Chromosomes and Chromosomal Abnormalities

Question 1

What is the name for the short arm of a chromosome?

Answer 1

p

Question 2

What is the name for the long arm of a chromosome?

Answer 2

q

Question 3

What is a metacentric chromosome?

Answer 3

Centromere at mid point

Question 4

What is a submetacentric chromosome?

Answer 4

Smaller p than q arm

Question 5

What is an acrocentric chromosome?

Answer 5

Virtually no p arm

Question 6

What is the difference between dark bands and light bands on karyotypes?

Answer 6

Dark bands = gene poor heterochromatin

Light bands = gene rich euchromatin

Question 7

How many genes can be in a single band?

Answer 7

As many as 50+!

Question 8

What characteristics are used to identify chromosomes?

Answer 8

1. Size
2. Centromere position
3. Banding pattern

Question 9

What are 2 ways in which you can get double copies of chromosomes (tetraploidy)?

Answer 9

1. Furrow recession during cytokinesis

2. Multiple fertilization

Question 10

Nondisjunction tends to be associated with _________.

Answer 10

Advanced maternal age oocytes

Question 11

As many as ___% of spontaneous abortions are due to chromosomal abnormalities.

Answer 11

50%

Question 12

Noninvasive prenatal screening is helpful for detecting what?

Answer 12

Trisomy 13, 18, 21

Question 13

The majority of nondisjunction events occur in _____.

Answer 13

Meiosis I

Question 14

How does FISH work?

Answer 14

Make a probe complementary to a known unique sequence to identify aneuploidy.

Question 15

How do microarrays work?

Answer 15

Probes are fixed to a slide in unique positions and you wash the sample over the slide.

Make a hybrid of green (control) and red (fetal)

Measures the quantity of DNA…every spot SHOULD be yellow (red + green)

Red or green shows excess or loss of a gene

Question 16

What is another name for Trisomy 18?

Answer 16

Edwards Syndrome

Question 17

What are classic Trisomy 18 symptoms?

Answer 17

Rockerbottom feet
Clenched first 2nd and 3rd digits overlapping
Mental retardation, cardiac malformations

Question 18

What is another name for Trisomy 13?

Answer 18

Patau syndrome

Question 19

What are classic Trisomy 13 symptoms?

Answer 19

Body patterning is off:

Bilateral cleft lip
Mental retardation
Midline defects: cyclopia, absence of eyes
Congenital heart and urogenital defects

Question 20

what does t(14;21) indicate in a karyotype?

Answer 20

translocation between chromosomes 14 and 21

Question 21

What is a Robertsonian translocation?

Answer 21

Translocation involving acrocentric chromosomes

Question 22

What are common Trisomy 21 symptoms?

Answer 22

Hypotonia
Short stature
Flat nose
Palmar crease
Mental retardation
Congenital heart defects
Early onset Alzheimers

Question 23

What are common symptoms of Turner syndrome?

Answer 23

Webbed neck
Short stature
Amenhorrea
Gonadal dysgenesis
Infertility

Question 24

What is the genotype of patients with Turner syndrome?

Answer 24

45, X

Question 25

What are symptoms of Kleinfelter Syndrome?

Answer 25

Long limbs Hypogonadism Gynecomastia Behavioral problems

Question 26

What is a parAcentric inversion?

Answer 26

A block of DNA on a chromosome that moves AWAY from the centromer

Question 27

What is a perIcentric inversion?

Answer 27

A block of DNA that moves INVOLVING the centromere

Question 28

What is a consequence of paracentric inversion?

Answer 28

Unbalanced offspring and genomic instability

Question 29

What is a consequence of pericentric inversion?

Answer 29

Unbalanced offspring

Question 30

What is spectral karyotyping (SKY)?

Answer 30

Individual probe sets labelled in 24 different colors--makes it easy to determine origin of extra DNA and for translocations

Question 31

What test is especially useful for detecting translocations?

Answer 31

Spectral karyotyping

Question 32

What is a Philadelphia chromosome?

Answer 32

bcr-abl fusion protein formed due to a reciprocal translocation between chromosomes 9 and 22

Question 33

What disease develops from the formation of a Philadelphia Translocation

Answer 33

Chronic Myelogenous Leukemia

Question 34

In the case of defective x chromosomes, what are the priorities for inactivation/preservation?

Answer 34

1. Preserving activity of one x-chromosome equivalent | 2. Preserving autosomal sequences

Question 35

Can some genes escape X inactivation?

Answer 35

Yes

Question 36

What is cri du chat?

Answer 36

5p 15 deletion

Question 37

What are the symptoms of Cri du chat?

Answer 37

``` Cat cry Mental retardation Microcephaly Epicanthal folds Low set ears Heart defects ```