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MED101 BIOLOGY > Meiosis > Flashcards

Meiosis Flashcards

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1
Q

What is asexual reproduction?

A

A single individual passes genes to its offspring without the fusion of gametes.

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2
Q

What is a clone?

A

A group of genetically identical individuals from the same parent.

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3
Q

What type of cell division are gametes produced by?

A

Meiosis

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4
Q

What is the fertilised egg called?

A

Zygote

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5
Q

Which type of cells does the zygote produce by mitosis?

A

Somatic cells

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6
Q

What is the cell division process that reduces the chromosome number by half?

A

Meiosis

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7
Q

What are the 2 cell types in humans?

A

Somatic cells and Gametes

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8
Q

How many sets of chromosomes do somatic cells have?

A

2 sets - 46 chromosomes (23 pairs)

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9
Q

How many sets of chromosomes do gametes have?

A

One set of chromosome - 23 chromosomes

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10
Q

What is a karyotype? SOS

A

An ordered display of the pairs of chromosomes from a cell

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11
Q

What are the 2 chromosomes in each pair called?

A

Homologous chromsomes

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12
Q

What are homologous chromosomes? SOS

A

Chromosomes are the same length and shape and carry genes controlling the same inherited characters. But they may carry different alleles of those genes. In each pair, there is a paternal homolog and a maternal homolog.

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13
Q

Describe the 23 pairs of chromosomes

A

Human Karyotype :
22 pairs - autosomes
23rd pair - sex chromosomes - XX : female XY : male

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14
Q

What do each replicated chromosome contain after DNA replication?

A

2 identical sister chromatids

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15
Q

What are the gonads in humans?

A

Ovaries and testes

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16
Q

Difference between animals and other organisms cell division cycles ?

A

Animals : only diploid divides by mitosis
Other organisms : both haploid and diploid cells divides by mitosis.
In all organisms only diploid cells can undergo meiosis.

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17
Q

What process happens after meiosis and mitosis?

A

DNA replication

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18
Q

What are the 2 sets of cell division meiosis takes place in?

A

Meiosis I and Meiosis II

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19
Q

What is the final amount of daughter cells formed by the end of meiosis?

A

4 daughter cells

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20
Q

What happens in meiosis I?

A

Pairing and separation of homologous chromosomes.
Results in 2 haploid daughter cells with replicated chromosomes

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21
Q

What happens in meiosis II ?

A

Sister chromatids separation.
4 haploid daughter cells with unreplicated chromosomes

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22
Q

What is the chromosome number after meiosis I in humans?

A

23 chromosomes

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23
Q

What is the chromatid number after meiosis I in humans?

Study These Flashcards
A

46 chromatids because there is 2 chromatids per chromosomes

24
Q

What is the chromosome number after meiosis I in humans?

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A

23 Chromosomes

25
What is the chromatid number after meiosis II in humans?
23 chromatids - chromosomes only have 1 chromatid each then
26
What process is Meiosis I preceded by?
Interphase
27
What are the 3 processes in interphase?
G1 , S , G2
28
What do chromosomes duplicate to form after DNA replication during interphase?
Sister chromatids
29
Describe sister chromatids
Genetically identical and joined at the centromere
30
What happens to the centrosome during interphase?
It replicates forming 2 centrosomes
31
What are the 4 phases of meiosis I?
Prophase I Metaphase I Anaphase I Telophase I and cytokinesis
32
What happens during Prophase I?
Chromosomes begin to condense Homologous chromosomes pair Each pair of chromosomes forms a tetrad
33
What is a tetrad?
X-shaped regions which have one or more chiasmata where crossing over occurs.
34
What is genetic recombination?
Another word for crossing over. Exchange of DNA segments between non-sister chromatids of homologous chromosomes. This is a random process.
35
What happens in metaphase I?
Tetrads line up at the metaphase plate with each homologous chromosome facing each pole.
36
What are the microtubules attached to?
Microtubules from one pole are attached to the kinetochore of one chromosome of each tetrad. Microtubules from the other pole are attached to the kinetochore of the other chromosome.
37
What happens in Anaphase I?
Homologous pairs of chromosomes separate. Each homologous chromosome moves towards the opposite pole. Sister chromatids remain attached at the centromere and move as one unit toward the pole.
38
What is the chromosome and chromatid composition in the cells in telophase I and cytokinesis?
Each half of the cell has a haploid set from chromosomes. Each chromosome still consists of two sister chromatids.
39
What happens in cytokinesis?
Cytoplasm divides to form 2 haploid daughter cells. Animal cells - cleavage furrow forms Plant cells - a cell plate forms
40
What are the 4 phases in Meiosis II?
Prophase II Metaphase II Anaphase II Telophase II and cytokinesis
41
What happens in early prophase II?
Spindle apparatus forms
42
What happens in late prophase II?
Chromosomes move toward the metaphase plate
43
What happens in Metaphase II?
Sister chromatids are arranged at metaphase plate. Kinetochores of sister chromatids attach to microtubules extending from opposite poles. If crossing over has occurs, the 2 sister chromatids of each chromosome may no longer be genetically identical.
44
What happens in Anaphase II?
Sister chromatids separate. Sister chromatids of each chromosome now move as 2 newly individual chromosomes towards opposite poles.
45
What happens at Telophase II?
Chromosomes arrive at opposite poles. Nuclei reform and chromosomes decondense
46
What happens in cytokinesis?
Cytoplasm divides
47
Compare mitosis and meiosis
Mitosis conserves the number of chromosome sets, producing cells that are genetically identical to the parent cell. Meiosis reduces the number of chromosomes sets from diploid to haploid, producing cells that differ genetically from each other and the parent cell. Mitosis produces 2 diploid cells from 1 diploid cell. Meiosis produces 4 haploid cells from 1 diploid cell.
48
What are the 4 mechanisms that contribute to genetic variation?
Genetic recombination (crossing over) Independent assortment of chromosomes Random fertilisation Mutations
49
What does genetic recombination produce?
Recombinant chromosomes which combine DNA inherited from each parent
50
When does crossing over begin?
In the beginning of prophase I
51
What happens in crossing over?
Homologous portions of 2 non-sister chromatids exchange places
52
How does crossing over contribute to genetic variation?
By combining DNA from 2 parents into a single chromosome
53
If crossing over does occur, what do the 4 daughter cells produced in meiosis consist of?
1 paternal homologue, 1 maternal homologue, 2 recombinant chromosomes
54
What occurs in independent assortment of chromosomes?
Each pair of chromosomes sorts maternal and paternal homologues into daughter cells independently of the other pairs.
55
How does random fertilisation contribute to genetic variation?
Any sperm can fuse with any ovum.
56
How do mutations contribute to genetic diversity?
Changes the organism's DNA. They create different versions of genes (alleles). When these alleles are reshuffled they contribute to genetic variation.
57
What is natural selection?
Accumulation of genetic variations favoured by the environment

MED101 BIOLOGY (6 decks)

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