CHROMOSOMAL REARRANGEMENTS AND EXTRA QUESTIONS

Several people asked for additional practice questions: I have added a few (quite challenging ones!) on the Paper-saving page, and you'll find more on my loppins blog.

PLEASE POST HERE ALL YOUR QUESTIONS ON INVERSIONS!

REGARDING CHROMOSOMAL REARRANGEMENTS WE SAID...

Assumptions for diploids in BIOL334=> we only deal with rearrangements that do NOT BREAK genes.

The main things to remember are that:

- at meiosis, homologous bits of chromosome do anything it takes to pair up;

- if a rearrangement involves a very small portion of a chormosome (at the base-pairs scale), the energy required to 'twist and bend' in order to pair is too high, so that region will just stay unpaired

- once you figure out what the chromosomes look like as they are paired up at meiosis, you can start predicting what will be the consequences of no crossovers, crossovers in a given region, crossovers in a different region, etc.

Generally speaking... 

A homozygous for a chromosomal rearrangement will produce all viable gametes, regardless of where crossovers happen (pairing does not require 'twisting, bending, and looping' of chromosomes);

A heterozygous for a large enough inversion will produce some viable and some lethal gametes (i.e. will have decreased fertility). Single/odd numbers of crossovers within the inverted region result in non-viable gametes. From a RF perspective, the RF between genes that are on either side of the inverted region will be decreased.

TRANSLOCATIONS will be discussed on Friday.

Cheers

Pam