Lecture 1: Meiosis and Gametogenesis Flashcards
True or False: Chromosomal abnormalities due to meiotic errors are the leading cause of miscarriages and intellectual disability syndromes
True
Label the following:
Which stage of mitosis are you looking at?
A. Cytokinesis
B. Telophase
C. Anaphase
D. Metaphase
D. Metaphase
- condensed chromosomes are only observed at metaphase
____: 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
Mitosis
Meiosis
True or False: Cytokinesis is the division of the cytoplasm
True
Microtubules attach to the ___, which are structures mounted on top of the centromeres
Kinetochores
True or False: Microtubule depolymerization is required to shorten tubulin structures and pull the chromosomes towards the centrosomes
True
Which stage of mitosis corresponds to the following: “Chromosome condensation and mitotic spindle formation”
A. Prometaphase
B. Metaphase
C. Prophase
D. Telophase
E. Anaphase
C. Prophase
True or False: The nuclear envelope is disassembled in prometaphase
True
At what stage of mitosis do centromeres and kinetochores split and sister chromatids begin migrating to opposite sides of the poles?
Anaphase
At what stage of mitosis do spindles and kinetochores disassemble, nuclear envelop forms, and chromatids decondense?
Telophase
True or False: Homologous chromosomes are involved in mitosis
False - SISTER CHROMATIDS
True or False: Meiosis involves one round of nuclear division and two rounds of DNA replication
True!
True or False: If gametes do not undergo a reduction from diploid to haploid before fertilization, the gametes will be quadraploid (n=4)
True
What is the longest stage of Meiosis I?
Prophase I
At which stage of Meiosis I does the chromosome condense and the kinetochores and spindles form?
Prophase I
At what stage of Meiosis I do chromosome homologs migrate to opposite poles?
Anaphase I
True or False: Separation of SISTER CHROMATIDS occurs at Meiosis I while separation of CHROMOSOME HOMOLOGS occurs at Meiosis II
False -
Meiosis I: separation of chromosome homologs
Meiosis II: separation of sister chromatids
Synapsis and Chismata occur at which phase of Meiosis I?
Prophase I
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
C. Telophase I
At what stage of Meiosis I does meiotic recombination occur?
A. Metaphase I
B. Prophase I
C. Telophase I
D. Anaphase I
B. Prophase I
True or False: Meiotic recombination involves enzyme-mediate DNA double stand break, as well as sister chromatids to repair DSB
False - while meiotic recombination involves enzyme mediate dsDNA breaks, chromosome HOMOLOGS are used to repair DSB
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
A. Non-Homologous End Joining Repair
Which mechanism of repair requires a SISTER CHROMATID as a template for repair?
A. Non-Homologous End Joining Repair
B. Homologous Recombination Repair
B. Homologous Recombination Repair
True or False: There is NO exchange of genetic info in Homologous Recombination Repair because template is an exact copy of damaged chromosome
True
True or False: Meiotic recombination only occurs in somatic cells
False - germ cells only
Which enzyme mediates and programs dsDNA breaks in meiotic recomb?
Spo11
In meiotic recombination, recombination occurs between ____ ___
chromosome homologs
True or False: There is not an exchange of genetic material in meiotic recombination
False - there IS an exchange of genetic material because recombination occurs between chromosome HOMOLOGS
Why does homologous recombination only occur during S and G2 phase of the cell cycle?
Because it requires a sister chromatid as a repair template
True or False: Defects in Homologous Recombination repair can lead to increased cancer susceptibility
True
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
A. Homologous Recombination Repair
True or False: In meiotic recombination (prophase I), the chromosome homologs will recombine
True
True or False: Spo11 topoisomerase II-like protein will induced DSB’s
True
What are the four stages of Prophase I?
Leptonema, Zyginema, Pachynema, Dipolnema
True or False: Sister chromatids are identical copies of each other
True
___: a pair of chromatids after DNA replication joined together by a centromere
Sister chromatids
True or Cells: Daughter cell produced via mitosis are diploid while daughter cells produced via meiosis are haploid
True
At what phase of Prophase I does the synaptonemal complex become established?
A. Leptotene
B. Zygotene
C. Pachytene
D. Diplotene
A. Leptotene
- pairing between chromosome homologs also occurs
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
B. Zygotene
True or False: Most double stranded DNA breaks are repaired through homologous recombination
False - most are repaired via: non-crossover pathways
True or False: double stranded DNA breaks that are repaired via homologous recombination result in crossovers
True
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
C. Pachytene
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
True
True or False: The synaptonemal complex is only observed during prophase I of meiosis
True
What is the function of the SC (synaptonemal complex)?
Maintains chromosome homologs held together through recombination process
- note: SC defects can result in infertility or subfertility
Compare and contrast mitosis and meiosis:
___: DNA structures that hold chromosome homologs together and counteract pulling forces of meiotic spindle
Chiasmata
In prophase I, there is crossover assurance, which ensures ____. There is also crossover interference, which ensures ______.
Crossover Assurance: At least one CO per chromosome
Crossover Interference: No two COs will be too close together
How can we ensure that the
offspring is genetically
unique?
1) Independent assortment of
chromosome homologs
2) Genetic recombination
between chromosome
homologs
True or False: Crossing over and meiotic recombination results in exchange of genetic information between maternal and paternal chromosomes
True
____: 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
Non-disjunction
True or False: In non-disjunction, the formation of chiasmata
prevents early separation of
chromosome homologs (1 per
chromosome minimum)
True
Absence of crossing over could lead to random ___ and ___, which results in embryonic death or developmental defects
disjunction; aneuploidy
True or False: Most gametic aneuploid originates during oogenesis during first meiotic division
True
True or False: Aneuploid in gametes is major cause of miscarriages and birth defects
True
___: structures that resist spindle forces before anaphase I and hold chromosome homologs together, thus ensuring proper chromosomal segregation
Chiasma
True or False: Gametogenesis occurs in the gonads of mammals
True
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?
Primary spermatocytes (diploid
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?
Primary spermatocytes (diploid precursor cell)
Primary spermatocytes undergo meiosis to produce ___, which undergo meiosis II to produce four ____, which eventually become sperm cells
secondary spermatocytes, spermatids
A ___ is a mature haploid germ cell capable of fusion with another haploid germ cell; during sexual reproduction, produces a diploid zygote
gamete
Spermatogenesis occurs in the ____
testes
Primary spermatocytes undergo ____ while secondary spermatocyte undergo _____
1 spermatocytes = meiosis I
2 spermatocytes = meiosis II
True or False: Spermatogonia are considered stem cells, replicate mitotically, and are located in outer layer of seminiferous tubules
True
True or False: Spermatids undergo maturation
True
Which oocyte is arrested at prophase I until ovulation?
1 oocyte
Upon ovulation, meiosis I is completed and arrest at ___ occurs
meiosis II
When will the secondary oocyte undergoes meiosis II?
Upon fertilization by a spermatozoid
The mature ovum will fuse with a ___ and form a zygote
spermatozoid
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
extra
True or False: The formation of the chiasmata in oogenesis prevents premature separation of chromosome homologs
True
Prolonged arrest in ____ is thought to result in weakened chromosomal interactions thus leading to increased meiotic errors in aged oocytes
prophase I
compare and contrast oogenesis and spermatogenesis
