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1

What are the types of chromosome abnormalities that can occur?

1. translocations
2. deletions
3. inversions
4. ring chromosome
5. isochromosome

2

What are the two types of translocations?

1. reciprocal
2. robertsonian

3

What happens during a reciprocal translocation?

Exchange of genetic material between non homologous chromosomes

4

What effects may happen to those who are carriers of a reciprocal translocation?

may have no impact

may be cancerous

if in germline cells, may have a higher risk of spontaneous abortion

5

segregation at meiosis: reciprocal translocation?

will be quadrivalent

cells could show alternate segregation or adjacent segregation

6

What is alternate segregation?

cells may be normal or be a carrier of the translocation

7

what is a adjacent segregation?

incompatible with life.. sometimes will lead to some type of disorder

8

What happens during a t(9;22)?

there was a translocation between the 9th and 22nd chromosome

leads to chronic myelogenous leukemia due to the activation of an oncogene

Activation of BCR-ABL tyrosine kinase which is a proto-oncogene in hematopoietic cells

9

What happens during a t(8;14)?

Burkitt lymphoma

Dysregulation of c-Myc gene expression, leading to cancer

10

How does a robertsonian translocation occur?

it occurs between acrocentric chromosomes

there is a loss of the short arms; fusion of the long arms

11

effects during meiosis: robertsonian translocation?

forms a triavlent

can either have alternate segregation or adjacent segregation

12

What does a robertsonian translocation look like when the chromosomes go through adjacent segregation?

trisomy 14 and trisomy 21

13

How can microdeletion syndromes be detected?

karyotype, FISH, or CGH

depends on the size of the mutation

14

Cri-du-chat syndrome

deletion of the short arm of the 5 chromosome

features:

1. high-pitched, cat-like cry
2. intellectual disability
3. microcephaly
4. hypertelorism ( widely spaced eyes)
5. speech issues

15

How is cri-du-chat syndrome detected?

Can be detected by FISH or CGH, and can sometimes be detected by karotyping

16

22q11.2 deletion syndrome is known as what other names?

velocardiofacial or DiGeorge syndrome

17

What are some symptoms of 22q11.2?

1. congential heart defects
2. absence of the thymus
3. cleft lip and palate
4. facial anomalies
5. increased risk of schizophrenia

18

How to generically detect 22qll.2?

can use either FISH or CGH

19

Wolf-Hirschhorn syndrome

deletion of the short arm of the 4th chromosome

Features:
1. seizures
2. skeletal and cardial defects
3. intellectual disability
4. facial anomalies

20

What are two deletions of the 15q11-13 chromsome?

SNPRN and UBE3A

lead to either prader-willi or angleman syndrome

21

why might uniparental disomy occur?

trisomy rescue mechanism

chromosome reduplication

22

What happens during chromosome inversion?

changing in the chromosome banding pattern, thus can be detected by karotyping

usually balanced and no clinical problems occur

inversion can be pericentric (involves centromere or paracentric ( does not involve centromere)

23

what is an isochromosome?

loss of one arm of the chromosome and duplication of the other arm.

isochromosome of an autosome is usually lethal (unless mosaic)

isochromosome of the X chromosome leads to turners in females

24

what are ring chromosomes?

A ring chromosome forms when a chromosome loses
genetic material at the terminal portions & the ends fuse to form a ring like structure