Linked Genes and Sex Determination Flashcards
What is a wild type trait?
A trait that appears most often in a population, not necessarily dominant
What is the XX/X0 system?
Present in some insects, sex is determined by ratio of X chromosomes to autosomes(0.5= male, 1 = female)
What is the XX/XY system?
Present in humans, homogametic versus heterogametic. Males are XY, females are XX
What is the ZZ/ZW system?
Opposite of XX/XY, males are homogametic and females are heterogametic. present in some birds/ snakes
What is the haplo-diploid system?
Ploidy of cells. Diploid cells produce females, haploid produces males because there are no sex chromosomes
What is a key difference between the X and Y chromosome?
The X chromosome is much larger and has many more genes than the Y chromosome
What is a pseudoautosomal region?
Located at the tips of the X and Y chromosomes, these are small regions where the chromosomes are homologous which enables crossing over.
What is the SRY gene?
The sex-determining region Y; presence of this gene causes development of male reproductive organs and absence causes the default(female) state to develop
What is a Barr body?
The inactivated form of an X chromosome in females
What are characteristics of X inactivation?
It is random, independent, and females are mosaic
What is the formula for the number of Barr bodies?
X= n-1, where n is the number of X chromosomes present
What is the mechanism for Random X inactivation?
Assessment of how many X chromosomes are present, One X is selected to be active and the rest are inactivated. Each X chromosome has a XIST gene(x-inactive specific transcript), which is only expressed on the inactive X chromosomes. Xist codes for long RNA, which coats the X and makes it inactive.
What is the relationship between the number of genes and the number of chromosomes in a cell?
The number of genes > the number of chromosomes
What are linked genes?
Genes located near each other on the same chromosome that tend to be inherited together.
What is the recombination frequency?
The number of recombinants(genes that aren’t inherited together) out of the total population of the generation
