The Primary Function Of DNA Ligase Is To: Remove Bases That Might Have Been Inserted Incorrectly Seal Together Any Gaps In The DNA Strand Cut The Two Strands Of DNA Molecule Prior To Replication Attach Free Nucleotides To A Growing Chain Question 23 25% Question 25 1 Pts Which Of The Following Statements Regarding DNA Replication Is Correct?
The Correct Answer and Explanation is :
Correct Answer for the Primary Function of DNA Ligase
Seal together any gaps in the DNA strand
Explanation:
DNA ligase is a crucial enzyme in DNA replication and repair. Its primary function is to catalyze the formation of phosphodiester bonds between adjacent nucleotides, thereby sealing nicks (gaps) in the DNA backbone. These gaps arise naturally during DNA replication and repair processes.
During replication, DNA polymerase synthesizes the new strand of DNA in short fragments known as Okazaki fragments on the lagging strand. While the leading strand is synthesized continuously, the lagging strand is synthesized in these small fragments. DNA ligase is responsible for joining these fragments, ensuring a continuous and intact double-stranded DNA molecule.
Additionally, DNA ligase plays a significant role in DNA repair mechanisms, such as base excision repair (BER) and nucleotide excision repair (NER). When DNA is damaged by factors like UV radiation, chemicals, or replication errors, repair enzymes remove incorrect or damaged bases, leaving a gap in the DNA. DNA ligase then fills these gaps by linking the sugar-phosphate backbones of the DNA, restoring its integrity.
Without DNA ligase, the DNA strands would remain fragmented, leading to genomic instability and potential cell dysfunction or death. This enzyme is, therefore, essential for maintaining genetic continuity and preventing mutations.
Correct Answer for DNA Replication Question
The correct statement regarding DNA replication is:
“DNA replication is semi-conservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand.”
Explanation:
DNA replication follows a semi-conservative model, as demonstrated by the Meselson-Stahl experiment in 1958. This means that each daughter DNA molecule contains one original (parental) strand and one newly synthesized strand.
Key steps in DNA replication:
- Initiation:
- Helicase unwinds the double-stranded DNA, creating a replication fork.
- Single-stranded binding proteins (SSBs) stabilize the separated strands.
- Elongation:
- DNA polymerase adds new complementary nucleotides to the template strands in the 5′ to 3′ direction.
- The leading strand is synthesized continuously, while the lagging strand is synthesized in Okazaki fragments.
- Termination:
- DNA ligase seals gaps in the lagging strand.
- The replication process is completed, yielding two identical DNA molecules.
This process ensures genetic consistency during cell division, allowing organisms to pass on their genetic information accurately.