Question

the enzyme that unwinds the double stranded dna at the beginning of dna replication is called
a) helicase.

b) dna polymerase.

c) topoisomerase.

d) primase.

question 9 (5 points)
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rnai is a technique that silences genes by targeting them and degrading their mrna. how can this technique be used in scientific laboratories?
a) rnai allows scientists to turn off one gene specifically to study its effect.

b) rnai is observed in nature, but it can’t be used in laboratories.

c) rnai is a powerful tool for degrading mrna, but because it doesn’t degrade other types of rna its use is limited

Explanation:

First Question (Enzyme Unwinding DNA)

• Option A: Helicase is the enzyme responsible for unwinding the double - stranded DNA during DNA replication by breaking the hydrogen bonds between the base pairs.
• Option B: DNA polymerase is mainly involved in synthesizing new DNA strands by adding nucleotides, not unwinding DNA.
• Option C: Topoisomerase relieves the torsional stress that arises during DNA unwinding, but it does not perform the initial unwinding of the double helix.
• Option D: Primase synthesizes short RNA primers that are used as starting points for DNA polymerase to begin DNA synthesis, and it has no role in unwinding DNA.

Second Question (RNAi in Laboratories)

• Option A: RNAi (RNA interference) works by degrading the mRNA of a specific gene. By doing so, scientists can specifically "turn off" the expression of that gene and then observe the resulting phenotypic or functional changes. This helps in studying the function of the gene.
• Option B: RNAi can be and is widely used in laboratories for various research purposes, so this option is incorrect.
• Option C: The fact that RNAi targets mainly mRNA (and this is a specific and useful feature) does not limit its use. It is a powerful tool precisely because it can target specific mRNAs to study gene function, so this option's reasoning is wrong.

Answer:

A) helicase.