00:03
Starting with a population of genetically identical mice, you discover two independent mutant strains in which all the animals produce tumors at the base of their tails.
00:14
In both strains, you know that the tumors are due to single dna mutation.
00:19
You cross a mutant mouse from one strain to a mutant mouse from the second strain, and actually found none of their offspring produce tumors at the base of their tails.
00:34
From this experiment, what can you conclude about the mode of inheritance of the cross of the two mutant strains of the mice and the most likely position of the mutations? so in this case, we can actually tell that most likely the tumor is involved two different genes.
01:08
So it's not a single gene trait, it's actually two genes.
01:13
Let's say these two genes, we call them a and b.
01:19
So most likely in one of the strains, you have homozygous capital a and homozygous lower b.
01:32
Due to the homozygous lower b, which is recessive, you get tumor.
01:38
Strain two most likely has homozygous lower a but homozygous b.
01:52
Now when you have homozygous lower a, then this also cause tumor.
01:59
But when you cross the two strains, homozygous capital a and lower b cross with homozygous lower a and capital b.
02:13
Now you produce capital a and lower b gametes and this one produce lower a and capital b gametes...