Lecture 22 Flashcards
What are polyploidy and other chromosomal abberations?
Polyploidy is possession of multiple entire chromosome sets, other chromosomal aberrations are: loss, gain or rearrangement of parts of chromosomes.
How does polyploidy typically occur?
A meiotic error causes the gametes to have the standard unreduced amount of chromosomes, leading to offspring with multiple sets.
What is an autopolyploid? What is an allopolyploid?
An autopolyploid is a polyploid produced by breeding within the same species, an allopolyploid is produced from different species, note that a polyploid can be both, an autoallopolyploid.
Compare the relative breeding ability of auto and allopolyploids. What will make the weaker one able to breed?
Autopolyploids will typically be able to breed as long as the offspring does not have an odd number of chromosomes. Allopolyploids will typically be sterile due to no homologous chromosome pairs, however, if the chromosome number in these allopolyploids somehow doubles this will lead to a fertile individual.
What kind of polyploid is typically infertile? What is the problem with polyploid mammals and are these rules set in stone?
An odd numbered polyploid e.g triploid or pentaploid is typically infertile, polyploid mammals are typically unlikely due to X inactivation, some mammals get around this through missing certain chromosomes.
What possible chromosomal aberrations are there and what do they do?
deletion: removes a chromosomal segment.
Duplication: repeats a segment.
Inversion: reverses a chromosome segment
Translocation: moves a segment from one chromosome to another non homologous one, a reciprocal translocation is the most common, which involves exchanging fragments, nonreciprocal ranslocations occur though, in which a chromosome transfers a fragment without recieving one.
What is Lequene syndrome and what is its other name?
a syndrome which occurs due to deletion of the tip of the short arm on chromosome 5, also known as the cri du chat syndrome as babies with it cry like cats.
What is williams-Beuren syndrome? What symptoms does it have?
A syndrome caused by a deletion on chromosome 7 which is very small (microdeletion), symptoms are reduced spatial awareness/cognition, autism, ease with strangers, left handed-ness, love for music, social and cardiovascular problems. Subtle differences can occur based on how much is deleted.
What is the big problem inversion causes during meiosis?
Meiosis is very specific and leads to chromosomes unsuccessfully pairing up, this can lead to one chromosome ending up shorter and one ending up longer after splitting.
What is Philadelphia translocation, what is its major symptom and what is it treatable with?
A philadelphia translocation is a reciprocal translocation which occurs between chromosome 9 and 22 which leads to the abl gene of chromosome 9 merging with the bcr gene of 22, this altered abl gene doesn’t function properly, leading to chronic myeloid leukemia in 95% of patients but is treatable with gleevec in 90% of cases.
What is duchene muscular dystrophy? How can heterozygous women get it?
Duchenne muscular dystrophy is an X linked disease most common in men, women that are heterozygous can get it due to translocation of part of the DMD+ gene on chromosome 21.
What is familial down syndrome and what are the possible zygotes?
Down syndrome which occurs due to translocation between chromosome 14 and 21 in the gametes during meiosis leading to 3/6 lethal 1/6 with down syndrome, 1/6 as a translocation carrier (they are fine but can pass it on to offspring) and 1/6 normal
