Lesson 20: Meiosis Flashcards

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1
Q

What is synapsis?

A

The homologous chromosomes come together

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2
Q

What is a tetrad?

A

The synapse pairs (one chromosome inherited from the mother and one from the father)

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3
Q

What is a chiasma?

A

An X-shaped structure.
–The point at which the homologous chromosomes overlap, where chromosomes exchange segments resulting in genetic variability in daughter cells

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4
Q

What happens during Prophase 1?

A

Synapsis and chromosome segment exchange

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5
Q

What happens during Metaphase 1?

A

Chromosome pairs line up along the centerline of the cell DOUBLE-FILE (because the chromosome pairs are still synapsed)

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6
Q

What happens during Anaphase 1?

A

Synapsed chromosomes separate. Chromosome pairs move to opposite ends of the cell (homologous chromosomes are separated as opposed to the separation of sister chromatids in Mitosis)

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7
Q

What happens during Telophase 1?

A

Chromosomes reach the poles of the cell

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8
Q

How do you count the number of chromosomes in a cell?

A

By counting the number of centromeres present in the cell

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9
Q

What happens during Prophase 2?

A

Duplicated chromosomes begin to move to the middle of the cell

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10
Q

What happens during Metaphase 2?

A

The chromosomes line up along the center line of the cell

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11
Q

What happens during Anaphase 2?

A

The sister chromatids move to opposite ends of the cell becoming independent chromosomes

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12
Q

What happens during Telophase 2?

A

The chromosomes reach the poles of the cell

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13
Q

What type of division is Meiosis 1 known as?

A

A reduction division because it results in a reduction in the number of chromosomes

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14
Q

What is the major difference between Mitosis and Meiosis 2?

A

In Meiosis 2 the cell only has 1 complete set of chromosomes (is haploid), whereas in Mitosis there are two complete sets of chromosomes (diploid)

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15
Q

Is Meiosis 2 considered a reduction division?

A

NO, only in Meiosis 1 are the number of chromosomes divided in half

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16
Q

What happens during Prophase 1 in both Meiosis and Mitosis?

A

Chromosomes become visible

17
Q

How many cells result from Meiosis?

A

4

18
Q

How many cells result from Mitosis?

A

2

19
Q

What is segregation?

A

The process by which homologous pairs become segregated (there is a 50% chance that a daughter cell will inherit the maternal chromosome and a 50% chance that it will inherit the paternal chromosome)

20
Q

What is crossing over or recombination?

A

The process by which segments of a chromosome are exchanged with its corresponding homologous (non-sister chromatid) chromosome

21
Q

Suppose the gene for protein XYZ is on chromosome 17. How many copies of gene XYZ are present in a cell in the G1 phase? At the beginning of mitosis?

A
  • -Two. One on each chromosome of the homologous pair

- -Four. One on each sister chromatid of each chromosome of the homologous pair

22
Q

What main process happens during Meiosis 1?

A

Homologous chromosomes are separated

23
Q

What main process happens during Meiosis 2?

A

Sister chromatids are separated

24
Q

Suppose the gene for protein XYZ is on chromosome 17. How many copies of gene XYZ are present in a cell in G1 phase?

A

Two. One on each chromosome of the homologous pair (one from each parent)

25
Q

What is the formula used to calculate the number of potential combinations for a given chromosome number (assuming no crossing over)?

A

2^n, where n=number of homologous pairs

26
Q

After telophase 1 of Meiosis, what is the chromosomal makeup of each daughter cell?

A

Haploid; and the chromosomes are each composed of two chromatids

27
Q

What is Meiosis?

A

The process in the nucleus which divides the chromosome number in half

28
Q

What are homologous chromosomes?

A

Chromosomes which contain genes which regulate the same phenotypes, but may or may not have the same genotype
–One chromosome from the father and one from the mother