AP BIOLOGY

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THE MOLECULAR BASIS OF INHERITANCE

DNA REPLICATION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
A protein called hemoglobin transports oxygen in red blood cells. Some people have hemoglobin molecules in which a single amino acid differs from the amino acid that belongs in that position in ordinary hemoglobin. Which of the following is the most likely cause of this condition?
A
Enzymes have repaired an error that occurred during the proofreading phase of DNA transcription.
B
Environmental factors have caused an error in the folding of the hemoglobin molecule.
C
An extra amino acid has been added to the hemoglobin during translation.
D
The hemoglobin contains a point mutation.
Explanation: 

Detailed explanation-1: -Red blood cells contain a protein called hemoglobin, which carries oxygen from the lungs to all parts of the body.

Detailed explanation-2: -Sickle cell anemia is caused by homozygous sickle mutation (Hb SS). The sickle mutation causes substitution of a valine for glutamic acid as the seventh amino acid of the beta globin chain. The resulting hemoglobin tetramer (alpha2/betaS2) is poorly soluble when deoxygenated.

Detailed explanation-3: -Hemoglobin contains iron, which allows it to pick up oxygen from the air we breathe and deliver it everywhere in the body. You can think of hemoglobin as the iron ("heme"), oxygen transport protein, ("globin") found in red blood cells. It’s the hemoglobin that gives red blood cells their color, too.

Detailed explanation-4: -Sickle cell disease is caused by mutations in the beta-globin (HBB) gene that lead to the production of an abnormal version of a subunit of hemoglobin-the protein responsible for carrying oxygen in red blood cells. This mutated version of the protein is known as hemoglobin S.

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