Exam 3: Lectures 12-17

Question 1

Meiosis

Answer 1

Produces gametes; reduces hereditary material in daughter cells by 50%

Question 2

Mitosis

Answer 2

Forms somatic cells; the amount of hereditary material in the daughter cells is the same as in the parent cells

Question 3

Cell cycle

Answer 3

24-hour process during which cells do not divide continuously; cycle between a dividing phase (M) and non-dividing phase (interphase)

Question 4

What did Howard and Pelc find?

Answer 4

Watched radiolabeled DNA during chromosome replication and followed where the label went; found that chromosomes replicate during interphase before M phase –> synthesis (S) phase

Radiolabeled thymidine and counted the number of cells undergoing mitosis over time; found that cells undergoing mitosis only start after a 4-5 hour gap phase

Question 5

Describe the cell cycle’s two main phases

Answer 5

Interphase
- about 16 hours
- no cell division
- G1: cells perform normal functions
- S: synthesis; chromosomes replicate
- G2: normal cell functions; doesn’t happen in rapidly-dividing cells

M phase
- cell division occurs
- prophase, metaphase, anaphase, telophase

Question 6

Chromatin

Answer 6

All DNA and associated protein in the nucleus, uncondensed

Question 7

Chromosome

Answer 7

Condensed chromatin, composed of sister chromatids

Question 8

Sister chromatids

Answer 8

One of two identical double-stranded DNA molecules connected at a centromere

Question 9

Centrosome

Answer 9

Microtubule organizing center that is part of the mitotic spindle

Question 10

Centrioles

Answer 10

Two small cylindrical structures that form the centrosome

Question 11

Centromere

Answer 11

Indentation where sister chromatids attach to each other

Question 12

Kinetochores

Answer 12

Plate-like structures at the outer surface of the centromere where spindle fibers attach

Question 13

Interphase

Answer 13

When chromosomes are replicated (S phase), so the chromosomes are now two sister chromatids attached at a centromere; centrosomes are duplicated, forming two paired centrioles

Question 14

Prophase

Answer 14

Chromosomes condense and become visible; the mitotic spindle forms and begins moving to opposite sides of the cell

Question 15

Metaphase

Answer 15

The nucleus disappears and the nuclear envelope breaks down; spindle fibers attach to sister chromatids as chromosomes move to the middle of the cell and line up on the metaphase plate; the mitotic spindle completes formation with centrosomes at opposite poles of the cell

Question 16

Anaphase

Answer 16

Spindle fibers shorten and pull the sister chromatids apart to opposite poles

Question 17

Telophase

Answer 17

Nuclear envelope forms around each set of chromosomes; the mitotic spindle disintegrates and the chromosomes decondense; two nuclei have formed

Question 18

Cytokinesis

Answer 18

Cleave furrow