05b: Chromosomes

Question 1

The short arm of the chromosome is called:

Answer 1

The P arm

Question 2

The long arm of the chromosome is called:

Answer 2

The q arm

Question 3

Location of centromere in meta centric chromosome

Answer 3

Middle

Chromosome has nearly equal P and q arms.

Question 4

Location of centromere in submetacentric chromosome

Answer 4

Closer to one side, so P arms shorter than q arms

Question 5

Location of centromere in acrocentric chromosome

Answer 5

Very close to one end of chromosome (almost no p arm)

Question 6

The less condensed the chromosomes are, the (less/more) bands appear.

Answer 6

More

Question 7

A(n) (X) stain is used to image chromosomal banding patterns.

Answer 7

X = giemsa

Question 8

Dark chromosomal bands are gene (rich/poor) and has which type of chromatin?

Answer 8

Poor; heterochromatin

Question 9

Light chromosomal bands are gene (rich/poor) and has which type of chromatin?

Answer 9

Rich (50+ genes per band); euchromatin

Question 10

(Heterochromatin/euchromatin) is lightly packed and actively transcribed.

Answer 10

Euchromatin

Question 11

Chromosomes can be profiled based on:

Answer 11

1. Size
2. Centromere position
3. Banding pattern

Question 12

What are the tissue sources used to profile chromosomes?

Answer 12

1. Blood (somatic cells)
2. Cheek swab (somatic cells)
3. Amniocentesis/CVS (prenatal screen)

Question 13

A normal male karyotype would have what nomenclature?

Answer 13

46, XY

Question 14

Multiple fertilization could result in (X)ploidy. Give potential nomenclature for this individual.

Answer 14

X = tetra- (4n)

96, XXXX

Question 15

Presence of an abnormal number of chromosomes, but does not include a difference of one or more complete sets of chromosomes (just certain genes).

Answer 15

Aneuploidy

Question 16

Nondisjunction usually associated with (sperm/oocytes/both equally).

Answer 16

Oocytes

Question 17

At what maternal age does incidence of trisomy start to skyrocket?

Answer 17

34-35

Question 18

Why would mitotic post-zygotic nondisjunction be (more/less/equally) severe as meiotic nondisjunction?

Answer 18

Less severe! Cell with just one chromosome usually won’t contribute

Question 19

A male with trisomy 18 would have what nomenclature?

Answer 19

47, XY, +18

Question 20

In DNA microarray, what’s being compared/assessed?

Answer 20

Compare quantity of DNA between normal control sample and fetal sample

Question 21

What do the colors in DNA microarray indicate?

Answer 21

Yellow: equal amount DNA
Red: extra amount DNA
Green: missing amount DNA

Question 22

In DNA microarray, is the sample or probe or neither fixed?

Answer 22

Probes fixed, wash sample over them

Question 23

Nuclear genome accounts for over (X)% of human genome.

Answer 23

X = 99

Question 24

Mitochondrial genome allows the organelle to synthesize its own (X), that function in:

Answer 24

X = proteins

Cell respiration (ETC)

Question 25

Why are (nuclear/mitochondrial) genes especially susceptible to mutation?

Answer 25

Mitochondrial; Respiration and oxidative phosphorylation produce substantial amounts of reactive oxygen species (ROS), which damage DNA

Question 26

What's mitonuclear match?

Answer 26

Nuclear genes match rates of mutation/evolution of mitochondrial genes in order for the proteins to co-evolve and keep machinery in sync

Question 27

Define heteroplasmy.

Answer 27

Tissues, within same individual, vary with the amount of mutant mitochondria since the segregation isn't regulates

Question 28

Why are mitochondria inherited through (paternal/maternal) descent only?

Answer 28

Maternal; Inherited with the cytoplasm (eggs contain 100,000 and sperm only 100)

Question 29

T/F: a cell with a few mutant mitochondria may have normal phenotype.

Answer 29

True - must pass threshold for phenotypic expression

Question 30

Analysis that detects small deletions and duplications (less than 0.5 million bp).

Answer 30

Chromosomal microarray

Question 31

Analysis that detects deletions and duplications greater than 7-10 million bp.

Answer 31

Karyotype

Question 32

Which analysis can detect both copy number variation and positioning?

Answer 32

Karyotype (NOT microarray)

Question 33

Edwards syndrom, aka (X), has which key symptoms?

Answer 33

X = trisomy 18 Clenched fist (2nd finger overlaps 3rd), low-set ears, mental retardation, cardiac malformations

Question 34

Trisomy 13 is also called:

Answer 34

Patau syndrome

Question 35

Trisomy 21 is also called (X). A male patient would have the nomenclature:

Answer 35

X = Down syndrome 47, XY, +21

Question 36

What's a chromosomal translocation?

Answer 36

Chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes

Question 37

Example of female with Robertsonian translocation nomenclature:

Answer 37

46, XX, t(14; 21), +21

Question 38

An individual with chromosomal translocation (i.e. Robertsonian) has how many chromosomes?

Answer 38

46

Question 39

T/F: You can be an asymptomatic carrier of Robertsonian translocation.

Answer 39

True

Question 40

T/F: Aneuploidy is only really found in autosomal chromosomes.

Answer 40

False - in sex chromosomes also

Question 41

How do mammals carry out dosage compensation for sex chromosomes?

Answer 41

X-inactivation

Question 42

Genes subject to escaping X-inactivation are found on (p/q/both) arm(s).

Answer 42

Primarily on P-arm

Question 43

T/F: Genes that escape X-inactivation are expressed in two copies for males as well as females.

Answer 43

False - only in females

Question 44

The only viable monosomy, (X), has the nomenclature:

Answer 44

X = Turner syndrome 45, XO OR... 46, XX, i(Xq)

Question 45

Give example of a syndrome that results, despite X-inactivation.

Answer 45

Klinefelter's syndrome

Question 46

List the two types of chromosomal inversions.

Answer 46

1. Paracentric (not involving centromere) | 2. Pericentric (involving centromere)

Question 47

Consequence of paracentric inversion in offspring.

Answer 47

Unbalanced offspring AND genomic instability (one chromosome has no centromere, the other has two)

Question 48

Consequence of pericentric inversion in offspring.

Answer 48

Unbalanced offspring

Question 49

What's one assay that's especially useful to look for translocations?

Answer 49

Spectral Karyotyping (SKY) with 24 different color labels for each chromosome

Question 50

A Philadelphia chromosome is the result of (balanced/unbalanced) (X). What disease associated?

Answer 50

Balanced; X = reciprocal translocation Chronic myelogenous leukemia

Question 51

What defines a balanced translocation?

Answer 51

Cells still diploid (no extra/missing chromosomal material)

Question 52

(X) fusion protein, a result of a (Y) translocation, is problematic in that it:

Answer 52

``` X = bcr-abl Y = reciprocal ``` Acts as kinase in wrong time/place

Question 53

T/F: Vast majority of reciprocal translocations create Philadelphia chromosome.

Answer 53

False

Question 54

Principles of X-inactivation:

Answer 54

1. Random choice of Xi | 2. If one X is defective, choice no longer random

Question 55

If an X chromosome is defective, how is priority set for the Xi chosen?

Answer 55

1. Preserve activity of one entire X chromosome equivalent | 2. Preserve autosomal sequences, if possible

Question 56

What defines an isochromosome?

Answer 56

Structural abnormality in which the chromosome are mirror images of each other

Question 57

5p15 chromosomal deletion:

Answer 57

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