Chapter 5 (Topic 3)

Question 1

What are lethal alleles?

Answer 1

Lethality occurs when two copies of a mutant allele are inherited, can be pinpointed if during crosses two dominant phenotypes crossed don’t produce all dominant ever.

Question 2

What is penetrance? Give an example

Answer 2

The percent of individuals with a mutation that show the phenotype, can be nonpenetration or incomplete or variable penetrance. Ex: Osteogemesis imperfecta, a dominant disorder of bone formation, but some never develop symptoms

Question 3

What is expressitivity?

Answer 3

Differing levels that a phenotype is expressed, can be variable expressivity as in individual show differing degrees of the phenotype, for ex: Polydactyly in cats

Question 4

What are three reasons individuals with the same mutation don’t show exactly the same phenotype?

Answer 4

environment- things we eat can activate diff gene pathways
othere genes- the genetic background and other genes can effect how certain genes are expressed
Subtlety of mutant phenotypes- missed classification- you can miss classify a mutation by thinking its the same when it’s something else.

Question 5

How can phenotypes not be expressed due to mutations?

Answer 5

Some times wild type phenotypes are usually created by a sequence of genes. if you have a mutation in one of the genes the phenotype will no loner be wildtype.
For example: Eye color in Drosophilia, goes from white (enzyme A) to Pink (enzyme B) to purple (enzyme C) to Red (WT), if mutation in any enzyme you don’t get the right phenotype