Meiosis Flashcards

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1
Q

Meiosis def

A

Type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes.

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2
Q

Similarities and differences between meiosis and mitosis

A

Both begin after the cell has progressed through the G1, S, and G2 phases of the cell cycle. Both have the same phases, prophase, metaphase, anaphase and telophase.
Meisiosis involves two divisions, meiosis 1 (two cells with n) and meiosis 2 (4 cells with n) and mitosis only has one.

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3
Q

Stages of prophase 1

A
  1. Leptotene- chromosomes contract, visible
  2. Zygotene- chromosomes condense, homologous pairs pair up and begin synopsis.tetrad
  3. Pachytene- chromosomes become shorter and thicker synaptomal complex develops
  4. Diplotene- centromeres of the paired chromosomes move apart. Homologous pairs remain attached at chias,tats. Result of crossing over
  5. Diakinesis- synaptonemal complex completely disappears
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4
Q

Metaphase 1 def

A

Homologous pairs of chromosomes align along the metaphase plate. Microtubule from each pole attach to each chromosome of the homologous pair.

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5
Q

Anaphase 1

A

Separation of homologous chromosomes. The two chromosomes of a pair are pulled toward opposite poles . Sister chromatids remain attached and travel together.

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6
Q

Telophase 1 def

A

The chromosomes arrive at the spindle poles and cytoplasm divides

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7
Q

Interkinesis def

A

Period between meiosis 1 and 2 where the nuclear membrane reforms around the chromosome clustered at each pole, the spindle breaks down and the chromosomes relax

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8
Q

Prophase 2 def

A

Events of interkinesis are reversed: chromosomes recondense, spindle reforms and nuclear envelope breaks down.

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9
Q

Metaphase 2

A

The individual chromosomes line up on the metaphase plate, with sister chromatids facing opposite poles.

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10
Q

Anaphase 2 def

A

The kinetochores of the sister chromatids separate and are pulled apart to opposite poles. Each chromatid is now a distinct chromosome.

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11
Q

Telophase 2 def

A

The chromosomes arrive at the spindle poles, nuclear envelope reforms, cytoplasm divides and chromosomes relax, no longer visible.

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12
Q

Sources of genetic variation in meiosis

A

Each original cell produces four cells.
Chromosomes number is reduced by half
Cells produces are genetically different from one another and from parent cell.
Genetic differences result from crossing over and random separation of homologous chromosomes.

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13
Q

Crossing over def

A

Crossing over takes place in prophase 1, Initiated in zygotene. Refers to the exchange of genetic material between two non sister chromatids. Crossing over is the basis for intrachromosomal recombination, creating new combinations of alleles on a chromatid.

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14
Q

Random separation of homologous chromosomes def

A

Occurs during anaphase 1 after their random alignment in metaphase 1. When the chromosomes pairs separate in anaphase, the separation is random and many different outcomes are possible.
Shuffles alleles on different chromosomes into new combinations.

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15
Q

Spermatogenesis def

A

The production in a male animal takes place in the testes.

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16
Q

Spermatagonia def

A

Diploid cells produced by spermatogenesis

17
Q

Primary spermatocyte def

A

Spermatagonium entered into prophase 1, diploid because the homologous pairs have not yet separated. Each primary spermatocyte completes meiosis 1, giving rise to two haploid secondary coermatocytes that undergo meiosis 2, producing two haploid spermatids.

18
Q

Spermatids def

A

Formed after meiosis 2. Haploid, 4 produces, mature and develop into sperm.

19
Q

Oogenesis def

A

Production of female gametes in animals. Takes place in ovaries.

20
Q

Oogonia

A

Diploid primordial germ cells divide mitotically to produce oogonia.

21
Q

Primary oocytes

A

Diploid cells in prophase 1. Each primary oocyte completes meiosis 1 and divides.

22
Q

Secondary oocyte def

A

Haploid cell. Most of the cytoplasm is allocated in one of the two haploid cells- the secondary oocyte.

23
Q

First polar body def

A

The smaller cell, haploid but only contains a small part of the cytoplasm. May not divide further.

24
Q

Ovum def

A

Meiosis 2 occurs and again cytokinesis is unequal resulting in a larger cell- ovum. The ,ature female gamete.

25
Q

Second polar body def

A

Smaller cell. Only a small amount of cytoplasm, the rest went to the ovum.