2.3 - Cell cycle & division

0.0(0)
Studied by 0 people
call kaiCall Kai
Locked
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
GameKnowt Play
Card Sorting

1/30

encourage image

There's no tags or description

Looks like no tags are added yet.

Last updated 4:27 PM on 8/24/26
Name
Mastery
Learn
Test
Matching
Spaced
Call with Kai
Chat

No analytics yet

Send a link to your students to track their progress

31 Terms

1
New cards

How does eukaryotic DNA manage to fit into the nucleus?

It is cut into shorter lengths & each length is tightly wrapped up with histone proteins to form chromatin

<p>It is cut into shorter lengths &amp; each length is tightly wrapped up with <strong>histone proteins </strong>to form <strong>chromatin</strong></p>
2
New cards

What does the chromatin form following replication?

The chromatin coils up even tighter to form X-shaped, visible chromosomes during mitosis

3
New cards

What are the two arms of a chromosome called & what are they joined by?

The two identical arms of the chromosome are called chromatids & are joined at the centromere

<p>The two identical arms of the chromosome are called <strong>chromatids</strong> &amp; are joined at the <strong>centromere </strong></p>
4
New cards

What is the cell cycle & what are the 3 main stages?

A regulated process where cells divide into 2 identical daughter cells:

  1. interphase

  2. mitosis

  1. cytokinesis


<p>A regulated process where cells divide into 2 identical daughter cells:</p><ol><li><p>interphase</p></li><li><p>mitosis</p></li></ol><ol start="2"><li><p>cytokinesis</p></li></ol><p></p>
5
New cards

What are the sub-divisions of interphase?

  • G1 phase: growth (organelles replicated & cell size doubles)

  • S phase: DNA & histone synthesis

  • G2 phase: spindle fibres synthesised, ready for mitosis


6
New cards

What is the purpose of mitosis?

  • Growth

  • Repair & replacement

  • Asexual reproduction

  • Artificial cloning


7
New cards

What are the stages of mitosis?

  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase


8
New cards

What happens during interphase before mitosis?

  • No chromosomes visible

  • DNA, histones & centrioles are all replicated


<ul><li><p>No chromosomes visible</p></li><li><p>DNA, histones &amp; centrioles are all replicated</p></li></ul><p></p>
9
New cards

What happens during prophase in mitosis?

  • Chromosomes condense & become visible

  • Centrioles appear at opposite poles of cell

  • Nucleolus breaks down


<ul><li><p>Chromosomes condense &amp; become visible</p></li><li><p>Centrioles appear at opposite poles of cell</p></li><li><p>Nucleolus breaks down</p></li></ul><p></p>
10
New cards

What happens during metaphase in mitosis?

  • Nuclear envelope disappears

  • Chromosomes align along the equator of the cell

  • Spindle fibres connect centrioles to chromosomes by their centromeres


<ul><li><p>Nuclear envelope disappears</p></li><li><p>Chromosomes align along the equator of the cell</p></li><li><p>Spindle fibres connect centrioles to chromosomes by their centromeres</p></li></ul><p></p>
11
New cards

What happens during anaphase in mitosis?

  • Centromeres split, allowing chromatids to separate

  • Chromatids are pulled to opposite poles of cell


<ul><li><p>Centromeres split, allowing chromatids to separate</p></li><li><p>Chromatids are pulled to opposite poles of cell </p></li></ul><p></p>
12
New cards

What happens during telophase in mitosis?

  • Spindle fibres disperse

  • Nuclear envelopes form

  • Chromatids uncoil & become too thin to see


<ul><li><p>Spindle fibres disperse</p></li><li><p>Nuclear envelopes form</p></li><li><p>Chromatids uncoil &amp; become too thin to see</p></li></ul><p></p>
13
New cards

What happens during cytokinesis (animal & plant cells) in mitosis?

Animal cells:

  • a ring of actin filaments forms around the equator of the cell, tightens to form a cleavage furrow & splits the cell in two

Plant cells:

  • vesicles move to the equator, line up & fuse to form a cell plate


<p><strong><u>Animal cells:</u></strong></p><ul><li><p>a ring of actin filaments forms around the equator of the cell, tightens to form a cleavage furrow &amp; splits the cell in two</p></li></ul><p><strong><u>Plant cells:</u></strong></p><ul><li><p>vesicles move to the equator, line up &amp; fuse to form a cell plate</p></li></ul><p></p>
14
New cards

What is meiosis?

A form of cell division that occurs twice, producing four genetically different haploid cells (gametes)

15
New cards

What happens during interphase I in meiosis?

DNA, histones & centrioles are all replicated

<p>DNA, histones &amp; centrioles are all replicated</p>
16
New cards

What happens during prophase I in meiosis?

Chromosomes condense & homologous chromosomes join together to form bivalents

<p>Chromosomes <strong>condense</strong> &amp; homologous chromosomes join together to form<strong> bivalents </strong></p>
17
New cards

What happens during metaphase I in meiosis?

Bivalents line up on the equator of the cell

<p>Bivalents line up on the <strong>equator</strong> of the cell </p>
18
New cards

What happens during anaphase I in meiosis?

  • Bivalents separate & homologous chromosomes move to opposite poles

  • Chromatids do not separate


<ul><li><p>Bivalents<strong> separate</strong> &amp; homologous chromosomes move to<strong> opposite poles</strong></p></li><li><p>Chromatids<strong> do not</strong> separate</p></li></ul><p></p>
19
New cards

What happens during telophase I & cytokinesis I in meiosis?

  • Two nuclei form with replicated, uncoiled chromosomes

  • Cells divide, but remain joined


<ul><li><p><strong>Two nuclei </strong>form<strong> </strong>with replicated, uncoiled chromosomes</p></li><li><p>Cells <strong>divide, </strong>but remain<strong> joined</strong></p></li></ul><p></p>
20
New cards

What happens during interphase II in meiosis?

  • Meiosis division II proceeds immediately without any interphase

  • There is no replication of DNA


21
New cards

What happens during prophase II in meiosis?

  • Centrioles move to form new poles at 90° to original poles

  • Chromosomes already condensed


<ul><li><p><strong>Centrioles</strong> move to form new poles at <strong>90° </strong>to original poles</p></li><li><p>Chromosomes already condensed</p></li></ul><p></p>
22
New cards

What happens during metaphase II in meiosis?

Chromosomes line up on the new equator

<p>Chromosomes line up on the new equator </p>
23
New cards

What happens during anaphase II in meiosis?

  • Centromeres finally split, separating chromosomes

  • Chromatids move to opposite poles of the cell


<ul><li><p><strong>Centromeres </strong>finally split, separating chromosomes</p></li><li><p><strong>Chromatids</strong> move to <strong>opposite poles </strong>of the cell</p></li></ul><p></p>
24
New cards

What happens during telophase II & cytokinesis II in meiosis?

  • Nuclear envelopes form around each set of chromosomes

  • Cells divide, but remain joined to form a tetrad


<ul><li><p><strong>Nuclear envelopes</strong> form around <strong>each set of chromosomes</strong></p></li><li><p>Cells divide, but remain joined to form a<strong> tetrad</strong></p></li></ul><p></p>
25
New cards

What is crossing over & how does it produce genetic variation?

  • While paired in a bivalent during prophase I, homologous chromosomes exchange corresponding segments at the chiasmata

  • Produces new combinations of alleles


<ul><li><p>While paired in a <strong>bivalent </strong>during <strong>prophase I</strong>, homologous chromosomes exchange corresponding segments at the<strong> chiasmata</strong></p></li></ul><ul><li><p>Produces <strong>new combinations of alleles</strong></p></li></ul><p></p>
26
New cards

What is independent assortment & how does it produce genetic variation?

  • Homologous pairs of chromosomes align randomly during metaphase I

  • Leads to different combinations of chromosomes in gametes


<ul><li><p>Homologous pairs of chromosomes <strong>align randomly </strong>during<strong> metaphase I</strong></p></li><li><p>Leads to <strong>different combinations of chromosomes </strong>in gametes</p></li></ul><p></p>
27
New cards

What are chromosome mutations?

Large-scale changes to the structure or number of chromosomes

28
New cards

What is a translocation mutation?

  • One part of a chromosome is swapped with a part of a different chromosome

  • Swapped parts can be unequal in size & between non-homologous chromosomes


<ul><li><p>One part of a chromosome is swapped with a part of a different chromosome</p></li><li><p>Swapped parts can be unequal in size &amp; between non-homologous chromosomes</p></li></ul><p></p>
29
New cards

What is a non-disjunction mutation?

Chromosomes fail to separate correctly during anaphase in meiosis → gametes may end up with one extra copy or no copies of a particular chromosome

<p>Chromosomes fail to separate correctly during anaphase in meiosis → gametes may end up with one extra copy or no copies of a particular chromosome</p>
30
New cards

How can non-disjunction lead to polysomy?

If a gamete with an extra chromosome is fertilised by a normal gamete, the zygote will show trisomy (three chromosome copies, instead of two) → e.g. Down’s syndrome (caused by trisomy 21)

<p>If a gamete with an extra chromosome is fertilised by a normal gamete, the zygote will show trisomy (three chromosome copies, instead of two) → e.g. Down’s syndrome (caused by trisomy 21)</p>
31
New cards

How can non-disjunction lead to monosomy?

If a gamete with a missing chromosome is fertilised by a normal gamete, the zygote will show monosomy (one chromosome copy, instead of two) → e.g. Turner’s syndrome (X0)

<p>If a gamete with a missing chromosome is fertilised by a normal gamete, the zygote will show monosomy (one chromosome copy, instead of two) → e.g. Turner’s syndrome (X0)</p>