Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > 3.3 > Flashcards

3.3 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is meiosis

A

a form of nuclear division that produces four haploid nuclei from one diploid nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What happens prior to meiosis

A

the DNA of the cell is replicated during the S phase of interphase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens n sexual reproduction

A

two diploid individuals each contribute half of their DNA to produce offspring with a new and unique combination of alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are reproductive cells called

A

gametes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are they two cycles of division in meiosis

A

meiosis I and II

each have four phases
prophase, metaphase, anaphase and telophase

at the end cytokinesis occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does cytokinesis do

A

divides the cytoplasm of the parent cell to create two daughter cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What type of nuclei does meiosis produce

A

haploid nuclei

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is reduction division

A

cells begin with two copies of each chromosome and end with only one

DIploid (2n) - haploid (n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens in Prophase I

A

Chromosomes become visible due to supercoiling

replicated chromosomes from closely linked homologous pairs (tetrads of bivalents) which have two chromosomes and four total chromatids

non sister chromatids may cross over at chiasmata and exchange equivalent segments of DNA

centrioles If present migrate to opposite poles and spindle fibres start to form, the nucleolus and nuclear membrane disintegrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where does crossing over take place

A

in prophase I

between the non-sister chromatids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens in metaphase I

A

Homologous pairs move together along the metaphase plate, maternal and homologs show random orientation towards the pole

spindle fibres attach to the centromeres of each chromosome and gently pull to align them along the equatorial metaphase plate

spindle fibres connect each chromosome to one pole only

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

When does random orientation take place

A

Metaphase I

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens in Anaphase 1

A

Spindle microtubules shorten, pulling homologous chromosomes apart towards opposite poled, unlike mitosis, sister chromatids remain connected at the centromere and move to the same pole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens during telophase I

A

the first meiotic division effectively ends when the chromosomes arrive at the poles, each chromosomes consists of a pair of chromatids,

the chromatids partially uncoil and a nuclear membrane then reforms around each nucleus formed.

cytokineses results in two daughter cells with haploid nuclei from meiosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

When does cytokinesis generally take place

A

during telophase 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When does reduction division take place

A

Meiosis 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does meiosis 1 do to the cell

A

DIploid to haploid
2n to n

cells with two copies to only one

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happens to the cell in meiosis II

A

separation of chromatids in haploid cells (n- n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens in prophase !!

A

chromosomes condense again

centrioles migrate to opposite poles and spindle fibres start to form

nuclear membrane and nucleolus disintegrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens in Metaphase II

A

Spindle fibres attach to the centromere and connect each centromere to both poles, they exert a gentle pull to align them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What takes place during Anaphase II

A

centromeres divid and chromatids are moved to opposite poles by spindle fibres

once sister chromatids are separated they are celled chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What happens during telophase II

A

Chromosomes reach opposite poles and uncoil, cytokinesssis then takes place

four haploid daughter cells are now produced and they are all genetically distinct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Draw the stages of meiosis

A

kogntiy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Where does crossing over happen

A

prophase I

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is a tetrad

A

also known as a bivalent, homologs chromosomes pair up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How many chromatids does a tetrad have

A

four chromatids

two homologs chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is a chromatid

A

a long single strand of double helical DNA organized by histones proteins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are non sister chromatids

A

they have the same gene but different alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are sister chromatids

A

identical and joined at the centromere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Whaat does crossing over include

A

when equivalent portions of the non-sister chromatids are exchanges between homologs chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is a chiasmata

A

a point where crossing over can occur multiple times in the same tetrad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What does crossing over do

A

crates new combinations of alleles that were not present in either original chromosomes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What contributes to genetic variation

A

crossing over

34
Q

What happens after crossing over has taken place

A

the tetrads complete the process of condensation and move towards the equatorial plate.

the tetrad is then separated in anaphase I and then the sister crhoamtids are separate during anaphase II of meiosis II

35
Q

What is the longest phase of meiosis

A

Prophase I

involves,ves pairing of homologous chromosomes

crossing over followed by condensation of DNA into highly organized chromosomes

36
Q

What is it called when sister chromatids separate

A

becomes a chromosome

37
Q

Between which structures does crossing over typically occur?

A

Between non-sister homologous chromatids

38
Q

In what phase of meiosis does crossing over occur?

A

prophase I

39
Q

What does a tetrad consist of

A

2 pairs of sister chromatids

40
Q

Where does random orientation take place

A

metaphase I

41
Q

What is the difference in mitosis and meiosis between the metaphase

A

in mitosis, homologues line up in the eqautor where is meiosis, chromosomes line up individually for genetic differences

42
Q

What causes chromosomes to arrange themselves in pairs instead of individually

A

reduction division

random orientation

43
Q

What happens as a result of reduction division

A

daughter cells contain only half of the chromosomes that were present in the parent cell, the parent cell had four chromosomes the daughter has to

44
Q

What happens as a result of random orientation

A

When pairs of homologous chromosomes line up at the equator of the cell, the paternal copy, has an equal chance of facing either pole, the orientation of one pair does not impact the orientation of any other pair, each gamete gets one copy of each chromosome but a random assortments of the maternal and paternal inherited versions

45
Q

how many generations are actually involved in meiosis

A

three

two from mother

one from father

46
Q

What is genetic variation responsible for

A

all unique and distinctive forms that life has taken on Earth. it also accounts for the diversity we see within each species

47
Q

What is the original source of all genetic variations

A

mutations

48
Q

How doe genetic variation play a role in natural selection

A

helpful variations become more common in a population as harmful variations diminish, enabling the species toe evolve.

49
Q

How does meiosis allow for genetic variation

A

through crossing over

random orientation

50
Q

How does crossing over allow for genetic variation

A

in prophase I, homologous chromosomes come together and sections are exchanges between non-sister chromatids, allowing the mixing of alleles from the two parental chromosomes to form new combinations

51
Q

How does random orientation increase genetic variation

A

tetrads during metaphase I, the orientation of the homologs chromosomes at the equatorial plate during metaphase I determines which pole each pair of sister chromatids will move toward during anaphase I

the orientation is independent of other such pairs, thus, the allele is inherited differently which is known as independent assortment

52
Q

What is independent assortment

A

the allele inherited for one gene will not affect the allele inherited for another cause by random orientation

53
Q

How does sexual reproduction also increase genetic variation

A

by fusion of gametes from different parents

54
Q

What is non-disjunction

A

when II sister chromatids fail to separate, leading with two copies of a particular chromosome and another game without any copies

55
Q

What does non-disjunction lead to

A

trisomy, zygotę with three copies of a homologue

56
Q

Where can non-disjunction occur

A

in Anaphase I and II

57
Q

What is trisomy

A

having an extra copy of a single chromosome (2n + 1)

58
Q

What is there correlation between non-disjunction

A

between father age and non-disjunction but it I difficult to establish a clear connection

59
Q

Which is the most common cause of Down syndrome?

A

Non-disjunction during meiosis in the mother

60
Q

What is a karyogram

A

An image of a cell’s homologous chromosome pairs ordered by decreasing size

61
Q

What can a karyotype check for

A

the number and type of chromosomes

62
Q

When is the human an embryo

A

first 10 weeks

63
Q

when does the baby become a fetus

A

after 10 weeks

64
Q

What are two ways of obtaining fetal cells for karyotyping or other tests

A

Amnioticentesis and chronic villus sampling (CVS)

65
Q

When does amniocentesis take place

A

14 - 20 weeks

66
Q

when does CVs take place

A

10 - 13 weeks

67
Q

What is the source of fetal cells in amniotic fluid

A

Amniotic fluid

68
Q

What is the source of fetal cells in chorionic villus sampling

A

chorion (membrane)

69
Q

What is the risk of miscarriage in amniocentesis

A

< less than 1%

70
Q

What is the risk of miscarriage in chorionic villus sampling

A

less than 2%

71
Q

What happens during amniocentesis

A

as the fetus develops in the uterus, it is cushioned by amniotic fluid. Amniocentesis is usually performed between 14 weeks and 20 of progeny. A doctor r uses ultrasound imagery to guide a syringe needle through the abdomen and uterine wall without piercing the fetus. The needle is then used to withdraw a small amount of amniotic fluid. Fetal cells floating in the fluid are cultured and karyotyped

72
Q

What happens during chorionic villus sampling (CVS)

A

in early pregnancy through 10-13 weeks, CVS can be used with ultrasound imagnign to guide the medical proffesinal during the sampling and avoid harm to the developing embryo or fetus. Fetal cells are sampled by inserting a suctioning tool through the vagina or abdomen to reach the fetal cells in the chorion. The chorion is a membrane that surrounds the fetus and develops into part of the placenta.

73
Q

If a diploid cell has 12 chromosomes in prophase I, how many chromatids will the cell have at the completion of anaphase I and anaphase II?

A

12 and then 6

74
Q

During which phase of meiosis are chromatids pulled to opposite poles of the cell?

A

Anaphase II

75
Q

When one diploid nucleus divides by meiosis, how many haploid nuclei are formed?

A

4

76
Q

During which phase of meiosis do homologous pairs of chromosomes line up along the equator of the cell?

A

Metaphase I

77
Q

Spindle fibres start to form during prophase I of meiosis. Where do spindle fibres attach during meiosis?

A

between the centromere of chromosomes and the centrioles

78
Q

Which phase of cell division is photographed in order to make a karyogram?

A

metaphase of mitosis

79
Q

Which genetic condition can be diagnosed by karyotyping?

A

Trisomy 21

80
Q

What types of information are needed to construct a karyotype?

A

size of chromosomes

81
Q

During which phases of meiosis does the nuclear envelope break down?

A

prophase I and II

Biology (51 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions