Mutations S1M1

Any change in the base sequence of DNA

Mutations are heritable. Once the mutation arises, it stays and is passed on.

It can lead to a faulty or missing protein.

No, mutations in somatic cells can do a lot of damage as well.

• Transition - Pyr for a Pyr (T-C; A-G)
• Transversion Pyr for a Pur or vice a vs

Aging and Cancer

In gametes or the precursors of gametes. Can lead to genetic diseases

During crossing over in Meiosis

Only two

A Purine base, and a deoxyribose

The coding sequence of the gene

Any cell but those in the germline

An abnormal growth

• 100 new mutations.
• − Most of these mutations are harmless.
• − A few are slightly unfavorable. They contribute to polygenic diseases.
• − Rarely, a single mutation is bad enough to cause a disease.
• − Favorable mutations are very rare

Those carrying the genes usually die or can't reproduce

• Recessive can be passed without ever manifesting itself
• Dominant always express themselves, but remain low causing disease. This is when natural selection kicks in, therefore dominant

• Spontaneous tautomeric shifts
• Ionizing radiation (X-rays, radioactivity)
• UV radiation (sunlight)
• Chemicals

A change in a bases in nucleic acid, shift between keto and enol forms or between amino and imino forms

• Age,
• Increased maternal age is a risk factor for aberrations in chromosome number.
• Advanced paternal age is a risk factor for point mutations.

• 
• This is for lesions that are large enough to distort the geometry of the DNA double helix
• The removed gap is filled by DNA polymerase and DNA ligase

• Xeroderma pigmentosu
• Cockayne syndrome

• − Defect of genome-wide nucleotide excision repair
• − Sunburn, skin cancer
• − Autosomal recessive
• − 7 different types
• 

• − Defect of transcription-coupled nucleotide excision
• repair
• − Poor growth, neurological problems, early senility
• − Autosomal recessive
• − 2 different types
• 

• Happens most in quickly dividing cells
• − Defect of post-replication mismatch repair
• − ≥50% risk of colon cancer
• − Also increased risk of other cancers
• − Autosomal dominant inheritance

When mismatched DNA is found it is removed (while still attached to the original strand) and then repaired by DNA polymerase and ligase

All cells have a heterozygous defect in a mismatch repair protein. When a somatic mutation disrupts the single intact copy of the gene, the cell becomes a mutator. Some of these mutator cells become cancerous.

• Caused by a mutation in a signaling protein required for the repair of DNA double-strand breaks.
• Abnormalities:
• Cerebellar ataxia (loss of body movement) starting in early childhood
• Dilation of small blood vessels
• Sensitivity to ionizing radiation

• 1. Can knock off electrons off orbitals
• 2. Can hit DNA directly
• 3. Makes hydroxyl radicals

Thymine

Wherever oxydation takes place

5-Bromouracil

Mutagenic and is used as a preservative in meat

A base is deleted

• AP endonuclease, polymerase beta remove wrong material
• Polymerase Beta replaces with correct nucleotide
• Ligase fills the small gap leftover

The deamination of uricil to cytosine is not detected and therefore won't be repaired

• Its deamnination produces thymine that won't be detected to be repaired by incision repair
• This is what makes CG sequences a hot spot for mutations

Is one of the most important repair systems!!

Removal of an amine. Because base pair excision can't recognize this it is considered a hot spot for mutations

Aromatic structures that place themselves between base pairs pushing them apart. These can contribute to small insertions and deletions