Inheritance Flashcards
Define “loci”
The position of a gene on a chromosome
What is gene linkage?
Genes with loci on the same chromosome are linked
Why are genes with loci on the same chromosome linked? 3
- They stay together during independent assortment
- Will be passed on as a pair to the same gamete
- Will be inherited together
What is the relationship between distance between genes on a chromosomes and their linkage?
The closer together the loci of 2 genes on a chromosome, the more closely they are linked
Define “autosomal”
All the non sex chromosomes
Apart from independent assortment, why is it that when genes are closer together they are more likely to be linked?
Less likely to separated by crossing over between the pair
What does sex linkage mean?
The expression of alleles with a locus on a sex chromosome depends on the sex of the individuals
Why does the Y chromosome carry less genes than the X chromosome?
It is smaller
Why do males express all sex linked recessive genes?
- Only have one X chromosome
- Only has one allele for sex linked genes
- So they express this characteristic even if recessive
Name two examples of sex linked conditions
- Haemophilia
- Colour blindness
What is haemophilia?
Disease causing blood not to clot properly
Why do females not express all sex linked recessive genes?
- Females have two X chromosomes
- Must be homozygous recessive to suffer
How can phenotype ratio show sex linkage is taking place?
Female carrier: Male sufferer
1:1
