Genetics 1 and 2 Flashcards
Describe an acrocentric chromosome
chromo with centromere near telomere
What is Rob translocation
Occurs when a piece of a chromosome becomes attached to a nonhomologous chromosome.
The two pieces are exchanged equally
- short arm of one acrocentric chromsomes exchanged with long arm of another- metacentric chromosome
- only between acrocentric chromosomes
- Trivalent formation
What is reciprocal translocation?
If two nonhomologous chromosomes synapse and undergo crossing over during meiosis I
when two chromosomes exchange terminal pieces of genetic material
Quadrivalent formation
a balanced reciprocal translocation involving 2 different chromosomes can lead to what?
the formation of a quadrivalent.
to main homologous pairing
What causes translocation Downs?
Robertsonion translocation of chromosomes 14 and 21 whereby there is fusion of the long arms of chr 14 and chr 21
What is an isochromosome?
- chromosome with 2 identical arms (2 p arms, 2 q arms)
- Due to centromere fission
- Always unbalanced genetic material
- Always leads to partial trisomy or partial monosomy
What is a ring chromsome?
- When chromosome break in 2 places
- Ends of chromosome arm fuse together to form circular structure
- Deleted genetic material nears ends of chromosome is lost
What is genetic mosaicism?
2 or more cell populations with distinct karyotypes or genotypes in one individual
What is the karyotype for Mosaic Down Syndrome?
46,N/47 +21
Describe a sub-metacentric chromosome
closer to one telemore
Describe a metacentric chromosome
centromere in the middle
How does aneuploidy occur?
- aneuploid gametes can be generated by meiotic nondisjunction
- nondisjunction during maternal meiosis I is the most common cause of aneuploidy
