Genetics Week 13 Flashcards
What is translocation
- It is the interchange of genetic material between non homologous chromosomes
Name the 2 types of Translocation
- Reciprocal Translation
-Robertsonian Translocation
What does Reciprocal Translocation involve
-Involve breaks in two different chromosomes with mutual exchange of material.
Resulting in derivative chromosomes.
When does Robertsonian Translocation occur
- They occur when the short arms of 2 acrotentric chromosomes(13,1415,21+22) are lost and the long arm fuses at the centromere to form a single chromosome
Explain the what happens to the carriers + offspring of Reciprocal Translocation
Carriers:
-Usually have a normal phenotype as the genetic material is balanced.
-Offspring may inherit duplications or deletions, leading to partial trisomies or monosomies with abnormal phenotypes.
Explain what happens to the carriers and offspring with Robertsonian Translocation
Carriers:
-Have 45 chromosomes but are phenotypically normal.
-Offspring may inherit unbalanced chromosomes, leading to monosomies or trisomies of the long arms.
Why do deletions occur
They occur due to a chromosome break, leading to the loss of genetic material
Name the 2 types of deletions
- Terminal deletions
-Interstitial deletions
What is terminal deletions
-The loss of the chromsomes tip following a single breake
What is interstitial deletions
- Loss of material between two breaks
How are zygotes formed with deletions
A gamete with a deletion usually combines with a normal gamete, forming a zygote with one normal chromosome and one with a deletion.
Give an example of a Deletion syndrome
Cri-du-chat syndrome
What is Cri-du-chat syndrome
- Deletion of the distal short arm of chromosome 5 (46,XY,del(5p)).
What are characteristics of Cri-du-chat syndrome
-“cat-like” cry in infants.
-Intellectual disability
When does UniParental Disomy occur(UPD)
Uniparental disomy (UPD) occurs when both copies of a chromosome come from one parent, and none are contributed by the other parent.
What are the 2 types of UniParent Disomy
Isodisomy:
Heterodisomy
Explain the types of UniParental Disomy
Isosidomy: Parent contributes 2 copies of one homolog
-Heterodisomy: Parent conntributes one copy of each homolog
Explain the mechanism of the offspring getting a autosomal recessive disease in relation to UniParental Disomy
- A parent conrtibutes 2 copies of a chromosome carrying a reccesive mutation, causing autosomal recessive disease
Name 3 conditons linked to UniParentalSyndrome
- Cystic fibrosis
-Prader willi syndrome
-Angel man Syndrome
What are microdeletions
- They are small chromosome deletions often detected using advance molecular techniques like FISH and aCGH
How are Microdeletions detected
-By molecular techniqes like FISH and aCGH
Name 3 examples of microdeletion syndromes
- Williams syndrome
-Wolf-Hirschorn Syndrome
-WAGR syndrome
What is the mechanism for how Micro deletions occur
- Low copy repeated sequences at deletion boundaries promote unequal crossing over, resulting in duplications and deletions
What is the Di George sequence caused by
- A primary defect in the migration of neural crest cells, leading to secondary abnormalities affecting the thymus, parathyroid glands and heart
What are clinical features of Di George sequence
- Structural or functional thymus defects
- Heart defects
-Learning disabilities9
What is the chromosomal cause of Di george and Velocardiofacial syndrome
- Microdeletion of chromosome 22q11.2
What are clinical characterisitcs of Velocardiofacial syndrome
- Cleft palate
-Heart malformatioms
What are clastogens
-Agents that cause chromosomal breakage
Give examples of clastogens
ionising radiations and infections
What is the fucntion of SOX9
- A gene which promotes male development and represses ovarian development
What is the function of SRY
-A gene which initiates male sex development
What happens when the SRY gene is expressed
-Produces a protein which regulates expression of SOX9
