Lecture 46 Flashcards
What are the types of chromosome abnormalities that can occur?
- translocations
- deletions
- inversions
- ring chromosome
- isochromosome
What are the two types of translocations?
- reciprocal
2. robertsonian
What happens during a reciprocal translocation?
Exchange of genetic material between non homologous chromosomes
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
segregation at meiosis: reciprocal translocation?
will be quadrivalent
cells could show alternate segregation or adjacent segregation
What is alternate segregation?
cells may be normal or be a carrier of the translocation
what is a adjacent segregation?
incompatible with life.. sometimes will lead to some type of disorder
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
What happens during a t(8;14)?
Burkitt lymphoma
Dysregulation of c-Myc gene expression, leading to cancer
How does a robertsonian translocation occur?
it occurs between acrocentric chromosomes
there is a loss of the short arms; fusion of the long arms
effects during meiosis: robertsonian translocation?
forms a triavlent
can either have alternate segregation or adjacent segregation
What does a robertsonian translocation look like when the chromosomes go through adjacent segregation?
trisomy 14 and trisomy 21
How can microdeletion syndromes be detected?
karyotype, FISH, or CGH
depends on the size of the mutation
Cri-du-chat syndrome
deletion of the short arm of the 5 chromosome
features:
- high-pitched, cat-like cry
- intellectual disability
- microcephaly
- hypertelorism ( widely spaced eyes)
- speech issues
How is cri-du-chat syndrome detected?
Can be detected by FISH or CGH, and can sometimes be detected by karotyping
22q11.2 deletion syndrome is known as what other names?
velocardiofacial or DiGeorge syndrome
What are some symptoms of 22q11.2?
- congential heart defects
- absence of the thymus
- cleft lip and palate
- facial anomalies
- increased risk of schizophrenia
How to generically detect 22qll.2?
can use either FISH or CGH
Wolf-Hirschhorn syndrome
deletion of the short arm of the 4th chromosome
Features:
- seizures
- skeletal and cardial defects
- intellectual disability
- facial anomalies
What are two deletions of the 15q11-13 chromsome?
SNPRN and UBE3A
lead to either prader-willi or angleman syndrome
why might uniparental disomy occur?
trisomy rescue mechanism
chromosome reduplication
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)
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
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
