Download Name: _____ Date: ________________ Period: ______ Sickle

Name: __________________________________ Date: ____________________ Period: ______
Sickle-Cell Allele and Malaria
The allele for sickle-cell disease is most common in people of African ancestry. The reason for this
probably has to do with the relationship between the sickle-cell trait and malaria. Malaria, a disease
common in parts of Africa, affects red blood cells. Carriers of the sickle-cell allele are resistant to
malaria. Scientists think that the sickle-cell trait helps carriers resist malaria. The map on the left
shows the distribution of malaria worldwide today. The map on the right shows the distribution of the
sickle-cell allele.
1. Where is malaria most common today? ___________________________________________
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2. Where is the sickle-cell allele most frequent? ______________________________________
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3. Malaria is caused by a microscopic parasite that infects the blood. Based on this fact, hypothesize
why people with sickle-cell trait are resistant to malaria.
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4. Suppose malaria were eliminated as a human disease. Predict how the frequency of the sickle-cell
allele might change over time. Explain your prediction.
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Mutations Worksheet
CA Biology Standards: Students know the general pathway by which ribosomes synthesize proteins, using tRNAs to translate genetic information in
mRNA. Students know how mutations in the DNA sequence of a gene may or may not affect the expression of the gene or the sequence of amino
acids in an encoded protein.
There are three ways that DNA can be altered when a gene mutation (change in DNA sequence) occurs.
1. Substitution – one base-pair is replaced by another
2. Insertion – one or more base pairs is added to a sequence
3. Deletion – one or more base pairs is lost from a sequence
There are four possible results of a mutation.
1. Silent mutation: When a base pair is substituted but the change still codes for the same amino acid in the
sequence. Example: TCT and TCC both code for the amino acid Serine
2. Substitution: When a base pair is substituted and the new codon codes for a different amino acid. Example: TCT
codes for Serine and CCT codes for Proline
3. Codon Deletion or Insertion: A whole new amino acid is added, or one is missing.
Example: GTGGTCCGAAACACC –– GTGGTCTGCCGAAACACC
Val-Val-Pro-Asn-Thr
Val-Val-Cys-Pro-Asn-Thr
4. Frameshift Deletion or Insertion: When a deletion or insertion results in a different base pair being the beginning
of the next codon, changing the whole sequence of amino acids.
Example: GTGGTCCGAAACACCT –– GTGGTCGAAACACCT
Val-Val-Pro-Asn-Thr
Val-Val-Glu-Thr-Pro
1. Look at the following sequence: THE FAT CAT ATE THE RAT. Delete the first H and regroup the letters in
groups of three, then write out the new groups of three. Does the sentence still make sense? What type of
mutation is this an example of? (2 points)
Sickle Cell Anemia is a genetic disorder caused by a mutation in the DNA. People with Sickle Cell have red blood cells
with sickle shaped hemoglobin that cannot hold as much oxygen. They get out of breath easily and have a lot of pain.
2. Below is the base sequence for the normal protein for normal hemoglobin and the base sequence for the
sickle cell hemoglobin. Transcribe and translate the normal and sickle cell DNA. (4 points)
GGG CTT CTT TTT
Normal:
GGG CAT CTT TTT
Sickle:
mRNA:
mRNA:
Amino Acid:
Amino Acid:
a. Identify this as a substitution or a frameshift mutation. Explain. (2 points)
b. If the DNA base sequence read G G G C T T C T T A
hemoglobin? Explain and show how you know. (2 points)
3. Name 3 amino acids that have more than one codon. (1 point)
A A instead, would this result in sickle cell
4. Name 2 amino acids that have only one codon. (1 point)
5. Given the following three mRNA sequences, 2 code for the same protein. Which two? Show your work! (3pts)
#1 A G U U U A G C A A C G A G A U C A
#2 U C G C U A G C G A C C A G U U C A
#3 A G C C U C G C C A C U C G U A G U
In each of the following DNA sequences, you will use the mRNA and amino acid sequences to identify the mutation that
occurred and the effects of each. Look and analyze carefully! (Original = 2 pts; Mutated Sequences = 3 points each)
Original DNA Sequence:
T A C A C C T T G G C G A C G A C T
mRNA Sequence:
Amino Acid Sequence:
Mutated DNA Sequence #1:
T A C A T C T T G G C G A C G A C T
What’s the mRNA sequence? (Circle the change)
What will be the amino acid sequence? (Circle the change)
Will there likely be effects?
What kind of mutation is this?
Mutated DNA Sequence #2:
T A C G A C C T T G G C G A C G A C T
What’s the mRNA sequence? (Circle the change)
What will be the amino acid sequence? (Circle the change)
Will there likely be effects?
What kind of mutation is this?
Mutated DNA Sequence #3:
What’s the mRNA sequence? (Circle the change)
What will be the amino acid sequence?
Will there likely be effects?
What kind of mutation is this?
T A C A C C T T A G C G A C G A C T