Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Clinical Genetics > Chromosomes > Flashcards

Chromosomes Flashcards

(69 cards)

Start Studying
1
Q

What is mitosis?

A

A type of cell division that results in diploid daughter cells

These have the same number and type of chromosomes as the parent nucleus

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

What happens during interphase?

What do the chromosomes look like?

A

The cell has copied its DNA

Each chromosome consists of 2 connected sister chromatids

They are not visible as they are in the uncondensed form of chromatin

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

What happens during prophase of mitosis?

A

the cell starts to break down some structures and others build up

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

What are the 3 main things that happen during prophase?

A
  1. chromosomes condense
  2. mitotic spindles begin to form, and in late prophase the microtubules start capturing chromosomes
  3. the nucleolus disappears and then the nuclear envelope breaks down
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where do microtubules bind to chromosomes?

A

At the kinetochore

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

What is the kinetochore?

A

A patch of protein found on the centromere of each sister chromatid

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

What is the centromere?

A

The region of DNA where the sister chromatids are most tightly condensed

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

What happens during metaphase of mitosis?

A

The chromosomes align at the metaphase plate

This is at the equator of the cell

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

How are the chromosomes arranged relative to each other at the metaphase plate?

A

The 2 kinetochores of each chromosome should be attached to microtubules from opposite spindle poles

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

What checkpoint occurs before anaphase?

What does it do?

A

The spindle checkpoint

It ensures all the chromosomes have reached their metaphase plate with their kinetochores correctly attached to microtubules

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

What is the purpose of the spindle checkpoint?

A

It ensures sister chromatids will split evenly between the 2 daughter cells when they separate

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

What happens during anaphase of mitosis?

A

Sister chromatids are separated from each other and are pulled to opposite poles of the cell

The centromere will divide

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

What are the 4 main things that occur during telophase?

A
  1. spindle is broken down
  2. 2 nuclei form, one from each set of chromosomes
  3. chromosomes return to the threadlike form of chromatin
  4. cytokinesis starts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 3 stages of interphase?

A

G1 (gap) phase

S (synthesis) phase

G2 (gap) phase

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

What happens during the G1 phase of interphase?

A

The cell grows larger and makes a copy of its organelles

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

What happens during the S phase of interphase?

A

The cell synthesises a complete copy of the DNA in its nucleus

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

What happens during the G2 phase of interphase?

A

The cell grows and makes proteins and organelles

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

What happens during the M (mitotic) phase of the cell cycle?

A

The cell divides its copied DNA and cytoplasm to make 2 new cells

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

What do the chromosomes look like during the M phase?

A

The DNA condenses into visible chromosomes which are pulled apart by the mitotic spindle

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

What happens during cytokinesis in the M phase?

A

The cytoplasm of the cell is split into two to make two new cells

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

What happens during the G0 phase of the cell cycle?

A

This is a resting state

The cell is not actively preparing to divide and it is performing its function

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

Is the G0 phase permanent?

A

It is a permanent state for some cells

Others may start to divide again if they get the right signals

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

Why is meiosis described as a reduction division?

A

It produces haploid gametes which contain only 23 chromosomes

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

How does meiosis ensure that every gamete is unique?

A

Re-assortment of genes through crossing over and independent segregation of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What happens during prophase I of meiosis?
Chromosomes condense and line up in their homologous pairs
26
Why are chromosomes described as homologous?
They contain the same genes in the same sequence
27
What occurs during prophase I in relation to genetic assortment?
Crossing over Genes are exchanged between paired chromosomes leading to chromosomes with unique combinations of alleles
28
What happens in prophase I after crossing over has occurred?
The spindle attaches to the chromosomes at the metaphase plate
29
How do the chromosomes attach to the spindle in meiosis?
Each chromosome attaches to microtubules from just one pole of the spindle The two homologues of a pair bind to microtubules from opposite poles
30
How do the homologue pairs line up at the metaphase plate?
They line up in their homologous pairs The orientation of each pair of homologues when they line up is random
31
What happens during anaphase I of meiosis?
The homologues are pulled apart and move to opposite poles of the cell
32
What happens during telophase of meiosis I?
The chromosomes arrive at opposite poles of the cell
33
What type of cells are entering meiosis II?
Haploid cells with one chromosome from each homologous pair
34
What happens during prophase II?
The centrosomes move apart allowing the spindle to form between them The two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles
35
What happens during metaphase II?
The chromosomes line up individually along the metaphase plate
36
What happens during anaphase II?
Sister chromatids separate and are pulled to opposite poles of the cell
37
What happens during telophase II?
Nuclear membranes form around each set of chromosomes The chromosomes decondense Cytokinesis splits the cytoplasm forming 4 haploid cells
38
How does crossing over produce genetic variation during meiosis?
crossing over involves exchanging genetic material between homologous pairs of chromosomes This leads to independent reassortment of genes
39
What happens during metaphase I that leads to genetic variation being produced?
Random orientation of homologue pairs This allows for the production of gametes with many different assortments of homologous chromosomes
40
How is DNA arranged within a chromosome?
DNA is wound around histone proteins to form the nucleosome
41
How are the nucleosomes packaged?
The nucleosomes are packaged into a thread to form chromatin The chromatin fibre is coiled into a solenoid
42
How is a chromatosome formed?
From the addition of a H1 protein to the nucleosome
43
When are chromosomes the most compact?
During metaphase
44
How are chromosomes stained? What must be performed before the stain is added?
Metaphase chromosomes are treated with trypsin to partially digest the chromosome They are then stained with Giemsa stain
45
Which regions of the chromosome will stain more darkly with Giemsa stain?
Heterochromatic regions These tend to be AT-rich and relatively gene stable These are the "dark bands" or "g-bands"
46
What type of chromatin is contained within dark bands? When do they replicate?
They contain condensed chromatin and are rich in adenine and thymine DNA Dark bands replicate late
47
When will the light bands replicate? What type of chromatin do they contain?
They contain less condensed chromatin that is GC-rich They replicate early in S phase as they are more transcriptionally active
48
What is the difference between an allele and a locus?
Alleles are alternative forms of the same gene A locus is the position of a gene on the chromosome
49
What is a karyotype?
It shows the number and appearance of all the chromosomes in the nucleus of a eukaryotic cell This is a complete set of chromosomes
50
What different arms are present in a chromosome?
Each chromosome has a shorter p arm and a longer q arm These are separated by the centromere
51
During mitosis, how do spindle fibres attach to the centromere?
Via the kinetochore
52
What is a telomere and what is its function?
It is a DNA and protein cap on the ends of a chromosome It prevents chromosomes from sticking together It also protects the genetic information during cell division
53
What is the arrangement of: i. metacentric ii. sub-metacentric iii. acrocentric iv. telocentric chromosomes?
i. centromere is positioned in the centre ii. there are slightly shorter p arms iii. there are even shorter p arms iv. there are very short or no p arms and the centromere is at the top of the q arm
54
Which chromosomes are acrocentric? What is their DNA like?
13, 14, 15, 21, 22 They have inactive repetitive DNA that is mostly non-coding
55
When does a deletion or monosomy occur?
When there is only one copy of a particular gene This results in half the normal amount of protein
56
What usually causes a numerical chromosomal anomaly? What does this mean in future pregnancies?
De novo errors in meiosis This means there is a very low reoccurrence risk in future pregnancies
57
What is aneuploidy?
The presence of an abnormal number of chromosomes in a cell e.g. 45 or 47 instead of 46
58
What is polyploidy?
The presence of more than two paired sets of chromosomes
59
What is the difference between aneuploidy and polyploidy?
Polyploidy involves replication of the whole complement of chromosomes, rather than just a single chromosome
60
What are examples of structural anomalies? What causes them?
Deletions, duplications, inversions, translocations They are due to de novo errors but can be inherited
61
What happens if there are anomalies in different cell lines? When does this occur?
Mosaicism This occurs post-zygotically during mitosis
62
How would the normal male karyotype be written?
46,XY There are 46 chromosomes in total XY shows the male chromosome constitution
63
What is shown by the karyotype: 46,XX,dup(2)(p13p22)
a female with 46 chromosomes duplication of the short arm from chromosome 2 from bands 13-22
64
How does the chance of a de novo mutation during meiosis change with age in men?
Rate of sporadic mutations increases with paternal age due to the greater number of germ cell divisions As paternal age increases, the chance of a de novo mutation increases
65
What increases the chance of non-disjunction in women?
Increasing maternal age The longer the cells are kept in stasis, the more chance the chromosomes will not separate
66
What happens if non-disjunction occurs during meiosis I?
The segregation of both homologues to one spindle pole Both chromosomes of a pair are in the SAME daughter cell
67
What is the result of the gametes produced from non-disjunction during meiosis I?
Both disomic and nullisomic gametes The other 22 pairs of chromosomes are not affected
68
What happens if non-disjunction occurs during meiosis II?
Incorrect separation of sister chromatids Both sister chromatids are segregated to one spindle pole
69
What is the result of the gametes from non-disjunction in meiosis II?
Disomic and nullisomic gametes as well as 2 normal monosomic gametes

Clinical Genetics (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions