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PB Biology💜 > Cell Division > Flashcards

Cell Division Flashcards

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1
Q

Why do cells divide?

A

They get too big and don’t have enough surface area for volume, to replace dead or damaged cells and grow, or to reproduce new organisms for single-celled organisms.

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2
Q

Asexual cell reproduction vs. sexual cell reproduction

A

In asexual, one cell duplicates its DNA to split in two. Mitosis. In sexual, the DNA is exchanged and the offspring have different DNA than parents. Meiosis.

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3
Q

How many chromosomes do humans have?

A
  1. 23 from each parent.
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4
Q

What is the cycle of cell reproduction overall?

A

Gametes–>fertilization–>zygote–>mitosis–>somatic cells–>meiosis–>gametes

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5
Q

What is a gamete?

A

A cell that is either egg or sperm.

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6
Q

What is a zygote?

A

A fertilized cell with the full number of chromosomes. It undergoes mitosis to form all of our DNA.

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7
Q

What is mitosis?

A

Asexual reproduction. Division of cells/cell nucleus to produce somatic cells.

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8
Q

What are somatic cells?

A

They are body cells with specialized functions. They go through meiosis to produce gametes.

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9
Q

What are somatic cells without jobs called?

A

Stem cells. These can turn into a variety of cells.

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10
Q

What is meiosis?

A

Sexual reproduction of somatic cells in gonads to produce gametes.

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11
Q

What are chromosomes?

A

Two sister chromatids joined by a centromere. Organized, tightly-coiled DNA structures. (DNA is only tightly coiled during mitosis.) They exist as homologous pairs.

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12
Q

What is chromatin?

A

Spread-out DNA that’s loosely coiled.

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13
Q

When is the only time DNA is tightly coiled?

A

Mitosis.

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14
Q

What three stages does interphase consist of?

A

G1, Synthesis, and G2

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15
Q

What stage of the cell cycle does the cell spend the most time in?

A

Interphase. 2/3 of its lifetime.

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16
Q

Why is DNA spread out during interphase?

A

To be able to access the DNA information.

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17
Q

What happens to the DNA during interphase? Why?

A

It duplicates so that each daughter cell gets one copy of DNA from mitosis.

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18
Q

What are the stages G1 and G2?

A

They consist of the growth and synthesis of proteins and RNA.

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19
Q

What is synthesis?

A

The second stage of interphase in which DNA is replicated.

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20
Q

What does DNA replication refer to?

A

Copying the chromosome to make two identical sister chromatids during interphase.

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21
Q

What connects the two sister chromatids at the center?

A

The centromere.

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22
Q

How many chromosomes do humans have?

A

46; 23 from each parent.

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23
Q

What is a homologous pair?

A

How chromosomes exist. A set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization. The genes are the same, but the specifics may be different, with one chromosome from mom and one from dad.

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24
Q

Diploid

A

2n. The total number of chromosomes. Humans have 46.

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25
Q

Haploid

A

n. The total number of homologous pairs. Humans have 23.

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26
Q

Do most of our cells have diploid numbers or haploid numbers?

A

Diploid.

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27
Q

How many chromosomes do bacteria have?

A

One.

28
Q

What are the stages of mitosis in order?

A

Prophase, metaphase, anaphase, telophase (and cytokinesis).

29
Q

Prophase

A

The first stage of mitosis. Nucleus begins to dissolve. Centrioles in animal cells migrate to opposite poles. Chromatin shortens and thickens into chromosomes. Spindle fibers start to appear.

30
Q

Metaphase

A

The second stage. Chromatids move toward the center and line up. The nucleus is completely gone. Centromeres of each chromatid attach to spindle fibers. Some spindle fibers attach from centriole to centriole.

31
Q

Anaphase

A

The third step. Spindle fibers contract, pulling apart sister chromatids. In late anaphase, the cell membrane of animal cells begins to pinch together; for plant cells, the cell plate starts to appear.

32
Q

Telophase

A

The fourth and final stage of cell division. Spindles begin to break down, chromatin is formed from DNA loosening, nucleus begins to reform, centrioles replicate. In plant cells, cell plate forms.

33
Q

Cytokinesis

A

Occurs during the end of telophase. Translates to “cell cutting.” The end of cell division including the division of the cytoplasm and the rest of the cell into two complete daughter cells. (Not really a step).

34
Q

Autosomes

A

Every chromosome except for the sex chromosome. Includes 1-22.

35
Q

Sex chromosomes

A

Chromosome 23. Determines gender. XX=female, XY=male.

36
Q

Does mitosis use diploid or haploid?

A

Diploid. 2n.

37
Q

Does meiosis use diploid or haploid?

A

Haploid. n.

38
Q

What is meiosis?

A

Cell division to produce gametes in the gonads.

39
Q

How many times does the cell divide in meiosis?

A

Twice.

40
Q

How many daughter cells are produced in meiosis?

A

Four.

41
Q

What does meiosis do with the number of chromosomes?

A

It must reduce it to the haploid number.

42
Q

What happens during prophase 1?

A

Synapsis, when homologous chromosomes move together to form a tetrad, and crossing over, in which DNA from sister chromatids breaks and switches places.

43
Q

What happens during metaphase 1?

A

Homologous pairs line up in the center and spindle fibers attach to centromeres.

44
Q

What happens during anaphase 1?

A

Spindle fibers shorten, homologous pairs are pulled to the poles, and the tetrads are separated.

45
Q

What happens during telophase 1?

A

The nuclear membrane may reform or cell may move quicly into meiosis 2. The chromosomes stay together, but the tetrads are broken as there are now two complete daughter cells. The centrioles replicate, and the chromosomes may uncoil.

46
Q

What is crossing over?

A

When the homologous chromosomes overlap and exchange parts of the chromosomes. The sister chromatids are different afterward.

47
Q

What are the steps of meiosis 1?

A

Prophase 1, metaphase 1, anaphase 1, and telophase 1.

48
Q

What are the steps of meiosis 2?

A

Prophase 2, metaphase 2, anaphase 2, and telophase 2.

49
Q

What happens during prophase 2?

A

The nuclear membranes of the two daughter cells disappear, their centrioles migrate to opposite poles, the chromatin recondenses, and the spindle fibers appear.

50
Q

What happens during metaphase 2?

A

The chromosomes line up. The spindle fibers attach to the centromeres of the chromosomes. (Each daughter cell has 1/2 the number of chromosomes that the parent cell started with.)

51
Q

What happens during anaphase 2?

A

The spindle fibers contract, pulling apart sister chromatids.

52
Q

What happens during telophase 2?

A

There are now four daughter cells that are separated. The number of sister chromatids is cut in half again. There is genetic variation in the four daughter cells because of the crossing over during prophase 1.

53
Q

If a somatic cell starts with 12 chromosomes, how many tetrads will be formed during prophase 1? How many homologous pairs are there?

A

6 tetrads, 6 homologous pairs.

54
Q

If a somatic cell starts with 10 chromosomes, how many will each daughter cell have after telophase 1 and after telophase 2?

A

After telophase 1, each will have five chromosomes. After telophase 2, each will have 5 chromatids, which is basically five half-chromosomes.

55
Q

Which step in meiosis determines the combination of chromosomes present in the gamete and why?

A

Metaphase 1 because however the tetrads line up during metaphase determines which cell will get which chromosomes when they are separated. This is random.

56
Q

If n=3 by the end of telophase 2, how many full chromosomes did the parent cell start with?

A

6 chromosomes.

57
Q

How do you find the number of possible gamete combinations?

A

2^n.

58
Q

Why is meiosis so important? (Hint: it’s one of the differences between meiosis and mitosis.)

A

Meiosis is so important because it provides genetic variation.

59
Q

What are the main differences between mitosis and meiosis?

A

Mitosis: Zygote produces somatic sister cells, 2 daughter cells are made, diploid number, 4 steps, identical cells produced. Meiosis: somatic cells produce gametes, 4 daughter cells produced, haploid number, 8 steps, genetic variation.

60
Q

What is female meiosis called?

A

Oogenesis.

61
Q

What is male meiosis called?

A

Spermatogenesis.

62
Q

What does it mean for unequal division to occur in oogenesis?

A

It means that although there are four daughter cells produced, there is only one ootid/ovum (egg) produced; the other 2-3 cells are polar bodies. They are nonviable, meaning they cannot be fertilized.

63
Q

Which of the four daughter cells in female meiosis (oogenesis) takes the mitochondria?

A

The big cell: the egg/ootid. This is how mitochondrial DNA is passed down from the mother.

64
Q

What are the differences between spermatogeneis and oogenesis?

A

Spermatogenesis: equal division (four spermatid), from puberty till death, billions of sperm produced; oogenesis: starts before birth, from puberty till menopause, around 400 eggs produced, unequal division.

65
Q

What is the advantage of equal division in spermatogenesis?

A

There are many sperm to make the journey to fertilize the egg.

66
Q

What are the advantages of unequal division in oogenesis?

A

The larger cell, the ovum, has many nutrients for the journey. Also, older women cannot get pregnant, which is good because at that age pregnancy is painful and birth defects may occur.

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