Week 3 Flashcards
Why are human males hemizygous?
Because only one allele is present on the gene locus, as males possess two different sex chromosomes
What is a reciprocal cross?
Female phenotypeA x male phenotypeB
Reciprocal is:
Female phenotypeB x male phenotypeA
- the crosses have different outcomes of the gene is on a sex chromosome
When is a reciprocal cross used?
To determine if a gene locus is on a sex chromosome
What are some examples of X linked traits?
White eye in drosophila
Haemophilia in humans
Define pseudoautosomal region
Homologous regions on the ends of the X and Y chromosome
Define heterogametic sex
A sex that has two types of sex chromosomes
Define homogametic sex
A sex which has one type of sex chromosome
Define hermaphrodite
Having both male and female reproductive organs
What are Barr bodies?
Dark bodies on the perimeter of interphase cells of females not seen in males
An inactive X chromosome
When does X inactivation occur in humans?
15-16 days (500 cell stage)
What does X inactivation mean for heterozygous female
Mosaic body pattern due to random X inactivation
What is a XIST?
An X-inactivation specific transcript
- a gene locus on the X chromosome which is transcribed from the inactive c chromosome
What is a sex influenced trait?
A trait Influenced by sex of individual
What is a sex limited trait?
A phenotype limited to one sex but can be passed to offspring by both sexes
Define heterogeneity/ heterogenous trait
A phenotype which may be the result of mutations at more than one locus
