D 1.3 Mutations

What are mutations?

Any change to the dna or rna sequence

What are the 3 types of mutations?

substitution, insertion, deletion

What is substitution?

When one base in the coding sequence is replaced by a different gene. CCT->CGT

What is insertion?

a nucleotide is inserted so there is an extra base in the sequence CCT->CCTA

What is deletion?

a nucleotide is deleted from the sequence CCT-> CC

Point mutation vs frameshift mutation

point mutation means a change in a single nucleotide base affects only 1 codon

frameshift is when insertions or deletions are NOT in multiples of 3

Silent mutation

there is no change in amino acid

Missense vs nonsense

Stop this nonsense meaning nonsense mutation is a chnage in dna that causes a stop codon.

Missense is a change in dna that changes amino acid

What are SNPs?

S- single N- nucleotide P- polymorphism

It is point mutations when only 1 nucleotide has changed

Why are SNPs important?

They can influence how likely you are to get a disease and how you respond to drugs.

what are the consequences of frameshift mutations?

polypeptides might cease to function because the amino acid changed

CCR5

example of consequences of insertion or deletion

HIV virus binds to CC receptor protein of white blood cells

Carriers of this mutation are resistant to HIV

High 5 stands for CCR5 high stands for HIV

Where is CCR5 found?

cell surface of white blood cells

What is CCR5?

Receptor protein

Where is CCR5 gene?

chromosome 3

What kind of mutation is CCR5 mutation?

delta 32 which is deletion of a portion of CCR5

DEL in delta is for delete

ABCD C for CCR5 D for deletion

What is HTT gene?

gene coding for huntington protein

What causes huntingtons disease?

a frameshift insertion mutation of the HTT gene

insertion has a T in it HTT has too many Ts

What normal vs mutated HTT gene?

the normal one has less than 27 CAG repeats

mutated one shows several insertions of additional CAG which leads to neuronal degeneration in the brain

3 causes of mutations

1. error in DNA repair

2. error in DNA replication

3. mutagen - anything that causes a mutation

Ex: the Sun can cause skin cancer

What are the 3 types of mutagens?

1. radiation

2. chemicals

3. infectious agents

2 examples of radiation mutagens

UV from sunlight, x rays

3 examples of chemical mutagens

1. carcinogens ex : cigarette

2. processed foods ex: hotdogs

3. cosmetics, cleaning products, medicine

What makes radiation more dangerous interms of frequency or wavelength

high frequency and short wavelength the more dangerous the radiation.

frequency and radiation

higher frequency means more dangerous for radiation and short wavelength

wavelengh radiation

short wavelenght is more dangerous for radiation

purines vs pyridamines

purines are A and G pyridamines are C, U, T

purines- pure as gold where there is A and G

pyridamines- CUT the pie

Transistions

exchange for a purine for a purine (A/G) or pyrimidine for a pyrimidine (C/T)

occur easily

Transversions

Replace a purine with a pyramidines or vice versa and alters structural shame of DNA ex: A-C G-T

Germ line cell

Is in sperm and egg

Somatic cells

Are jn body cells

What happens if a mutation occurs in the DNA of a germ cell?

The mutation will happen in all body cells and tissues and gametes produced will carry and pass on the mutation.

What happens if a mutation occurs in somatic cells?

there are limited consequences and only affect these particular body cells and none of the gametes produced will carry the mutation

Why are mutations essential for evolution

because they are essential of evolution by natural selection and without it the variation in population would decline

Gene flow

the movement of genes between different populations of organisms

Meiosis

crossing over and independent assortment during the formation of egg and sperm which leads to the creation of new combinations of alleles

Sexual reproduction

random fertilization between egg and sperm of different parents

Harmful mutations

cause a change in dna that results in proteins not functionally normally or at all

Neutral mutations

Have no observable effect on an organism and they can be the result of a silent mutation.

Gene knockout

is a technique for investiagtion the funcion of a gene by making it inoperative

CRISPR Cas9

it is gene editing based on a natural system that exsists in many species of prokaryotes which use it as a defense agaisnt viral attack

Three main steps to edition in crispr

1. Cas9 moves along the target Dna molecules and brings the dna adjacent to the variable base sequence of the spacer in the guide RNA

2. If mathcing dna is encounter the guide rna the rna cas9 binds to it

3. Cas9 contains 2 endonucleases to cut the dna strands to destroy the foreign dna

Conserved sequences

specific segment of dna that remains largely unchanged accorss different species. Some are highly concerved and have remained unchanged through much of the evolution of life on earth

Example of conserved sequence

Hox genes code for proteins called transcription factors that regulate gene expression and control cell differentiation during embryonic developement

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