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BIO311D: Biology > MEIOSIS AND SEXUAL LIFE CYCLES > Flashcards

MEIOSIS AND SEXUAL LIFE CYCLES Flashcards

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1
Q

What are gametes?

A

Gametes are reproductive cells that act as vehicles that transmit genes from one generation to the next

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2
Q

What are the only haploid cells in the human body?

A

Gametes

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3
Q

How are gametes produced?

A

Gametes are the only cells in the human body not produced by mitosis. They develop from specialized cells called germ cells in the gonads

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4
Q

What are somatic cells?

A

Somatic Cells are all the cells of the body minus the gametes and their porecursors

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5
Q

What is asexual reproduction?

A

Offpring from asexual reproduction have a single parent and are genetical copies which receive copies of all its genes without the fusion of gametes

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6
Q

What is sexual reproduction?

A

Offspring of sexual reproduction are producted by 2 parents and inherit unique gene combinations

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7
Q

What are sex chromosomes?

A

X and Y chromosomes

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8
Q

What are autosomes?

A

Other chromosomes minus X and Y

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9
Q

What are diploid cells?

A

Diploid cells are any cell with 2 chromosome sets (2n)

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10
Q

What is the diploid number for humans?

A

2n = 46

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11
Q

What are haploid cells?

A

Any cell containing a single set of chromosomes (n)

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12
Q

What is the haploid number for humans?

A

n = 23

This set of 23 chromosomes consists of 22 autosomal chromosomes plus a single sex chromosome

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13
Q

What is fertilization?

A

The fusion of a haplold sperm from the father with a haploid egg from the mother

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14
Q

What does fertilization do to the number of chromosome sets?

A

The number of chromosome sets is doubled from 1 to 2

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15
Q

What is the result of fertilization?

A

Fertilization results in a zygote, a diploid cell which received 2 haploid sets of chromosomes bearing genes representing the maternal and paternal family lines

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16
Q

What is the alternation of generations in a sexual life cycle?

A

The alternation of generations is a second type of life cycle exhibited by plants and some algae

Incudes both diploid and haploid stages that are multicellular. Cells of the gametophyte give rise to gametes by mitosis; fusion of 2 haploid gametes results in a diploid zygote, which develope into the next sporophyte generation

17
Q

What is meiosis?

A

Meiosis is cell division used for gamete formation. It reduced the number of chromosome sets from 2 to 1 in the gametes, counterbalancing the doubling that occurs in fertilization; it produces cells that differ genetically differ from their parents and each other

18
Q

What does meisos do to the number of chromosome sets?

A

The number of chromosome sets are reduced from 2 to 1

19
Q

What is the result of meisos?

A

Human sperm and eggs are returned to a haploid (n) state

20
Q

How many daughter cells are produced by mitosis?

A

2

21
Q

What events are unique to meiosis?

A
  1. Synapsis - during prophase I, replicated homologous chromosomes line up and become physically connected by a zipper-like protein complex called the synaptonemal complex
  2. The alignment of homologous pairs at the metaphase plate during metaphase I
    1. In meiosis, homologous pairs line up
    2. In mitosis, individual chromosomes line up
  3. The separation of homologous during anaphase I
    1. In meiosis, duplicated chromosomes of each homologous pair move towards opposite poles, but the sister chromatids remain attached
    2. In mitosis, the sister chromatids separate
22
Q

What is mitosis?

A

Mitosis conserves the number of chromosome sets and produced daughter cells genetically identical identical to their parent cells and each other

23
Q

How many daughter cells are produced by meiosis?

A

4, each with only half as many chromosomes as th parent cell (1 set rather than 2)

24
Q

What mechanisms contribute to genetic variation arising from sexual reproduction?

A
  1. Independent assortment of chromosomes - random orientation of homologous pairs at metaphase plate during metaphase I
    1. 50/50 chance that a daughter cell of meiosis I will get the maternal chromosomes of a certain homolog pair, and a 50/50 chance for the paternal chromosome
  2. Crossing over - produces recombinant chromosomes with new combinations of maternal and paternal alleles
    1. Combines inherited DNA from 2 parents into 1 chromosome
  3. Random fertilization - any sperm can fuse with any egg
25
Q

What separates in meiosis I?

A

Homologous chromosomes

26
Q

What separates in meiosis II?

A

Sister chromatids

27
Q

What happens during prophase I?

A

During prophase I, chromosomes begin to condense and pair up. Tetrads are formed by synapsis of homologous chromosomes, and crossing over occurs, which can be seen as chiasmata, allowing the exchange of DNA material

28
Q

What happens during metaphase I?

A

During metaphase I, homologous pairs (not individual chromosomes) line up at the metaphase place in random orientation for separation

29
Q

What happens during anaphase I?

A

During anaphase I, the homologues are pulled apart and moved towards opposite ends of the cell (sister chromatids remain attached)

30
Q

What happens during telophase I?

A

During telophase I, chromosomes arrive at opposite poles of the cell and 2 haploid daughters are produced through cytokinesis, each containing 2 chromatids

31
Q

What happens during prophase II?

A

During prophase II, chromosomes condense and spindle microtubules begin to capture chromosomes

32
Q

What happens during metaphase II?

A

During metaphase II, the chromosomes line up individually along the metaphase plate

33
Q

What happens during anaphase II?

A

During anaphase II, the sister chromatids separate and are pulled towards opposite poles of the cell

34
Q

What happens during telophase II?

A

During telophase II, nuclear membranes form around each chromosome set and cytokinesis splits them into new cells, forming 4 haploid cells, each containing 1 chromatid

35
Q

What is the formula to detemine the number of chromosomal combinations possible for gametes?

A

2^n

36
Q

What is nondisjunction?

A

Nondisjunction is the failure of 1+ pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei

BIO311D: Biology (14 decks)

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