mutation, evolution and disease Flashcards
how do mutations happen?
- spontaneous OR
- introduced by a mutagen
how do mutagens cause mutations?
- they chemically change a base
- they introduce a non-A,T, G,C base which is copied wrong
- it sits in between the strands of DNA and causes mutations
- in the case of UV-irradiation/ radioactive decay the mutation is caused by damages to the bonds in between DNA
how is DNA damage actively detected and repaired by the cell?
-enzymes can remove the incorrect base and/or nucleotide and allow the correct one to be incorporated
how does the system know which base/ nucleotide has mutated?
- it looks at the other strand of DNA which tells it if it is complimentary
- Base excision repair (BER)
- Nucleotide excision repair (NER)
- Mismatch repair (MMR)
what are the stages of base excision repair (BER)?
- it rapairs damage to a single base
- the damaged base is removed by DNA glycosylase
- the sugar phosphate is then removed by the AP endonuclease
- new nucleotides are inserted by DNA polymerase
- its then joined up by DNA ligase
why are polymorphisms useful to researchers
- for DNA fingerprinting for criminal forensics
- paternity testing
- recent + distant ancestry studies
how do mutations cause harm?
-a change in the coding sequence may lead to an altered protein
- altered proteins may not work or may do something their not meant to
- the protein may not work as well (loss of function)
- the protein may do something it shouldn’t (gain of function)
what is a silent mutation?
it is a mutation that has no effect on the phenotype as the genetic code is the same
what is a mis-sense mutation?
it is when a point mutation leads to a change in the amino acid which may or may not lead to a change in the function of the protein or the phenotype
what is a nonsence mutation?
its when a mutation alters the codon so it is now a stop codon so the polypeptide is shorter than its meant to be
what is a frameshift mutation?
its when 1 or 2 nucleotides are inserted/ deleted in the genetic code. this normally alters the phenotype as all the amino acids in the protein have been changed
name some simple genetic disorders?
Recessive and dominant
Recessive
- albianism
- cystic fibrosis
- galactosemia
- phenylketonuria
- tay-sachs disease
Dominant
-huntingtons disease
what is cystic fibrosis caused by?
its caused by a mutation in the CFTR gene (on chromosome 7),which codes for a membrane protein. this membrane protein usually moves chlorine ions out of the lung cell. the mutation leads to water leaving the cell too, making the lungs moist. mucus is also secreted by epithelial cells which is thick and sticky which causes constant chest infections and lung damage
is the mutation of the CFTR gene the same in all cystic fibrosis cases?
no, theres over 1,000 different mutations that have been detected
the most common one is where 3 nucleotides have been deleted where phenylalanine Phe 508 has been deleted so the protein doesnt function properly
what is the hardy-weinburg equlibrium?
it states that the frequency of dominant and recessive alleles will remain constant from generation to generation
