Question

sickle cell anemia is the result of a type of mutation in the gene that codes for part of the hemoglobin molecule. hemoglobin carries oxygen in your red bloods cells. the mutation causes these red blood cells to become stiff & sickle - shaped when they release their oxygen. the sickled cells tend to get stuck in blood vessels, causing pain and increased risk of stroke, blindness, damage to the heart & lungs, and other conditions. analyze the dna strands below to determine what amino acid is changed and what type of mutation occurred normal hemoglobin dna cacgtagactgaggactc... normal hemoglobin mrna normal hemoglobin aa sequence sickle cell hemoglobin dna cacgtagactgaggacac... sickle cell hemoglobin mrna sickle cell hemoglobin aa sequence 1. what type of mutation is this? please explain why.

Explanation:

Step1: Transcribe DNA to mRNA

Normal DNA: \(CACGTAGACTGAGGACTC\)
Using base - pairing rules (\(A - U\), \(T - A\), \(C - G\), \(G - C\)), the normal mRNA is \(GUGCAUCUGACUCCUGAG\)
Sickle - cell DNA: \(CACGTAGACTGAGGACAC\)
The sickle - cell mRNA is \(GUGCAUCUGACUCCUGUG\)

Step2: Translate mRNA to amino - acid sequence

Using the genetic code (where each triplet of nucleotides (codon) codes for an amino acid).
For the normal mRNA (\(GUGCAUCUGACUCCUGAG\)):
Breaking into codons: \(GUG\) (Val), \(CAU\) (His), \(CUG\) (Leu), \(ACU\) (Thr), \(CCU\) (Pro), \(GAG\) (Glu)
For the sickle - cell mRNA (\(GUGCAUCUGACUCCUGUG\)):
Breaking into codons: \(GUG\) (Val), \(CAU\) (His), \(CUG\) (Leu), \(ACU\) (Thr), \(CCU\) (Pro), \(GUG\) (Val)

Step3: Identify the mutation type

A point mutation (specifically a missense mutation) has occurred. A single base change in the DNA (\(CTC\) in normal DNA to \(CAC\) in sickle - cell DNA) leads to a change in the mRNA codon (\(GAG\) to \(GUG\)) and thus a change in the amino acid (Glu to Val)

Answer:

This is a point (missense) mutation. A single base change in the DNA sequence (\(CTC
ightarrow CAC\)) causes a change in the mRNA codon (\(GAG
ightarrow GUG\)) and results in the substitution of the amino acid Glu (from \(GAG\)) with Val (from \(GUG\))