Advanced mendelian genetics 1 Flashcards
Define what a gene allele is and what we mean by dominant and recessive alleles Explain why an allele of a gene encoding a working version of isn enzyme is usually dominant over a mutant allele that encodes a non-working enzyme Define haploinsufficiency and the nature of dominant negative alleles, give examples to illustrate how these work Give one example where alleles of several genes combine to give different phenotypes
What is an allele?
An allele is a different variant of the same gene
What is a dominant allele?
A dominant allele produces an effect on the phenotype when present in either one or two copies
What is a recessive allele?
A recessive allele produces an effect only when there is no dominant allele present
What is usually dominant and what is usually recessives?
Dominant: normal copy (if heterozygous can still work)
Recessive: mutant
What is haploinisufficiency?
The presence of half the normal amount of protein (from one functional allele) IS NOT ENOUGH to give the normal phenotype (dominant mutant)
What does haploinsufficiency cause?
The exact level of the gene product is critical for normal metabolism
50% of the normal amount of the protein results in a mutant phenotype
What is Rubinstein-Taybi syndrome? (5)
Autosomal dominant condition Very rare 1/125000 Usually a new mutation Malformation of heart, broad thumbs and big toes, beaked nose Mental development affected
How does Rubinstein-Taybi syndrome occur?
CBP gene encoding wrong - mutant gene encodes non-functional CBP
