Lecture--Chapter 18 Flashcards
Gene mutations have both good and bad aspects. What are they?
- They allow variation in gene alleles and are essential for evolutionary change.
- Most mutations are harmful.
a group of processes by which a cell identifies and corrects damage to its DNA
DNA repair
Human cells have approximately how many molecular lesions per cell every day?
~1 million
relatively small changes in DNA sequence
gene mutations
What are the different types of gene mutations?
- Base substitutions
- Deletions or additions of one or more basepair
- Spontaneous or induced biochemical changes
What are the different types of base substitutions?
- point mutations
- transition mutations
- transversion mutations
a change in a single basepair
point mutation
a change of one purine (pyrimidine) to another purine (pyrimidine)
transition mutation
exchange of a purine and a pyrimidine
transversion mutation
A silent base substitution has how many amino acids altered and what is the likely effect on protein function?
none; none
A missense base substitution has how many amino acids altered and what is the likely effect on protein function?
one; neutral or inhibitory
A nonsense base substitution has how many amino acids altered and what is the likely effect on protein function?
many; inhibitory
A frameshift addition or deletion has how many amino acids altered and what is the likely effect on protein function?
many; inhibitory
a hereditary blood disorder for homozygotes, characterised by RBCs that have an abnormal, rigid, sickle shape
sickle cell disease
Heterozygotes for sickle cell disease have some protection against which disease?
malaria
Gene mutation of the promoter sequence may have what effect?
May increase or decrease the rate of transcription.
Gene mutation of the regulatory element/operator site sequence may have what effect?
May disrupt the ability of the gene to be properly regulated.
Gene mutation of the 5’-UTR/3’-UTR sequence may have what effect?
May alter the ability of mRNA to be translated; may alter mRNA stability.
Gene mutation of the splice recognition sequence may have what effect?
May alter the ability of pre-mRNA to be properly spliced.
Mutation effects at the genotype level:
- Wildtype (WT) allele
- Mutant allele
- Revertant allele
Mutation effects at the phenotype level:
- Deleterious mutation
- Lethal allele
- Beneficial allele
- Conditional mutants
- Suppressor mutations
a relatively prevalent allele in a population
wildtype (WT) allele
derived from a WT allele, relatively rare occurrence
mutant allele
a mutant allele changed back to a WT allele
revertant allele
decreases chance of survival and reproduction
deleterious mutation
results in death of the organism
lethal allele
improves individual survival and reproduction
beneficial allele
the phenotype is apparent under limited situations
conditional mutants
second site mutations that convert the mutant phenotype to a WT phenotype
suppressor mutations
Examples of suppressor mutations:
- intragenic
- intergenic (redundant function)
- intergenic (common pathway)
A 1st mutation disrupts normal protein function. A suppressor mutation in the same protein restores function. This is known as:
intragenic
A 2nd mutation alters a different protein to carry out that function. (gain of new enzyme function) This is known as:
intergenic (redundant function)
