Linkage, Crossing-Over and Mapping in Eukaryotes Flashcards
Why did Mendel not find Linkage?
Mendel did not find linkage as he used 7 genes when pisum sativum also has 7 chromosomes
What is Linkage?
Genes that are part of the same chromosome
Genes undergo segregation (True or False)
False (Answer: the alleles at all loci of a chromosome would be transported as a unit during meiosis, unless it is crossing over)
What is crossing over
Crossing over results in the reshuffling of the alleles between homologous and always occurs during the tetrad stage
How do you measure the distance of one gene to that of another gene?
Genes are separated by distance are measured in map units or centiMorgan
How do you determine the frequency of crossing over
%recombination = number of recombinants/total number
The frequency of crossing over between any 2 loci on a single chromosome is proportional to the distance between them (True or False)
True
Crossing over can happen between sister chromatids (True or False)
False (Answer: Crossing over involves only nonsister chromatids)
complete linkage
genes so close to each other that crossover-events are too infrequent to be easily detected
The distance between 2 genes is directly proportional to the percentage of recombinant gametes (True or False)
True
Linkage Group
Genes located on the same chromosome show evidence of linkage to one another
number of Linkage groups is equal to the diploid number of a chromosome (True or False)
False (Answer: Haploid, humans have 23 linkage groups)
What was the source of gene separation?
Chiasma - present points of genetic exchange
Why did the frequency of the separation vary depending on the genes studied?
Genes located relatively close to each other along a chromosome are less likely to have a chiasmata form between them than if the two genes are farther apart
