Question

1. which nucleotide base pairs with adenine in mrna during transcription?

a. uracil
b. cytosine
c. thymine
d. guanine

1. in which type of mutation is a new nucleotide inserted into the dna sequence?

a. frameshift mutation
b. deletion mutation
c. insertion mutation
d. substitution mutation

1. what is the role of ligase in dna replication?

a. adds nucleotides to the growing strand
b. seals gaps between okazaki fragments
c. unwinds the double helix
d. initiates replication

Explanation:

Question 10

During transcription, DNA is used as a template to make mRNA. In DNA, adenine (A) pairs with thymine (T), but in RNA, thymine is replaced by uracil (U). So adenine in DNA (template) pairs with uracil in mRNA.

• Frameshift mutation: Caused by insertion or deletion of nucleotides (not in multiples of 3), altering the reading frame. But the question is about insertion of a new nucleotide.
• Deletion mutation: Involves removal of nucleotides.
• Insertion mutation: Defined as the addition (insertion) of one or more nucleotides into the DNA sequence.
• Substitution mutation: One nucleotide is replaced by another, no insertion.

So the mutation where a new nucleotide is inserted is insertion mutation.

• Option a: DNA polymerase adds nucleotides to the growing strand, not ligase.
• Option b: DNA ligase's role in DNA replication is to seal the gaps (phosphodiester bonds) between Okazaki fragments on the lagging strand.
• Option c: Helicase unwinds the double helix.
• Option d: Initiation of replication involves proteins like initiator proteins, not ligase.

So ligase seals gaps between Okazaki fragments.

Answer:

a. Uracil

Question 11