Lecure #2 Meiosis

Question 1

What are the similarities between mitosis and meiosis? What are the differences?

Answer 1

Similar: only 1 interphase, second division results in the splitting of sister chromatids

Differences:(in meiosis)first division results in the separation of homologous chromosomes, 4 genetically uniques daughter cells are created and they are haploid

Question 2

Mitosis vs. Meiosis

Answer 2

Mitosis: occurs in stems cells, 2 diploid daughter cells created, daughter cells are genetically identical, process is always happening

Meiosis: single event, occurs in sex cells, 4 haploid daughter cells, each daughter cell is genetically unique

Question 3

What happens in prophase 1 (meiosis 1)

Answer 3

Chromosomes become visible
DNA has replicated
Homologous chromosomes condense and undergo synapsis
Bivalent forms (homologous chromosomes line up together)

Question 4

What occurs during crossing over

Answer 4

A bivalent is formed between homologous chromosomes and form a chiasma( chromatids [non-sister and sister] cross over an swap DNA) to overall make recombinant chromatids

Question 5

What happens in prophase 1 (meiosis 1)

Answer 5

Chromosomes continue to shorten/thicken and chiasma(crossing over becomes more apparent)

Nuclear envelope starts to break down

Question 6

What happens in prometaphase 1?

Answer 6

Spindles attach to kinetochores on chromosomes

Question 7

What happens during metaphase 1

Answer 7

Homologous pairs line up in the centre of the cell and bivalents are organized randomly with respect to each other

Question 8

Mitosis metaphase vs meiosis 1 metaphase

Answer 8

Mitosis: 46 chromosomes aligned in one plane, spindles attached to kinetochores on opposite ends of the sister chromatids, no recombinations

Meiosis: 23 pairs of homologous chromosomes are aligned in one plane, spindles attached to kinetochores on the same side of the sister chromatid, recombination between homologous chromosomes

Question 9

What happens during anaphase 1

Answer 9

Homologous chromosomes separate (sister chromosomes do not)

Question 10

What happens during telophase 1 and cytokinesis

Answer 10

Daughter cells are ready to move into prophase 2

Question 11

What is the ploidy level after cytokinesis in meiosis 1

Answer 11

n, cells went from diploid to haploid

Question 12

What happens in prophase 2

Answer 12

Nuclear envelope breaks down
Chromosomes condense

Question 13

What happens during prometaphase 2

Answer 13

Spindles attach to kinetochores on chromosomes

Question 14

What happens during metaphase 2

Answer 14

Chromosomes align in the centre of the cell

Question 15

What happens during anaphase 2

Answer 15

Sister chromatids separate

Question 16

What happens during telophase 2 and cytokinesis

Answer 16

Nuclear envelope reforms and cytoplasm divides

Question 17

What is the differences between mitosis and meiosis in female vs male germ cells

Answer 17

Males: continuous, embryo(mitosis) to adult (meiosis), four sperm cells created

Females: 2 “arrests”, meiosis 1 arrest in 1+ ochres during each menstrual cycle, meiosis 2 arrests in fertilization, mitosis occurs rapidly

Question 18

Name the proteins that help to regulate the cell cycle and name their functions

Answer 18

Cyclins - appear and disappear in cyclical functions to activate CDKs

Cyclin-dependent kinases (CDK) - controls progression through the cell cycle

Cyclin-CDK complexes - phosphorylation target proteins that promote cell division

Question 19

What are the different cyclin-CDK complexes and what are their functions?

Answer 19

M cyclin-CDK: prepares cell for mitosis

S cyclin-CDK: helps to initiate DNA synthesis

G1/s cyclin-CDK: prepares cell for DNA replication