Genetic Control of Protein Structure
- Created by: Alice Fisher
- Created on: 07-05-15 00:15
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- Genetic Control of Protein Structure
- Mutations
- transition; base change
- transversion; swap base with opposite one
- Missense mutation; change from one amino acid to another
- Nonsense; change from one amino acid to a stop codon
- Neutral; change from one amino acid to another similar one
- Silent; change in codon so that the same amino acid is specified
- Frameshift; addition or deletion of one or a few base pairs leads to a change in reading frame
- Spontaneous mutation
- Due to wobble base pairing e.g guanine can wobble base pair with thymine during replication producing one wild type and one mutant
- Due to looping out errors during DNA replication. Can lead to base insertion or base deletion.
- Chemical changes; depurination - adenine or guanine is lost from the DNA backbone. If not repaired a random base is inserted
- Deamination - cytosine is deaminated to uracil. If not repaired uracil pairs with adenine
- Mutation rate of 1.1x10-8 per position per haploid genome
- Induced Mutations
- Ionising, xray Have high energy which can break covalent bonds leading to point mutations
- UV radiation; low energy causes pyrimidine dimers between and within stands. Leads to DNA replication problems
- Chemical
- Base analogues e.g. 5-bromouracil normally pairs adenine but it can also pair guanine - transition mutation
- Base modifiers alter the chemical structures of bases e.g. alkylating agents like MMS, methylguanine pairs thymine
- Addition/deletion mutation caused by an intercalating agent
- Sickle cell anaemia
- Recessive mutation in haemoglobin that affects its ability to bind to oxygen
- At low oxygen the rbc loses concave shape and becomes sickle shaped
- Missense mutation at residue 6 of Hb-A changing glutamate to valine. Replacing a charged residue with a neutral one. Change observed by electrophoresis
- Recessive mutation in haemoglobin that affects its ability to bind to oxygen
- Evolution
- Dominant traits are usually gain-of-function. Recessive traits are usually loss-of-function
- Conserved motifs (sequences). E.g. SH2 in drosophila and humans. Structurally conserved protein domain within the Src oncoprotein
- Proto-Oncogene tyrosine protein kinase is a non-receptor protein tyrosine kinase that is encoded by the Src gene.The sequence alignment of Src kinases from various phyla is similar
- Molecular recycling; protein designs are duplicated, adapted and modified
- Mutations
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