Cell Division

Question 1

What are the roles of mitosis?

Answer 1

Tissue repair/replacement, organism growth, asexual reproduction and development (of embryos)

Question 2

What is mitosis?

Answer 2

The stage of the cell cycle where the nucleus divides

Question 3

What is the cell cycle?

Answer 3

Strict sequence of events that takes place within a cell to make two genetically identical daughter cells

Question 4

What is interphase?

Answer 4

One of the major phases of the cell cycle that is referred to as the ‘resting’ phase

Question 5

What happens in interphase?

Answer 5

Three stages; G1, S and G2

Question 6

What happens in the G1 stage?

Answer 6

Protein synthesis for organelles, cell size increases, cytoplasm increases, organelles replicate

Question 7

What happens in the S stage?

Answer 7

DNA synthesis

Question 8

What happens in the G2 stage?

Answer 8

Cell size continues to increase, energy stores are increased and error checking occurs for the duplicated DNA

Question 9

What stage comes after interphase?

Answer 9

Mitotic stage (mitosis)

Question 10

What are checkpoints in the cell cycle?

Answer 10

Control mechanisms to ensure that each stage of the cell cycle are successful

Question 11

When are the checkpoints in the cell cycle?

Answer 11

G1 checkpoint- end of G1
G2 checkpoint- end of G2
Spindle assembly checkpoint- metaphase of mitosis

Question 12

What is G0?

Answer 12

Resting state of the cell (does not duplicate)

Question 13

What are some examples of cells that enter G0?

Answer 13

Specialised cells, neurons, aging cells, dormant (quiescent) cells

Question 14

What are chromatids?

Answer 14

A single DNA molecule

Question 15

What are sister chromatids?

Answer 15

Two identical copies of a single replicated chromosome

Question 16

What are chromosomes?

Answer 16

A pair of two chromatids joined by a centromere

Question 17

What are homologous chromosomes?

Answer 17

Genetically identical pair of chromosomes

Question 18

What are the properties of chromatin?

Answer 18

Loosely packed into the nucleus, occurs in non-dividing cells, accessible for transcription

Question 19

What are the properties of chromosomes?

Answer 19

Tightly wound and condensed, can be segregated and transported easily, only for a short time, cannot be transcribed

Question 20

What are the stages of mitosis?

Answer 20

Prophase, metaphase, anaphase, telophase

Question 21

What happens in prophase?

Answer 21

Chromatin condense into chromosomes, nucleolus disappears, nuclear envelope disassembles, spindle fibres begin to form and centrioles align at equator

Question 22

What happens in metaphase?

Answer 22

Chromosomes align at equator (metaphase plate), spindle fibers attach to centromeres of chromosomes

Question 23

What happens in anaphase?

Answer 23

Chromosomes separate into sister chromatids and are pulled to either pole of the cell, spindle fibers contract to pull chromatids, organelles also seperate

Question 24

What happens in telophase?

Answer 24

Nuclear envelope reforms, reformed chromosomes now uncoil, nucleolus reforms, spindle fibers detach from chromosomes

Question 25

What is cytokinesis?

Answer 25

The actual division of the cells

Question 26

How is cytokinesis different for animal cells?

Answer 26

The plasma membrane forms a cleavage furrow via an actin ring

Question 27

How is cytokinesis different for plant cells?

Answer 27

The rigid cell wall cannot form a cleavage furrow so instead forms a phragmoplast from vesicles from the golgi

Question 28

What is meiosis?

Answer 28

A form of cell division that forms gametes (haploid cells)

Question 29

What is the role of meiosis?

Answer 29

Sexual reproduction

Question 30

How many chromosomes does a human cell have?

Answer 30

46

Question 31

How many chromatids does a gamete have?

Answer 31

23

Question 32

What is an allele?

Answer 32

A different variation of the same gene that code for the same characteristic, e.g. eye colour, but different colours

Question 33

What are the stages of meiosis?

Answer 33

Meiosis I and meiosis II

Question 34

What happens in meiosis I?

Answer 34

The reduction division where the homologous chromosomes are separated into two cells

Question 35

What happens in meiosis II?

Answer 35

Chromatids separate similar to mitosis, four haploid daughter cells are produced

Question 36

What happens in prophase I?

Answer 36

Same as mitosis, except homologous pairs form bivalents which causes crossing over

Question 37

What are bivalents?

Answer 37

A pair of sister chromatids

Question 38

What is crossing over?

Answer 38

When genes cross over between the bivalents and allows for genetic variation

Question 39

What happens in metaphase I?

Answer 39

Same as mitosis, except independent assortment occurs for whole chromosomes aligning at equator rather than chromatids

Question 40

What is independent assortment?

Answer 40

Chromosomes align at the equator randomly and allows for genetic variation (2^n where n = number of chromosomes)

Question 41

What happens in anaphase I?

Answer 41

Same as mitosis, except whole chromosomes are pulled to the poles. Chiasmata ensues to form recombinant chromatids

Question 42

What are recombinant chromatids?

Answer 42

When genes swap between chromatids

Question 43

What is chiasmata?

Answer 43

When parts of chromatids break off and rejoin, which allows for genetic variation

Question 44

What happens in telophase I?

Answer 44

Same as mitosis

Question 45

What happens in prophase II?

Answer 45

Same as prophase I

Question 46

What happens in metaphase II?

Answer 46

Same as mitosis

Question 47

What happens in anaphase II?

Answer 47

Same as mitosis

Question 48

What happens in telophase II?

Answer 48

Same as mitosis

Question 49

How is cytokinesis different for meiosis II?

Answer 49

4 haploid daughter cells are formed