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Genetics Test I - Jourdan > Meiosis > Flashcards

Meiosis Flashcards

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0
Q

Meiosis:

A

Production of haploid gametes

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1
Q

What are the sources of genetic variation?

A

Mutation
Sexual reproduction
—Meiosis: crossing over, independent assortment
Fertilization

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2
Q

Fertilization:

A

The fusion of haploid gametes

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3
Q

Genetic variation:

A

Consequences of meiosis

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4
Q

Meiosis interphase:

A

DNA synthesis and chromosome replication phase

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5
Q

Meiosis I:

A

Separation of homologous chromosome pairs, and reduction of the chromosome number by half

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6
Q

Meiosis II:

A

Separation of sister chromatids, also known as equational division

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7
Q

What are the major results of Meiosis?

A

Increase in cell numbers sometimes
Daughter cells are not genetically identical
Daughter cells are haploid
Meiosis results in the formation of gametes

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8
Q

What are the two types of gametogenesis?

A

Spermatogenesis and oogenesis

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9
Q

What are the products of gametogenesis?

A

Gametes: Egg and sperm

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10
Q

What is the pairing of homologous chromosomes?

A

synapsis

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11
Q

What are the major events in meiosis?

A

Synapsis and crossing over

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12
Q

What does meiosis require?

A

Two consecutive cell divisions BUT only one cycle of DNA replication

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13
Q

When does crossing over occur in meiosis?

A

During prophase I, segments of nonsister chromatids are exchanged

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14
Q

What produces variation without crossing-over?

A

independent assortment

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15
Q

When does reduction division occur?

A

The end of meiosis I

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16
Q

When does equational division occur?

A

At the end of meiosis II

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17
Q

Name the stages of prophase I

A 
Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis
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18
Q

What happens during leptotene?

A

Chromosomes are threadlike
Each chromosome consists of two chromatids
Chromosomes begin to condense and become visible

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19
Q

Describe the zygotene stage

A

Chromosomes continue to condense
Homologous chromosomes pair (synapsis)
Synaptonemal complex forms
Synapsis results in bivalents (or tetrads)

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20
Q

Describe the pachytene stage

A

Maximum coiling occurs and chromosomes become shorter and thicker
Tetrads become visible
Crossing-over begins

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21
Q

Describe the diplotene stage

A

Crossing-over continues

Chiasmata are well-defined

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22
Q

Describe the diakinesis stage

A

Crossing-over is complete
Terminalization occurs
Spindle apparatus is in place
Nuclear membrane is disrupted

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23
Q

Synapsis:

A

Close pairing of homologous chromosomes

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24
Q

Tetrad:

A

Closely associated four-sister chromatids of two homologous chromosomes

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25
Q

Crossing over:

A

Crossing over of chromosome segments from the sister chromatid of one chromosome to the sister chromatid of the other synapsed chromosome

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26
Q

What is the first mechanism of generating genetic variation in newly formed gametes?

A

Exchange of genetic information during crossing over

27
Q

Describe metaphase I

A

Tetrads line up along equatorial plate

Centromeres do not divide

28
Q

Describe anaphase I

A

Homologous chromosomes move to opposite poles
Each homologue consists of two chromatids because sister chromatids remain attached
Chromatids are not genetically identical because of crossing-over
Daughter cells will be haploid

29
Q

Describe Telophase I

A

Cytokinesis occurs
Nuclear membranes reform
Spindle apparatus disassembles
Chromosomes may uncoil to varying degrees
Chromosome number is halved
Haploid daughter cells are genetically unique

30
Q

What is the second mechanism of generating genetic variation in the newly formed gametes?

A

Random distribution of chromosomes into two newly divided cells

31
Q

When does interkinesis occur and what happens during the stage?

A 
Interkinesis happens after telophase I 
Nuclear membranes reform 
Spindle apparatus disassembles
Chromosomes may uncoil to varying degrees
Spindle usually breaks down
32
Q

Describe prophase II

A

Chromosomes again condense
Nuclear membranes disappear
Spindle apparatus reforms in each cell
Each chromosome consists of two chromatids
Each daughter cell has one complete set of chromosomes (haploid)

33
Q

Describe metaphase II

A

Chromosomes line up on equatorial plate

Kinetochores face opposite poles

34
Q

Describe anaphase II

A

Centromeres of sister chromatids separate
Chromosomes move to opposite poles
Each chromosome consists of a single chromatid

35
Q

Describe telophase II

A

Chromosomes uncoil
Spindle apparatus disintegrates
Cytokinesis is complete
Nuclear membranes reform

36
Q

What is the end result of Meiosis

A

Four genetically unique haploid daughter cells

37
Q

What holds chromatids together during early part of mitosis?

A

Cohesin

38
Q

What does the break down of cohesin allow in mitosis?

A

Sister chromatids to separate during mitosis anaphase

39
Q

In meiosis, what holds homologous chromosomes together at chiasmata through metaphase I?

A

Cohesin along chromosome arms

40
Q

What keeps sister chromatids together during anaphase I and later stages in meiosis?

A

Meiosis-specific cohesin at centromere. They are the cohesins that remain after the breakdown of other cohesin when homologs separate during Anaphase I

41
Q

What is the meiosis-specific cohesin at the centromere protected by?

A

shugoshin

42
Q

What breaks down cohesin at the end of metaphase?

A

Separase

43
Q

What is kept inactive during interphase and early mitosis?

A

Separase

44
Q

What breaks down meiosis-specific cohesin at centromere? During what stage?

A

Separase during end of metaphase II

45
Q

What keeps separase inactive during interphase and early mitosis?

A

Securin

46
Q

What keeps sister kinetochores oriented towards the same pole during metaphase I?

A

Monopolins

47
Q

In what process does the end result include daughter cells that are genetically identical?

A

Mitosis

48
Q

In what process does the end result include the daughter cells being genetically unique?

A

Meiosis

49
Q

In Spermatogenesis, what do primordial germ cells divide mitotically to produce?

A

Spermatogonia

50
Q

PGCs are diploid or haploid?

A

Diploid

51
Q

Describe spermatogonia

A

Diploid
Can undergo repeated rounds of mitosis to produce more spermatogonia
May initiate meiosis and enter prophase I to give rise to primary spermatocyte

52
Q

Describe primary spermatocytes

A

Diploid

Undergo meiosis I to produce haploid secondary spermatocytes

53
Q

Describe Secondary spermatocytes:

A

Haploid

Undergo meiosis II to produce haploid spermatids

54
Q

Describe spermatids:

A

Haploid

Differentiate into haploid sperm

55
Q

Describe PCGs in oogenesis

A

Diploid

Divide mitotically to produce diploid oogonia

56
Q

Describe oogonia

A

Diploid
Can undergo repeated rounds of mitosis to produce more oogonia
Eventually initiate meiosis and enter into prophase I to gove rise to primary oocytes

57
Q

Describe primary oocytes

A

All become frozen at diplotene stage of prophase I
Will not resume meiosis until beginning of puberty and then a number will resume meiosis during each menstrual cycle until they are all used up

58
Q

When will some primary oocytes resume meiosis until metaphase II

A

During menstrual cycle

59
Q

in most mammals, the egg is ovulated at what stage?

A

Metaphase II

60
Q

When meiosis I has been completed in oogenesis what results?

A

Unequal cytokinesis

Large ovum and small polar body

61
Q

When will meiosis resume after meiosis I?

A

Not until egg is fertilized

62
Q

What will potentially result at the end of oogenesis?

A

One large egg and three small polar bodies

63
Q

Describe secondary oocytes

A

Haploid

Result of unequal cytokinesis resulting in one secondary oocyte and one polar body

64
Q

ootids:

A

haploid egg

65
Q

Polar bodies:

A

three (?) haploid small “cells” for each ootid

Genetics Test I - Jourdan (6 decks)

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