Brainscape's Knowledge GenomeTM

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


See full index

Medical Genetics > Sheet 2 > Flashcards

Sheet 2 Flashcards

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

What are genes?

A

Segments of DNA that carry genetic information for a specific trait

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

What are alleles?

A

Different versions of a gene

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

Approximately ____ of all newborn humans have a chromosomal abnormality

A

0.6-1%

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

Chromosomal aberration are noted in:

A

1) 20-27% of individuals having sex reversal or pubertal anomalies
2) 33-67% of spontaneous miscarriages (fetuses die due to chromosomal abnormalities)
3) 2-5% of couples have a history of multiple miscarriages
4) The majority of cells from leukemia samples or solid tumors

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

What are some research uses for cytogenetic evaluation?

A

1) Localization of DNA onto a chromosome
2) Determination of genomic complement
3) Characterization of genetic changes
4) Recognition of chromosomal changes following treatment or in vitro culturing

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

The first step for studying chromosomes is:

A

Determining where we should extract the chromosomes from.

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

What does the location for extraction of the chromosome depend on?

A

1) Type of the disease

2) Purpose of the study

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

What is a karyotype?

A

A photograph/diagram of an ordered arrangement of chromosomes from a cell. 

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

How are the chromosomes arranged in a karyotype?

A

A standard order by length (Chromosome 1 is the longest, 22 is the shortest, last one is sex chromosomes)

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

The karyotype is obtained from:

A

A dividing cell (M phase, specifically metaphase)

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

Why is the karyotype obtained from cells in metaphase?

A

Because that is when the chromosomes are most condensed and arranged as homologous pairs.

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

What is an ideogram?

A

A diagrammatic representation of the

different banding patterns of the chromosomes which we use to distinguish them in order to make the karyotype

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

What is an ideogram used for?

A

1) To show the relative size of the chromosomes

2) The chromosomes’ characteristic banding patterns.

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

Each chromosome has __(the same/different) banding patterns.

A

Different

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

The location of the dark or light bands for the same chromosome is __(the same/different) among different types of banding methods.

A

Different

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

How many banding techniques are there? What are they?

A

5; G,R,C,Q,T

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

Which stain is used for G-banding?

A

Giemsa stain.

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

During which stage of the cell cycle is banding done?

A

Metaphase, because the chromosomes are highly condensed and easily seen

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

Since most of the cells are in the interphase, what should be done?

A

Cells must be induced to enter the cell cycle and reach the M phase and then stop there.

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

The majority of the cells obtained are either at:

A

1) G0 (at rest)
2) Interphase
Both of them have diffused chromosomes

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

What are the steps to induce cells to enter the M phase?

A

1) Blood is taken and placed in a petri dish with media (to keep the sample alive) and a mitogen.
2) After that, a mitotic inhibitor is added
3) The cells are centrifuged at low speed to remove the media.
4) A hypotonic solution is added = cells become swollen and fragile.
5) Suspended cells are dropped onto slides. Cells burst and chromosomes will be scattered on the slide.
6) Giemsa stain is added to show the chromosomes

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

What is a mitogen?

A

A chemical that induces the cell to enter the cell cycle

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

What is an example of a mitogen?

A

Phytohemaglutenin

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

What is media?

A

Sterile water with nutrients [sugars, proteins, amino acids]

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

What is an example of a mitotic inhibitor?

A

Colchicine

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

What does a mitotic inhibitor do?

A

Stops the cells at the M phase, specifically at metaphase.

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

How does colchicine work?

A

Prevents the assembly and polymerization of microtubule filaments of the centrosome = stops their function

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

What is the standard and most commonly used stain?

A

Giemsa stain

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

What is the standard banding technique?

A

G-banding (GTG)

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

Adenine binds with ___ through how many hydrogen bonds?

A

Thymine; 2

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

Guanine binds with ___ through how many hydrogen bonds?

A

Cytosine; 3

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

Where are gene rich regions located?

A

In the euchromatic areas of the chromosomes

33
Q

What are the euchromatic areas of the chromosome?

A

Less condensed areas= easily accessed by transcription enzymes

34
Q

Where are gene poor regions located?

A

In the heterochromatic areas of the chromosomes

35
Q

Staining of the chromosomes involves the interaction between:

A

Giemsa and a certain part of the DNA molecule (found more in AT rich parts than GC rich)

36
Q

Before staining, the chromosomes are first treated briefly with ___.

A

Trypsin

37
Q

What is trypsin?

A

A digestive enzyme that degrades peptide bonds between the amino acids of proteins = partially digests some of the chromosomal proteins = relaxes the chromatin structure and allows the Giemsa dye to access the DNA

38
Q

The AT rich areas are stained ___(lightly, darkly), while the GC rich areas are stained ___(lightly, darkly)

A

Darkly; lightly

39
Q

G-banding normally produces __ bands among the 23 pairs of human
chromosomes.

A

300-400

40
Q

Each G-band represents __ nucleotides.

A

Several million-10 million.

41
Q

What does the R stand for in R-banding?

A

Reverse (of G-banding)

42
Q

The dark regions in R banding are ___, while the light regions are ___.

A

Euchromatic (GC rich); Heterochromatic (AT rich)

43
Q

How is the banding pattern in R-banding produced?

A

By heating the chromosomes (breaking the hydrogen bonds) before Giemsa stain is applied.

44
Q

Why is the AT region light when doing R-banding?

A

Because the 2 hydrogen bonds are destroyed, therefore it will not bind the Giemsa stain.

45
Q

Why is the GC region dark when doing R-banding?

A

Because the 3 hydrogen bonds are only weakened, therefore they can still bind the Giemsa stain.

46
Q

What are fluorochromes used for?

A

Sharpening the color to be more enhanced.

47
Q

When do we use R-banding?

A

1) With G-banding to determine whether there are deletions of some regions or not.
2) To help confirm the findings of G-banding when there are some bands that aren’t clear (flipping the colors might help).

48
Q

Arm region numbering starts from:

A

The centromere (center) toward the telomere (end)

49
Q

Which chromosomes are acrocentric?

A

13, 14, 15, 21, 22

50
Q

The “P arm” of ALL acrocentric chromosomes contains two distinct regions:

A

1) Satellite (Darkly stained heterochromatic region)

2) Stalk (Lightly stained euchromatic region)

51
Q

What is a satellite?

A

A repetitive sequence of base pairs that does not code for genes.

52
Q

What is a stalk?

A

DNA regions that can be transcribed into RNA (codes for genes).

53
Q

Where does RNA originate from?

A

The stalk of the P arm of ALL acrocentric chromosomes

54
Q

Does the P arm of an acrocentric chromosome have any clinical significance?

A

No, because all 5 acrocentric chromosomes have the same DNA sequence in their P arm (they can compensate for the rRNA production).

55
Q

How many nucleotides need to be damaged in order to see them by G or R banding?

A

About 3 million nucleotides or more

56
Q

To detect nucleotide damage, which form do the chromosomes have to be in?

A

The less condensed form in order to easily determine the location of the abnormalities.

57
Q

In which phase of the cell cycle does high resolution banding take place?

A

Prophase or pro-metaphase (before maximal condensation).

58
Q

How many bands can we see for all chromosomes during metaphase?

A

300-450 per haploid set

59
Q

How many bands can we see for all chromosomes during prophase or pro-metaphase?

A

800 per haploid set

60
Q

High-resolution banding allows for:

A

The detection of less obvious abnormalities usually not seen with conventional banding

61
Q

What is a centromere?

A

The genetic locus required for chromosome segregation.

62
Q

What does a centromere contain?

A

Structural DNA (no genes) and proteins

63
Q

What kind of region is the centromere?

A

A heterochromatic region

64
Q

What will we find by sequencing a centromere?

A

An alpha satellite: A tandem repeat of 171 base pairs and proteins (The same 171 base pairs repeat).

65
Q

All chromosomes have the same ___ in humans.

A

Alpha satellite

66
Q

What are telomeres?

A

Specialized structures at the ends of eukaryotic chromosomes.

67
Q

What is the sequence found in telomeres?

A

TTAGGG tandemly repeated thousands of times.

68
Q

Does the entire telomere have the same sequence?

A

Yes.

69
Q

What does the telomere sequence code for?

A

Nothing; it is a structural region.

70
Q

What is the function of telomeres?

A

Maintain chromosomal integrity by preventing end-to-end fusion of chromosomes.

71
Q

What replicates telomeres?

A

1) DNA Polymerase

2) Telomerase

72
Q

Which region is associated with aging? Why?

A

Telomeres; because as we get older, the activity of telomerase decreases. (Each time a cell divides, the telomeres get shorter).

73
Q

Once the telomeres are too short and the cell can no longer divide, what is it termed? What happens then?

A

Senescent (inactive); the cell dies.

74
Q

How do telomeres protect against cancer?

A

It limits the amount of times a cell can divide.

75
Q

What property do cancer cells have?

A

High activity/unlimited activity of telomerase.

76
Q

The sequence of telomeres is __(not universal/universal).

A

Universal

77
Q

The sequence of the sub-telomeric region is __(not universal/universal).

A

Not universal

78
Q

True or false:

The sequence of the sub-telomeric region is common and identical among all chromosomes.

A

False; they can be common but they are not identical among all chromosomes. (Some sequence homology exists)

79
Q

The most accessible cells that can proliferate in cultures and used for karytotypes are:

A

WBCs (T-Lymphocytes)

Medical Genetics (7 decks)

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