Lecture 1: Meiosis and Gametogenesis

Question 1

True or False: Chromosomal abnormalities due to meiotic errors are the leading cause of miscarriages and intellectual disability syndromes

Answer 1

True

Question 2

Label the following:

Answer 2

Question 3

Which stage of mitosis are you looking at?
A. Cytokinesis
B. Telophase
C. Anaphase
D. Metaphase

Answer 3

D. Metaphase
- condensed chromosomes are only observed at metaphase

Question 4

____: process of nuclear division by which a mother cell generates two daughter cells of identical genetic composition

____: specialized nuclear division that produces a haploid cell from a diploid precursor

Answer 4

Mitosis

Meiosis

Question 5

True or False: Cytokinesis is the division of the cytoplasm

Answer 5

True

Question 6

Microtubules attach to the ___, which are structures mounted on top of the centromeres

Answer 6

Kinetochores

Question 7

True or False: Microtubule depolymerization is required to shorten tubulin structures and pull the chromosomes towards the centrosomes

Answer 7

True

Question 8

Which stage of mitosis corresponds to the following: “Chromosome condensation and mitotic spindle formation”
A. Prometaphase
B. Metaphase
C. Prophase
D. Telophase
E. Anaphase

Answer 8

C. Prophase

Question 9

True or False: The nuclear envelope is disassembled in prometaphase

Answer 9

True

Question 10

At what stage of mitosis do centromeres and kinetochores split and sister chromatids begin migrating to opposite sides of the poles?

Answer 10

Anaphase

Question 11

At what stage of mitosis do spindles and kinetochores disassemble, nuclear envelop forms, and chromatids decondense?

Answer 11

Telophase

Question 12

True or False: Homologous chromosomes are involved in mitosis

Answer 12

False - SISTER CHROMATIDS

Question 13

True or False: Meiosis involves one round of nuclear division and two rounds of DNA replication

Answer 13

True!

Question 14

True or False: If gametes do not undergo a reduction from diploid to haploid before fertilization, the gametes will be quadraploid (n=4)

Answer 14

True

Question 15

What is the longest stage of Meiosis I?

Answer 15

Prophase I

Question 16

At which stage of Meiosis I does the chromosome condense and the kinetochores and spindles form?

Answer 16

Prophase I

Question 17

At what stage of Meiosis I do chromosome homologs migrate to opposite poles?

Answer 17

Anaphase I

Question 18

True or False: Separation of SISTER CHROMATIDS occurs at Meiosis I while separation of CHROMOSOME HOMOLOGS occurs at Meiosis II

Answer 18

False -

Meiosis I: separation of chromosome homologs

Meiosis II: separation of sister chromatids

Question 19

Synapsis and Chismata occur at which phase of Meiosis I?

Answer 19

Prophase I

Question 20

At which stage of Meiosis I do the kinetochores and spindles dis-assemble; nuclear envelop forms; and chromatids de-condense?
A. Metaphase I
B. Prophase I
C. Telophase I
D. Anaphase I

Answer 20

C. Telophase I

Question 21

At what stage of Meiosis I does meiotic recombination occur?
A. Metaphase I
B. Prophase I
C. Telophase I
D. Anaphase I

Answer 21

B. Prophase I

Question 22

True or False: Meiotic recombination involves enzyme-mediate DNA double stand break, as well as sister chromatids to repair DSB

Answer 22

False - while meiotic recombination involves enzyme mediate dsDNA breaks, chromosome HOMOLOGS are used to repair DSB

Question 23

Which of the following mechanisms of repair is faster and more mutagenic, requiring NO homology for repair?
A. Non-Homologous End Joining Repair
B. Homologous Recombination Repair

Answer 23

A. Non-Homologous End Joining Repair

Question 24

Which mechanism of repair requires a SISTER CHROMATID as a template for repair?
A. Non-Homologous End Joining Repair
B. Homologous Recombination Repair

Answer 24

B. Homologous Recombination Repair

Question 25

True or False: There is NO exchange of genetic info in Homologous Recombination Repair because template is an exact copy of damaged chromosome

Answer 25

True

Question 26

True or False: Meiotic recombination only occurs in somatic cells

Answer 26

False - germ cells only

Question 27

Which enzyme mediates and programs dsDNA breaks in meiotic recomb?

Answer 27

Spo11

Question 28

In meiotic recombination, recombination occurs between ____ ___

Answer 28

chromosome homologs

Question 29

True or False: There is not an exchange of genetic material in meiotic recombination

Answer 29

False - there IS an exchange of genetic material because recombination occurs between chromosome HOMOLOGS

Question 30

Why does homologous recombination only occur during S and G2 phase of the cell cycle?

Answer 30

Because it requires a sister chromatid as a repair template

Question 31

True or False: Defects in Homologous Recombination repair can lead to increased cancer susceptibility

Answer 31

True

Question 32

Which pathway requires resection of DNA ends to generat ssDNA region that will be used to recombine with SISTER CHROMATID A. Homologous Recombination Repair B. Non-Homologous Recombination Repair

Answer 32

A. Homologous Recombination Repair

Question 33

True or False: In meiotic recombination (prophase I), the chromosome homologs will recombine

Answer 33

True

Question 34

True or False: Spo11 topoisomerase II-like protein will induced DSB's

Answer 34

True

Question 35

What are the four stages of Prophase I?

Answer 35

Leptonema, Zyginema, Pachynema, Dipolnema

Question 36

True or False: Sister chromatids are identical copies of each other

Answer 36

True

Question 37

___: a pair of chromatids after DNA replication joined together by a centromere

Answer 37

Sister chromatids

Question 38

True or Cells: Daughter cell produced via mitosis are diploid while daughter cells produced via meiosis are haploid

Answer 38

True

Question 39

At what phase of Prophase I does the synaptonemal complex become established? A. Leptotene B. Zygotene C. Pachytene D. Diplotene

Answer 39

A. Leptotene - pairing between chromosome homologs also occurs

Question 40

At what phase of Prophase I does the synapsis along the chromosome homologs occur and the SC is fully formed? A. Leptotene B. Zygotene C. Pachytene D. Diplotene

Answer 40

B. Zygotene

Question 41

True or False: Most double stranded DNA breaks are repaired through homologous recombination

Answer 41

False - most are repaired via: non-crossover pathways

Question 42

True or False: double stranded DNA breaks that are repaired via homologous recombination result in crossovers

Answer 42

True

Question 43

At what phase of Prophase I does meiotic recombination occur and chiasmata is formed (physical linkage of chromatids) A. Leptotene B. Zygotene C. Pachytene D. Diplotene

Answer 43

C. Pachytene

Question 44

True or False: The SC breaks down and chromosomes begin to separate, but remain held together at the chiasmata at the Diplotene stage of Prophase I

Answer 44

True

Question 45

True or False: The synaptonemal complex is only observed during prophase I of meiosis

Answer 45

True

Question 46

What is the function of the SC (synaptonemal complex)?

Answer 46

Maintains chromosome homologs held together through recombination process - note: SC defects can result in infertility or subfertility

Question 47

Compare and contrast mitosis and meiosis:

Answer 47

Question 48

___: DNA structures that hold chromosome homologs together and counteract pulling forces of meiotic spindle

Answer 48

Chiasmata

Question 49

In prophase I, there is crossover assurance, which ensures ____. There is also crossover interference, which ensures ______.

Answer 49

Crossover Assurance: At least one CO per chromosome Crossover Interference: No two COs will be too close together

Question 50

How can we ensure that the offspring is genetically unique?

Answer 50

1) Independent assortment of chromosome homologs 2) Genetic recombination between chromosome homologs

Question 51

True or False: Crossing over and meiotic recombination results in exchange of genetic information between maternal and paternal chromosomes

Answer 51

True

Question 52

____: process by which MT's pull an extra chromatid to one pole, which results in one daughter cell with an extra copy of a chromosome and another missing one copy of a chromosome

Answer 52

Non-disjunction

Question 53

True or False: In non-disjunction, the formation of chiasmata prevents early separation of chromosome homologs (1 per chromosome minimum)

Answer 53

True

Question 54

Absence of crossing over could lead to random ___ and ___, which results in embryonic death or developmental defects

Answer 54

disjunction; aneuploidy

Question 55

True or False: Most gametic aneuploid originates during oogenesis during first meiotic division

Answer 55

True

Question 56

True or False: Aneuploid in gametes is major cause of miscarriages and birth defects

Answer 56

True

Question 57

___: structures that resist spindle forces before anaphase I and hold chromosome homologs together, thus ensuring proper chromosomal segregation

Answer 57

Chiasma

Question 58

True or False: Gametogenesis occurs in the gonads of mammals

Answer 58

True

Question 59

Male mammals are born with spermatogonial stem cells that continuously proliferate through mitosis. At puberty, a cohort of this stem cell population matures into which cell type?

Answer 59

Primary spermatocytes (diploid

Question 60

Male mammals are born with spermatogonial stem cells that continuously proliferate through mitosis. At puberty, a cohort of this stem cell population matures into which cell type?

Answer 60

Primary spermatocytes (diploid precursor cell)

Question 61

Primary spermatocytes undergo meiosis to produce ___, which undergo meiosis II to produce four ____, which eventually become sperm cells

Answer 61

secondary spermatocytes, spermatids

Question 62

A ___ is a mature haploid germ cell capable of fusion with another haploid germ cell; during sexual reproduction, produces a diploid zygote

Answer 62

gamete

Question 63

Spermatogenesis occurs in the ____

Answer 63

testes

Question 64

Primary spermatocytes undergo ____ while secondary spermatocyte undergo _____

Answer 64

1 spermatocytes = meiosis I 2 spermatocytes = meiosis II

Question 65

True or False: Spermatogonia are considered stem cells, replicate mitotically, and are located in outer layer of seminiferous tubules

Answer 65

True

Question 66

True or False: Spermatids undergo maturation

Answer 66

True

Question 67

Which oocyte is arrested at prophase I until ovulation?

Answer 67

1 oocyte

Question 68

Upon ovulation, meiosis I is completed and arrest at ___ occurs

Answer 68

meiosis II

Question 69

When will the secondary oocyte undergoes meiosis II?

Answer 69

Upon fertilization by a spermatozoid

Question 70

The mature ovum will fuse with a ___ and form a zygote

Answer 70

spermatozoid

Question 71

Non-disjunction can occur during oogenesis. When it occurs, microtubules pull both pairs of sister chromatids to one pole, which result in one oocyte with an ___ copy of a chromosome and another missing one copy of a chromosome

Answer 71

extra

Question 72

True or False: The formation of the chiasmata in oogenesis prevents premature separation of chromosome homologs

Answer 72

True

Question 73

Prolonged arrest in ____ is thought to result in weakened chromosomal interactions thus leading to increased meiotic errors in aged oocytes

Answer 73

prophase I

Question 74

compare and contrast oogenesis and spermatogenesis

Answer 74

Question 75

Answer 75