Mutation

Nitrous acid- deaminates bases, changes cytosine to uracil and adenosine to hypoxyanamthine (pairs w/ cytosine) Tautomeric shifts: small changes in the molecules which causes changes in the H bonding properties so bases bond with non- complimentary bases Base analogs: eg 5-bromouracil is similar to thymine so can be inserted in thymines place but it bonds with guanine not adenosine

Causes adjacent thymines to bond together to from thymine dimers- leads to single and so double strand breaks

Replication errors- Rna instead of dna, slippage, dna legions Free radicals produces from metabolism Transposable elements

Sequences of DNA which move to random sites in the DN sequence. They could insert in a gene, intron, promoter sequence ect, causing various effects.

Transition is between same types of bases (A-G or T-C-U)

It is used when polymerase put in the wrong base(s). Errpors in BER can lead to SSB and this can lead to DSS. This is how the BRCA1 gene defect causes breast cancer

DNA repair- homologous/ non homologous end joining, base excision repair ect Senescence- arrests cell cycle Apoptosis- purposeful cell death

A mutation that changes the amino acid coded for in the polypeptide

A mutation that does not result in a new amino acid being coded for

Insertion or deletion or 1/2 nucleotides moving the reading frame meaning all amino acids downstream of the mutation are different

A triplet coding for a normal amino acid is mutated to code for a stop codon (UAA, UAG or UGA) and so the polypeptide is cut shorter

Can mutate the promoter/ enhancer sequence, can alter cleavage site of poly A polymerase, can prevent splicing, can change initiation sequence so it cannot start

Deletion, duplication, inversion, translocations, insertions

Aneuploidy is loss or gain of chromosomes- called trisomy or monosomy. Polyploidy is changes in the number of chromosome sets, usually due to fertilisation by > 1 sperm. Called triploidy or tetraploidy.

Non- disjunction (2 chromosomes go same way) or anaphase lag (one stays in the middle and is destroyed.)

Downs syndrome- Low muscle tone in babies (hypertonia) Furrowed tongues Skin folds in corner or eye lids Heart defects Early Alzheimer's High prevalence of leukaemia

Edwards syndrome: Small lower jaw Large back of head Overlapping fingers Usually only live 5-15 days

Patau syndrome: Multiple congenital abnormalities Polydactyly Most die in prenatal period

Turners syndrome: Some genes in common areas of the sex chromosomes (PAR1 and PAR2) need to be present twice. Causes short stature (only 1 SHOX gene) Heart defects Infertility- rudimentary ovaries Puffiness of hands and feet

Klinefelter syndrome- these individuals are usually fine as the 2nd x is inactivated. People with XXXY or XXXXY are at greater risk of symptoms

none really but generally more ‘manly’- taller, more muscular, more aggressive and less intelligent.

Where one part of a chromosome breaks off and swaps with another part. They are generally healthy because all the genetic info is still there.

In alternative segregation the gametes are all healthy. One cell gets both normal chromosomes and the other gets both translocated chromosomes, they therefor have all the genetic info (balanced) In adjacent segregation the gametes produced are unbalanced, this is because each cell gets one normal and one translocated chromosome, so some info is there twice and some is missing. In the second adjacent segregation homologous centromeres go the same way, this is rare as is basically like non-disjunction of both translocated chromosomes. You can also get 3:1 nondisjunction where one cell gets both homologous chromosomes and one of the other and the other only gets one chromosome from one of the pairs.

Where the long arms (q) of two acrocentric chromosomes fuse to create one very long chromosome and one made of the two short arms (p)- this chromosome is usually degraded and lost.