Lec 11. Linkage, Recombination, and Euk gene mapping Flashcards
Where is the gene for pattern baldness located?
On the x chromosome, leading to the discovery that it is influenced by variation in the androgen receptor gene
What are the 3 laws mendel stated?
Principle of segregation, independent assortment, and recombination
What is the principle of segregation?
alleles separate during meiosis
What is independent assortment?
Alleles at one locus sort independently from alleles at another locus.
What is recombination?
alleles sort into new combinations
What is one exception to independent assortment? What is it good for?
Linked genes dont assort independently. Good for mapping the genome
Complete linkage leads to what?
Leads to nonrecombinant gametes and nonrecombinant progeny
What disrupts linked genes? What does it lead to?
Crossing over. Leads to recombinant gametes and recombinant progeny
How did we start mapping genes?
One way is to establish genes are on the same chromosome by breeding them. Then we can start asking questions about crossing over. Crossing over leads to rearrangement of alleles. If genes are really far apart they appear to be unlinked because of so much recombination. The closer they are the less recombination happens. Thus when crossing over events are set up for mapping, half of crossing over events are invisible to us since they are taking place between sister chromatids
What happens with a single crossover?
Half nonrecombinant gametes, half recombinant gametes
How can the degree of linkage be calculated by?
Comparing the observed frequencies to expected frequencies for complete linkage vs independent assortment.
How does crossing over frequency increase and decrease?
Increases with distance and decreases with proximity
How does one determine if two genes are segregating independently?
Doing a chisquare analysis.
How are genetic maps determined by?
Recombinant frequency.
What is the map unit?
centiMorgan
