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biology > genetics 2 - meiosis > Flashcards

genetics 2 - meiosis Flashcards

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1
Q

What is a homologous chromosome?

A

Two chromosomes carrying the same genes but not the same alleles. One is originated from the sperm, and the other is originated from the ovum.

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2
Q

What is a chiasma?

A

The point of contact between two chromatids exchanging genetic information

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3
Q

What is meiosis?

A

A special cell division that occurs in the germ cells for reproductive purposes

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4
Q

What are the two processes of meiosis?

A

Genetic reduction and genetic recombination

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5
Q

Where does meiosis occur?

A

The ovaries/testes

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6
Q

What does meiosis create?

A

Genetically different haploid gametes.

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7
Q

What is fertilization?

A

The fusion of haploid male and female gametes which forms a diploid zygote

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8
Q

What is a zygote?

A

A group of cells that are going to become the child

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9
Q

What happens in interphase?

A

G1, S, and G2 phases occur before meiosis. DNA replication takes place, parent cells contain duplicated chromosomes, and the sister chromatids are held together at the centromere.

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10
Q

What happens in prophase I?

A

Synapsis, the homologous chromosomes cross-over to exchange genes, the chromatin condense. The cell has two centrosomes which move to the poles and form mitotic spindles.

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11
Q

What happens in Metaphase I?

A

The spindle fibres attach to the centromere of each chromosome, and the homologous pairs of chromosomes line up at the equatorial plate. The chromosomes of maternal and paternal origins are at opposite poles.

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12
Q

What does the chromosomes lining up have to do with gametes?

A

Depending on how the pairs of homologous chromosomes line up, you can have a different number of combinations of the genetically distinct gametes (2^n, n=number of haploid chromosomes). Since humans have 23 haploid chromosomes, we can make up to 2^23 combinations=8,366,608

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13
Q

What happens in anaphase I?

A

The homologous chromosomes separate to opposite poles of the cell and are pulled apart by the shortening of the spindle fibres. Here, it goes from diploid to haploid (92 chromatids –> 46 chromatids, 46 chromosomes –> 23 chromosomes)

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14
Q

What happens in telophase I?

A

The homologous chromosomes uncoil and the spindle fibres disappear. The nuclear envelope and nucleolus reappear, and cytokinesis follows.

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15
Q

When does DNA duplication take place?

A

During the S phase of interphase.

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16
Q

When does synapsis occur? Prophase I

A

Prophase I

17
Q

When do chromatids condense?

A

Prophase I and II

18
Q

When do homologous chromosomes cross-over to exchange genetic information?

A

Prophase I

19
Q

When do the two centrosomes move to the poles and form mitotic spindles?

A

Prophase I and II

20
Q

When do spindle fibres attach to the centromere of each chromosome?

A

Metaphase I

21
Q

When do the pairs of homologous chromosomes line up at the equatorial plate?

A

Metaphase I

22
Q

When do the chromosomes of maternal and paternal origins go to different poles?

A

Metaphase I

23
Q

When do the homologous chromosomes separate to opposite poles of the cell?

A

Anaphase I

24
Q

When are the homologous chromosomes pulled apart by the shortening of spindle fibres?

A

Anaphase I

25
Q

When do the chromosomes and chromatids go from diploid to haploid?

A

Anaphase I

26
Q

When does the nuclear envelope and nucleolus reappear?

A

Telophase I

27
Q

When do the homologous chromosomes uncoil?

A

Telophase I

28
Q

When do the spindle fibres disappear?

A

Telophase I

29
Q

What happens to the chromosomes and chromatids after anaphase I?

A

92 chromatids –> 46 chromatids 46 chromosomes –> 23 chromosomes

Diploid –> Haploid

30
Q

Difference between meiosis I and II?

A

During meiosis I homologous chromosomes separate, and in meiosis II, sister chromatids separate

31
Q

During meiosis, genetic variation in the gametes is achieved by

A

Crossing over and independent assortment

32
Q

What happens in prophase II?

A

The chromatin coils to condense into chromosomes, the centrosomes appear at opposite ends of the cell and form spindle fibres, and the nuclear membrane and nucleolus disappear

33
Q

Difference between prophase I and II?

A

Prophase I includes the separation of homologous chromosomes, while prophase II involves the separation of sister chromatids. In prophase I, homologous chromosomes cross-over, while they don’t in prophase II.

34
Q

What causes genetic variation?

A

Crossing-over and independent assortment of homologous chromosomes and chromatids.

35
Q
A

biology (12 decks)

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