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Unit 5 Part 1: Is cancer in our genes?. Do Now.

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Unit 5 Part 1: Is cancer in our genes?

Do Now

The function of the BRCA1 protein is to prevent our cells from becoming cancerous. If a cell is dividing too much, the BRCA1 protein can repair the cell so that it undergoes mitosis normally. A portion of the BRCA1 gene (the DNA with instructions on how to make the BRCA1 protein) is shown below.


  • Write out the sequence of mRNA that would be produced during transcription of the BRCA1 gene.

Use the genetic code chart to determine the amino acids that make up this portion of the BRCA1 protein.

What would happen if a person’s BRCA1 protein was not functional?

What is this diagram saying?

Nucleotide Sequence

Amino Acid Sequence

Protein Shape

Protein Function

What is this diagram saying?

Nucleotide Sequence

Amino Acid Sequence

Protein Shape

Protein Function





Protein SHAPE determines FUNCTION.

FACT:Many people with breast cancer have BRCA1 proteins that are the wrong shape or missing amino acids.

How does this happen?


3 Types of Mutations

Identify the Mutation

Mutation A: ___________________________

Mutation B: ____________________________

Mutation C: ____________________________

Stop and Jot

Based on what you have learned thus far, create your own definition of what a “mutation” is

Word of the Day

Mutation- a random change in the sequence of bases.

Discussion Question

Insertions and deletions are often called “frameshift mutations” and are far more dangerous than substitution mutations. Why would an insertion or deletion be worse than a substitution?

Cancer Connection

Compare the beginning sequence of Theresa’s BRCA1 gene to the normal sequence below.



Cancer Connection

How would her mRNA codons be different than a normal person’s?

How would her amino acid sequence be different than a normal person’s?

Cancer Connection

State how the BRCA1 protein function would be altered as a result of this mutation.

Cancer Connection

Synthesize all of the information that you learned today to describe why so many people in Theresa’s family have breast cancer.

Cancer Connection

Sample data from a patient is shown below. Fill in the patient’s missing codon.

Cancer Connection

The patient’s BRCA1 protein is normal despite the fact that the BRCA1 gene has a mutation. Explain how this is possible in terms of the genetic code.

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