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IB Biology > 10.1 Meiosis > Flashcards

10.1 Meiosis Flashcards

1
Q

What is interphase?

A

An active process that precedes meiosis

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2
Q

Why is interphase needed?

A

As it involves key events needed to prepare the cell for successful division

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3
Q

When is DNA replicated during interphase?

A

During the S phase

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4
Q

What does the replication of DNA during interphase result in?

A

Chromosomes that contain two identical DNA strands

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5
Q

What are genetically identical strands called?

A

Sister chromatids

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6
Q

How are sister chromatids held together

A

By a central region called the centromere

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7
Q

When do sister chromatids separate?

A

During meiosis II

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8
Q

What do the sister chromatids become once they’ve separated?

A

Independent chromosomes each made of a single DNA strand

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9
Q

What would not be necessary if DNA replication did not happen before meiosis?

A

A second meiotic division

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10
Q

What does the fact that DNA replication occurs suggest?

A

That meiosis evolved from mitosis

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11
Q

What is a benefit of the duplication of chromosomes?

A

It increases the potential for genetic recombination to occur

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12
Q

How many divisions of meiosis are there?

A

Two

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13
Q

What are the stages of meiosis?

A

Prophase
Metaphase
Anaphase
Telophase

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14
Q

What is the second growth phase called?

A

Interkinesis

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15
Q

When may interkinesis occur?

A

between meiosis I and II

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16
Q

What does not happen during interkinesis?

A

DNA replication

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17
Q

What happens in the first meiotic division?

A

Homologous chromosomes are separated

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18
Q

What type of division is the first meiotic division?

A

A reduction division from diploid to haploid

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19
Q

What happens in Prophase I?

A

Chromosomes condense
Nuclear membrane dissolves
Homologous chromosomes form bivalents
Crossing over occurs

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20
Q

What happens in metaphase I?

A

Spindle fibres from opposing centrosomes connect to bivalents at centromeres and align them along the middle of the cell

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21
Q

What happens in Anaphase I?

A

Spindle fibres contract and split the bivalent
Homologous chromosomes move to opposite poles of the cell

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22
Q

What happens in telophase I?

A

Chromosomes decondense
Nuclear membrane may reform
Cytokinesis happens forming two haploid daughter cells

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23
Q

What happens in the meiosis second division?

A

Sister chromatids separate

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24
Q

Why may sister chromatids not be identical?

A

Due to crossing over in prophase I

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25
What happens in prophase II?
Chromosomes condense Nuclear membrane dissolves Centrosomes move to opposite poles (perpendicular to before)
26
What happens during Metaphase II?
Spindle fibres from opposing centrosomes attach to chromosomes at the centromere and align them along the cell equator
27
What happens at Anaphase II?
Spindle fibres contract and separate the sister chromatids Chromatids are now chromosomes and move to opposite poles
28
What happens in Telophase II?
Chromosomes decondense Nuclear membrane reforms Cytokinesis occurs to form four haploid daughter cells
29
What is the result of meiosis?
Four haploid daughter cells
30
How may the daughter cells be genetically distinct?
If crossing over occurs in prophase I
31
What is independent assortment?
How pairs of alleles separate independently from one another during gamete formation
32
What is the inheritance of one gene/trait independent of?
The inheritance of any other gene/trait
33
What causes independent assortment?
The random orientation of pairs of homologous chromosomes in meiosis I?
34
What are the two ways chromosomes line up on the equator during metaphase I?
Maternal copy left/ paternal copy right or paternal copy left/ maternal copy right
35
What is the orientation of each homologous pair?
Random
36
What doesn't affect the orientation of each homologous pair?
The orientation of any other homologous pair
37
What do alleles on one chromosome have an equal chance of?
Being paired with or separated from any allele on another chromosome
38
When will independent assortment not occur?
If two genes are located on the same chromosome
39
What is it called if two genes are on the same chromosome?
Linked genes
40
What is the process called when homologous chromosomes become connected?
Synapsis
41
What are two connected chromosomes known as?
A bivalent
42
What are four chromosomes known as?
A tetrad
43
What connects chromosomes?
A protein-RNA complex called the synaptonemal complex
44
What type of chromosomes often remain unpaired?
Sex chromosomes
45
What always undergoes synapsis during meiosis?
Autosomes
46
What happens to non sister chromatids during synapsis?
They may break and recombine with their homologous partner
47
Where do non sister chromatids remain physically connected?
Regions called chiasmata
48
What is the singular of chiasmata?
Chiasma
49
What does chiasmata do?
Hold thee homologous chromosomes together as a bivalent until anaphase I
50
What can chiasmata formation between non sister chromatids result in?
The exchange of alleles
51
What are chiasmata?
Chiasmata are X shaped points of attachment between non sister chromatids of a homologous pair
52
What causes chiasmata to form?
Crossing over
53
What will non sister chromatids show?
An exchange of genetic material
54
What helps make it clearer to see the exchange of genetic material?
When homologous chromosomes are differentially colour coded
55
What can happen to DNA when chiasmata form between bivalents?
It can be exchanged between non sister homologous chromatids
56
What does crossing over produce?
New allele combinations on the chromosomes
57
What are recombinant chromosomes?
Chromosomes that contain genetic material from both homologous chromosomes
58
What does crossing over increase?
The genetic diversity of potential offspring
59
Where do the new combinations of alleles happen?
In haploid cells
60
What does crossing over produce?
New combinations of alleles in haploid cells

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