete; crossing over occurs

Question 22

What occurs in diplotene?

Answer 22

synaptonemal complex begins to break down; homologs begin to separate but remain attached at chiasmata

Question 23

What occurs in diakinesis?

Answer 23

reach maximum condensation, separation of homologs and transitions stage into metaphase

Question 24

What forms the synaptonemal complex?

Answer 24

transverse filaments between homologs

Question 25

When do homologs separate?

Answer 25

anaphase I

Question 26

When do sister chromatids separate?

Answer 26

anaphase II

Question 27

When is the human female meiosis arrested?

Answer 27

after diplotene (meiosis I)

Question 28

What is nondisjunction?

Answer 28

homologs fail to separate properly

Question 29

What is aneuploid?

Answer 29

cells with abnormal chromosome number

Question 30

What is euploid?

Answer 30

cells with normal number of chromosomes

Question 31

How many gametes can be produce?

Answer 31

2^n

Question 32

primordial germ cells are found in all vertebrae _____ and give rise to ______

Answer 32

embryos; gametes

Question 33

In mammals the dividing egg is _____ for few rounds of cell division, then differentiate into _______

Answer 33

totipotent; primordial germ cells

Question 34

True or false? Primordial germ cells are uncommitted to cell fate

Answer 34

True

Question 35

Does the sperm or the egg determine the sex of the embryo?

Answer 35

sperm

Question 36

What gene is necessary and sufficient for testis development in mammals?

Answer 36

SRY gene

Question 37

What is the yolk of an egg for?

Answer 37

nutritional reserve, rich in lipids, protein and polysaccharides

Question 38

What is the egg coat?

Answer 38

glycoprotein rich extra cellular matrix that protects from mechanical damage

Question 39

How do eggs achieve large size?

Answer 39

extra gene copies in the cell

Question 40

When does meiosis begin for sperm?

Answer 40

puberty

Question 41

Where does spermatogenesis occur?

Answer 41

seminiferous tubules

Question 42

What is capacitation?

Answer 42

process required for a sperm to acquire capacity to fertilize an egg

Question 43

Requirements for fertilization

Answer 43

albumin: extracts cholesterol from membrane, increasing ability to fuse with acrosomal membrane Ca2+ and HCO3-: activate adenyl cyclase in sperm to produce cAMP

Question 44

What must capacitated sperm penetrate?

Answer 44

granulosa cells

Question 45

What does the sperm bind to? what does this do?

Answer 45

sperm binds to zona pellucida to act as species barrier

Question 46

What does the zone pellucid do?

Answer 46

induces sperm to undergo acrosome reaction

Question 47

What membrane proteins are crucial to binding?

Answer 47

ZP 1, 2, 3 ZP 2 and 3 form long filaments ZP 1 cross links the filaments

Question 48

Fusion with sperm induces what?

Answer 48

cortical reaction, meiosis resumes

Question 49

What does the cortical reaction do?

Answer 49

releases enzymes that change zone pellucid so sperm can't penetrate, inactivation of ZP3 so it no longer binds sperm or induces acrosome reaction