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Mutations

Mistakes in the sequences of DNA bases lead to mutations

In regards to evolution, mutations don’t matter if they occur in your body cells.
They won’t affect your children, or their descendants.

Mutations only matter in evolution if they occur in a sperm or egg cell.
These could be passed on to the next generation.

Mutations are not “good” or “bad” – they are just random changes.
Some are helpful; some are harmful.
Some are “silent” (you don’t notice them at all.)

Mutations of genes

Substitution mutation – one nucleic acid is substituted for another

Original strand: TAC GCA TGG ACG …

Mutated strand: TAC GTA TGG ACG …

Affects only one amino acid in a protein.

{ https://islaslab.wikispaces.com/Mutation }
substitutionjpg

Insertion mutation – one nucleic acid is added in.

Original strand: TAC GCA TGG ACG…

Mutated strand: TAT CGC ATG GAC G…  (see the extra “T” ?! )

This messes up how the cell reads these genes.
The cell always reads three bases at a time.
So now it messes up every single amino acid after the insertion!
Called a frameshift mutation.

Example of how this works, if we used English words:

Normal DNA THEREDFOXATETHEBIGRAT…

Read 3 at a time:
THE RED FOX ATE THE BIG RAT

Insertion mutation:  (See how there is an extra “E” ?!)
THEEREDFOXATETHEBIGRAT…

Read the words 3 letters at a time:
THE ERE DFO XAT ETH EBI GRA T…

See how the message is all messed up?

Deletion mutation – one nucleic acid is left out.

Original strand: TAC GCA TGG ACG…

Mutated strand: TCG CAT GG ACG… (See how the first “A” is missing here?)

This messes up how the cell reads these genes.
Another frameshift mutation

Normal DNA:
THEREDFOXATETHEBIGRAT…

Read 3 at a time:
THE RED FOX ATE THE BIG RAT

Deletion mutation:
THREDFOXATETHEBIGRAT…

Read the words 3 letters at a time:
THR EDF OXA TET HEB IGR AT        (See how the first “E” is missing?)
See how the message is all messed up?

{ https://islaslab.wikispaces.com/Mutation }
deletionmutation

Mutations can fall into these functional categories:

A. Silent mutations

B. beneficial mutations

C. deleterious (harmful) mutations

Examples of beneficial mutations

A. Extra skin pigmentation for people who live closer to the equator

1. Reduces the amount of UV light that penetrates one’s skin; reduces one’s risk of skin cancer

B. Less skin pigmentation for people who live further from the equator

1. Humans need some UV light to process vitamin D
2. Lack of vitamin D processing leads to disease

a. Rickets – childhood disease, impeded growth, deformity of the long bones

b. Osteomalacia – bone-thinning disorder that occurs exclusively in adults

Examples of harmful mutations: genetic diseases

A. Sickle cell anemia

B. Cystic fibrosis

C. Huntington’s disease

D. Tay-Sach’s diesase

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Those were mutations of just one gene. What if an entire chunk of a chromosome got damaged? That would affect hundreds of genes at the same time!

Chromosomal Mutations

{ http://www.goldiesroom.org/Note%20Packets/19%20Applied%20Genetics/00%20Applied%20Genetics–WHOLE.htm }

Chromosome Mutations

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