Do NowDo 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.

• TAC TGA GTT ACA CGA• 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

HIS LEU VALGLY

Protein Protein SHAPESHAPE determines determines FUNCTIONFUNCTION..

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

How does this happen?How does this happen?

Mutations!Mutations!

Mutation Type

Description Example DNA Sequence

Substitution One base is switched with another

Original : ATCTGGMutated : TTCTGG

Insertion A base is added to a sequence

Original :ATCTGGMutated:ATCTGGG

Deletion A base is removed from a sequence.

Original : ATCTGGMutated : ATCTG

3 Types of Mutations

Identify the Mutation

Mutation A: ___________________________

Mutation B: ____________________________

Mutation C: ____________________________

GTTACGAA

GTTACTGAA

GTACGAA

GTTATGAA

Based on what you have learned thus far, create your own

definition of what a “mutationmutation” is

Stop and JotStop and Jot

MutationMutation- a random change in the sequence of bases.

Word of the DayWord of the Day

Discussion QuestionDiscussion 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 ConnectionCancer ConnectionCompare the beginning sequence of Theresa’s BRCA1 gene to the normal sequence below.

Theresa’s BRCA1 gene: TACTGAGTTACTACGA

Normal BRCA1 gene: TACTGAGTTACACGA

Cancer ConnectionCancer Connection

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

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

Cancer ConnectionCancer Connection

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

Cancer ConnectionCancer Connection

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

Cancer ConnectionCancer ConnectionSample data from a patient is shown below. Fill in the patient’s missing codon.

DNA Sequence

mRNA Sequence

A. AcidSequence

Protein Shape

Normal TAC TGA GTT ACA CGA

AUG ACU CAA UGU GCU

Met Thr Gln Cys Ala

Normal BRCA1

Patient TAC TGT GTT ACA CGA

AUG ____CAA UGU GCU

Met Thr Gln Cys Ala

NormalBRCA1

Cancer ConnectionCancer ConnectionThe 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.