genetic linkage Flashcards
What is genetic linkage?
Genetic linkage refers to the phenomenon where genes located close to each other on the same chromosome tend to be inherited together during meiosis.
What was the Bateson, Saunders, and Punnett experiment?
he experiment involved crossing two plants with different traits (purple flowers/long pollen vs. red flowers/round pollen) to study if genes for these traits assort independently or show linkage.
What did Bateson, Saunders, and Punnett observe in their experiment?
The expected 9:3:3:1 ratio of F2 offspring was not observed, suggesting that the genes were linked rather than assorting independently.
How does the Chi-Square test help in genetic experiments?
The Chi-Square test helps determine if observed deviations from expected genetic ratios are statistically significant, helping to rule out random chance.
What are the three types of genetic linkage?
Complete Linkage - Genes on the same chromosome are inherited together without crossing over.
No Linkage - Genes are on separate chromosomes or far apart on the same chromosome.
Incomplete Linkage - Genes are on the same chromosome but undergo some recombination during meiosis.
What did Thomas Hunt Morgan discover in his Drosophila experiment?
Morgan showed that genes for body color and wing shape in fruit flies are linked because they are located on the same chromosome, but some recombination still occurs during meiosis.
What is sex linkage?
Sex linkage refers to genes located on the sex chromosomes (X or Y) and often exhibit different inheritance patterns based on the sex of the individual.
What is complete linkage?
Complete linkage occurs when two genes are very close to each other on the same chromosome and always inherit together without any recombination.
What is incomplete linkage?
Incomplete linkage occurs when genes are on the same chromosome but can undergo recombination during meiosis, leading to some genetic variation.
In Morgan’s genetic linkage experiment, what was the expected and observed result for body color and wing type?
Expected ratio if genes were unlinked: 1:1:1:1
Observed ratio (linked genes): 965 grey body & normal wings, 944 black body & vestigial wings, 185 black body & normal wings, 206 grey body & vestigial wings.
How does recombination affect genetic linkage?
Recombination, or crossing over, can occur between homologous chromosomes, leading to recombinant chromosomes and breaking the linkage between genes, although genes that are close together are less likely to recombine.
How is recombination frequency (Rf) calculated?
RecombinationFrequency(Rf)=
Totalnumberofoffspring/
Numberofrecombinantoffspring
×100
What did Sturtevant contribute to genetic mapping?
Sturtevant used recombination frequencies to construct the first genetic map, demonstrating that genes on chromosomes are arranged in a specific order.
What is a map unit (or centimorgan)?
One map unit (1 cM) represents a 1% recombination frequency, indicating that genes are 1% apart on a chromosome.
How does recombination frequency relate to genetic distance?
The larger the recombination frequency, the farther apart two genes are on a chromosome. Genes with 50% recombination frequency are either very far apart or on different chromosomes.
