Single genes and disorders Flashcards
Define:
Allele
Genotype
Phenotype
Allele: one of two or more alternative forms of a gene
Genotype: genetic constitution of an organism
Phenotype: Observable properties of an organism produced by a combination of genotype and environment
What is a mutation?
Nonsense? Missense? Synonymous? Point?
Alteration in DNA or chromosome sequence or structure. The sources of alleles and genetic variation.
Nonsense - change in sequence coding for a stop codon
Missense - change to amino acid sequence of protein
Synonymous - base substitution but no change to amino acid
Point - single base substitution
What can an insertion or deletion lead to?
Can lead to a frameshift mutation which throws off all the codons for the amino acids.
How can a mutation in an intron have an effect?
A gene being transcribed has regulatory points where proteins bind and if these change, the proteins will not bind and this affects transcription.
What is a homozygote?
A heterozygote?
Homozygote = a diploid organism having the same alleles at one or more genes
Heterozygote = a diploid organism having different alleles at one or more genes
What is a haploinsufficent gene?
The heterozygote makes 50% of normal level gene product but this is not enough for normal function.
What are the two types of autosomal inheritance?
Dominant and recessive
Give some rules on inheritance patterns in autosomal dominant inheritance
- Males and females affected equally
- Probability of an affected child is 50% is one parent is homozygous recessive and the other is heterozygous dominant
Give some rules on Sex (X) linked recessive inheritance
- More frequent in males as they have only one X chromosome
- Cannot be passed from father to son as Y chromosome comes from father
- All daughters of affected fathers are carriers
- By probability, half the sons of a carrier will be affected and half their daughters will be carriers.
Give a point on multifactorial inheritance
Most common traits are multifactorial: arising from the action of two or more genes and interaction between genes and the environment.