Chapter 6 Questions Flashcards
(14 cards)
When do chromosome rearrangements occurs?
When double strand breaks occur in DNA molecules found within a chromosome.
When do problems in chromosome pairing occur in heterozygotes?
During prophase I in meiosis.
How do duplications and deletions often arise?
From unequal crossing over, in which duplicated segments of chromosomes misalign during the process.
What is gene dosage?
The amount of a particular protein synthesized by a cell is often directly related to the number of copies of its corresponding gene: an individual organism with 3 functional copies of a gene often produces 1.5 times as much protein encoded by that gene as an individual with 2 copies.
Why do chromosome duplications often result in abnormal phenotypes?
Because developmental processes depend on the relative amounts of proteins encoded by different genes.
How is pseudodominance produced by a chromosome deletion?
When a wild-type allele on a homologous chromosome gets deleted.
What can an inversion do?
Break a gene into two parts and one part may move to a new location and destroy the function of the gene in that location.
What is the difference between an individual who is homozygous for an inversion and one who is heterozygous?
Someone who is homozygous will have no special problems arising in meiosis and the 2 homologous chromosomes can separate normally. In heterozygous inversion, the sequences of the homologous chromosomes can only align if the two chromosomes form an inversion loop, they also exhibit reduced recombination.
When is a dicentric chromosome produced?
During crossing over in a heterozygous paracentric inversion.
How can translocations effect the phenotype?
They can physically link genes that were formally on different chromosomes, they can break a gene and disrupt its function.
What is the outcome of a robertsonian translocation?
One large chromosome and one very small chromosome with two very short arms.
Why are sex chromosome anueploidies more common than autosomal anueploidies?
Dosage compensation prevents additional copies of X linked genes in mammals, and there is little information on the Y chromosome so extra copies of X and Y have little effect on development.
Why does autopolyploidy usually result in sterility?
Because all chromosome sets are from the same species, they are homologous and when they attempt to line up in prophase I of meiosis it results in sterility. On
What is the significance of polyploidy?
An increase in chromosome number is often associated with an increase in cell size.
