Linkage and Mapping Flashcards
What is linkage phase?
The arrangement of alleles on the two chromosomes. If an individual is heterozygous for two genes, they will have two different phases.
What happens if no crossovers occur between linked genes?
Only parental gametes will be made.
What is the definition of linked genes?
When the number of parental type gametes exceeds the number of recombinant type gametes.
What does it mean if two genes are syntenic?
They are found on the same chromosome.
How can one identify that genes are unlinked?
An equal number of parental and recombinant type gametes are produced.
What does the distance of 1 map unit represent?
1% recombinant frequency; the further away two genes are on a chromosome, the greater the chance of crossing over.
What is the locus of a gene?
The place on the chromosome where the gene is located.
Can the recombinant frequency between two genes exceed 50%?
No.
Why are smaller map distances more accurate than larger ones?
Genes that are far apart are more likely to have double crossovers, which appear as parentals. Thus, the number of recombinants and the map distance becomes underestimated.
Why don’t double crossovers (2-strand, 3-strand, or 4-strand) increase the recombinant frequency between two genes?
2-strand double crossovers, which produce only parental gametes, and 4 stand double crossovers, which produce only recombinant gametes, occur with equal frequency, meaning they sum to contribute to 50% recombinant frequency. 3-strand double crossovers all produce 50% recombinant gametes.
What is chromosomal interference?
When the observed number of double crossover phenotypes is smaller than the expected number, calculated by multiplying the two single crossover frequencies together.
What are chiasmata?
The sites of recombination during meiosis.
