Genetic Linkage Flashcards
What is Mendel’s principle of segregation?
… states that for a diploid individual. the two alleles at a particular gene locus separate during meiosis and up in different gametes.
What is Mende’s principle of independent assortment?
… states that segregation of alleles at a particular genes locus occurs independently of the segregation of alleles at other loci.
What are the conditions for Mendel’s principle of independent assortment?
a) the genes in question are on separate chromosomes.
b) the genes are widely separated on the same chromosome.
Mendel’s second rule DOES NOT apply to many dihybrid crosses.
Where are genes located?
On chromosomes
Do homologous pairs segregate independently of other homologous pairs?
Yes!
How can Mendel’s principle of independent assortment be violated?
When genes are present on the same chromosomes ,i.e., they show a strong tendency to stay together and therefore co-inherited.
What are linked genes?
Genes locates close together on the same chromosome
What is a linkage group?
All of the genes on a single chromosome. They do not assort independently but tend to be co-inherited belong to a linkage group.
(rather than independently assorting during cell division, they move as a unit)
What are Syntenic genes?
Genes that reside on the same chromosomes
What is Linked Gene Inheritance?
Genes that DO NOT assort independently.
(Syntenic genes show linked gene inheritance)
How does Recombination occur?
(Hint: from P to F1)
P generation: AABB x aabb
(gamete formation)
Gametes AB ab
Fertilization
F1 generation AaBb
(gamete formation)
Gametes AB ab Ab aB
(parental combination (new combination
-nonrecombinant -recombinant
alleles) alleles)
What is the expected phenotypic ratio in F2 progeny after selfing the F1 generation in a dihybrid cross for a digenic trait? Is this seen in linkage?
The expected phenotypic ratio is- 9:3:3:1
This is NOT seen in linkage/ non-independent assortment of digenic traits.
Instead there is a predominance of progeny showing the parental type.
What are recombinant gametes?
New combinations of alleles that are not seen in the parental gametes.
What are non-recombinant gametes?
Original combinations of alleles that are found in the parental gametes.
What is the expected test cross ratio in a dihybrid cross for a digenic trait? Is this seen in linkage?
The expected test cross ratio is- 1:1:1:1
This is NOT seen in the linkage/ non-independent assortment of digenic traits.