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Life Sciences > Meiosis > Flashcards

Meiosis Flashcards

1
Q

What is the control centre for all cellular activities?

A

The nucleus

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2
Q

What happens just before cell division?

A

The chromatin network contracts and becomes visible as individual chromosomes

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3
Q

What does each chromosome consist of?

A

DNA molecules wrapped around proteins

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4
Q

What makes up genes?

A

DNA molecules

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5
Q

Do all organisms have the same number of chromosomes?

A

No

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6
Q

How many chromosomes do humans have?

A

46

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7
Q

What happens during DNA replication?

A

single-stranded chromosomes replicate to become double stranded

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8
Q

What does a double-stranded chromosome consist of?

A

two chromatids joined by a centromere

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9
Q

What joins chromatids?

A

a centromere

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10
Q

What does replication ensure?

A

that all daughter cells contain the same hereditary information as the parent cells

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11
Q

When are chromosomes arrached in pairs called homologous chromosomes?

A

just before cell division

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12
Q

What is similar between each chromosome of the homologous pair?

A

They are the same length and contain the same genes

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13
Q

How many chromatids does one pair of homologous chromosomes contain?

A

4

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14
Q

What are autosomes?

A

The are chromosomes that control features in males and females

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15
Q

What are gonosomes?

A

They are sex chromosomes that determine the sex of the organism.

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16
Q

How many types of gonosomes are there?

A

2 (X & Y)

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17
Q

What are some features that could be controlled by autosomes?

A

eye colour

blood group

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18
Q

What is meiosis?

A

A special type of cell division necessary for sexual reproduction

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19
Q

What type of cell does the process of meiosis begin with?

A

one diploid (2n) cell

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20
Q

What does diploid imply?

A

That it is a cell containing two copies of each chromosome

One copy from the organism’s father; one copy from the organism’s mother

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21
Q

Define karyotype

A

The number and appearance of chromosomes in the nucleus of a cell

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22
Q

What does the process of meiosis produce?

A

four haploid cells

These are all genetically different from each other

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23
Q

Define fertilisation

A

When one of the haploid male gametes fuses with one of the haploid female gametes

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24
Q

What does fertilisation produce?

A

a diploid zygote

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25
Q

What describes the complete set of chromosomes in a species or in an individual organism?

A

Karyotype

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26
Q

Where does meiosis occur?

A

In the gonads

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27
Q

What are the gonads?

A

Reproductive organs (testes and ovaries)

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28
Q

What are the cells produced by meiosis called?

A

gametes

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29
Q

What can the process of meiosis also be called?

A

gametogenesis

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30
Q

What are the male gametes called?

A

spermatozoa (sperm cells)

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31
Q

What process are sperm cells produced by?

A

spermatogenesis

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32
Q

What are female gametes called?

A

ova (egg cells)

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33
Q

What process are egg cells produced by?

A

oogenesis

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34
Q

What is the order of phases in meiosis?

A 
IPMAT
Interphase
Prophase
Metaphase
Anaphase
Telophase
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35
Q

What are the gametes of plants called?

A

spores

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36
Q

In plants, where does meiosis occur in males?

A

In the anther

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37
Q

What does meiosis produce in male plants?

A

pollen grains

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38
Q

In plants, where does meiosis occur in females?

A

In the ovary

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39
Q

What does meiosis produce in female plants?

A

Ovule

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40
Q

What does paternal mean?

A

originating from the male parent

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41
Q

What type of cell does meiosis begin with?

A

one diploid cell

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42
Q

What does meiosis follow in the cell cycle?

A

Interphase

43
Q

Why does DNA replication take place?

A

To double the genetic material

44
Q

In which phase of the cell cycle does DNA replication take place?

A

Interphase

45
Q

When do the chromosomes duplicate?

A

During DNA replication

46
Q

What does DNA replication produce?

A

An identical copy of each maternal and paternal chromosome

47
Q

What are copies produced by DNA replication called?

A

homologous chromosomes

48
Q

What is each chromosome made up of?

A

two chromatids joined by a centromere

49
Q

What happens in prophase I?

A

Nuclear membrane starts to disappear
Chromatin network becomes visible as chromosomes
Chromosomes arrange themselves into homologous pairs
Crossing over occurs

50
Q

What does crossing over involve?

A

Homologous chromosomes lie next to each other
Touch at points along the chromatids called chiasma
Where they touch, there is an exchange of genetic material

51
Q

What are the points where genetic material is exchanged called?

A

chiasma

52
Q

In what stage of meiosis do chromosomes arrange themselves into homologous pairs?

A

Prophase I

53
Q

In what stage of meiosis does the nuclear membrane start to disappear?

A

Prophase I

54
Q

What can meiosis I be referred to as?

A

A reduction division

55
Q

What is the main thing that is happening in meiosis I?

A

homologous chromosomes are getting separated resulting in two separate daughter cells

56
Q

What is a does each daughter cell (resulting from meiosis I) contain?

A

Half the number of chromosomes found the original cell (this is the haploid number)

57
Q

What happens in metaphase I?

A

A spindle thread forms
homologous pairs randomly arrange along equator
centromeres attach to spindle threads

58
Q

What do the spindle threads consist of?

A

protoplasmic threads

59
Q

What are the things that form the spindle threads?

A

centrioles

60
Q

What happens in anaphase I?

A

Spindle threads contract

Whole chromosomes move towards the poles

61
Q

What happens in telophase I?

A 
Chromosomes uncoil and lengthen
spindle disappears
nuclear membrane reforms
cytoplasm divides
two new cells genetically different (due to crossing over)
62
Q

Are the cells produced at the end of meiosis I haploid or diploid?

A

two haploid daughter cells form

63
Q

Basically, what happens in meiosis II?

A

The chromatids of the chromosomes now separate from each other, creating four haploid daughter cells

64
Q

What happens in prophase II?

A

chromosomes are visible as two chromatids

centromere splits between the sister chromatids

65
Q

What forms when the sister chromatids split?

A

Daughter chromosomes

66
Q

What happens in metaphase II?

A

the daughter chromosomes randomly arrange along the equator

centromere of each daughter chromosome attaches to the spindle threads

67
Q

What happens in anaphase II?

A

spindle threads contract

centromere splits allowing spindle threads to pull daughter chromosomes apart

68
Q

What happens in telophase II?

A

the chromosomes uncoil and lengthen
spindle disappears
cytoplasm divides
nuclear envelope (membrane) forms

69
Q

What does meiosis ultimately result in?

A

four haploid daughter cells

that are genetically different from each other

70
Q

Why is meiosis important?

A

formation of gametes
counteracts doubling effect of fertilisation (due to haploid cells being created)
introduces genetic variation

71
Q

What are the reasons for genetic variation in meiosis?

A

crossing over

random arrangement of chromosomes during metaphase

72
Q

Define gametogenesis

A

the process whereby gametes are formed

73
Q

What are the two different types of gametogenesis called?

A

spermatogenesis and oogenesis

74
Q

Where does oogenesis take place?

A

In a cell inside a follicle in a ovary

75
Q

Where does spermatogenesis take place?

A

In a germinal epithelial cell in testes

76
Q

What does spermatogenesis result in?

A

4 haploid spermatids

77
Q

What does oogenesis result in?

A

1 mature ovum

78
Q

What does a reduction of the chromosome number prevent in the process of reproduction?

A

Prevents the chromosome number from doubling when fertilisation occurs

79
Q

What does crossing over result in?

A

The exchange of genetic material between the paternal and maternal chromosome of each homologous pair

80
Q

What does crossing over ensure?

A

That all gametes of both parents contain a unique combination of genes

81
Q

What happens when different gametes of the same parents combine during fertilisation?

A

the resultant offspring will al contain a unique karyotype, ensuring variation in the offspring

82
Q

Explain random separation of chromosomes

A

when each homologous chromosome pair is randomly arranged along the equatorial line

83
Q

What does random arrangement ensure?

A

that the combination of genetic material received by each gamete is random

84
Q

What are chromosomal mutations?

A

When chromosomal abnormalities occur when the process of meiosis does not occur properly

85
Q

What happens to chromosomal mutations as women increase in age?

A

As women increase in age, the frequency of chromosomal mutation increases.

86
Q

What do chromosomal mutations result in?

A

a change in the structure or distribution of one or more of the chromosomes.
(I.e. there has been a change to the cell’s karyotype)

87
Q

What is non-disjunction?

A

When a chromosome is lost or gained when they do not separate correctly during meiosis

88
Q

When does non-disjuction occur in terms of the cell cycle?

A

During meiosis I or meiosis II

89
Q

What happens if one pair of chromosomes fail to separate?

A

Non-disjuction occurs

One cell receive two copies of that chromosome while the other does not receive any

90
Q

What is aneuploidy

A

a type of non-disjunction

when gametes have have one extra or one less chromosome

91
Q

What is polyploidy?

A

When gametes have an entire extra set of chromosomes

E.g. 3n

92
Q

When does does trisomy occur?

A

When an individual has three of the same chromosome in a cell instead of two.
This condition is usually fatal or results in abnormal physical and mental characteristics.

93
Q

When does Down’s syndrone occur?

A

When chromosome 21 pair does not separate during metaphase I of meiosis.
This results in a gamete that contain two #21 chromosomes

94
Q

What happens due to trisomy of chromosome 21?

A

This is the cause of Down’s Syndrome in humans

95
Q

How many chromosomes does a human with Down’s Syndrome have

A

47 (instead of 46)

96
Q

What are some similarities between mitosis and meiosis?

A

DNA replication takes place
The nucleus divides
The cytoplasm divides
New cells are formed

97
Q

Where does mitosis occur?

A

In somatic cells

98
Q

How many times does the nucleus divide in mitosis?

A

once

99
Q

How many times does the nucleus divide in meiosis?

A

twice

100
Q

Do homologous chromosomes pair in the process of mitosis?

A

No

101
Q

Do homologous chromosomes pair in the process of meiosis?

A

Yes

102
Q

Does the exchange of genetic material occur in the process of mitosis?

A

No

103
Q

Do homologous chromosomes lie on the equator during metaphase of mitosis or do homologous chromosomes lie on the equator?

A

single chromosomes

104
Q

Does the centromere divide during anaphase in mitosis?

A

Yes

Life Sciences (7 decks)

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