8/22/14 - Cytogenetic Principles

Question 1

What 3 techniques can be used to detect abnormalities of chromosome number/structure?

Answer 1

1. FISH 2. Comparative genome hybdrization 3. G-banding

Question 1

What is a metacentric chromosome?

Answer 1

Centromere is near the middle, Q and P arms are near equal length

Question 1

What is the result of non-disjunction during meiosis I?

Answer 1

Gametes produced have one maternal and one paternal copy of the extra chromosome.

Question 2

What is the difference between P and Q arms on a chromosome?

Answer 2

P “petite” arm is short. Q arm is long.

Question 4

What are some common cell types used for cytogenetic analysis?

Answer 4

Dividing, nucleated cells are used. Includes T-cells, amniotic cells, fibroblasts, and bone marrow cells.

Question 5

Why do carriers of Robertsonian translocations appear to have a normal phenotype?

Answer 5

The lost satellite regions normally contain copies of genes encoding rRNA which are found elsewhere in the genome. There is no real loss of genetic information.

Question 7

What are some clinical indications for cytogenetic analysis?

Answer 7

1. Issues with growth/development 2. Family hx of known/suspected chromosomal abnormality 3. Hx of infertility, miscarriage, or maternal age > 35

Question 9

Compare monosomy and partial monosomy?

Answer 9

Monosomy occurs when an entire copy of a chromosome is deleted. Partial monosomy occurs when only a portion of a chromosome is deleted and the rest remains intact.

Question 10

True/False: The numbering of a chromosome begins at the ends and extends inward toward the centromere.

Answer 10

False. The numbering extends outward from the centromere.

Question 10

What is chromosomal translocation?

Answer 10

An exchange of chromosomal segments between non-homologous chromosomes.

Question 11

What is the result of non-disjunction during meiosis II?

Answer 11

Gametes produced have either two maternal or two maternal copies of the extra chromosome.

Question 12

Draw a diagram of how a balanced translocation can give rise to unbalanced offspring.

Answer 12

Question 13

Identify the disorder in the karyotype:

Answer 13

Trisomy 21, leads to Down Syndrome

Question 14

What is a Robertsonian translocation?

Answer 14

A translocation on an acrocentric chromosome. The two Q arms fuse and the satellite regions are lost.

Question 15

What is a balanced chromosomal rearrangement?

Answer 15

A rearrangement that results in no gain or loss of genetic information.

Question 16

Draw the results of non-disjunction during meiosis I and II.

Answer 16

Question 17

What are some common genetic diseases caused by chromosomal microdeletions?

Answer 17

1. Angelman/Prader-Willi 2. Neurofibromatosis 3. Charcot-Marie-Tooth Disease 4. DiGeorge/Velocardio-facial syndrome 5. Cat eye syndrome 6. Williams syndrome

Question 18

What is an ancrocentric chromosome?

Answer 18

The centromere is located very near one end. The short arm is called the chromosomal satellite, and usually contains many repeated genes that encode rRNA.

Question 19

Which mode of chromosomal segregation is most likely to result in normal offspring from an unbalanced carrier?

Answer 19

2:2 alternate segregation

Question 20

What is a submetacentric chromosome?

Answer 20

Centromere is off-center, Q and P arms differ in length significantly