Transcript Normal BRCA1 gene

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.
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 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?
Mutations!
3 Types of Mutations
Mutation Description
Type
Substitution One base is
switched with
another
Insertion A base is added
to a sequence
Deletion
A base is
removed from
a sequence.
Example DNA
Sequence
Original : ATCTGG
Mutated : TTCTGG
Original :ATCTGG
Mutated:ATCTGGG
Original : ATCTGG
Mutated : ATCTG
Identify the Mutation
GTTACGAA
GTTACTGAA
GTTATGAA
GTACGAA
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.
Theresa’s BRCA1 gene: TACTGAGTTACTACGA
Normal BRCA1 gene: TACTGAGTTACACGA
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.
DNA
mRNA
A. Acid
Protein
Sequence Sequence Sequence Shape
Normal TAC TGA
GTT ACA
CGA
Patient TAC TGT
GTT ACA
CGA
AUG ACU
CAA UGU
GCU
AUG ____
CAA UGU
GCU
Met Thr
Gln Cys
Ala
Met Thr
Gln Cys
Ala
Normal
BRCA1
Normal
BRCA1
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.