mod 6 Flashcards
What is a mutagen?
an agent that causes genetic mutation.
What is a mutation?
A permanent alteration to the nucleotide sequence of an organism’s genome
What are the three main types of mutagens?
electromagnetic radiation (uv light, xrays), chemicals (tobacco) and naturally occurring mutagens (viruses, HPV)
How does electromagnetic (ionising) radiation cause mutation?
It interferes with DNA molecules causing hydrogen bonds within DNA structure to break thus changing the chemical composition. This results in deletion or rearranged nucleotides. E.G. UV rays from sunlight, x-rays for medical uses.
How do chemicals cause mutation?
They can either break hydrogen bonds in DNA or affect processes in DNA repair and replication. E.G. carcinogen (cigarettes), cleaning products, processed foods and preservatives.
How do naturally occurring mutagens/infectious agents cause mutation?
They can insert their own DNA into an organisms existing cells and ‘take over’ (viruses E.G. HPV) or they can induce inflammation which can reduce efficiency of DNA repair systems (bacteria E.G. helicobacter)
What is a point mutation?
mutation which only changes/effects one (or a few) nucleotides within a gene sequence
What types of point mutations are there?
Substitution = when one nucleotide switches with out for a different one
Frameshift (insertion/deletion) = shifts the whole sequence up or down
Silent = mutation has no effect on codon production or protein
Missense = mutation affects one codon, introducing new amino acid into protein sequence
Nonsense = introduced premature STOP codon, dysfunctional protein
What is chromosomal mutation?
a mutation which changes or affects a long segment of DNA/ whole chromosomes
What types of chromosomal mutations are there?
Deletion = section of a chromosome is removed Inversion = section of a chromosome is inverted and re-inserted Translocation = when a portion of a chromosome is moved to a non-homologous chromosome (e.g. 21 to 22) Duplication = when a section of a chromosome is doubled
What is an example of a disease as a result of a point mutation (SNP)?
Sickle cell anaemia - SUBSTITUTION of A to T resulting in the codon GTG (valine amino acid) instead of GAG (glutamic amino acid).
What is an example of a disease as a result of a chromosomal mutation?
Down syndrome - “nondisjunction.” Nondisjunction results in an embryo with THREE copies of chromosome 21 instead of the usual TWO. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.
What is a somatic mutation?
A genetic alteration which cells acquire, which may be passed on to daughter cells by cell division (mitosis in humans) and only affect a certain area of the organism. A somatic mutation will not alter genetic composition of other cells in the body and IS NOT passed onto offspring. E.G. skin cancer
What is a germ-line mutation?
A mutation in germ cells (gametes) which CAN BE passed onto offspring during fertilisation. It depends if the mutation happens on both chromosomes (e.g. both of chromosome 21) or on only one chromosome as to whether the child is a carrier or affected. E.G. Sickle cell, colour blindness
Assess the significance of ‘coding’ and ‘non-coding’ DNA segments
‘coding’ DNA is used for protein synthesis and hence affects cell function. ‘non-coding’ DNA can be further described as ‘junk DNA’, enhancers and silencers, promoters, introns and terminators and play a role in
