Brainscape's Knowledge GenomeTM

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


See full index

IB biology > topic 3.3/10.1- meiosis > Flashcards

topic 3.3/10.1- meiosis Flashcards

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

describe meiosis

A

when one diploid nucleus divides to produce 4 haploid nuclei

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

what are the 2 divisions in meiosis known as

A

meiosis I and meiosis II

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

define a diploid nucleus

A

has two chromosomes of each type

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

chromosomes of the same type are known as….

A

homologous chromosomes

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

define a haploid nucleus

A

has one chromosome of each type

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

meiosis is also known as…because…

A

a reduction division because it involves a halving of the chromosome number

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

the halving of the chromosome number allows

A

a sexual life cycle with fusion of gametes

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

what does sexual reproduction involve in eukaryotic organisms?

A

fertilisation (the fusion of gametes)

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

when in the sexual life cycle does meiosis occur?

A

any stage, but in animals it happens during the process of creating gametes

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

main events in meiosis

A

x2:
- prophase
- metaphase
- anaphase
- telophase

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

prophase I

A

-Chromosomes condense
- nuclear membrane dissolves
- homologous chromosomes form bivalents (synapsis)
- crossing over occurs

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

metaphase I

A

Spindle fibres from opposing centrioles connect to bivalents (at centromeres) and align them along the middle of the cell

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

orientation of paternal and maternal chromosomes on either side of the equator is…

A

random and independent of other homologous pairs

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

anaphase I

A
  • homologous pairs separated by spindle fibres
  • one chromosome of each pair moves to each pole
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

telophase I

A
  • chromosomes decondense
  • nuclear membrane may reform
  • cell divides (cytokinesis) to form two haploid daughter cells.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

prophase II

A
  • Chromosomes condense
  • nuclear membrane dissolves
  • centrioles move to opposite poles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

metaphase II

A

Spindle fibres from opposing centrioles attach to chromosomes (at centromere) and align them along the cell equator

18
Q

anaphase II

A

centromeres separate and chromatids are moved to opposite poles

19
Q

telophase II

A
  • chromatids reach opposite poles
  • nuclear envelope forms
  • cytokinesis occurs
20
Q

what is meiosis preceded by?

A

interphase- DNA is replicated to produce chromosomes consisting of two sister chromatids

21
Q

diploid human cell

A

46 chromosomes in 23 pairs

22
Q

n

A

=23=haploid no of chromosomes

23
Q

what three things promote genetic variation in meiosis?

A
  • random orientation
  • crossing over
  • fusion of gametes from different parents
24
Q

random orientation

A

in metaphase I, the orientation of bivalents is random and the orientation of one bivalent does not influence the orientation of the others.
- this generates genetic variation among genes that are on different chromosome types

25
Q

for every additional bivalent, the no of possible chromosome combinations in a cell produced by meiosis…

A

doubles

26
Q

crossing over

A

in prophase I:
- new gene combinations are formed on chromatids (recombination)

27
Q

gametes fuse to form a

A

zygote

28
Q

define crossing over

A

the exchange of DNA material between non-sister homologous chromatids

29
Q

what are chiasmata?

A

connection points where non-sister chromatids continue to adhere after crossing over has occurred

30
Q

chiasmata formation between non-sister chromatids can result in

A

an exchange of alleles

31
Q

what causes Down syndrome?

A

non-disjunction- this can cause other chromosome abnormalities as well

32
Q

define non-disjunction

A

when homologous chromosomes fail to separate at anaphase - both of the chromosomes move to one pole and neither to the other pole, resulting in a gamete that either has an extra chromosome or is deficient in a chromosome (fertilization= individual w either 45/47 chromosomes)

33
Q

Describe:
- Down syndrome

A
  • trisomy 21: non-disjunction event leads an individual with three of chromosome 21 rather than 2
  • hearing loss, heart and vision disorders, mental and growth retardation
34
Q

give 3 other common non-disjunction disorders

A

trisomy 18 and 13
Klinefelter’s syndrome (caused by having the sex chromosomes XXY)
Turner’s syndrome (caused by having only one sex chromosome, X)

35
Q

State two methods used to obtain cells for karyotype analysis

A
  • amniocentesis : passing a needle through the mother’s abdomen wall, using ultrasound to guide the needle which withdraws a sample of amniotic fluid containing metal cells from the amniotic sac
  • chorionic villus sampling; sampling tool enters the vagina is used to obtain cells from the chorion, one of the membranes from which the placenta develops
36
Q

describe the risks associated with chorionic villus sampling and amniocentesis

A

amniocentesis- risk of miscarriage is 1%
Chronic villus sampling- risk is 2%

37
Q

why does independent assortment of genes occur?

A

due to the random orientation of pairs of homologous chromosomes in meiosis I
- the pole to which each chromosome in a pair moves depends on which way the pair is facing - this is random
- the direction in which one pair is facing does not affect the direction in which any other pairs are facing

38
Q

bivalent =

A

tetrad, composed of 4 chromatids - the combination of homologous chromosomes when they align beside each other

39
Q

describe the process of crossing over w a diagram

A
  1. at one stage in prophase I all of the chromatids of two homologous chromosomes become tightly paired up together (synapsis)
  2. the DNA molecule of one of the chromatids is cut. A second cut is made at exactly the same point in the DNA of a non-sister chromatid
  3. the DNA of each chromatid is joined up to the DNA of the non-sister chromatid. this has the effect of swapping sections of DNA between the chromatids
  4. in the later stages of prophase I the tight pairing of the homologous chromosomes ends, but the sister chromatids remain tightly connected. The X shaped structure after crossing over is called a chiasma
40
Q

give 4 ways in which meiosis I differs from mitosis and meiosis II

A
  • sister chromatids remain associated w each other
  • homologous chromosomes behave in a coordinated fashion in prophase
  • homologous chromosomes exchange DNA leading to genetic recombination
  • meiosis I is a reduction division

IB biology (60 decks)

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