lecture 21 Flashcards
chromosomal rearrangements
what are the two types of BALANCED chromosomal rearrangements?
inversions and translocations
what is a balanced chromosomal rearrangement?
there is a change in the chromosome gene order but no duplication or deletion of DNA in the chromosome
what type of chromosomal rearrangement involves an internal segment of a chromosome being broken twice(DSB), and rejoined?
inversion
what type of chromosomal rearrangement involves fragments of two non-homologous chromosomes trading places?
translocation
how do oncogenes form in an inversion?
if the break occurs in the middle of two genes, the resulting gene fusion once the ends have been flipped can be an oncogene(cancerous)
what is it called when the centromere is OUTSIDE of the inversion?
paracentric
what is it called when the centromere is INCLUDED in the inversion?
pericentric
in order for alleles to line up after an inversion has taken place, what must form?
an inversion loop
what is the result of an inversion loop?
crossing-over, resulting in decreased recombination
in paracentric heterozygote inversions, what is the name of the fragment that is lost?
acentric fragment
what is the name of the chromosome part that connects the two chromosomes in a paracentric heterozygote inversion?
paracentric bridge
what is the RF for a paracentric heterozygote inversion?
0% because the recombinants are all lethals because the paracentric bridge gets cut in half during telophase I resulting in half the genetic material in the gametes
what is the RF is pericentric heterozygote inversions?
0% because only the parental gametes survive because the recombinants have a genetic imbalance as they have double some genes and lack other genes
what is it called when two non‐homologous chromosomes mutate by exchanging parts?
translocation
what type of structure forms in prophase I in a reciprocal translocation?
cross-like structure of two chromosomes
what are the results of alternate segregation in reciprocal translocation?
viable gametes with reduced fertility
what are the results of adjacent-1 segregation in reciprocal translocation?
non-viable gametes
what are the results of adjacent-2 segregation in reciprocal translocation?
non-viable gametes, doesn’t occur basically at all
what are the two types of unbalanced chromosomal rearrangements?
deletions and duplications
what is the double of genetic information on one part of a chromosome called?
duplication
what is an intragenic deletion?
a small deletion WITHIN a gene that inactivates it
how many chromosome breaks occur in an intragenic deletion?
two
how is an intragenic deletion different than a single nucleotide mutation?
a single nucleotide mutation can be repaired
what is multigenic deletion?
deletion on a chromosome resulting in the loss of multiple genes
what is it called when alleles for recessive traits seem to show dominance over normal phenotypes?
pseudodominance
how does pseudodominance occur?
if there is a deletion, there is only one allele that can be expressed, if it is recessive it may appear that it is masking the dominant allele that was actually deleted
what happens in a tandem duplication?
the genetic material for a gene(s) is implanted into a chromosome next to where that gene(s) already resides
what happens in an insertional duplication?
the genetic material for a gene(s) is implanted at some point in the chromosome that is not near where that gene(s) already resides
what is it called when two non-homologous chromosomes mutate only by the exchange of genetic information going from one to the other?
non-reciprocal translocation
what are the results of a non-reciprocal translocation?
an insertion in one chromosome and a deletion in the other
