Chapter 2 Cell Cycle, Mitosis, Meiosis 2.1-2.2

Question 1

Diploid (2n)

Answer 1

Contain two copies of each chromosome, autosomal cells.

Question 2

Haploid (n)

Answer 2

Contain only one copy of each chromosome, germ cells.

Question 3

The cell cycle

Answer 3

Four stages of the cell cycle: G1, S, G2, M.

Question 4

Interphase

Answer 4

The first three stages of the cell cycle (g1, s, g2). The longest part of the cell cycle, actively dividing cells spend about 90% of their time in interphase.

Question 5

Chromatin

Answer 5

Less condensed form of a chromosome. Chromosomes are not visible during interphase because they are in this less condensed form because DNA must be available to RNA polymerase so that genes can be transcribed.

Question 6

G1 Phase of the cell cycle

Answer 6

Presynthetic gap

Cells increase in size and create organelles such as mitochondria, ribosomes, and endoplasmic reticulum. This is part of the cell interphase cycle.

Side note: passage from g1 to s phase is governed by a restriction point.

Question 7

S phase of the cell cycle

Answer 7

Synthesis of DNA

The cell replicates its genetic material so that each daughter cell will have identical copies. After replication, each chromosome consist of two identical chromatids that are bound together at a specialized region known as the centromere. Cells entering G2 have twice as much DNA as cells in G1. This is part of the cells interphase cycle.

Side note: the ploidy of the cell does not change even though the number of chromatids doubles.

Question 8

G2 stage of the cell cycle

Answer 8

Postsynthetic gap

G2 phase is a quality control checkpoint. DNA has already been duplicated, and the cell checks to ensure that there are enough organelles and cytoplasm for two daughter cells. This is part of the cells interphase.

This checkpoint is very important because the cell makes sure that DNA replication has proceeded correctly to avoid passing on an error the daughter cells.

Question 9

M stage of the cell cycle

Answer 9

Mitosis

Consist of mitosis and cytokinesis. Divided into four phases: prophase, metaphase, anaphase, and telophase.

Question 10

Molecules responsible for the cell cycle

Answer 10

Cyclins and cyclin dependent kinases (cdk).

Question 11

Transcription factor

Answer 11

Transcription factors promote transcription of genes for the next stage of the cell cycle. Phosphorylated by CDK – cyclin complex.

Question 12

The main protein in control of checkpoints of the cell cycle.

Answer 12

P53

p53 is a tumor suppressor protein that regulates cell cycle checkpoints, while cyclins are proteins that control cell cycle progression.

Question 13

Mitosis

Answer 13

Consist of prophase, metaphase, anaphase, telophase. Creates two identical daughter cells.

(MIghty people are PROs at METAmorphosing with ANAbolic TEstosterone - Mitosis: prophase, metaphase, anaphase, telophase)

Keywords: centrosome, centriole, spindle fibers.

Question 14

Prophase

Answer 14

Chromosomes condense, spindles form. The nuclear membrane dissolves during prophase, allowing spindle fibers to contact the chromosomes. The nuclei become less distinct and may disappear completely.

Question 15

Centrioles

Answer 15

barrel-shaped organelles that help organize microtubules and other cell components in animal cells.

Question 16

Metaphase

Answer 16

The centriole pairs are now at opposite ends of the cell. Chromosomes align at the metaphase plate (equatorial plate) via kinetocore fibers interacting with the fibers of the spindle apparatus.

Question 17

Anaphase

Answer 17

The centromeres split so that each chromatid has its own distinct centromere thus allowing the sister chromatids to separate. Chromatids are pulled towards the opposite poles of the cell by the shortening of the kinetochore fibers.

Question 18

Telophase and cytokinesis

Answer 18

Telophase is essentially the reverse of prophase. The spindle apparatus disappears, a nuclear membrane reform around each set of chromosomes, and the nuclei reappear. The chromosomes uncoil, resuming their interphase form.

Cytokinesis is the separation of the cytoplasm giving rise to two daughter cells with enough materials to survive on their own. Each cell undergoes a finite number of divisions before programmed death. 20-50 cell divisions in humans until apoptosis occurs.

Question 19

Meiosis

Answer 19

Occurs in gametocytes (germ cells) and results in up to four non-identical sex cells called gametes.

Question 20

Meiosis I

Answer 20

Generates haploid daughter cells by separating homologous chromosomes. This is known as reductive division.

Crossing over between homologous chromosomes happens in meiosis I (prophase I).

2n to n

Question 21

Meiosis II

Answer 21

Similar to mitosis, in that it results in the separation of sister chromatids without of change in ploidy. Known as equational division.

Question 22

Prophase I

Answer 22

Similar to prophase in mitosis up to the point after homologous chromosomes come together. Genetic recombination occurs by crossing over of sister chromatids.

Question 23

Metaphase I

Answer 23

Homologous pairs (tetrads) form up in a line at the metaphase plate in each pair attaches to a separate spindle fiber by its kinetochore.

Question 24

Anaphase I

Answer 24

Homologous pairs separate and are pulled to opposite poles of the cell, a process called disjunction.

Question 25

Telophase I

Answer 25

Nuclear membrane forms around each new nucleus. The cells are now haploid. The cell divides into two daughter cells by cytokinesis.

Question 26

Meiosis II

Answer 26

Sister chromatids are separated from each other. Similar to Mitosis.

Question 27

Prophase II

Answer 27

Nuclear envelope dissolves, nucleoli disappear, the centrioles migrate to the opposite poles, and the spindle apparatus begins to form.

Question 28

Metaphase II

Answer 28

Chromosomes lineup on the metaphase plate.

Question 29

Anaphase II

Answer 29

The centromeres divide, separating the chromosomes into sister chromatids. The chromatids are pulled to opposite poles by spindle fibers.

Question 30

Telophase II

Answer 30

A nuclear membrane form around each new nucleus, cytokinesis follows, and two daughter cells are formed. After completion up to four haploid daughter cells are produced per gametocyte.

Question 31

Key concept image of mitosis and meiosis

Answer 31