Meiosis

Question 0

Meiosis:

Answer 0

Production of haploid gametes

Question 1

What are the sources of genetic variation?

Answer 1

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

Question 2

Fertilization:

Answer 2

The fusion of haploid gametes

Question 3

Genetic variation:

Answer 3

Consequences of meiosis

Question 4

Meiosis interphase:

Answer 4

DNA synthesis and chromosome replication phase

Question 5

Meiosis I:

Answer 5

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

Question 6

Meiosis II:

Answer 6

Separation of sister chromatids, also known as equational division

Question 7

What are the major results of Meiosis?

Answer 7

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

Question 8

What are the two types of gametogenesis?

Answer 8

Spermatogenesis and oogenesis

Question 9

What are the products of gametogenesis?

Answer 9

Gametes: Egg and sperm

Question 10

What is the pairing of homologous chromosomes?

Answer 10

synapsis

Question 11

What are the major events in meiosis?

Answer 11

Synapsis and crossing over

Question 12

What does meiosis require?

Answer 12

Two consecutive cell divisions BUT only one cycle of DNA replication

Question 13

When does crossing over occur in meiosis?

Answer 13

During prophase I, segments of nonsister chromatids are exchanged

Question 14

What produces variation without crossing-over?

Answer 14

independent assortment

Question 15

When does reduction division occur?

Answer 15

The end of meiosis I

Question 16

When does equational division occur?

Answer 16

At the end of meiosis II

Question 17

Name the stages of prophase I

Answer 17

Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis

Question 18

What happens during leptotene?

Answer 18

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

Question 19

Describe the zygotene stage

Answer 19

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

Question 20

Describe the pachytene stage

Answer 20

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

Question 21

Describe the diplotene stage

Answer 21

Crossing-over continues

Chiasmata are well-defined

Question 22

Describe the diakinesis stage

Answer 22

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

Question 23

Synapsis:

Answer 23

Close pairing of homologous chromosomes

Question 24

Tetrad:

Answer 24

Closely associated four-sister chromatids of two homologous chromosomes

Question 25

Crossing over:

Answer 25

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

Question 26

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

Answer 26

Exchange of genetic information during crossing over

Question 27

Describe metaphase I

Answer 27

Tetrads line up along equatorial plate | Centromeres do not divide

Question 28

Describe anaphase I

Answer 28

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

Question 29

Describe Telophase I

Answer 29

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

Question 30

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

Answer 30

Random distribution of chromosomes into two newly divided cells

Question 31

When does interkinesis occur and what happens during the stage?

Answer 31

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

Question 32

Describe prophase II

Answer 32

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)

Question 33

Describe metaphase II

Answer 33

Chromosomes line up on equatorial plate | Kinetochores face opposite poles

Question 34

Describe anaphase II

Answer 34

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

Question 35

Describe telophase II

Answer 35

Chromosomes uncoil Spindle apparatus disintegrates Cytokinesis is complete Nuclear membranes reform

Question 36

What is the end result of Meiosis

Answer 36

Four genetically unique haploid daughter cells

Question 37

What holds chromatids together during early part of mitosis?

Answer 37

Cohesin

Question 38

What does the break down of cohesin allow in mitosis?

Answer 38

Sister chromatids to separate during mitosis anaphase

Question 39

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

Answer 39

Cohesin along chromosome arms

Question 40

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

Answer 40

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

Question 41

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

Answer 41

shugoshin

Question 42

What breaks down cohesin at the end of metaphase?

Answer 42

Separase

Question 43

What is kept inactive during interphase and early mitosis?

Answer 43

Separase

Question 44

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

Answer 44

Separase during end of metaphase II

Question 45

What keeps separase inactive during interphase and early mitosis?

Answer 45

Securin

Question 46

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

Answer 46

Monopolins

Question 47

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

Answer 47

Mitosis

Question 48

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

Answer 48

Meiosis

Question 49

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

Answer 49

Spermatogonia

Question 50

PGCs are diploid or haploid?

Answer 50

Diploid

Question 51

Describe spermatogonia

Answer 51

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

Question 52

Describe primary spermatocytes

Answer 52

Diploid | Undergo meiosis I to produce haploid secondary spermatocytes

Question 53

Describe Secondary spermatocytes:

Answer 53

Haploid | Undergo meiosis II to produce haploid spermatids

Question 54

Describe spermatids:

Answer 54

Haploid | Differentiate into haploid sperm

Question 55

Describe PCGs in oogenesis

Answer 55

Diploid | Divide mitotically to produce diploid oogonia

Question 56

Describe oogonia

Answer 56

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

Question 57

Describe primary oocytes

Answer 57

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

Question 58

When will some primary oocytes resume meiosis until metaphase II

Answer 58

During menstrual cycle

Question 59

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

Answer 59

Metaphase II

Question 60

When meiosis I has been completed in oogenesis what results?

Answer 60

Unequal cytokinesis | Large ovum and small polar body

Question 61

When will meiosis resume after meiosis I?

Answer 61

Not until egg is fertilized

Question 62

What will potentially result at the end of oogenesis?

Answer 62

One large egg and three small polar bodies

Question 63

Describe secondary oocytes

Answer 63

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

Question 64

ootids:

Answer 64

haploid egg

Question 65

Polar bodies:

Answer 65

three (?) haploid small "cells" for each ootid