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Biology 2.4 > Meiosis and sexual reproduction > Flashcards

Meiosis and sexual reproduction Flashcards

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1
Q

What does asexual reproduction leave population vulnerable to

A

changes in the environment

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2
Q

Whats the difference between mitosis and meiosis in term of daughter cells

A

mitosis:
daughter cells re identical to parent cells
meiosis:
daughter cells are not identical to parent cells

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3
Q

Give examples of organisms in which sexual reproduction is the main type of reprodution

A

animals and flowering plants

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4
Q

What is sexual production

A

The production of a new individual resulting from the joining of two specialised cells known as gametes

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5
Q

Whats a great advantage if sexual reproduction

A

Increases genetic variations

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6
Q

What is a diploid cells (2n)

A

A cell containing two full sets of chromosomes

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7
Q

What are haploid cells

A

A cell containing one complete set of chromosomes

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8
Q

When does sexual reproduction occur

What is this process called

A

When two haploid nuclei fuse to form a new diploid cell known as a zygote
Fertilisation

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9
Q

Where are gametes formed

A

In special sex organs

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10
Q

What are gonads

A

sex organs in animals

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11
Q

What is polypidy

A

When a cell or organism has more than two sets of chromosomes

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12
Q

In plants what is the following:

1) anthers
2) Ovaries

A

a) Anthers-male sex organs

b) Ovaries-female sex organs

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13
Q

Where are the male gametes in plants formed

A

In pollen

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14
Q

Where are the female gametes in plants formed

A

Ovules

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15
Q

What is the male gonad in animals

what does it produce

A

Testes

sperm

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16
Q

What is the female gonad in animals

what does it produce

A

Ovaries

Ova/eggs

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17
Q

Why does the number of chromosomes in both daughter cells need to be halved in meiosis

A

To give the necessary haploid nuclei

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18
Q

What is meiosis

A

A reduction division and occurs only in sex organs

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19
Q

What special cells does meiosis in flowering plants form for:
Males
Females

A

Microspores

Megaspores

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20
Q

In meiosis what does the two nuclear divisions cause

A

It gives rise to four haploid daughter cells, each with its own unique combination of genetic material

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21
Q

What are the differences between the stages of meiosis and mitosis

A

1) The two chromosomes of each pair (homologous chromosomes) stay close together
2) Crossing over or recombination takes place
3) Centromere does not split in the first division, so pairs of chromatid move to opposite sides of pole
4) Cytokinesis takes place giving 4 haploid daughter cells
5) Daughter cells later develop into gametes

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22
Q

What are chromosome mutations

A

When during meiosis, parts of the chromosomes break off and become reattached to the wrong place

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23
Q

Whats one of the most common forms of chromosome mutations

When does this type of chromosomal mutation take place

A

Translocation

When one pair of homologous chromosome breaks off and reattaches to one of a completely different pair of chromosomes

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24
Q

Are all translocations bad/unhealthy

A

No if its balanced its healthy but if its unbalanced it causes huge changes within the phenotype of an individual

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25
Q

In humans what should each gamete carry

A

Contain 23 chromosomes, including ONE SEX CELL

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26
Q

What is non-disjunction

A

The process that occurs when members of a pair of chromosomes fail to seperate during the reduction division of meiosis, resulting in one gamete with two copies of a chromosome and one gamete with no copies if that chromosome

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27
Q

What happens if one of these abnormal gametes joins with a normal gamete and is fertilised

A

The individual who results will either have monosomy with only one member of the homologous pairs present from the normal gamete or polysomy with three or more rather than two chromosome of a particular type

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28
Q

What is meant by Aneuploidy

A

When a cell contains too few or too many chromosomes

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29
Q

What is an example of:

a) Polysomy disease
b) monosomy disease

A

a) down syndrome

b) Turners syndrome

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30
Q

What are people that have down syndrome born with

A

They are born with trisomy of chromosome 21

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31
Q

What does the extra chromosome in down syndrome affect

A

It affects both mental and physical developement

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32
Q

What problems do kids born with down syndrome suffer from

A

Heart abnormalities, learning difficulties , lack of muscle tone and visual problems

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33
Q

What genotype does turners syndrome suffers have

A

XO

The affected person is female but does not have any sex cells and is infertile. They also cannot undergo puberty

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34
Q

What is Kleinfelter’s syndrome

A

When you have the genotype XXY

small testes and can develope breast. May also be infertile

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35
Q

What are primordial germ cells

A

Special cells in the gonads that divide, grow, divide again and then differentiate

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36
Q

What is Gametogenesis

A

The formation of the ganetes by meiosis in the swx organs

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37
Q

What is spermatogenesis

A

Formation of spermatozoa

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38
Q

What does each primordial germ cell in the testes result in

A

Large number of spermatozoa

39
Q

What are the number of primordial germ cells in the testes producing millions of spermatozoa on regular basis

A

1) diploid primodal germ divides by mitosis several times to form diploid spermatogonia
2) spermatogonia then grow without further division until they’re big enough to be called primary spermatocytes
3) spermatocytes undergoes meiosis.First meiotic division forms two haploid cells known as secondary spermatocytes
4) Second meiotic division results in 4 haploid cells called spermatids
5) Spermatids then differentiate in the tubules of the testes to form spermatozoa, the active gametes capable of fertilising an ovum

40
Q

What is oogenesis

A

The formation of ova

41
Q

Describe the process of oogenesis

A

1) The diploid primodial germ cell divides several times by mitosis to form diploid oogonia
2) Most oogonia degenerate but only one continues to grow
3) The large cell is known as the primary oocyte
4) The oocyte undergoes meiosis
5) The first meiotic division results in un equal size and the larger size one is known as the secondary oocyte
6) The smaller sized one is known as the first polar body
7) oocytes at this stage do not divide until after ovulation

42
Q

What do we call ova in the ovaries

A

secondary oocytes

43
Q

When is the second meiotic division completed

A

After fertilisation occurs

44
Q

What does the secondary oocytes divide to form

A

The haploid ovum and another polar body

45
Q

What does the first polar body divide to form

A

Two more polar bodies

46
Q

Whats the one function of the polar bodies

A

To receive the chromosomes in the meiotic divisions

47
Q

Charecteritics of male gametes (spermozoa)

A

.50um long
.must remain in suspension in the semen so they can be transported through the female reproductive tract
.penetrate the protective barrier around the ovum and deliever the male haploid genome safely

48
Q

Charecteritics of female gametes (Ova)

A

.0.1nm across
.Contaoin food for development if embryo
.large food stores

49
Q

why is the formation of gametes in flowering plants more complex

A

Because plants have two phases to their life cycle

50
Q

What are the two phases to the plant’s life cycle

Explain what each one means

A

The sporophyte generation
.diploid
.produces spores by meiosis

The gametophyte generation
.Haploid
.gives rise to the gametes in mitosis

51
Q

What is the main body of the plant that we see

A

the diploid sporophyte

52
Q

What are the haploid gametophytes reduced to

A

Parts of the contents of the anther and the ovary

53
Q

What does each anther contain

A

Four pollen sacs where pollen grain develops

54
Q

What is there in each pollen sac

How do they divide

A

Large numbers of microspore mother cells

They’re diploid and divide via meiosis to form haploid microspores

55
Q

What are the gametes formed from in plants

What do they contain

A

From the microspores by mitosis

Two haploid nuclei, tube nucleus, and the generative nucleus

56
Q

What’s the function of the tube nucleus

A

Producing a pollen tube that penetrates through stigma, style, and ovary and into the ovule

57
Q

How are new individuals formed in plants

A

the generative nucleus fuses with the nucleus of the ovule

58
Q

What does meiosis result in plants

A

The formation of a relatively small number of ova contained within ovules inside the ovary

59
Q

Where is the ovule attached

A

To the wall of the ovary by a pad of a special tissue called the placenta

60
Q

What is the nucellus

A

A complex structure of integuments that form around tissues

61
Q

Why do diploid megaspores mother cells divide by meiosis

A

To give rise to four haploid megaspores

62
Q

Wat di the megaspore undergo

What does this result in

A

Three mitotic divisions

Results in an embryo sac containing an egg cell, two polar nuclei, and various other small cells

63
Q

What is pollination

A

The transfer of pollen from the anther to the stigma, often from one flower to another

64
Q

What are the two main categories in which animals make sure gametes meet

A

1) External fertilisation

2) Internal fertilisation

65
Q

What is External fertilisation

What species is this common in

A

The process of fertilisation in which the female and male gametes are released outside of the parental bodies to meet and fuse in the environment

aquatic species

66
Q

What is internal fertilisation

A

The fertilisation of the female gamete by he makes gamete takes place inside the body of the mother

67
Q

Which lasts longer the:

sperm or ovum

A

Sperm lasts much longer

68
Q

What happens as the sperm moves through the female reproductive tract

A

The acrosome region matures so it is able to release enzymes and penetrate the ovum

69
Q

What is the ovum released at ovulation

What is it surrounded by

A

secondary oocyte with one polar body

The protective gel-like layer known as zona pellucida

70
Q

when is the acrosome reaction triggered

A

As soon as the sperm goes head to head with the ovum

71
Q

what do the enzymes release from the acrosomes digest

A

it digests the follicle cell and the zona pellucida

72
Q

What happens when the protective layer is weakened by many sperm cells

A

Eventually, one sperm cell will wiggle its way through and touch the surface membrane of the oocyte

73
Q

What happens when the sperm touches the surface membrane of the oocyte

A

The oocytes complete its second meiotic division providing a haploid egg nucleus to fuse with the haploid male nucleus

74
Q

What would happen if more than one sperm enters the egg

A

It will be fertilised bu too many sperms (polyspermy)and would produce a nucleus containing too many sets of chromosomes

75
Q

What prevents more than one sperm entering the egg

How long does this last

A

The ion channels in the cell membrane of the ovum open and close so that the inside of the cell, instead of being electrically negative with respect to the outside, becomes positive

Until the tough fertilisation membrane forms around the fertilised ovum

76
Q

What part of the sperm fertilises with the egg

A

The head

77
Q

What happens once the head of the sperm is inside the ovum

A

It absorbs water and swells, releasing its chromosomes to fuse with those of the ovum and forms a diploid zygote

78
Q

Where is the male gamete contained within plants

A

The pollen grain

79
Q

where is the female gamete embedded

A

Deep in the tissue of the ovary

80
Q

How does the fertilisation in plants take place

A

.The pollen grain lands on the surface of the stigma of the flower during pollination.
.The molecule on the surface of the pollen grain and the stigma interact
.If they recognize each other as being from the same species the pollen grain begins to grow or germinate.
.Germination will take place if they are the same species but from different plants
.A pollen tube begins to grow out from the tube cell of the pollen grain through the stigma into the style
.Tip of the pollen produces a hydrolytic enzyme to digest the tissue of the style, so pollen tube can make its way down between the cells
.Digestive tissue =nutient source of the pollen tube as it grows
.As the pollen tube grows down towards the ovary, the generative cell containing the generative nucleus travels down it
.The nucleus of this cell divide via mitosis as it moves down the tube to form two male nuclei
.Pollen tube grows through the ovary to reach an ovule and eventually the tip of the pollen tube passes through the micropyle of the ovule
.Two male nuclei are passed into the ovule so that fermentation can occur

81
Q

What is Double fermentation

A

The process that occurs in plants in which one male nucleus fuses with the nuclei of the two polar nuclei to form the endosperm nucleus and the other fuses with the egg cell to form the diploid zygote

82
Q

What is totipotent

Give an example

A

A cell is able to develop into all different cell types

A fertilised egg cell or zygote

83
Q

What is the first step following fertilisation

Explain this process

A

Cleavage
A process involving a special type of mitosis with no interphase that results in a mass of a small, undifferentiated cell

84
Q

When does cleavage happen

A

As the embryo travels down the oviduct

85
Q

What is a result of the cleavage

A

A mass of small, identical and undifferentiated cells forming a hollow sphere known as he blastocyte

86
Q

What is a blastocyte

How long does this process take

A

A hollow ball of cells formed around five days of fertilisation

In humans, it takes 5-6 days

87
Q

What is an embryonic stem cell

A

Cells in the early embryo that have the potential to form many other types of cells

88
Q

What is meant by pluripotent

A

A cell is able to develop into most different cell types

89
Q

What are pluripotent embryonic stem cells

A

Embryonic stem cells that can form many other types of cells

90
Q

What is meant by cell determination

A

The predestination of cells to become particular types of tissues from early in the development of the embryo

91
Q

What is meant by differentiate

A

Develop into significant types of cells

92
Q

What is cell determination closely linked to

A

The position of the cells in the embryo

93
Q

What happens as cell differentiation takes place

A

Different types of cells produce more and more protein specific to their cell type

Biology 2.4 (1 decks)

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