Translocations Flashcards
What are the three ways in which translocated homologous chromosomes can separate?
Alternate segregation, adjacent I segregation and adjacent II segregation.
Which types of segregation produces balanced gametes?
Alternate.
What is a Robertsonian translocation?
Fusion of the long arms of two acrocentric chromosomes to form one new metacentric chromosome.
In chromosomes with what kind of short arms in viable Robertsonian translocation possible?
If the short arms doesn’t contain viable genes.
What is a trivalent?
The structure formed during meiosis in a heterozygote for a Robertsonian translocation.
What are the three possible outcomes of meiosis in a heterozygote for Robertsonian translocation?
Normal (two seperate original chromosomes), balanced (Robertsonian chromosome) and unbalanced.
How can Robertsonian translocations contribute to Down syndrome?
The long arm of chromosome 21 may fuse with a long arm of chromosomes 14, 13, 15 or 22.
How can Robertsonian translocations contribute to speciation?
Heterozygotes have reduced fertility, meaning the two different homozygotes interbreed with their own kind.
What is an Iso-chromosome?
There is loss of one arm of a chromosome and duplication of the other, forming a mirror metacentric chromosome.
What Iso-chromosome is common and what syndrome does is often cause?
X, Turner syndrome
Is fragile-X syndrome dominant or recessive, fully penetrant or not?
Dominant with incomplete penetrance.
How can a woman with a premutation for fragile-X syndrome have a son with a full mutation?
The premutation can expend (increase in the number of repeats) to a full mutation.
How does a greater number of small nuclear repeats decrease gene expression?
The greater the number of repeats, the greater the methylation, reducing transcription.
How can repeat expansion occur?
Their may be slippage during meiosis/mitosis and poor pairing.
