genetic consequences of inversion and translocation

Question 1

What is translocation

Answer 1

-occur when one segment of chromosome breaks off and rejoin:
can be interchromosome (between two chromsome) or intrachromosome (in the same chromosome)
can be reciprocal or non reciprocal

Question 2

The effects of translocations on chromosomal segregation

Answer 2

•Translocations can create new linkage groups
•Different outcomes depending on if the translocation is homozygous (occur on both sister chromatids) or heterozygous (only one of the sister)

Question 3

The effects of translocations on chromosomal segregation of Translocation homozygote

Answer 3

•loci previously on separate chromosomes are now physically and genetically linked

Question 4

The effects of translocations on chromosomal segregation of Translocation heterozygote

Answer 4

•Chromosome segregation will lead to balanced or unbalanced gametes
•Only half of the gametes produced will be viable
•This will result in pseudo-linkage because independent assortment will not occur

Question 5

Method of seperation for translocational heterozygous

Answer 5

-alternative segregation

Question 6

What is Inversion

Answer 6

when a segment of the chromosome are reversed

Question 7

Two type of inversion

Answer 7

Paracentric inversion: does not include centromere
Pericentric inversion : does include centromere

Question 8

The effects of inversions on crossing over

Answer 8

•Inversions alter linkage groups
•Different outcomes depending on if the inversion is homozygous or heterozygous

Question 9

The effects of inversions on crossing over Inversion homozygote

Answer 9

•loci are physically located either closer together or further apart
Homozygous for inverted chromosomes canpair normally

Question 10

The effects of inversions on crossing over Inversion heterozygote

Answer 10

•Chromosomes pair via an inversion loop – physically obstructs crossing over
•Crossing over within an inversion loop leads to imbalanced chromosomes

Question 11

Outcomes of a single crossover -paracentric inversion

Answer 11

•Chromosome deletions
•Viable gametes contain only the original chromatids lead to the production of:
•Dicentric chromatid (two centromere), the dicentric bridge break randomly
•Production of acentric fragment ( no centromere)
1 normal, 2 deletion product ,1 inversed product

Question 12

Outcomes of a single crossover -pericentric inversion

Answer 12

•Sister chromatids segregate normally (II)
•4 chromosomes produced after recombination
•Harbour deletions and duplications
only two viable products

Question 13

Inversions “suppress”recombination

Answer 13

-Crossing over inside the inverted region -> problematic gametes
-Crossing over outside the inverted region produces normal gametes