Mutations

Mutations

Mutations

​MUTATION= Any change of the genetic code.

Can occur on a single gene (letters)

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Ex. ATA should be transcribed as UAU, but what if it’s miscopied as GAU?

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Or can occur on the chromosome (entire chunks of DNA)​

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Ex. What if when the cell divides, the chromosomes don’t split in metaphase and one gets stuck together?

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Single gene mutations (letter changes)

When can gene mutations occur?

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1) DNA replication

(s-phase of cell cycle)

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Single gene mutations (letter changes)

2) Transcription

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(step 1 of protein synthesis)

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Note! Gene mutations can occur in translation as well, but are less common

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​Types of gene mutations

​1) SUBSTITUTION or POINT:

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one letter is swapped out, or substituted, for another letter at a single point.

​Point Mutation Example

​Hemoglobin is the protein in your blood cell that carries oxygen.

It is made from 574 amino acids.

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Sickle cell disease is caused because of 1 wrong amino acid.​

Wrong protein shape= nonfunctional!!

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​Substitution/Point Effect

​Missense - switches one amino acid in the chain for another.

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Nonsense - results in a shorter chain because of an early stop codon.

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Silent - amino acids do not change at all.

​Most mutations are silent and harmless due to the built in redundancy of the genetic code. In other words, multiple codons can code for the same amino acid.

Multiple Choice

How many letters of RNA are in a codon?

• 1

• 2

• 3

• 4

​Recall...

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​Cells can only read 3 letters at a time, no more no less.

So, what happens if you add or remove a base?

The cell still reads in triplet!!

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​the cat ate the rat

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thc ata tet her at?

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​Types of gene mutations

​2) FRAMESHIFT- the insertion or deletion of a base that causes a shift in the reading frame.

Frameshift Effects

Insertion and deletion mutations don’t just change a single codon, but change ALL the codons from that point on!

Multiple Choice

This type of mutation swaps one base out for another.

• Insertion

• Deletion

• Substitution

• Frameshift

• Point

Multiple Choice

This type of mutation removes a base.

• Insertion

• Deletion

• Substitution

• Frameshift

• Point

Multiple Choice

This type of mutation adds a base.

• Insertion

• Deletion

• Substitution

• Frameshift

• Point

Multiple Choice

This type of mutation shifts the entire reading frame left or right.

• Insertion

• Deletion

• Substitution

• Frameshift

• Point

Multiple Choice

This type of mutation changes a single base or codon.

• Insertion

• Deletion

• Substitution

• Frameshift

• Point

​Chromosomal mutations

​What happens when entire chunks of DNA change?

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When do these occur?

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Chromosomal mutations typically occur during cell division (mitosis or meiosis)​

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​What causes chromosomal mutations?

​Chromosomal mutations happen when sister chromosomes swap material when they aren’t supposed to or stick together.

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So most chromosomal mutations occur in METAPHASE (a) AND ANAPHASE (b)

Types of Chromosomal Mutations​

​Deletion-loss of part of the chromosome

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Duplication- extra copy made of part of the chromosome

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Types of Chromosomal Mutations​

Inversion - switches sections on a chromosome

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​Translocation - part of one chromosome moves to another

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​Visual Memory Reminder

​Recall: There are two main types of cells in the body.

​Two categories of cells:

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1) Somatic cells - body cells

(skin, kidney, blood, hair, muscle, bone . . . almost everything)

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2) gametes - sex cells

(sperm and egg)

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Multiple Choice

Which do you think will get passed onto offspring... a mutation on a somatic cell or a mutation on a gamete/sex cell?

• Somatic Cell

• Gamete / Sex Cell

​Impact on Offspring

​Since offspring are created by a sperm and egg joining, only mutations in GAMETES can be passed on to the next generation!

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Multiple Select

Compare these two lines. What type of mutation has occurred here?

the cat ate the rat

the bat ate the rat

• Substitution

• Deletion

• Insertion

• Point

• Frameshift

Multiple Select

Compare these two lines. What type of mutation has occurred here?

the cat ate the rat

thc ata tet her at

• Substitution

• Deletion

• Insertion

• Point

• Frameshift

Multiple Select

Compare these two lines. What type of mutation has occurred here?

the cat ate the rat

the cat ate the mat

• Substitution

• Deletion

• Insertion

• Point

• Frameshift

Multiple Select

Compare these two lines. What type of mutation has occurred here?

the cat ate the rat

the cat mat eth era t

• Substitution

• Deletion

• Insertion

• Point

• Frameshift

​the mad cat had the hat