chapter 15 Flashcards
Why are fruit flies a good experimental model for genetic studies?
They produce many offspring; A generation can be bred every two weeks; They have only four pairs of chromosomes
What notation did Morgan use to indicate wild type and mutant type?
He used lower case letters to represent traits and a superscript plus sign to represent the dominant, wild type traits
Why did Morgan use a different notation from regular dominant / recessive traits?
The traits he was studying were generated in his lab, and not natural traits
Describe sex-linked genes
A gene that is located on either sex chromosome
How do sex-linked genes affect gene expression?
For a recessive X-linked trait to be expressed: A female needs two copies of the allele (homozygous), A male needs only one copy of the allele (hemizygous); X-linked recessive disorders are much more common in males than in females
How are sex-linked genes different from linked genes?
Linked genes are genes located on the same chromosome that tend to be inherited together and are found on the autosomes
Describe x-linked traits
Genes on the X chromosome
Are x-linked traits more commonly expressed in males or females?
males
Why can mothers, but not fathers, pass x-linked genes to their sons?
Because fathers give a Y to their sons, but mothers give an X
What is X inactivation?
the X chromosomes in each cell is randomly inactivated during embryonic development
How does the inheritance pattern of linked genes differ from the inheritance pattern described by Mendel?
Rather than having a 9:3:3:1 ratio from a dihybrid cross and recombination of the parental phenotypes, it will have a 3:1 ratio and only the parental phenotypes
Drosophila melanogaster
the scientific name of the fruit fly used by Morgan
wild type
natural phenotype of fruit fly
mutant type
phenotypes developed in the lab by Morgan
double mutant
has a mutant allele for two genes
