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Fundamental Molecular Biology
Wednesday, 5 December 2018

08:52

Mutations: "Changes in the genetic material of a cell (or virus)" -Campbell et al
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Albinism
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Cretinism
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rare) = weak albinism
• OCA4: SLC45A2 Protein (helper) = mild albinism
• There are several other albinism-like syndromes e
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Hermansky-Pudlak
Syndrome
Alkaptonuria
• First human "Mendelian" disorder
• Gene on chromosome 3- homogentisate 1,2-dioxygenase
• Mutants cannot convert homogentisic acid to maleylacetoacetic acid
• Homogentisic acid- black, expelled in urine
Phenylketonuria
• High levels of phenylpyruvic acid
• Progressive brain dysfunction
• Mutation on phenylalanine hyrdoxylase gene
• Treat: test at birth- low phenylalanine diet
Phenotype: the outward physical manifestation of the organism
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Think from mutant allele's point of view
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Most recessive mutations are loss-of-function (most loss-of-function
mutations are recessive)
- Most genes = one functioning allele needed for WT phenotype
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Evolution- affects how mutation behaves in population (can natural selection
affect heterozygotes?)
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Informs biology
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Look at sequence- predict exons, use homology
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5% exons
- 35
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5% the same
◊ Study: use micro + minisatellites (used in forensics)
◊ Typically 3-12 bp
Indels: insertions/deletions
- Can be very small, 1bp, 2bps…
- Cause frameshift etc
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- Can affect Open Reading Frame (ORF) = affect protein product
- Most silent- outside genes, in introns
Copy Number Variants (CNVs)
- Variation in number of segment of a chromosome
- 500-1 million base pairs
- Private: ~200 de novo point mutations
- Fairly common: allele frequency <1% = variant
- Very common: allele frequency >1% = polymorphism
- Typically 2 versions at locus
SNPs: Single nucleotide polymorphisms
- Rare SNPs: between 1% and 4

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