Topic 7 - Genetics, populations, evolution and ecosystems. Flashcards
When does inheritance by multiple occurs?
It occurs when more than 2 alternative alleles exist for a particular gene locus.
How many alleles does an individual inherit for these genes?
Only 2 alleles.
What does the immunoglobulin (I) gene code for?
It codes for the antigens on the surface of the red blood cells.
What are dihybrid crosses?
Dihybrid crosses is the inheritance of the characteristics controlled by different genes.
How can dihybrid crosses be used?
They can be used to show the likelihood of offspring inheriting certain combinations of the two characteristics.
What does it mean if alleles are co-dominant?
They can both be expressed in the phenotype as neither one is recessive.
What is sex-linkage?
Sex linkage is the expression of an allele dependent on the gender of the individual.
How is the size of the chromosomes relevant in relation to sex-linkage?
The Y chromosome is smaller and therefore most of the sex-linked genes are formed on the X chromosome.
How do men differ from women when expressing alleles linked to the X chromosome?
Men only have one X chromosome therefore whether the allele is recessive or dominant, it will be expressed.
What causes haemophilia?
Recessive X-linked gene.
What are autosomes?
Chromosomes that aren’t sex chromosomes.
What happens in an autosomal linkage?
Two or more genes are on the same autosomal chromosomes.
