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A Level Biology OCR > Chapter 2.6 Cell Division > Flashcards

Chapter 2.6 Cell Division Flashcards

1
Q

What happens in Interphase?

A

First stage of mitosis where chromosomes replicate

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2
Q

What is the longest stage of the cell cycle?

A

Interphase

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3
Q

Outline the G1, S and G2 phases.

A

G1: Cell grows larger and organelles synthesised
S: Complete DNA replication
G2: Organelles grow and preparation for mitosis

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4
Q

When do the G1, S and G2 phases occur?

A

In Interphase

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5
Q

What is the purpose of the G1 and G2 checkpoints?

A

G1: Checks that correct chemicals are present
G2: Checks that DNA has been replicated correctly

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6
Q

What’s the G0 phase?

A

After cells have differentiated and cannot differentiate again

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7
Q

Mitosis: Outline what happens in Prophase.

A

Chromosomes become more distinct, nucleolus becomes less prominent, centriole divides, chromosomes consist of two chromatids joined by centromere and nuclear envelope breaks down

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8
Q

Mitosis: Outline what happens in Metaphase

A

Each centriole is at a pole, centrioles produces spindle fibres, chromosomes line p at equator and spindle fibres attach to centromere

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9
Q

Define: Centrioles, Centromere and Spindle fibres

A

Centrioles: Cylindrical organelles that release spindle fibres
Centromere: Links a pair of sister chromatids together during cell division
Spindle fibres: Form a protein structure that divides the genetic material in a cell

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10
Q

Mitosis: Outline what happens in Anaphase.

A

Centromeres divide into two - chromatids pulled to opposite sides of the cell

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11
Q

Mitosis: Outline what happens in Telophase.

A

Daughter chromatids reach opposite sides of cell, cytoplasm begins to split, spindles fibres disappear and nuclear envelop + nucleolus begin to reform

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12
Q

Mitosis: Outline what happens in Cytokinesis.

A

Cell divides
Animal cells: Starts by constriction of edges
Plant cells:
Cell wall is laid down first

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13
Q

What does Mitosis produce?

A

Two genetically identical daughter cells (diploid)

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14
Q

Define homologous pairs

A

Two chromosomes in a pair - one inherited from the father and one from the mother creating a bivalent

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15
Q

Meiosis: Outline Prophase I

A

Chromosomes of the same homologous form bivalents - in a human cell there will be 23 bivalents,
Chromatids of one bivalent cross over

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16
Q

Define ‘crossing over’

A

Where chromatids join at the chiasmata and exchange information

17
Q

Meiosis: Outline Metaphase I

A

Centrioles move to opposite poles and spindle fibres attach to centromeres, bivalents line up across equator

18
Q

What protein are spindle fibres made from?

A

Tubulin (meiosis and maybe mitosis)

19
Q

Meiosis: Outline Anaphase I

A

Chromosomes pulled to opposite poles and separated into haploid sets

20
Q

Define haploid

A

A cell that contains a single set of chromosomes

21
Q

Meiosis: Outline Telophase I

A

Nuclear envelope reforms,
Cytokinesis of cytoplasm, chromosomes haploid

22
Q

Meiosis: Outline Prophase II

A

Nuclear membranes break down, Centrioles move to opposite poles, Spindle fibres form and chromosomes shorten and thicken

23
Q

Does prophase II occur in plant cells?

A

No

24
Q

Meiosis: Outline Metaphase II

A

Chromosomes line up at equator, spindle fibres attach chromosomes to centromeres

25
Q

Meiosis: Outline Anaphase II

A

Centromeres divide,
Spindle fibres contract and pull chromosomes to opposite poles

26
Q

Meiosis: Outline Telophase II

A

Nuclear membranes reform, spindle fibres break down, centrioles reform - produces 4 haploid cells

27
Q

In meiosis, how can variation occur?

A

Crossing over (prophase I),
Random assortment (metaphase I), Independent assortment (metaphase II), Production of haploid gametes that fuse randomly, mutations

28
Q

Define the difference between random and independent assortment

A

The law of independent assortment covers how the alleles of different genes assort into gametes, and the law of random assortment covers how alleles of the same gene assort into different gametes

29
Q

What are diploid cells used for?

A

Tissue growth etc

30
Q

What are haploid cells used for?

A

Reproduction - gametes

A Level Biology OCR (18 decks)

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