Ib biology HL : D1.3 - mutation and gene editing

gene mutation 

change in sequence of base pairs in a DNA molecule, which may result in an allele

types of genes mutations

• substitution 

• insertion 

• deletion

insertion mutations

An extra base pair got added, change of amino acid, and has knock on effects on the nucleotide sequences and on other amino acids, has a higher chance of causing negative knock on effects on polypeptides. is going to change all triples after mutation.

type of frameshift mutation

deletion mutation

when a nucleotide is removed, change of amino acid, and has knock on effects on the nucleotide sequences and on other amino acids, has ahigher chance of causing negative knock on effects on polypeptides

type of frameshift mutation

causes of gene mutations 

• ionising radiation / UV light - may trigger formation of free radicals in nucleus

• chemical substances: mustard gas, benzene rings

• random change during duplication - DNA polymerase mess up

• certain bacteria ( helicobacter pylori - can cause stomach cancer )

point mutation

change of one DNA base pair, due to degeneracy of code, may or my not have an effect

outline how point mutations can affect DNA

proteins are made of amino acids

codons code for amino acids

codons are made of a sequence of 3 base pairs

if one base pair gets changed, and the amino acid changes and causes a different protein to get made.

outline how insertion mutations affects the proteins

• One or nucleotide base pairs are added to the sequence 

• This creates a frameshift, changing the nucleotide sequence, 

• changing the codons, causing a change in amino acid sequence

• leading to the change in the primary structure of the polypeptide, and therefore to the entire structure of he nucleotide

• The proteins function can be entirely changed

Base substitution mutation

point mutation, known as single-nucleotide polymorphisms (SNPs). when one nucleotide is replace by another nucleotide. 

synonymous substitution

mutations which do not change amino acid sequences, due to code degeneracy

non synonymous substitution

mutations which change amino acid sequence

places where mutations are more likely to happen

• CGC parts of sequence

• uncoiled DNA (and not wrapped around histone proteins)

germ cells

cells that are going to lead to new cells

• very early stem cells

• gametes

somatic cells

All the other cells in the body

mutation of germ cells 

have knock on effects; a mutation on them will have effect on all the produced somatic cells 

what’s a big source of genetic variation ?

mutation