Cytogenetics 2

Question 1

Contiguous Gene Syndromes

Answer 1

AKA microdeletion and duplication syndromes.

Clinical features are due to loss of 1 or more continuous genes in the region.

Mechanism is low copy repeated sequences.
- aberrant recombination results in deletions of variable size

Question 2

Parthenogenesis

Answer 2

Reproduction without fertilization

• Not possible for humans to have a completely maternal or paternal genome
• Androgenetic (extra embryonic membrane, but no fetus growth)
• Gynogentic (fetus growth, but no embryonic membrane)

Question 3

Genomic Imprinting

Answer 3

Imprinted genes are found in clusters on chromosomal regions under the control of an imprinting control region (ICR) which differerntially regulates methylation

During gametogenesis, parental imprints are erased

Imprinting is re-established when gender-specific patterns of de novo methylation are initaited within GC-rich areas of the ICRs

Imprinting is retained in somatic cells but reversible in gametes