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Biology A-Level OCR > Cell Division > Flashcards

Cell Division Flashcards

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1
Q

What are the roles of mitosis?

A

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

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2
Q

What is mitosis?

A

The stage of the cell cycle where the nucleus divides

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3
Q

What is the cell cycle?

A

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

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4
Q

What is interphase?

A

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

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5
Q

What happens in interphase?

A

Three stages; G1, S and G2

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6
Q

What happens in the G1 stage?

A

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

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7
Q

What happens in the S stage?

A

DNA synthesis

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8
Q

What happens in the G2 stage?

A

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

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9
Q

What stage comes after interphase?

A

Mitotic stage (mitosis)

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10
Q

What are checkpoints in the cell cycle?

A

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

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11
Q

When are the checkpoints in the cell cycle?

A

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

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12
Q

What is G0?

A

Resting state of the cell (does not duplicate)

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13
Q

What are some examples of cells that enter G0?

A

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

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14
Q

What are chromatids?

A

A single DNA molecule

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15
Q

What are sister chromatids?

A

Two identical copies of a single replicated chromosome

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16
Q

What are chromosomes?

A

A pair of two chromatids joined by a centromere

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17
Q

What are homologous chromosomes?

A

Genetically identical pair of chromosomes

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18
Q

What are the properties of chromatin?

A

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

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19
Q

What are the properties of chromosomes?

A

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

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20
Q

What are the stages of mitosis?

A

Prophase, metaphase, anaphase, telophase

21
Q

What happens in prophase?

A

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

22
Q

What happens in metaphase?

A

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

23
Q

What happens in anaphase?

A

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

24
Q

What happens in telophase?

A

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

25
Q

What is cytokinesis?

A

The actual division of the cells

26
Q

How is cytokinesis different for animal cells?

A

The plasma membrane forms a cleavage furrow via an actin ring

27
Q

How is cytokinesis different for plant cells?

A

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

28
Q

What is meiosis?

A

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

29
Q

What is the role of meiosis?

A

Sexual reproduction

30
Q

How many chromosomes does a human cell have?

A

46

31
Q

How many chromatids does a gamete have?

A

23

32
Q

What is an allele?

A

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

33
Q

What are the stages of meiosis?

A

Meiosis I and meiosis II

34
Q

What happens in meiosis I?

A

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

35
Q

What happens in meiosis II?

A

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

36
Q

What happens in prophase I?

A

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

37
Q

What are bivalents?

A

A pair of sister chromatids

38
Q

What is crossing over?

A

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

39
Q

What happens in metaphase I?

A

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

40
Q

What is independent assortment?

A

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

41
Q

What happens in anaphase I?

A

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

42
Q

What are recombinant chromatids?

A

When genes swap between chromatids

43
Q

What is chiasmata?

A

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

44
Q

What happens in telophase I?

A

Same as mitosis

45
Q

What happens in prophase II?

A

Same as prophase I

46
Q

What happens in metaphase II?

A

Same as mitosis

47
Q

What happens in anaphase II?

A

Same as mitosis

48
Q

What happens in telophase II?

A

Same as mitosis

49
Q

How is cytokinesis different for meiosis II?

A

4 haploid daughter cells are formed

Biology A-Level OCR (26 decks)

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