1. Most mutations have no effect on an organism A) True B) False 2. CRISPR (shor
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Question
1. Most mutations have no effect on an organism
A) True
B) False
2. CRISPR (short for clustered regularly interspersed short palindromic repeats) is a recently discovered technique that allows biologists to alter (edit) a single nucleotide, of choice, in the genome of a cell. Which of the following disorders could potentially be treated by such a technique?
A. any X-linked disorder
B. sickle cell anemia
C. down syndrome
D. methanol poisoning
3. Histones can be modified to open up resulting in unwound DNA which can regulate transcription.
A. True
B False
Explanation / Answer
True. Most mutations have no effect on an organism. It is because the mutations either get repaired by the DNA repair mechanisms or the mutations occur in a region of DNA with no function (intron) or the mutations occur in a protein coding region but the mutation does not alter the amino acid sequence of the protein (silent or neutral mutations). So, the correct option is option A, true. CRISPR can be used to treat sickle cell anemia. Sickle cell anemia is a genetic disorder that is due to a single nucleotide mutation (A to T) in the beta-globin gene of haemoglobin molecule. This results in the substitution of valine amino acid instead of glutamic acid at position 6 of beta-globin protein. This leads to the formation of abnormal oxygen carrying haemoglobin protein resulting in sickle shaped red blood cells and sickle cell anemia. So, the correct option is option B, sickle cell anemia. True. Histones, alkaline proteins found in eukaryotic nuclei, package and order DNA into nucleosomes. Histone acetylation removes the positive charge on histones. As a result the interaction between the histone tail and nucleosome is reduced leading to the nucleosomes to open up. This allows transcription machinery to bind to DNA template resulting in gene transcription. Histone deacetylation results in a tight association between histone tail and nucleosomes. This forms a compact nucleosome assembly. As a result gene transcription is turned off. So, the correct option is option A, true.
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