MCGB - Mutations Flashcards
What is a mutation?
A change in the DNA sequence.
Give some things that can cause mutations.
DNA replication errors during cell division, exposure to ionising radiation/chemicals, infection by viruses
What are germ-line mutations?
Mutations that occur in the eggs/sperm which affect all cells in body and can be passed on to offspring
Is a somatic mutation passed on to offspring?
No, as these occur in body cells and are therefore not passed on.
Why are RNA errors more common than DNA errors?
RNA polymerase don’t proofread
Why is it not as bad to have a mistake in the RNA compared to the genome?
RNA is not passed on from generation to generation, but the genome is
True or false - mitochondrial DNA is also prone to somatic mutations?
True - it has a limited ability to repair itself so mutations build up over time
Why is it unlikely for a spontaneous mutation to cause an autosomal recessive disorder?
The individual must have suffered a spontaneous mutation of the same gene on both chromosomes
What can be caused by duplicated chromosomes not pairing properly at the metaphase plate?
Anaphase lag (one cell has two copies of chromosome while other has none).
What is a primordial follicle?
A primary oocyte surrounded by flattened epithelial cells.
Why do primordial germ cells only start to differentiate into spermatozoa at puberty?
They are only needed when oocytes are available to fertilise.
True or false - not many miscarriages are due to chromosomal abnormalities?
False - 75% of clinically recognised pregnancy loss is due to this
Give some causes of somatic mutations.
Mutagens, radiation, viruses
Are tumours more likely to be due to somatic or germ-line mutations?
Somatic
Is the majority of radiation received by the UK population natural or artificial?
Natural - 50% comes from radon gas in the ground
What are “transposable elements”?
Sequences of DNA known as “jumping genes” that move from one location in the genome to another.
Which is the odd one out? Deletion, duplication, inversion, substitution, translocation, non-disjunction.
Non-disjunction - the rest are all mutations.
What is a transition single nucleotide base?
When a base is swapped for another of the same type, so purine to purine or pyramidine to pyramidine
What is a transversion single nucleotide change?
Change to a different type of base - purine to pyramidine or vice versa.
What causes sickle cell anaemia?
Mutation is amino acid sequence - glu to val
What is a missense mutation?
Single nucleotide change that changes the amino acid
What is a silent/neutral/synonymous mutation?
A mutation that has no effect
What is a nonsense mutation?
When a stop codon is created prematurely.
Why does it often not matter if the is a mutation in DNA?
Because a large amount of DNA is non-coding
