Question

1. scientists have made the claim if both parents are carriers, their children have a 25% chance of having sickle cell anemia.

complete the punnett square below to show the possible genotypes of the offspring.

1. analyze the results of the punnett square above. use evidence to support or refute the claim made in question 8.

ii. a change in dna can change the protein

sometimes, one of the letters in dna gets switched with another letter, causing a mutation in the dna. many mutations dont have any effects, but some will change the amino acid made by the ribosomes. in the case of sickle cell anemia, just a single letter change alters the shape of the hemoglobin protein.

1. use the codon chart to determine the amino acids created from each dna.

1. circle the codon in the normal dna that is altered in someone with sickle cell

Explanation:

Step1: Fill Punnett Square (top-left)

Combine parent alleles A and A: $AA$

Step2: Fill Punnett Square (top-right)

Combine parent alleles A and a: $Aa$

Step3: Fill Punnett Square (bottom-left)

Combine parent alleles a and A: $Aa$

Step4: Fill Punnett Square (bottom-right)

Combine parent alleles a and a: $aa$

Step5: Analyze Punnett Square for question 9

Count genotypes: 1 $AA$, 2 $Aa$, 1 $aa$. Sickle cell anemia is recessive ($aa$), so $\frac{1}{4} = 25\%$ chance.

Step6: Translate Normal DNA to amino acids (question10)

• mRNA codons: $CCU$, $GAA$, $GAA$.
• $CCU$ = Proline; $GAA$ = Glutamic Acid

Step7: Translate Sickle Cell DNA to amino acids (question10)

• mRNA codons: $CCU$, $GUA$, $GAA$.
• $CCU$ = Proline; $GUA$ = Valine; $GAA$ = Glutamic Acid

Step8: Identify altered codon (question11)

Compare Normal DNA G G A C T T C T T and Sickle Cell DNA G G A C A T C T T: the altered codon is CTT (third DNA codon).

Answer:

Question 8 Completed Punnett Square:

	A	a
a	Aa	aa

Question 9

The claim is supported. The Punnett square shows 1 out of 4 (25%) possible offspring genotypes is $aa$, which is the homozygous recessive genotype that causes sickle cell anemia.

Question 10

• Normal DNA amino acids: Proline, Glutamic Acid, Glutamic Acid
• Sickle Cell DNA amino acids: Proline, Valine, Glutamic Acid

Question 11

The altered codon in Normal DNA is CTT (the third set of three nucleotides in the Normal DNA sequence).