Untit 1.4 Flashcards
What is the purpose of DNA replication?
To carefully preserve the genetic information encoded within the nucleotide base sequence.
What are mutations?
Changes in the genome that occur during DNA replication or cell division.
What are the two possible results of a mutation?
- No protein is expressed. 2. An altered protein is expressed.
What are single-gene mutations?
Mutations that affect only a few bases.
What are chromosome structure mutations?
Mutations that affect the structure of one or more chromosomes.
What is a substitution mutation?
The replacement of one nucleotide with another in a DNA sequence.
What is an insertion mutation?
The addition of one or more nucleotides into a DNA sequence.
What is a deletion mutation?
The removal of one or more nucleotides from a DNA sequence.
What is a point mutation?
A mutation that results in a change affecting only one codon.
What are the three types of point mutations?
Missense, nonsense, and splice-site mutations.
What is a missense mutation?
A mutation that changes the codon so a different amino acid is produced.
What is a potential result of a missense mutation?
It may change the shape of the protein, making it unable to carry out its function.
Can all missense mutations significantly affect the protein?
No, some changes in amino acids may not have a significant effect.
What is a nonsense mutation?
A mutation that changes a codon from an amino acid to a stop codon.
What is the effect of a nonsense mutation?
It results in a shorter protein, which is generally non-functional or its function is affected.
What is a splice-site mutation?
A mutation that affects the boundaries between exons and introns (splice sites).
How does a splice-site mutation affect a protein?
It can prevent splicing at that site, potentially leading to a very different protein due to post-transcriptional processing, with some introns included or exons removed.
Why are shortened proteins from nonsense mutations usually non-functional?
Because they are incomplete and lack essential regions for proper function.
What is a frame-shift mutation?
A mutation caused by insertions or deletions that shifts the codon reading frame by one codon.
What happens to the amino acids in a frame-shift mutation?
Completely different amino acids are coded for from the point of the mutation onwards.
What is the effect of a frame-shift mutation on the protein?
The resulting protein is significantly altered and is usually non-functional.
What are chromosome structure mutations?
Alterations that affect whole chromosomes and whole genes rather than just individual nucleotides.
What causes chromosome structure mutations?
Errors in cell division that cause a section of a chromosome to break off, be duplicated, or move onto another chromosome.
What is a deletion mutation in chromosomes?
A mutation where a section of a chromosome is removed.
What is a translocation mutation in chromosomes?
A mutation where a section of a chromosome is added to another chromosome that is not its homologous partner.
What is an inversion mutation in chromosomes?
A mutation where a section of a chromosome is reversed.
What is a duplication mutation in chromosomes?
A mutation where a section of a chromosome is added from its homologous partner.
Why are chromosome structure mutations often lethal?
Because they alter the structure of the chromosome, disrupting essential genetic information.
What is a mutation?
A rare, random change in a gene or chromosome that can be inherited.
How do mutations occur?
Mutations occur continuously and can be spontaneous or caused by factors such as ionising radiation or chemical mutagens.
What are examples of ionising radiation?
Gamma rays, X-rays, and ultraviolet rays.
What is an example of a chemical mutagen?
Tar from cigarette smoke.
What effect can mutations have on proteins?
Mutations can create faulty proteins by switching genes on or off, affecting their synthesis or function.
How can a mutation affect enzymes?
If a mutated enzyme’s active site is altered, the substrate may no longer fit, preventing the enzyme from functioning properly.
How can a mutation affect structural proteins like collagen?
It might cause the protein to lose its strength.
Do all mutations significantly affect proteins?
No, most DNA mutations do not alter a protein or only slightly alter it without changing its appearance or function.
What are the possible results of mutations in coding vs. non-coding DNA?
• Coding DNA: May change protein activity. • Non-coding DNA: May change how genes are expressed.
What are the possible consequences of mutations?
Mutations may result in phenotype changes, hidden effects, or serious conditions like genetic diseases (e.g., cystic fibrosis).
