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Life Sciences > Mitosis and Meiosis > Flashcards

Mitosis and Meiosis Flashcards

1
Q

Where are the chromosomes found

A

in the nucleus

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2
Q

what do chromosomes consist of

A

DNA

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3
Q

What are histones

A

Double helix DNA coiled around proteins

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4
Q

What does the chromosome appear as during interphase

A

chromatin network

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5
Q

What happens during the division of DNA

A
  • the DNA shortens and thickens

- it becomes a chromosome

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6
Q

What are sister chromatids

A

2 identical chromosome units

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7
Q

What are the sister chromatids connected by

A

A centromere

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8
Q

How many chromosomes do humans have

A

46

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9
Q

How many chromosomes does maize have

A

20

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10
Q

The more chromosomes a type of organism has the more _______ the organism is

A

complex

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11
Q

What is the homologous chromosome pair

A

the combination of the mother and father chromosome pair

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12
Q

Why is the number of chromosomes of the organism (sexually producing) always an even number

A

it consists of 2 sets of chromosomes

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13
Q

Chromosomes in each set are usually similar in what 3 factors

A
  • size
  • shape
  • genetic composition
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14
Q

What is mitosis

A

Type of cell division in which one cell divides to produce 2 new cells that are genetically identical

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15
Q

what are the 3 functions of mitosis

A
  • growth of an organism
  • replacement of worn/damaged tissue
  • reproduction of unicellular organisms
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16
Q

List the 5 phases of mitosis

A

interphase, prophase, metaphase, anaphase, telophase

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17
Q

Explain the process of interphase

A
  • cells normal metabolic response occurs
  • cell does what is was meant to do
  • chromatin network is always visible
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18
Q

Explain the process of Prophase

A
  • chromatin NW shortens and thickens
  • DNA replication already occurred therefore there are 2 sets of identical DNA molecules
  • chromosomes become visible
  • nuclear mem begins to disappear and nucleolus disintegrates
    nuclear plasma changes to a gel state
  • cell organelles move away from the nucleus
  • centrioles double and move to opposite poles
  • Spindles form between centrioles
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19
Q

Explain the process of Metaphase

A

Chromosomes are arranged on the equitorial plane of the cell so that the centromere connecting 2 chromatids lies on a spindle

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20
Q

Explain the process of Anaphase

A
  • spindles shorten
  • centromere divides into 2
  • chromatids separate
  • chromatids move to opposite poles
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21
Q

Explain the process of Telophase

A
  • daughter chromosomes uncoil to form chromatin NW
  • DNA of 2 cells are identical to one another
  • nuclear membrane and nucleolus reappear
  • division of the cytoplasm occurs (ensures cells are identical)
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22
Q

Provide a definition for cytokinesis

A

division of the cytoplasm occurs so that the 2 cells formed are identical to each other.

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23
Q

Definition for meiosis

A

Reduction division that takes place in the reproduction organs of animals and plants where the chromosome number in each cell is halved (diploid to haploid)

24
Q

During mitosis ________ are formed in animals and ______ are formed in plants

A

Gametes and spores

25
Q

What percentage of the cells time is spent in interphase

A

90%

26
Q

During which phase does DNA replication occur

A

Interphase

27
Q

Name the 2 distinct stages of meiosis

A
  • meiosis 1 and meiosis 2
28
Q

Explain the process during meiosis 1

A

chromosome number is halved and the genetic material exchanges and forms 2 identical cells

29
Q

Explain the process during meiosis 2

A

these 2 daughter cells undergo normal mitotic processes (daughter chromatids separate) to form 4 unidentical daughter cells)

30
Q

explain the process of prophase one in meiosis 1

A
  • chromatin NW shortens and thickens
  • chromatin becomes visible as chromosomes
  • homologous chromosome arrange themselves in pairs
  • 2 chromosomes of each homologous pair arrange tightly to form a bivalent
  • each chromosome of bivalent divides longitudinally into 2 identical chromatids (sister chromatids)
31
Q

Name the the place where chromatids cross over

A

Chiasma

32
Q

What occurs in crossing over

A

genetic info is exchanged between maternal and paternal chromosomes

33
Q

Explain the process of crossing over

A
  • centrioles move to opposite poles
  • spindle develops from the centrioles
  • nuclear membrane disintegrates
34
Q

explain the process of metaphase one in meiosis 1

A
  • bivalent arranges in a row on the equator (lie in a double row)
  • lie in a double row
  • centromere attaches to the spindles formed by the centrioles.
35
Q

explain the process of anaphase one in meiosis 1

A
  • spindle fibers contract, shorten and pull chromosomes towards the poles
  • homologous chromosomes separate
    cytokinesis
36
Q

Explain why independent, random division of maternal and paternal chromosomes is able to take place

A

due to the homologous chromosomes seperating.

37
Q

explain the process of telophase one in meiosis 1

A
  • chromosomes group themselves at the poles
  • spindle fibers disappear
  • nuclear membrane forms around each group of chromosomes and a nucleus forms I each cell nucleus.
  • cytokinesis is completed and 2 unidentical daughter cells are formed
  • each daughter cell posses 1 chromosome of each homologous oar
38
Q

explain the process of prophase 2 in meiosis 2

A
  • 2 chromosomes in each of the daughter cells now consists of 2 unidentical chromatids connected by a centromere
  • nucleolus and the nuclear membrane disintegrate
  • 2 centrioles move to poles
  • spindle fibers form (pole to pole)
39
Q

explain the process of metaphase 2 in meiosis 2

A
  • chromosomes arrange w their centromers on equaotr
  • chromsome centromere attaches to spindle fibers
  • 2 chromatids arranged on either side of equator
40
Q

explain the process of anaphase 2 in meiosis 2

A
  • centromere divided into 2
  • 2 unidentical chromatids break away from one another
  • spindle fibers shorten and pull the chromatids to opposite poles
  • chromatids at each pole are known as daughter chromomes
  • cytokinesis occurs
41
Q

explain the process of telophase 2 in meiosis 2

A
  • chromatids group together at 2 poles of 2 cells
  • spindle fibers disappear
  • nuclear mem forms around each chromosome and a nucleolus forms in each nucleus
  • cytokinesis occurs
  • after cytokinesis (4 daughter cells)
42
Q

State what happens to males in telophase 2

A

the daughter cells develop into sperm

43
Q

state what happens to females in telophase 2

A

of the 4 daughter cells, 3 disintegrate and the 1 becomes a ovum

44
Q

state 3 reasons why meioisis is such an important process

A
  • leads to formation of haploid gametes/spores
  • halving effect prevents doubling effect thus chromosome number maintained in generations
  • leads to genetic variation
45
Q

Explain how crossing over and exchange of genetic material during prophase 1 serves as a mechanism to introduce genetic variation by

A

each gamete of an individual carries different gene combo’s

46
Q

Explain how random arrangement of chromosomes on the equator can serve as a mechanism to introduce genetic variation

A

homologous chromosomes separate their grouping and therefore it leads to greater variation.

47
Q

How does random fertilization promote genetic variation

A

the sperm that fertilizes is completely random

48
Q

How do mutations cause variation?

A

It changes the genetic composition thus creating difference

49
Q

What are the 2 types of errors during meiosis

A
  • non- disjunction

- down syndrome

50
Q

What are the 2 types of results of non-disjunction

A
  • aneuploidy

- polyploidy

51
Q

What is non-disjunction errors of meiosis

A
  • incorrect distribution of chromosomes/chromatids
  • during A1 one of the homologous chromosomes don’t divide
  • during A2 sister chromatids of one or more chromosomes don’t divide.
52
Q

What is the difference between Aneuploidy and Polyploidy

A

aneu= presence of an extra chromosme or absence in a gamete

polyploidy= presence of an extra set of chromomes or absence in a gamete

53
Q

What is the other term for down syndrome

A

Trisomy 21

54
Q

List the errors that occur during meiosis that result in down syndrome

A
  • during Anaphase 1 chromosome 21 doesn’t divide

- during anaphase 2 the chromatids of chromosome 21 don’t separate

55
Q

Name some features of down syndrome

A
  • mental retardation
  • flat facial features
  • short
  • large head
  • abnormal ear shape
  • smallmouth and nose
  • reduced muscle tone
  • heart defects
  • happy and loving nature

Life Sciences (16 decks)

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