1. General Genetics Lecturer Alshehri, Dokhnah Saeed dalshehri@ut.edu.sa
(Practical Session) BIO221
Lecturer
Alshehri, Dokhnah Saeed
Alshehri, Dikhnah Saeed

2. 4th lab
Lethal genes
Alshehri, Dikhnah Saeed

3. Outlines: The definition of the lethal genes.
Some examples of lethal genes.
Some practical Exercises.
Alshehri, Dikhnah Saeed

4. What are Lethal Genes?
Genes which result in viability reduction of individual or become a cause for death of individuals carrying them. Some lethal genes cause death of zygote or the early embryos, while some genes express their effect in later stages of development.
Alshehri, Dikhnah Saeed

5. DOMINANT LETHAL ALLELES
Alshehri, Dikhnah Saeed

6. Exercise 1
In mice the allele for yellow fur (Y) is dominant to the allele for grey (y).
If a pair of yellow mice are mated the result is
2 yellow: 1 grey
If a yellow mouse mated with a gray one and the result was 1\2 yellow: 1\2 grey
Explain the result depending on the genetic basis?
Alshehri, Dikhnah Saeed

7. Home work
1- When a dextar cattle (short- legged) which is dominant trait mates with a Kerry cattle (long- legged) the result is 1\2 dextar and 1\2 Kerry. What are the genotype of the parents?
2- In the case of mating between two dextar the result was : 2 dextar : 1 Kerry . What are the genotypes of the parents, and explain why did the result was not 3 dextars:1 Kerry as the dextar dominant over the Kerry ?
Alshehri, Dikhnah Saeed

8. Alshehri, Dikhnah Saeed