Lecture #2

Question 1

What happens during Prophase I?

Answer 1

homologous chromosomes condense and undergo synapsis, crossing over occurs, each pair of homologous chromosomes form a bivalent, chromosomes shorten and thicken and chiasmata becomes apparent, nuclear envelop begins to breakdown

Question 2

What is crossing over?

Answer 2

formation and exchange of the chiasma, result is that new chromosomes have bits of both parental chromosomes

Question 3

What happens during Pro-metaphase I?

Answer 3

Spindles attach to kinetochores on chromosomes

Question 4

What happens during metaphase I?

Answer 4

Homologous pairs line up in the center of the cell with bivalents oriented randomly with respect to each other

Question 5

What happens during Anaphase I?

Answer 5

Homologous chromosomes separate, but sister chromatids do not

Question 6

What happens during telophase I?

Answer 6

Daughter cells are ready . to move into prophase II, daughter cells are haploids

Question 7

What happens during prophase II?

Answer 7

The nuclear envelope breaks down and the chromosomes condense

Question 8

What happens during pro-metaphase II?

Answer 8

Spindles attach to kinetochores on chromosomes

Question 9

What happens during metaphase II?

Answer 9

Chromosomes align in center of cell

Question 10

What happens during anaphase II?

Answer 10

Sister chromatids separate

Question 11

What happens during telophase II and cytokinesis?

Answer 11

The nuclear envelope reforms and the cytoplasm divides, produces haploid cells with half the amount of DNA

Question 12

Explain the process of the male germline.

Answer 12

• Starts with a primordial cell which goes through mitosis
• Then becomes a spermatogonium which then continues through mitosis
• Primary spermatocyte then goes through Meiosis I
• This produces a secondary spermatocyte which undergoes meiosis II
• The cells stay connected as spermatid until cytokinesis is complete and become sperm

Question 13

Explain the process of the female germline.

Answer 13

• Primordial germ cell goes through mitosis
• Produced an oogonium which continues through meiosis
• Primary oocyte goes through Meiosis I and stops (arrests) until it is released from the ovary and ovulated
• Produces a polar body and secondary oocyte that go through meiosis II but meiosis II also arrests until the ootid is fertilized
• Results in 3 polar bodies and one ovum

Question 14

How is the cell cycle regulated?

Answer 14

Progression through the cell cycle is controlled by proteins that appear and disappear in a cyclical fashion, and by several enzymes that become active and inactive, also in cycles

Question 15

How do cyclins work?

Answer 15

Cyclins bind to activate cyclin-dependent kinases (CDK) to control progression through the cell cycle, promotes cell division.

Question 16

What do cyclin-CDK proteins do?

Answer 16

Cyclin-CDK complexes phosphorylate target proteins that promote cell division

Question 17

What does M cyclin-CDK do?

Answer 17

Helps prepare the cell for mitosis

Question 18

What does S cyclin-CDK do?

Answer 18

Helps initiate DNA synthesis

Question 19

What does G1/S cyclin CDK do?

Answer 19

Prepares cell for DNA replication

Question 20

What is an oncogene?

Answer 20

cancer-causing gene

Question 21

What is a proto-oncogene?

Answer 21

normal genes important for promoting cell division that have the potential to become cancerous if mutated

Question 22

What is a tumor supressor?

Answer 22

genes that encode proteins whose normal activities inhibit cell division

Question 23

What difference occurs in the kinetochores during mitosis vs meiosis?

Answer 23

in mitosis spindle fibres attach to kinetochores that oppose each other, in meiosis spindle fibres attach to kinetochores that are side by side