Cell Division, Chromosome Segregation & Genetic Varieation

Question 0

List the four stages of the eukaryotic cell cycle.

Answer 0

1) G1 phase (gap 1)
2) S phase (synthesis)
3) G2 phase (gap 2)

These are collectively known as interphase. Followed by:
4) M phase

Question 1

What is mitotic cell division?

Answer 1

Chromosomes are replicated & then divided to form two identical daughter cells.

Question 2

Describe the interphase of the eukaryotic cell cycle.

Answer 2

The cells grows during G1, the first gap phase. Replication of chromosomes occurs during S phase, then prepares for division during G2 (gap 2).

Question 3

What two processes occur during M phase of the cell cycle?

Answer 3

Mitosis & cytokinesis.

Question 4

Define cytokinesis.

Answer 4

The process of the cytoplasm dividing after mitosis, separating the cell into two daughter cells. Final stage of the cell cycle.

Question 5

What are the four stages of mitosis?

Answer 5

1) prophase
2) metaphase
3) anaphase
4) telophase

Question 6

What are chromatids?

Answer 6

Chromosomes replicate during the interphase of the cell cycle to form sister pairs of chromatids.

Question 7

What occurs during the prophase of mitosis?

Answer 7

Sister pairs of chromatids become condensed enough to be visible under a light microscope. Nuclear envelope begins to break down.

Question 8

What occurs during metaphase of mitosis?

Answer 8

Chromosomes attach to mitotic spindle fibres and line up long the equator of the cell.

Question 9

What occurs during anaphase in mitosis?

Answer 9

Spindle Microtubules shorten, pulling chromatids a parting and resulting in equally segregated chromosomes at opposite ends of the cell.

Question 10

What occurs during telophase of mitosis?

Answer 10

New nuclear envelopes develop around the separate chromosomes. This is the end of mitosis and cytokinesis can the occur.

Question 11

What is meiosis?

Answer 11

The cell division which occurs to form gametes containing half the number of chromosomes.

Instead of two diploid cells the division results in four haploid cells.

Question 12

What are the phases of meiosis?

Answer 12

Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2

Question 13

What is recombination or genetic cross over?

Answer 13

During meiosis homologous chromosomes are physically paired together in a process known as synapsis.

Matching DNA sequences line up exactly, allowing the swapping of sections of DNA sequence. This is genetic recombination.

Question 14

What occurs during prophase 1 in meiosis?

Answer 14

Homologous chromosomes are physically paired up a the protein complex called synaptonemal complex.

This then dissembles leaving homologues held together by their crossover genes.

Question 15

What occurs during metaphase 1 of meiosis?

Answer 15

Homologous pairs of chromosomes still attached to each other are aligned at the metaphase plate (unlike mitosis where individual duplicates line up instead of pairs).

Question 16

In meiosis, what is independent assortment?

Answer 16

The random segregation of chromosomes due to the different orientations of the homologous pairs during metaphase 1.

Question 17

What occurs during anaphase 1 in meiosis?

Answer 17

Homologous pairs separate and move to opposite ends of the cell.

This is different to mitosis where individual sister chromatids segregate.

Question 18

what is the difference between a cell undergoing mitosis after telophase and a cell undergoing meiosis after telophase 1?

Answer 18

In mitosis the diploid cells are genetically identical. In meiosis genetic recombination and independent assortment have resulted in non identical diploid cells.

Question 19

What results from telophase 1 in meiosis?

Answer 19

Two diploid daughter cells, non identical to each other and the parent cell.

Question 20

What occurs during meiosis 2?

Answer 20

Chromosomes again align on the metaphase plate (again in random orientations) and the individual sister chromatids finally segregate during anaphase 2.

Question 21

What is the end result of meiosis?

Answer 21

Four haploid cells with a single copy of each chromosome.

These contain different genetic combinations from the diploid germ cell as a result of genetic recombination.