Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BMS2.03 Meiosis (SANTOLAYA) > Meiosis > Flashcards

Meiosis Flashcards

1
Q

Three characteristics used to determine chromosome:

A
  1. size
  2. centromere index
  3. G-bright
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Centromere Index:

A

= P-arm length/(total chromosome length X 100)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

G-bright areas:

A
  • bright regions are euchromatic, early-replicating and GC rich
  • rich in SINE and Alu sequences
  • contain “house-keeping” genes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the goal of meiosis?

A
  • to reduce the number of chromosomes in the parent cell (23 pairs; n = 46) by half and produce gamete cells (each with n = 23).
  • which two homologs go into a single gamete and that an offspring inherits is completely random
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Fertilization of an oocyte with a spermatocyte (each with 23 chromosomes) reconstitutes:

A
  • a diploid zygote
    • a cell with 23 pairs (46 individual) chromosomes
    • these chromosomes will make up all of the descendant cells in the offspring via mitosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Meiosis I separates:

A

homologue chromosomes

(sister chromatids remain attached at centromere)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Meiosis II separates:

A

sister chromatids

(sister chromatids separated at centromere)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The four stages of Meiosis I:

A
  1. Prophase I
  2. Metaphase I
  3. Anaphase I
  4. Interkinesis I
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Prophase I:

A
  • pairing of homologous chromosomes
    • leptotene and zygotene (synapsis)
  • chromosome condensation
    • pachytene
  • formation of sister chromatids
    • diplotene
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Metaphase I:

A
  • homologous chromosomes lined up in middle of cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Anaphase I:

A
  • Chiasmata at the chromosome ends.
  • Paired chromosomes migrate to opposite poles of the cell.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Interkinesis I:

A
  • formation of nuclei and 2 daughter cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Meiosis II:

A

Similar to mitosis:

  • Prophase II (no DNA synthesis)
  • Metaphase II
  • Anaphase II

Final result = 4 haploid cells (in males)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Meiosis in males:

A

STARTS AT PUBERTY

  • Meiosis I followed by meiosis II at puberty
  • final result = 4 haploid spermatids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Meiosis in females:

A
  1. Meiosis I begins in utero.
  2. Primary oocytes arrested in prophase I until puberty.
  3. Meiosis I completed at time of ovulation. First polar body ejected.
  4. Meiosis II completed at fertilization. Second polar body ejected.

FINAL RESULT:

1 MATURE OOCYTE; 2 LOST POLAR BODIES

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What stage of meiosis I are primary oocytes arrested in?

A
  • dictyotene of prophase I before birth
  • complete meiosis I at ovulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The first polar body created by meiosis in females contains:

A
  • one pair of sister chromatids
  • ejected at time of ovulation when meiosis I is completed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

The second polar body created by meiosis in females contains:

A
  • a single chromatid
  • ejected at time of fertilization when meiosis II is completed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Nondisjunction in meiosis I:

A
  • failure of homologous chromosomes to separate
  • will lead to abnormal gametes and aneuploidy in zygote
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Nondisjunction in meiosis II:

A
  • failure of sister chromatids to separate
  • will lead to abnormal gametes and aneuploidy in zygotes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Klinefelter Syndrome:

A

47, XXY

  • trisomy
  • tall, hypogonadism, gynecomastia (breasts)
  • more X, greater risk for mental retardation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Edward’s Syndrome:

A

47, XX, +18

  • trisomy
  • CNS, heart, renal, clenched hands
23
Q

Turner Syndrome:

A

45, X

  • monosomy, cystic hygroma, short stature, infertile
  • 4% survive; 96% die in utero
24
Q

Down Syndrome:

A

47, XX, +21

  • trisomy
25
Q

Patau Syndrome:

A

47, XY, +13

  • trisomy
  • CNS, renal, heart
26
Q

How do you answer the question did the nondisjunction event occur in meiosis I or meiosis II?

A
  1. Studying polymorphic DNA markers (CA repeats) can help determine parental origin.
  2. Studying polymorphic DNA markers near the centromere will help determine whether meiosis I or meiosis II.
27
Q

How do you know if a nondisjunction event occurred in meiosis I?

A
  • heterozygosity for both alleles from one parent near the centromere
28
Q

How do you know if a nondisjunction event occurred in meiosis II?

A
  • homozygosity for one parental allele near centromere
29
Q

Nullisomic gametes yield:

A
  • monosomic zygotes
  • lethal except for X chromosome
    • “Turner’s Syndrome”
30
Q

Disomic gametes yield:

A
  • trisomic zygotes
  • lethal except for X, Y, a few small autosomes (13, 18, 21)
31
Q

Balanced translocations in a parent raise the risk of:

A
  • partial trisomy/monosomy syndromes.
  • increases the risk of extra/less genetic material being inherited.
    • synapsis is driven by DNA homology, and translocations can lead to quadri-radial synapsis that does not separate properly.
32
Q

Quadri-radial synapsis due to balanced translocations in a parent can lead to how many possible segregations?

A

16

  • only 2/16 (12%) are balanced and will give rise to normal gametes
33
Q

Reciprocal translocations:

A
  • two non-homologous chromosomes break and exchange fragments.
  • Individuals carrying such abnormalities still have a balanced complement of chromosomes and generally have a normal phenotype, but with varying degrees of subnormal fertility.
  • quadri-radial synapsis must now form during meiosis, which leads to genetically unbalanced gametes 14/16 of the time
34
Q

Recombination of homologous chromosomes when one has an inversion leads to:

A
  1. Formation of an inversion loop to maximize pairing.
  2. Recombination within the inversion loop that leads to abnormal chromatids.
    • acentric/dicentric chromosomes with duplications/deficiencies of genetic material
35
Q

Pericentric inversions:

A
  • Inversions in which the rotated segment includes the centromere:
    • ABC - cen - DEFGH
    • AD - cen - CBEFGH
  • recombinant gametes will have altered gene dosage (a duplicated region and a deleted region)
36
Q

Paracentric inversions:

A
  • Inversions in which the rotated segment is located completely on one chromosomal arm and do not include the centromere:
    • cen - ABCDEFGH
    • cen - ADCBEFGH
  • recombinant gametes have altered gene dosage and centromere number (one acentric and one dicentric).
37
Q

The two reasons why a couple may be having miscarriages:

A
  • inversions
  • balanced translocations
38
Q

Barr bodies in 46, XY:

A

0

39
Q

Barr bodies in 46, XX

A

one Barr body in each nucleus

40
Q

Barr bodies in 47, XXX

A

2 Barr bodies in each nucleus

41
Q

Barr bodies in 48, XXXX

A

3 Barr bodies in each nucleus

42
Q

Lyon Hypothesis:

A
  • states that during early development (blastocyst stage) one of the X chromosomes in a female gets turned off
  • this is maintained in all descendant cells of the clone
43
Q

A “darkly staining” Barr body is:

A
  • the condensed, inactive X chromosome in females
44
Q

During the blastocyst stage (roughly 100 cells), all females inactivate a X-chromosome in each of the 100 cells. Which X-chromosome is deactivated is completely random.

This means that:

A
  • under normal conditions a female is a genetic mosaic in each tissue derived from somatic cells.
    • some tissues will express the allele from the father and some will express the allel from the mother
45
Q

If there is a translocation between an X-chromosome and an autosome, which X-chromosome in the nucleus is preferentially inactivated?

A
  • the normal X-chromosome is inactivated.
  • X-AUTOSOME TRANSLOCATIONS ARE PROTECTED/EXPRESSED.
46
Q

If there is a deletion/insertion in an X-chromosome, which X-chromosome in the nucleus is preferentially inactivated?

A
  • X-chromosomes with deletions/insertions are preferentially inactivated.
  • Normal X-chromosomes expressed.
47
Q

The three genes involved in X-inactivation in females:

A

Xic, Xist, and Tsix

48
Q

Xic:

A
  • X Inactivation Center
    • contains genes for Xist and Tsix that control inactivation of X-chromosomes in females
49
Q

Xist:

A
  • a gene that encodes a large non-coding RNA that is responsible for mediating the specific silencing of the X chromosome from which it is transcribed.
  • The inactive X chromosome is coated by Xist RNA.
50
Q

Tsix:

A
  • Antisense RNA strand to Xist
  • inactivates Xist, activating X-chromosome expression
51
Q

Uniparental disomy can occur via:

A
  • a random event during the formation of egg or sperm cells.
  • during trisomic rescue.
52
Q

Epigenetic:

A
  • changes in gene expression in response to the environment
53
Q

Prader-Willis Syndrome is due to a deletion on what chromosome and where?

A

paternal chromosome 15q11-13

  • Maternal disomy and Paternal deletion.
54
Q

Angelmann Syndrome is due to a deletion on what chromosome and where?

A

maternal chromosome 15q11-13

  • Paternal disomy and Maternal deletion

BMS2.03 Meiosis (SANTOLAYA) (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions