Mod 9- Effects Of DNA Mutations Flashcards
What are the effects of mutations on the information content of a gene?
Mutations can alter the information content by changing the sequence of nucleotides, potentially affecting gene expression and function.
This includes point mutations, insertions, deletions, and other types of mutations.
Define point mutation.
One base pair is replaced with another (one base pair changes)
This can be classified into transitions and transversions.
What is a transition mutation?
A mutation where a purine is replaced by another purine (A ↔ G) or a pyrimidine is replaced by another pyrimidine (T ↔ C).
What is a transversion mutation?
A mutation where a purine is replaced by a pyrimidine or vice versa (A or G ↔ T or C).
What occurs during an insertion mutation?
One or more base pairs are inserted into the DNA sequence.
What occurs during a deletion mutation?
One or more base pairs are deleted from the DNA sequence.
Define inversion mutation.
Two or more base pairs are excised and reinserted in the opposite orientation.
What is a synonymous mutation?
A mutation that has no effect on the amino acid sequence, also called a silent mutation.
What is a non-synonymous mutation?
A mutation that changes the amino acid sequence, also known as a missense mutation.
What is a nonsense mutation?
A mutation that changes a codon for an amino acid into a stop codon.
this is detrimental
What is a readthrough mutation?
A mutation that changes a stop codon to a codon for an amino acid.
This could change its function
What is a frameshift mutation?
A mutation that changes the reading frame, altering all downstream codons.
What are suppressive mutations?
Mutations that can reverse the effects of an earlier mutation, such as second site reversion.
What are monogenic disorders?
Inherited diseases caused by defects in individual genes.
What is one of the most common monogenic disorders in the UK?
Cystic Fibrosis.
What does the cystic fibrosis transmembrane regulator (CFTR) gene do?
It directs the synthesis of the CFTR protein, which is a chloride channel responsible for the proper balance of salt and water within a cell.
What is the most common mutation in CFTR among UK patients?
ΔF508 or F508del (68% of cases), which is a deletion of three nucleotides.
What does the ΔF508 mutation remove?
A codon for phenylalanine (F), which is the 508th amino acid in the polypeptide.
What is the second commonest CFTR mutation?
G542X (2.5% of cases), which is a nonsense mutation that changes glycine (G) at position 542 to a stop codon (X).
What is the third commonest CFTR mutation?
G551D (1.5% of cases), a non-synonymous point mutation that changes glycine (G) at position 551 to aspartic acid (D).
What is the treatment for Cystic Fibrosis that includes Ivacaftor and Lumacaftor?
Orkambi.
What are mutations important for in organisms?
Evolution and diversity of organisms
Some mutations may also cause disease.
What are monogenic disorders?
Inherited diseases caused by defects in individual genes.
What does phenotype refer to?
Biological characteristics.
What does it mean that most organisms are diploid?
They have two copies of each chromosome and gene.
What are alleles?
Alternate forms of a gene.
What is haploinsufficiency?
A condition where a mutation in just one gene causes disease.
What is an example of a disorder caused by haploinsufficiency?
Mandibulofacial Dysostosis Guion Almeida type (MFDGA).
What is a common result of large deletion mutations?
Diseases such as deletion of about 500 kb from the X chromosome.
What is trisomy?
Three copies of a chromosome.
What condition is caused by trisomy of chromosome 21?
Down syndrome.
What is monosomy?
Where one chromosome is missing.
What does a chromosome translocation involve?
Part of one chromosome becomes attached to another chromosome.
What is the Philadelphia chromosome?
A common cause of leukemia associated with the bcr-abl gene.
What happens when the bcr-abl gene is switched on all the time?
Cell division becomes uncontrolled.
True or False: Not all human mutations are harmful.
True.
What is the Apolipoprotein A-I ‘Milano’ variant associated with?
Low prevalence of cardiovascular disease in carriers.
What mutation is associated with high bone density?
G171V missense mutation in LDL-Receptor–Related Protein 5 (LRP5).
What is the relationship between red hair and pain sensitivity?
Individuals with red hair often require more anaesthesia due to a loss of MC1R function.
What is a characteristic of natural short sleepers?
Lifelong short sleep with no obvious adverse outcomes.
What mutation is associated with natural short sleep?
Missense mutation in DEC2 (DEC2-P384R).
