B1 - Alleles Flashcards
What does it mean to be heterozygous for a gene?
Having two alleles that are different, the dominant one is the one expressed.
What is an alleles and why do we have 2?
Alleles are different versions of the same gene. One is inherited from each parent.
What do we call it when we have 2 copies of the same alleles?
Homozygous
What is a dominant allele?
The dominant alleles is alway expressed if it is heterozygous - recessive cannot be expressed. Huntingtons disorder is caused by a dominant allele. There is a 50% chance that a child will inherit the disorder if one parent is a carrier
What is a recessive allele? Give an example.
Recessive alleles are expressed in offspring only when inherited from both parents. Cystic fibrosis is a recessive disorder and people with only one allele will not have the disorder - instead they would be a carrier. Both parents have to be carriers or sufferers for the child to inherit the disorder
What are the male and female sex chromosomes?
Female - XX
Male - XY
What happens if you have a Y chromosome?
You are genetically male
What happens if you do not have a Y chromosome?
You are genetically female
What does genotype refer to?
the genetic constitution (make up)of an individual organism
What does phenotype mean?
The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.