point mutations silent mutations

1-24-17 Warm up

Write the DNA for the amino acid sequence:

Met-Trp-Pro-Gly

Plans for the week• Monday – research a

geneticist• Tuesday – share your

brochure; mutations lesson• Wednesday – mutations

lesson• Thursday – review

molecular genetics• Friday – molecular genetics

exam

• DNA structure and function• Cell specialization and gene

expression• Chromosome structure• Karyotypes• DNA replication• formation of mRNA• Using a codon chart• role of mRNA, tRNA, and

ribosomes (rRNA) in the production of proteins

• Mutations types• Some important work by some

important scientists

1-24-17 Agenda

1. Warm up2. Mutations lesson until 11:30; 1:10; 2:153. Time to work on Brochure (last class time)

1. To have me print you must format to be 1 page back-to-back

Objective

Students will analyze point mutations and explain how the mutation affects the sequence of amino acids.

Mutations

What you know so far… DNA codes for ________

Proteins are made up of _____ ____

We can determine the order of the ___________ in a ______ by using a codon chart.

proteins

amino acids

amino acidsprotein

How this connects to our new lesson

Proteins must have exactly the right shape to work properly

Normal protein shape

Abnormal protein shape due to wrong amino acids

A mutation is a change in the genetic code that causes the protein that is coded for to have the wrong shape or not be made by the cell

What kinds of mutations are there? Bo Xishun 7’9”

Chandra Bahadur Dangi 21.5”

Point Mutations Changes in one or a few of the nitrogen

bases (letters) of the DNA code– There are 2 main types

1. Base substitution = a letter (or a few letters) is substituted for another

How could such a small change make a difference?

A change in the bases might lead to a change in the amino acid coded for

Add this diagram to your notes

Substitution of bases (letters) Different

amino acid

Wrong protein shape

Same amino acid

Same protein shape

No effect on person

Disease or disorder

Example:

Example:

Base Substitution Mutation

Think of it like a sentence:

Normal sentence would read – THE DOG BIT THE CAT

A base substitution mutation might make the sentence read:– THE DOC BIT THE CAT

This changes the meaning of the sentence

Changing a single base can cause a dramatic change:– Example: sickle cell anemia

PracticeNormal DNA: TAC GGC TTT

Mutated DNA: TAC GGC GTT

Step 1: Circle any mutations Step 2: Transcribe DNA to mRNAStep 3: Group mRNA into codonsStep 4: Use the codon chart to list the amino

acids

Q1: Where is the mutation in this DNA strand?

Q2: What amino acid was changed?

Q3: What kind of mutation is this?

PracticeNormal DNA: CAA ACC GGG

Mutated DNA: CAA ACT GGGStep 1: Circle any mutations Step 2: Transcribe DNA to mRNAStep 3: Group mRNA into codonsStep 4: Use the codon chart to list the amino acids

Q1: Where is the mutation in this DNA strand? Q2: What amino

acid was changed?

Q3: What kind of mutation is this?

Q4: How would the protein product be affected?

Not all mutations cause problems Viable mutations – mutations that do

not decrease the ability of an organism to survive and reproduce

Changing a single base may not cause any change at all:– Proline is coded for

by GGG, GGA, GGC, and GGT

List at least two amino acids that are coded for by 2 or more codons. Write the names of the amino acids and all their codons on your whiteboard.

Are any amino acids coded for by only 1 codon?

What are they?

We call these SILENT mutations

Add this to your diagram

Substitution of bases (letters) Different

amino acid

Wrong protein shape

Same amino acid

Same protein shape

No effect on person

Disease or disorder

Example:

Example:https://www.youtube.com/watch?v=o3yQZp5Rs-o

Practice Partner A:Normal DNA: GAC AAG TCCMutated DNA:GAC TAG TCC

Partner B:Normal DNA: TCC ACA CTGMutated DNA: GCC ACA CTG

Complete the sentence. Share with your partner and then share with the class.

What kind of mutation is it?

Will it affect the protein? Explain.

2. Frameshift mutation = the addition or deletion of 1 or a few base pairs

Frameshift Mutation

Think of it as a sentence again:– THE DOG BIT THE CAT

Adding an extra letter makes it:– THH EDO GBI TTH ECA T

It changes the entire sentence to nonsense. This kind of mutation always has a negative effect on the protein product.

Some diseases caused by frameshift mutations:

Breast cancer Cystic fibrosis

http://www.pbs.org/wgbh/nova/genome/program_t.html

More practice

Partner A:Original DNA:GGGTTTACCMutated DNAGGGATTTACC

Partner B: Original DNA:GGGTTTACCMutated DNAGGTTTACCQ1. What kind of mutation is this?

Q2. How would this mutation affect the protein product?

More practice Write a DNA sequence of 9 letters. Label it “Original DNA” Then write the same DNA sequence but

with one of the mutation types we are learning about.

Give it to your neighbor to solve. Complete this sentence using the

problem your neighbor gave you.

This is an example of a ________ mutation. I can tell because _________. This mutation will/will not change the protein because _________________.

Now try it on your own

Complete the three practice problems on the worksheet.

Have your teacher check it when you are finished.