Lecture 10-Mitosis, meiosis, and Non-disjunction

Question 1

What are the cell cyle stages?

Answer 1

G1
G0
S
G2
M

Question 2

What happens in the G1 stage of the cell cycle?

Answer 2

DIPLOID cells-cell growth and preparation for DNA replication
-G1 checkpoint checks for cell size, nutrients, growth factors, and DNA damage

Question 3

What happens in the S stage of the cell cycle?

Answer 3

DNA replication and duplication.
DNA proofreading activity of DNA polymerase is active

Question 4

What happens in the G2 phase?

Answer 4

More growth, DNA content is doubled -also checkpoint for post replication

Question 5

What is the role of p53 in the cell cycle?

Answer 5

1. DNA damage results in increase levels of p53- arresting the cell cycle.
2. Activates DNA repair systems
3. If to damaged-may cause apoptosis

Question 6

What happens in Prophase of Mitosis?

Answer 6

Nuclear enevelope dissolves, mitotic spindle forms, chromosomes bind to spindle
Homologous chromosomes (1 from each parent) join at the centromere

Question 7

What happens in Metaphase of Mitosis?

Answer 7

1. Chromosomes condense and are maximally visible
2. Visualized by karyotyping
3. Chromosomes align at equator
4. Mictrotubules attach to centromere kinetochores

Question 8

What happens in Anaphase in Mitosis?

Answer 8

1. Sister chromatids move to centrioles
2. Separation of sister chromatids
3. Non-disjunction during anaphase is mitotic non-disjunction

Question 9

What happens in Telophase of Mitosis?

Answer 9

1. Sister chromatids move to opposite poles
2. Nuclear envelope starts forming
3. Chromosomes less condensed
4. Two new daughter cells through cytokinesis

Question 10

What is Aneuploidy in daughter cells?

Answer 10

Haploid number of chromosomes is not 23. Due to sister chromatids of chromosomes fail to separate.
Results in mosaic

Question 11

What is the product of meiosis in males/females?

Answer 11

MALES: 4 gametes with each 23 chromosomes
FEMALES: results in formation of 1 23X and 3 polar bodies

Question 12

What is meiotic crossover?

Answer 12

Humologous chromosomes exchange genetic material called homologous recombination

Happens in PROPHASE I

Question 13

Meiosis occurs in two main stages.

Answer 13

Meiosis 1: homologous chromosomes separate (n,2d)
Meiosis 2: sister chromatids separate (n,d)

Question 14

When does random segregation of homolous chromosomes take place in meiosis?

Answer 14

Anaphase-1

Question 15

What is paternal/maternal uniparental disomy?

Answer 15

Both copies from dad/mom in a pair of homologous chromosomes

Question 16

Turner Syndrome

Karyotype, Phenotype, Genetic mechanism

Answer 16

45, X: female; infertility
Non-disjunction during meiosis 1 or meiosis 2 in dad or mom

Question 17

Klinefelter Syndrome

Karyotype, Phenotype, Genetic mechanism

Answer 17

47, XXY. Male; Infertility; Feminization of features
Nondisjunction in meiosis 1 or meiosis 2 in mom; Nondisjunction in meiosis 1 in dad

Question 18

47, XYY

Phenotype, Genetic mechanism

Answer 18

Male;? Learning disability
Nondisjunction in meiosis 2 in dad

Question 19

47, XXX

Phenotype, Genetic mechanism

Answer 19

Female; ?learning disability; ?Infertility
Nondisjunction in meiosis 1 or 2 in mom or dad

Question 20

Trisomy 21

Downs Syndrome

Answer 20

Male/Female-intellectual disability
Nondisjunction in meiosis 1 or 2 in mom or dad