Ch 4 Flashcards
What are mutations
Changes to dna
- spontaneous
- mutagens
What is a mutagen
Chemical/physical substances or events causing mutation
In somatic cells only the daughter cells are effected
In germ cells gamete cells are effected and can pass mutations onto offspring
Spontaneous mutations
DNA is exposed for replication during S phase and nitrogen bases are effect.
If not detected in G2 phase damaged DNA is duplicate into new cells.
For example adenosine undergoes chemical change to resemble Guanine which codes for the wrong base pair.
Physical mutagens
Uv light - cross-linking neighbouring nucleotides changing DNA structure
X-rays - gene and chromosome abrasions
Nuclear radiation - Breaks DNA into strands
chemical mutagens
Mustard gas - effects guanine causing substitution mutation
nitric acid - adenine in DNA is deaminated to behave line guanine
substitution mutation
when a DNA base is replaced by another
frame shift mutation
when a base is added or subtracted which changes all the codons after the mutation
non-sense mutation
substitution mutation - any genetic mutation causing the coding of a stop codon
missense mutation
substitution mutation - any genetic mutation that changing the resulting amino acid from one to another
silent mutations
substitution mutation - missense mutation
Codon codes for the same amino acid therefore doesnt effect protein produced
eg CCC and CCT both code for Gly
conservative mutations
missense mutation
mutations which change the amino acid coded to a similar type of amino acid eg both acidic or both polar
non-conservative mutations
missense mutation
the new amino acid is not of the same type
where do genetic mutations occur
mutations originate at the DNA level but appear at the protein level
insertion mutation
frame shift mutation - one or more nucleotide pairs have been added to a segment of DNA
deletion mutation
frame shift mutation - one or more nucelotide pairs are removed
point mutation
When a single base pair is altered through substitution, deletion or addition (frameshift)
effected sequences are called SNP’s or snips (single nucleotide polymorphisms)
nitric acid
adenine is deaminated so it acts line guanine
mustard gas
affects the base guanine causing a substitution mutation
biological agents
when invasive pathogens like bacteria or viruses causes a mutation by imbedding its DNA into the host cells causing mutations in the daughter cells.
what are the mechanisms of variation
Mutation
Sexual reproduction
Environmental factors
The diversity of genetic and phenotypic traits within and between populations
Neutral mutations
Protein produced is unaffected by the change, posing no threat to the organism
Deleterious mutations
Disruption in the function of a protein affecting the organisms ability to carry out vital processes
Beneficial mutation
When changes in the synthesis of a protein benefits the organisms survival rates eg HIV resistance due to the absence of a surface protein required for the virus to enter
what causes mutations
errors in DNA replication or cell division OR damage by chemical or physical environmental factors.
