Lecture 4 - mutation Flashcards
What is a mutation?
the process that produces a gene or chromosome set differing from that of the wild-type
What is a wild-type?
the form that predominates in nature
What are the effects of spontaneous mutation?
if not repaired, mutations will be passed down to all daughter cells - in multicellular organisms this will only be inherited by any progeny if the mutations is in the germline
What is the standard human karyotype?
46 chromosomes - 22 x 2 autosomal chromosomes
- XX or XY sex chromosomes: pair with each other
- written: 46,XX or 46,XY
What is polyploidy?
an unusual number of chromosome sets
What is triploidy?
3n
What is tetraploidy?
4n
What is monoploidy?
1n (when 2n is normal)
What is aneuploidy?
one or a few individual chromosomes extra/missing
What are 2 examples of human aneuploidies?
trisomy - 3 homologues instead of 2
monosomy - 1 homologue instead of 2
What are the 3 viable human autosomal aneuploids?
- 47, XX or XY + 13
- 47, XX or XY +18
- 47, XX or XY +21
What are the 2 sex chromosome aneuploidies?
47, XXY: Klinefelter syndrome
45, XO: Turner syndrome
What are the 3 types of large-scale chromosomal rearrangements?
Deletions - part of the chromosome is missing
Inversions - part of the chromosome has been flipped
Translocations - part of the chromosome has been moved
What are sources of mutation of individual genes differing from wild type?
mistake during replication:
- point mutations (a single nucleotide)
- small insertions/deletions –> frameshifts
genes interrupted by transposons (jumping gene)
DNA breaks incorrectly repaired
What are the 4 types of point mutations?
- Silent - no change to amino acid sequence
- Nonsense - introduction of a stop codon into the gene
- Missense - changes the amino acid sequence
- Null allele - total loss of function
