Mutations - DNA Unit Test #1 2023

What is the accuracy of DNA replication? (2)

• Quite accurate

• Error probability - 1 in 1 billion nucleotides

What is the speed of DNA replication in bacteria vs humans?

• Bacteria: 1000/s

• Humans: 50/s

What is a mutation?

Any change in the DNA sequence that affects the genetic information

• May or may not cause a change in the trait

What is a point mutation? (2)

A change in a single base pair in DNA (base substitution)

3 types - silent, nonsense, missense

What is a silent mutation?

A change of one base in the DNA/mRNA sequence but the new codon codes for the same amino acid

What is a nonsense mutation?

A change in the sequence that results in the code for a premature stop codon. The protein is incomplete + usually non-functional

What is a missense mutation?

A change in the sequence that results in a new codon for a new amino acid.

What is a frameshift mutation?

An addition or deletion of a single base, or the addition or deletion of a triplet (set of 3 bases)

What is more harmful - point mutation or frameshift?

Frameshift is more harmful - disrupts the whole amino acid chain, while point only disrupts one codon

What is a mutagen? + examples of mutagens

Any agent that can cause a change in DNA

Examples: radiation (x-rays), chemicals (benzene, asbestos)

The CFTR protein consists of 1480 amino acids, how many bases are involved?

4,440 bases

Which gene is mutated in cystic fibrosis?

CFTR gene

What is the function of the normal gene in CF?

Forms a channel that regulates the transport of chloride + water across membranes of various cells of respiratory + digestive systems

What happens when the gene is mutated in CF? (2)

• Alters the protein so the channel is blocked

• Chlorine + water aren’t transported out = abnormally thick sticky mucus lining the: lungs, pancreas, other digestive organs

Which chromosome is the CF gene found on?

Chromosome 7

What are some of the symptoms of CF? (2.3)

• Problems breathing

• Bacterial infections in lungs

  • chronic coughing

  • wheezing

  • inflammation

What are possible treatments of Cystic Fibrosis? (4)

• Chest physiotherapy

• Modified diet

• Use of antibiotics to control lung infection

• Lung transplants

What are the 4 types of chromosomal alterations/mutations?

• Deletion

• Duplication

• Inversion

• Translocation

What is the deletion chromosomal mutation?

A large section of chromosomes can be deleted or left out = loss of a number of genes

What is the duplication chromosomal mutation?

Some genes are duplicated + displaced twice on the same chromosome = a part of the chromatid breaks off and attaches to the sister chromatid

What is the inversion chromosomal mutation?

A region of DNA on the chromosome breaks off + reattaches backwards or reorients its arrangement

What is the translocations chromosomal mutation?

Occurs when part of one chromosome breaks off + is added to a different chromosome