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Molecular and Cell Biology Exam 1: Lectures 1-11 > Lecture 6: Meiosis, Germ Cells and Fertilization > Flashcards

Lecture 6: Meiosis, Germ Cells and Fertilization Flashcards

- understand how sexual reproduction and meiosis generate genetic diversity - review the development of germ cells and sex determination in mammals - understand the process of fertilization

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1
Q

Diploid

A

contains two sets of chromosomes, one from each parent

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2
Q

Haploid

A

contains one set of chromosomes

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3
Q

gametes

A

specialized reproductive cells; sperm or eggs generated through meiosis

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4
Q

fertilization

A

haploid gametes fuse to form a diploid cell

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5
Q

zygote

A

divides by mitosis to become a multicellular organism

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6
Q

germline cells

A

gametes and their precursors

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7
Q

somatic cells

A

form the rest of the body and leave no progeny

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8
Q

In what two ways does meiosis create genetic diversity?

A

random segregation of homologs during meiosis

crossing over

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9
Q

Are gametes haploid or diploid?

A

haploid

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10
Q

What phase is chromosomes replicated?

A

S phase

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11
Q

What are sister chromatids bound by

A

cohesion complexes

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12
Q

What happens in meiosis I?

A

homologs pair, recombine and separate

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13
Q

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

A

true

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14
Q

What happens in meiosis II?

A

sister chromatids are divided to produce 4 daughter haploid cells

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15
Q

What happens in prophase I?

A

homologs begin to pair

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16
Q

What is a bivalent?

A

4 chromatid structure

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17
Q

Where does crossing over occur in the bivalent?

A

the chiasma

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18
Q

What are the five phases of prophase?

A 
leptotene
zygotene
pachytene
diplotene
diakinesis
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19
Q

What occurs in leptotene?

A

homologs begin to condense/pair

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20
Q

What occurs in zygotene?

A

homologs pair and synaptonemal complexes form

21
Q

What occurs in pachytene?

A

synapsis is complete; crossing over occurs

22
Q

What occurs in diplotene?

A

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

23
Q

What occurs in diakinesis?

A

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

24
Q

What forms the synaptonemal complex?

A

transverse filaments between homologs

25
Q

When do homologs separate?

A

anaphase I

26
Q

When do sister chromatids separate?

A

anaphase II

27
Q

When is the human female meiosis arrested?

A

after diplotene (meiosis I)

28
Q

What is nondisjunction?

A

homologs fail to separate properly

29
Q

What is aneuploid?

A

cells with abnormal chromosome number

30
Q

What is euploid?

A

cells with normal number of chromosomes

31
Q

How many gametes can be produce?

A

2^n

32
Q

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

A

embryos; gametes

33
Q

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

A

totipotent; primordial germ cells

34
Q

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

A

True

35
Q

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

A

sperm

36
Q

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

A

SRY gene

37
Q

What is the yolk of an egg for?

A

nutritional reserve, rich in lipids, protein and polysaccharides

38
Q

What is the egg coat?

A

glycoprotein rich extra cellular matrix that protects from mechanical damage

39
Q

How do eggs achieve large size?

A

extra gene copies in the cell

40
Q

When does meiosis begin for sperm?

A

puberty

41
Q

Where does spermatogenesis occur?

A

seminiferous tubules

42
Q

What is capacitation?

A

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

43
Q

Requirements for fertilization

A

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

44
Q

What must capacitated sperm penetrate?

A

granulosa cells

45
Q

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

A

sperm binds to zona pellucida to act as species barrier

46
Q

What does the zone pellucid do?

A

induces sperm to undergo acrosome reaction

47
Q

What membrane proteins are crucial to binding?

A

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

48
Q

Fusion with sperm induces what?

A

cortical reaction, meiosis resumes

49
Q

What does the cortical reaction do?

A

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

Molecular and Cell Biology Exam 1: Lectures 1-11 (8 decks)

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