Mutations Flashcards
Define mutations?
Defined as heritable changes in DNA
Define somatic mutations
Occur in somatic (body) cells.
Mutations is passed to daughter cells, but not sexually produced offspring.
Define germline mutations
Occur in cells that prod gametes
Can be passed to next generation
What 2 scales con mutations occur?
Point mutations affecting just 1 or very few bases
Chromosomal mutations: affecting whole sections of chromosome (potentially 1000’s bases )
What are point mutations?t
What are silent mutations?
Have no effect on the protein because of the redundancy of genetic code
Define missense mutations?
Base substitutions results in amino acid substitution
E.g.)s ickle cell disease
Defected sickle-shaped red blood ou
Define nonsense mutations?
Base substitution results in a stop codon
Define frame-shift mutation?
Single bases inserted or deleted → usually leadig to non-functional proteins
Types of chromosomal mutations?
Deletions
Duplications
Inversions
Translocation
Define deletion
DNA molecule breaks at 2 points and 2 pieces rejoin leaving out DNA between break
Severe consequences unless it affects unnescemry genes or it missing genes are mashed by normal alleles on a homologous chromosome
Define dupli cation’s
Homologous chromosomes break in diff places and recombine with wrong patterns
May not be problem in original cell which still has 2 alleles for each gene but could cause problems in future generation as gametes formed by meiosis would pass on only one of these chrome comes
Define inversions
Breaking and rejoining but A segment is flipped
May have no effect unless the break site happens in the middle of gene
Define translocation
Segment of DNA break of f and is inserted into another non-homologous chromosome
Meiosis can be prevented as chromosome pairing may be impossible.
Define s spontaneous mutations?
No outside influence
Tautomerisation
A temporary change caused by migration of an atom within the molecule
A problem if this happens during DNA replication → this rare tauter binds with an A
Cytosine → common tauter
2.) de animation
Bases may change →spontaneous chemical changes remove AA
1 in 100 c would change in human lifetime if - not repaired
3.) DNA replication errors
Some escape detection and repair by proofreading ability of DNA polymerase
4.) non-disjunction in meiosis
Define induced mutation?
Due to an outside agent → a mutagen
Deamination
Chemicals such as nitrous acid (formed from nitrates)
Be laminated form of cytosine → uracil
2.) addition to bases
Benzopyrene → found in tobacco smoke adds a group to guanine and prevents base pairings
3.) ionising radiation
Ionising radiation con change bases break sugar phosphate bonds
4.) UV radiation is absorbed by thymine causing it to form covalent bonds with adjacent nucleotides
What do mutations provide?
Often produce an organism less fit for the environment
Mutations con improve organisms adaptation to its environment or be come favourable as conditions change
How does replication of gene expre’ssion in: prokaryotes takes place?
Usually a case of regulating transcription
RNA polymerase begins at a promoter where transaction is initiated
Selective gene transcriptions → a “descesion” is made about which genes will be transcribed
What are the 2 types of gene expression?
Negative regulation
→ gene is normally transcribed ( usually” on”)
→ binding of a depressor protein prevents transcription
Positive regulation
→ gene is not normally transcribed ( usually “off”)
→ activator protein binds to stimulate transcription
The lac open
?
Try open
Define Ind ucible system?
Control digestive /catabolic pathways
Turned Off when substrateis absent
Define repressible system?
Control biosynthetic /anabolic pathways
(Turned off when productis present)
