Question

Why are there several 'jumps' on the template? How does the DNA product differ from the RNA template?

Answer 1

Lesions such as breaks, apurinic sites, and UV damage in a DNA template can cause the extending primer to jump to another template during the polymerase chain reaction.

DNA replication errors sometimes involve insertions or deletions of nucleotide bases that occur during a process called strand slippage. Sometimes, a newly synthesized strand loops out a bit, resulting in the addition of an extra nucleotide base. Other times, the template strand loops out a bit, resulting in the omission, or deletion, of a nucleotide base in the newly synthesized, or primer, strand, causing jumps.Region s of DNA containing many copies of small repeated sequences are particularly prone to this type of error.

See figure for reference.

A template is a single-stranded DNA or RNA polymer that is used to direct synthesis of another polymer such as DNA, RNA, or protein. DNA is used as a template molecule for DNA replication, DNA repair, as well as for transcription. DNA polymerases use template DNA by covalently linking deoxyribonucleoside 5′-triphosphates that base pair with template DNA to form a new, complementary DNA strand. The polymerase ‘reads’ the template in the 3′→5′ direction, while synthesizing DNA in the 5′→3′ direction to form the antiparallel double-stranded DNA product. This process is essential for duplication of genomic DNA, which precedes cell division. RNA polymerases use template DNA similarly to create complementary strands of RNA, which are then used as messenger RNA and translated into proteins or used as RNA components of cellular machinery.

RNA is single stranded, while DNA is double stranded.

RNA nucleotides contain ribose sugars while DNA contains deoxyribose.

RNA uses uracil instead of thymine present in DNA.

RNA is transcribed from DNA by enzymes called RNA polymerases and further processed by other enzymes.

RNA serves as the template for translation of genes into proteins, transferring amino acids to the ribosome to form proteins, and also translating the transcript into proteins.

RNA is a polymer with a ribose and phosphate backbone and four different bases: adenine, guanine, cytosine, and uracil.

The first three are the same as those found in DNA, but in RNA thymine is replaced by uracil as the base complementary to adenine.

In DNA, uracil is readily produced by chemical degradation of cytosine, so having thymine as the normal base makes detection and repair of such incipient mutations more efficient.

Thus, uracil is appropriate for RNA, where quantity is important but lifespan is not, whereas thymine is appropriate for DNA where maintaining sequence with high fidelity is more critical.