Meiosis (Lec 2)

Question 1

What two key aspects of genetic variation occur in meiosis?

Answer 1

independent assortment, crossing over

Question 2

Define meiosis

Answer 2

production of haploid gametes

Question 3

Define fertilization

Answer 3

fusion of haploid gametes

Question 4

What happens in Interphase of meiosis?

Answer 4

DNA synthesis and chromosome replication phase

Question 5

What happens in meiosis I?

Answer 5

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

Question 6

What happens in 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, daughter cells are not genetically identical, daughter cells are haploid, formation of gametes

Question 8

What is the pairing of homologous chromosomes called?

Answer 8

synapsis

Question 9

What is the first stage of prophase I and what happens in it?

Answer 9

Leptotene; chromosomes begin to condense

Question 10

What is the second stage of prophase I and what happens in it?

Answer 10

Zygotene; Synaptonemal complex forms and homologous chromosomes pair (synapsis)

note: synapsis results in bivalents (tetrads)

Question 11

What is the third stage of prophase I and what happens in it?

Answer 11

Pachytene; crossing over

Question 12

What is the fourth stage of prophase I and what happens in it?

Answer 12

Diplotene; crossing over continues, chiasmata are well defined at this point

Question 13

What is the fifth and final stage of prophase I and what happens in it?

Answer 13

Diakinesis; crossing over is incomplete, spindle apparatus is in place, and nuclear membrane is disrupted

Question 14

Do centromeres divide?

Answer 14

no

Question 15

What happens in metaphase I?

Answer 15

tetrads line up along equatorial plate

Question 16

What happens in anaphase I?

Answer 16

homologous chromosomes move to opposite poles, each homologue consists of two chromatids because sister chromatids remain attached, daughter cells will be haploid

Question 17

What happens in telophase I?

Answer 17

cytokinesis occurs, nuclear membrane reform, chromosome number is halved, haploid daughter cells are genetically unique

Question 18

What happens in interkinesis?

Answer 18

spindle breaks down, chromosomes may uncoil

Question 19

What happens in prophase II?

Answer 19

chromosomes condense again, spindle apparatus reforms, each chromosome consists of two chromatids, each daughter cell has one complete set of chromosomes

Question 20

What happens in metaphase II?

Answer 20

chromosomes line up on equatorial plate, kinetochores face opposite poles

Question 21

What happens in anaphase II?

Answer 21

centromeres of sister chromatids separate, chromosomes move to opposite poles, each chromosome consists of a single chromatid

Question 22

What happens in telophase II?

Answer 22

chromosomes uncoil, cytokinesis completes, end result is four genetically unique haploid daughter cells

Question 23

What is cohesin?

Answer 23

enzyme that holds chromatids together during early part of mitosis, holds homologous chromosomes together at chiasmata through metaphase I in meiosis, meiosis-specific cohesin at centromere keeps sister chromatids together during anaphase;- protected by shugoshin

Question 24

What does separase do?

Answer 24

kept inactive during interphase and early mitosis, breaks down meiosis-specific cohesin at centromere during end of metaphase II

Question 25

What does securin do?

Answer 25

keeps separase inactive during interphase and early mitosis

Question 26

What does monopolins do?

Answer 26

keeps sister kinetochores oriented toward same pole during metaphase I

Question 27

In spermatogenesis, are primordial germ cells haploid or diploid?

Answer 27

diploid

Question 28

Primordial germ cells divide mitotically to produce diploid ___

Answer 28

spermatogonia

Question 29

Spermatogonia enter prophase I and give rise to ____ _____

Answer 29

primary spermatocytes

Question 30

Primary spermatocytes undergo meiosis I to produce haploid ___ _____

Answer 30

secondary spermatocytes

Question 31

Secondary spermatocytes undergo meiosis II to produce haploid _____

Answer 31

spermatids

Question 32

Spermatids differentiate into ___

Answer 32

sperm

Question 33

Primordial germ cells involved in Oogenesis divide mitotically to produce diploid ___

Answer 33

oogonia

Question 34

Oogonia initiate meiosis and enter into prophase I to give rise to ___ ____

Answer 34

primary oocytes

Question 35

Primary oocytes become frozen at what stage of prophase I

Answer 35

diplotene

Question 36

When does meiosis resume after being frozen in prophase I?

Answer 36

ovulation

Question 37

Meiosis stops again at what point?

Answer 37

metaphase II; resumes once egg is fertilized

Question 38

summarize oogeneis

Answer 38

primordial germ cell enters gonad, diploid oogonia undergo mitotic cell divisions before entering meiosis, primary oocytes are formed and arrest in prophase I of meiosis I, after ovulation process resumes and cytoplasm divides forming small polar body and large secondary oocyte which arrests in metaphase II, meiosis is finished after fertilization