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Biology 108 Test #2 > Meiosis > Flashcards

Meiosis Flashcards

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1
Q

What is the definition of genetics?

A

The scientific study of heredity and variation.

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2
Q

What is the definition of heredity?

A

The transmission of traits from one generation to the next.

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3
Q

What is variation?

A

The differences in appearance that offspring show from parents and sibling.

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4
Q

How do we acquire our physical traits?

A

Not from our parents in a literal sense, but from our GENES.

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5
Q

What are genes?

A

These are the units of heredity.

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6
Q

What are genes made of?

A

Segments of DNA.

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7
Q

What do genes control?

A

Traits.

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8
Q

How are genes passed to the next generation?

A

through reproductive cells (gametes).

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9
Q

What is the region where a specific gene is located on a chromosome called?

A

a locus

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10
Q

For a human, how many sets of chromosomes are received from each parent? This gives us a total of how many sets? How many pairs?

A

we receive 23 sets from each parent.

We have 46 total sets of chromosomes

23 pairs of chromosomes.

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11
Q

What is the definition of asexual reproduction?

A

one parent produces genetically identical offspring

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12
Q

what is the definition of a clone?

A

a group of genetically identical individuals from the same parent.

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13
Q

What is the definition of sexual reproduciton?

A

Two parents give rise to a genetically unique offspring with a combination of genes from the two parents.

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14
Q

What is a somatic cell?

A

any cell other than a gamete.

In humans these cells would all have 23 PAIRS of chromosomes.

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15
Q

What is the karyotype?

A

This is an ordered display of the pairs of chromosomes from a cell.

Cell must be in mitosis in order to be able to distinguish between chromosomes.

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16
Q

the human has 46 chromosomes made up of 23 pairs, what are the two chromosomes grouped to a pair called?

A

homologous chromosomes or homologs. (1 from mom and 1 from dad)

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17
Q

When are homologous chromosomes present in a somatic cell?

A

AT ALL TIMES

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18
Q

When would homologous pairs of chromosomes not be present?

A

IN A GAMETE.

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19
Q

Describe a homologous pair of chromosomes.

A

These chromosomes are the same length and carry genes that control the same traits (hair color, eye color).

SO..

Same sequence of GENES presents, but different sequence of DNA for each gene.

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20
Q

In a homologous chromosome each gene has a different sequence of DNA for the same trait, what are these different sequences called?

A

An allele

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21
Q

What are the two sex chromosomes labeled?

A

X and Y

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22
Q

What sequence of sex chromosomes does a human female have?

A

XX (homologous pair)

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23
Q

What sequence of sex chromosomes does a human male have?

A

XY

Y is shorter so wont be homologous.

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24
Q

So if 1 of 23 pairs of human chromosomes are called the sex chromosomes, what are the other 22 that don’t determine the sex called?

A

Autosomes.

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25
Q

Who determines the sex of offspring in humans?

A

MALES (they have the Y chromosomes)

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26
Q

What is the number of chromosomes in a single set represented by (haploid)? What would this be in humans?

A

n

n = 23 in humans

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27
Q

If a cell has two sets of each chromosome, what is it represented by (diploid)? What would this number be in humans?

A

2n

2n = 46 in humans

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28
Q

What happens in a cell where DNA synthesis occurs?

A

each chromosome is replicated. (STILL CONSIDERED 1 CHROMOSOME)

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29
Q

In a cell that has undergone DNA synthesis what is the end product for each chromosome?

A

each chromosome will consist of two sister chromatids. (STILL CONSIDERED ONE CHROMOSOME)

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30
Q

What is the glue that keep the two sister chromatids together called?

A

Cohesin

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31
Q

What is the haploid number for a human gamete (sperm or egg)?

A

n = 23

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32
Q

Each set of 23 chromosomes in a gamete contains?

A

1 sex chromosome

22 autosomes

33
Q

In a sperm, what is the potential sex chromosome?

What about in an egg?

A

Sperm - may be X or Y (male makes sperm, has X and Y sex chromosome)

Egg - only X (female gamete, females are XX)

34
Q

What is fertilization?

A

The union of male and female gametes.

35
Q

What is the product of fertlization?

A

zygote

36
Q

One the gametes (haploid) fertile, what do their chromosomes consist of?

How would they then reproduce?

A

A set from each parent, diploid.

Mitosis - 1 DNA duplication and 1 division (same number of chromosomes)

37
Q

At sexual maturity, what do the ovaries and testes produce in humans? What process is used?

A

gametes by meiosis - 1 DNA duplication and 2 divisions (resulting in half original chromosomes)

38
Q

In a human, all cells are produced by mitosis, EXCEPT FOR?

A

gametes

made by meiosis

39
Q

How many sets of chromosomes are in a gamete?

A

one

40
Q

Why is it important for mitosis and meiosis to alternate?

A

Lets say the production of gametes was done by mitosis instead of mitosis:

each gamete would have 46 chromosomes

gametes fertilize to form 92 chromosome zygote which would become adult by mitosis

92 chromosome adult would make 92 chromosome gamete by mitosis

gametes fertilize to form 184 chromosome zygote

AND SO ON…

Alternation allows for us to keep the same number of chromosomes from generation to generation, if not, they would continued to be doubled.

41
Q

the alternation of meiosis and mitosis is common to all organisms that perform what?

A

sexual reproduction.

42
Q

What are the three main types of sexual life cycles and what organisms exhibit them?

A
  1. Meiosis produces gametes and gametes DO NOT DIVIDE until they are fertilized, after fertilized and turn to zygote they divide by mitosis into multicellular organism - ANIMALS
  2. Alternation of generations: both diploid and haploid have a multicellular stage in this life cycle. gametes fertilize to form zygote. zygote matures to sporophyte (2n) multicellular organism that makes haploid spores (n) by meiosis. haploid spores divide by mitosis in multicellular haploid organism called gametophyte (n) which makes haploid gametes by mitosis. Gametes fertilize and form diploid sporophyte. - PLANTS AND SOME ALGAE
  3. Only diploid stage is single celled zygote, NO MULTICELLULAR DIPLOID, NO MITOSIS IN DIPLOID STAGE. Zygote produces haploid cell through meiosis. haploid cells grow through mitosis into multicellular haploid organism. multicellular haploid organism produces gametes through mitosis. FUNGI and some PROTISTS

THIS WILL LIKELY BE A ESSAY QUESTION ON TEST

43
Q

What are the only types of cells that can undergo meiosis?

A

DIPLOID

44
Q

What types of cells can undergo mitosis?

A

HAPLOID OR DIPLOID

45
Q

Do all three life cycles discussed in this chapter contribute to genetic variation?

A

YES

46
Q

Do chromosomes replicate before meiosis? How many times?

A

YES and once

47
Q

How many times does the cell divide in meiosis? How many daughter cells are produced from once cell the undergoes meiosis?

A

Two cell divisions (meiosis I and meiosis II)

4 daughter cells produced.

48
Q

How many chromosomes do the 4 daughter cells produced in meiosis have in comparison to the parent cell?

A

Half

49
Q

How does the first division of meiosis (meiosis I) differ from mitosis?

A

Homologous chromosomes are separated rather than sister chromatids.

50
Q

What the division name given for meiosis I? Why is it given that name?

A

Reductional phase

This division results in two HAPLOID daughter cells that have replicated chromosomes.

SO IT REDUCES THE TOTAL # OF CHROMOSOMES OF THE DAUGHTER CELLS BY HALF

51
Q

What is the division name given for meiosis II? Why?

A

equational division

Sister chromatids separated within each haploid daughter cell to form 4 haploid daughter cells with unreplicated chromosomes. KEEP EQUAL # OF CHROMOSOMES.

52
Q

What does interphase of meiosis I look like in comparison to mitosis?

A

similar in that they both replicate their DNA to form sister chromatids that are joined at the centromere

Centrosome also replicates into two

53
Q

What phase is not in meiosis I or II that occurs in mitosis?

A

prometaphase

54
Q

Does meiosis I division differ form mitosis?

A

YES

55
Q

Describe Prophase I. How does it differ from mitosis? How much of the time required for meiosis does this take up?

A
  • chromosomes condense
  • homologous chromosomes (each having sister chromatids) pair up and align gene by gene, process is called synapsis. This pair of chromosomes structure is called a tetrad. (this does not occur in mitosis).
  • after synapsis formed, crossing over occurs - DNA segments shared between nonsister chromatids. (does not occur in mitosis)

90% of time of meiosis required for this step

56
Q

Where does crossing over of DNA segments occur?

A

The chiasmata, usually there are multiple in a tetrad. X shaped region.

57
Q

Describe Metaphase I. How does it differ from mitosis?

A
  • Tetrads line up at metaphase plate, one chromosome faces each pole.
  • Microtubules from one pole attach to kinetochore of one chromosome (kinetochores of each sister chromatid have combined into one for each chromosome) of each triad, microtubules from other pole attach to other chromosome.

In mitosis replicated chromosomes are lining up, and microtubules attach to kinetochore of each sister chromatid.

58
Q

Describe anaphase I.

A
  • Cohesins that connect arms of replicated chromosomes together dissolve to allow for each chromosome to be pulled towards poles (centromeres remain connected by cohesins)
  • Pairs of homologous chromosomes separate towards each pole, guided by spindle apparatus.
  • sister chromatids remain attached at centromere and move as a unit.

IN MITOSIS THE SISTER CHROMATIDS ARE SEPARATED TOWARDS EACH POLE

59
Q

Describe telophase I and cytokinesis.

A
  • each half of cell now has haploid # of chromosomes that each consist of two sister chromatids
  • cytokinesis occurs simultaneously usually. this forms two haploid daughter cells.
  • cleavage furrow in animal cells, cell plate in plant cells.
  • sometimes the nuclear envelope reforms, sometimes it doesnt.
60
Q

At the end of meiosis I there are two haploid daughter cells, do they need to replicate their chromosomes before they begin meiosis II?

A

NO, their chromosomes are already replicated.

61
Q

Is meiosis II very similar to meiosis?

A

YES

62
Q

Describe prophase II.

A
  • spindle apparatus forms

- late in this stage chromosomes begin to move towards the metaphase plate, but have not reached it.

63
Q

Describe metaphase II. Are the sister chromatids identical? Why or why not?

A
  • chromosomes (each with sister chromatids) line up at metaphase plate
  • sister chromatids are NOT identical due to crossing over in meiosis I.
  • kinetochores of sister chromatids attaches to microtubules at opposite poles.
64
Q

are the daughter cells at the end of meiosis I haploid or diploid?

A

haploid

65
Q

Describe anaphase II.

A
  • sister chromatids separate towards opposite poles and are now individual chromosomes.
66
Q

Describe telophase II and cytokinesis.

A

Chromosomes arrive at opposite poles

nuclei form and chromosomes begin to decondense

cytokinesis occurs (cleavage furrow or cell plate)

four haploid daughter cells present that have unreplicated chromosomes. EACH ARE DISTINCT FROM ONE ANOTHER AND FORM PARENT

67
Q

What is the ultimate result at the end of meoisis II?

A

Four HAPLOID daughter cells that are GENETICALLY DISTINCT from each other and their parents.

68
Q

What is in the powerpoint is described as being virtually identical between meiosis and mitosis?

A

the mechanism for separating sister chromatids in meiosis II and mitosis.

69
Q

Be able to compare and contrast mitosis and meiosis. Write a chart describing the similarities and differences.

A

Look at last few meiosis ppt slides.

70
Q

What drives the process of evolution?

A

The genetic variation that arrives from sexual reproduction.

71
Q

What are the three things listed in the powerpoint that are unique meiosis, particularly meiosis I?

A
  • synapsis and crossing over in prophase I
  • during metaphase I of meiosis their are pairs of homologous chromosomes (tetrads) at the metaphase plate instead of individual replicated chromosomes.
  • In anaphase I of meiosis homologous chromosomes are separated as opposed to sister chromatids in mitosis
72
Q

At what point in mitosis are cohesins degraded?

At what two points are cohesins degraded in meiosis?

A

End of metaphase

chromosome arms in anaphase I and at centromeres in anaphase II

73
Q

What was the original source of genetic diversity?

A

Mutations that created different versions of genes, or alleles.

Can be sufficient in organisms that reproduce rapidly and early on.

74
Q

In organisms like us that don’t reproduce until later on and don’t have many offspring, what is the more efficient way of producing genetic variation?

A

Reshuffling of alleles using sexual reproduction.

NOT FORMING NEW ALLELES, JUST RESHUFFLING

75
Q

What are the three mechanisms that contribute to genetic variation in sexual reproduction?

A

Independent assortment of chromosomes - homologous chromosomes orient randomly at end of metaphase I. Homologues are sorted independently of other cells at metaphase plate. GOOD PICTURE IN PPT OF THIS.

Crossing over - recombinant chromosomes are product from this, combining genes inherited from each parent. Homologous portions of nonsister chromatids trade places.

Random fertilization - any sperm can fuse with any unfertilized egg.

76
Q

How do you calculate the number of combinations of chromosomes possible when they assort independently into gametes?

A

2^n

n = haploid number

humans = 2^23 = 8.4 million possible combinations of maternal and paternal chromosomes.

INDEPENDENT OF CROSSING OVER OR RANDOM FERTILIZATION

77
Q

In random fertilization the fusion of two human gametes (each with 8.4 million chromosome combinations possible from random assortment) produces a zygote with how many possible diploid combinations? Why is this significant?

A

8.4 mill x 8.4 mill = 70 trillion

Other than twins, this means that no two people have identical genetic information, everyone is unique.

78
Q

What is natural selection?

A

the accumulation of genetic variations favored by the environment

79
Q

Sexual reproduction contributes to genetic variate, but, where does genetic variation ORIGINATE from?

A

Mutations.

Biology 108 Test #2 (5 decks)

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