chapter 17 Flashcards
what is a pericentric inversion
an inversion that includes the centromere
what is a paracentric inversion
an inversion that does not include the contromere
what is produced when crossing over occurs within an inversion loop
aberrant recombinant chromatids
why do pericentric inversions in heterozygotes produce few recombinant progeny
the recombinant chromatids become non-viable because there will be a delesion and duplication of certain genes in the recombinant progeny
why do paracentric inversions produce few recombinant progeny
one recombinant will have 2 centromeres while the other will have none thus the ones remaining are the parental type chromatids
what are the consequences of inversions
disrupt a gene or alter its expression but doesnt add or remove DNA
what is reciprocal translocation
when two different chromosomes have a chromosome break and one fragment from each replaces the other (reciprocal exchange of fragments)
what is robertsonian translocation
a chromosomal break that occurs near centromeres of two acrocentric chromosome
what is the product of a robertsonian translocation
a latge metacentric chromosome and another one small chromosome which is usually lost
what can be a result of translocation in somatic cells
oncogene activation
what are the phenotypic effects of reciprocal translocation
most dont affect phenotype because DNA isnt added or removed but abnormal phenotypes can be caused if translocation breakpoint disupts a gene
what is the effect of a translocation homozygote
no genetic consequences
what brings about delesions, duplications, inversions, and translocations
chromosomal breakage
homozygosity for a large delesion usually results to what
lethality
heterozygousity for large deletiom usually causes what
genetic imbalance
