point mutations silent mutations
TRANSCRIPT
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.