mutations amd epigenetics Flashcards
what are mutations
random and spontaneous events and only inherited if they occur in gametes
change in the amount arrangement or structure of dna in an organism
mutation rates
normally low but can be increased with ionizing radiation and smoking
where are mutations most common?
organisms with short life cycles such as bacteria
when do mutations occur?
crossing over in prophase 1 and non disjunction in anaphase 1 and 2
what are gene or point mutations?
- addition or subtraction of a base
- substitution of base
thea both can change the amino acid
why do some pint mutations have no effect?
- in non coding region
- recessive allele so not expressed
- alters amino acid but not result in a change to the functioning of the protein
- is silent the base changes but the amino acid which it codes for doesn’t
what’s chromosome mutations?
- when chromosomes break and they may repair themselves but incorrectly
eg in down’s syndrome non disjunction of chromosome 21 where both copies enter the gamete
how does cancer form?
mutations in protooncogenes producing oncogenes that increase rate of cell dividing
what do tumor suppressor genes do?
prevent rapid replication of cells but if they are mutated may form tumour
what is epigentics?
control of gene expression by modifying dna or histones, without modification of the base sequence
Epigentic modifications are caused by:
dna methylation
addition of methyl to cytosine reducing transcription of gene
histone modification
means they can coil more tightly preventing gene expression or coil loosely allowing transcription and protein synthesis
consequences on epigenetic changes
genomic imprinting: if genes are inactivated in gametes- may be transferred to next gen
inactivation- switching off the whole chromosome (x chromosome inactivation)
what is a mutagen that causes cancer called?
carcinogen
