Lecture 10 Flashcards
How can genes behave as unlinked?
- They are on different chromosomes
- They are on the same chromosome but far enough away from each other
How does the probability of crossing over increase?
It increases with greater distance between gene loci
What is Recombination?
Any natural process in a diploid cell that generates new alleles or chromosomal combinations
What are the types of Recombination?
- Random fertilization
- Independent assortment
- Crossing over
What is Random Fertilization?
Random fusing of gamers to create organisms with new genotypes
What is Independent assortment?
When each synapses chromosome pair orients itself independently from other chromosomes pairs in Meiosis I
Each sister chromosome orients itself independently in Meiosis II
What is the formula for Recombination Frequency?
Sum of all recombinants/total number of progeny
Why are Recombination frequencies not higher than 50%?
If two genes on one chromosome are unlinked they have two equally likely locations to be in either on homologous chromosome I or II.
Why might recombination frequency not reflect true distances?
Cross overs are reduced near the centromere
Once a crossover occurs in an area, it tends to interfere with additional cross overs in that area
Genes that are far apart show a maximum of 50% recombination
What does the 3 Point Test-cross allow for?
Allows for the order and distance between three potentially linked genes to be determined in a single experiment
What occurs in a Three Point Test-cross?
A triple heterozygote and a triple recessive individual are crossed. Then you take the recombination frequency by looking at the number of recombination events between each pair of genes
In a Three point test cross, what will the realest progeny be?
Those types in which two cross over events have occurred
What is the formula to determine the different number of gametes/phenotypes?
2^(number of genes)
