Topic 4 Chormosomal Abnormalities Flashcards
What happens if repeater regions of dna are aligned
They can crossover and cause loss of some genes, deletion
What is gene balance
The number of genes that create the phenotype. If altered, it could affect the fertility of ppl and viablity of gamete
How do deletion loops form
In the chromosomes of deletion Heterozygote.
Recomb can only happen in homologous regions so if one chronometer has non homologous genes to the other chromosome, is form a deletion loop after affect genetic map distance
What are tandem duplications
Duplication of regions on one side of centromere
Same order : ABAB
reverse order: ABBA
What are nontandem duplications
Duplications that from on either side of centromere
BC. BC
BC CB
Why do duplicates genes over time change?
Because of the gradual accumulation of point mutations
What causes inversions
Chromosome breakage
What is a pericentric inversion
When inversion occur and carry’s the centromere with it. The breakage occurred on either side of the centromere
What are paracentric inversions
The inversion does not take the centromere with it
The points of breakage are one one side of the centromere
What happens if inversion occurs in a promoter
The inversion cause the promoter to turn on the wrong genes or not work at all
Why do inversion loops form
If one chromosome is inverted, the inversion loop makes the tightest possible alignment of it with the homologous regions of another homologous chromosome
What is the problem with each recombinant in a pericentric inversion Heterozygote resulting from crossing over
Each recombinant has a centromere, but has gene imbalance. Some regions are duplicated. Producing non viable zygotes
Why do oaracentric inversion heterozygotes make few if not any recombinant progeny
Because the chromosomes are lined up at the end, one recombinant will have two centromeres (dicentric, leading to it breaking, non viable)
And the other will have no centromeres, acentric. Meaning it’s lost during meiosis
What are balancer chromosomes
The chromosome in the inversion heterozygote that is not inverted
Why are inversion heterozygotes crossover suppressors
Because the recombinant gametes resulting from them are non viable and genetically imbalanced. Lead to seeing no crossover gametes
