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IB Biology > 10.1 Meiosis > Flashcards

10.1 Meiosis Flashcards

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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
Q

What happens in prophase II?

A

Chromosomes condense
Nuclear membrane dissolves
Centrosomes move to opposite poles (perpendicular to before)

26
Q

What happens during Metaphase II?

A

Spindle fibres from opposing centrosomes attach to chromosomes at the centromere and align them along the cell equator

27
Q

What happens at Anaphase II?

A

Spindle fibres contract and separate the sister chromatids
Chromatids are now chromosomes and move to opposite poles

28
Q

What happens in Telophase II?

A

Chromosomes decondense
Nuclear membrane reforms
Cytokinesis occurs to form four haploid daughter cells

29
Q

What is the result of meiosis?

A

Four haploid daughter cells

30
Q

How may the daughter cells be genetically distinct?

A

If crossing over occurs in prophase I

31
Q

What is independent assortment?

A

How pairs of alleles separate independently from one another during gamete formation

32
Q

What is the inheritance of one gene/trait independent of?

A

The inheritance of any other gene/trait

33
Q

What causes independent assortment?

A

The random orientation of pairs of homologous chromosomes in meiosis I?

34
Q

What are the two ways chromosomes line up on the equator during metaphase I?

A

Maternal copy left/ paternal copy right
or
paternal copy left/ maternal copy right

35
Q

What is the orientation of each homologous pair?

A

Random

36
Q

What doesn’t affect the orientation of each homologous pair?

A

The orientation of any other homologous pair

37
Q

What do alleles on one chromosome have an equal chance of?

A

Being paired with or separated from any allele on another chromosome

38
Q

When will independent assortment not occur?

A

If two genes are located on the same chromosome

39
Q

What is it called if two genes are on the same chromosome?

A

Linked genes

40
Q

What is the process called when homologous chromosomes become connected?

A

Synapsis

41
Q

What are two connected chromosomes known as?

A

A bivalent

42
Q

What are four chromosomes known as?

A

A tetrad

43
Q

What connects chromosomes?

A

A protein-RNA complex called the synaptonemal complex

44
Q

What type of chromosomes often remain unpaired?

A

Sex chromosomes

45
Q

What always undergoes synapsis during meiosis?

A

Autosomes

46
Q

What happens to non sister chromatids during synapsis?

A

They may break and recombine with their homologous partner

47
Q

Where do non sister chromatids remain physically connected?

A

Regions called chiasmata

48
Q

What is the singular of chiasmata?

A

Chiasma

49
Q

What does chiasmata do?

A

Hold thee homologous chromosomes together as a bivalent until anaphase I

50
Q

What can chiasmata formation between non sister chromatids result in?

A

The exchange of alleles

51
Q

What are chiasmata?

A

Chiasmata are X shaped points of attachment between non sister chromatids of a homologous pair

52
Q

What causes chiasmata to form?

A

Crossing over

53
Q

What will non sister chromatids show?

A

An exchange of genetic material

54
Q

What helps make it clearer to see the exchange of genetic material?

A

When homologous chromosomes are differentially colour coded

55
Q

What can happen to DNA when chiasmata form between bivalents?

A

It can be exchanged between non sister homologous chromatids

56
Q

What does crossing over produce?

A

New allele combinations on the chromosomes

57
Q

What are recombinant chromosomes?

A

Chromosomes that contain genetic material from both homologous chromosomes

58
Q

What does crossing over increase?

A

The genetic diversity of potential offspring

59
Q

Where do the new combinations of alleles happen?

A

In haploid cells

60
Q

What does crossing over produce?

A

New combinations of alleles in haploid cells

IB Biology (57 decks)

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