Question

1) The products of DNA replication are two DNA molecules. Which of the following statements about these two DNA molecules is false?

a) they are sister chromatids

b) they are both double-stranded DNA helices

c) they carry different sets of gene alleles

d) they each consist of one "old" strand, which was the template strand, and one "new" strand, which was just synthesized

2) In which of the following molecular processes is the formation of Watson-Crick type base pairs between DNA or RNA polynucleotides NOT critical to the mechanism?

a) PCR

b) transcription

c) DNA replication

d) no good answer - all of these depend to some degree upon base pairing interactions

e) translation

d) taking apart the nuclear membrane

Answer 1

1. Ans is option A.

DNA replication is a semi-conservative model, which means that, in a newly synthesised DNA molecule, one strand is form panrent DNA molecule and other strand is synthesised freshly. (Option D).

As replication generates an exact molecule of the parent DNA molecule by duplication, the genes present in it are always similar as the parent DNA.

When new DNA molecules are synthesied, it always makes a double stranded molecule by synthesise two strand,

'But, chromatids are a collection of DNA strands, that's why it is not possible that two DNA molecules synthesised from a parent DNA, will become a sister chromatids.

2. Taking apart the nuclear membrane.

Base pairing is a mechanism by which nuclotide bases pairs with each other depending on its ability to for hydrogen bond. Here adenine form two hydrogen bonds with thymine (in DNA) or Uracil (in RNA), Guanine form three hydrogen bonds with cytosine. During transcription complimentary bases form mRNA on DNA strand maintaining this pairing mechanism. During translation, codon of mRNA interacts with specific tRNA by maintain this base pairing formula.

In PCR also, this base pairing helps in attachement if the primer and synthesis of new DNA stand on the separated parent DNA molecule.

Whereas, taking apart the nuclear membrane is a gross process and nothing to do with base pairing or nucleotides. It occurs during cell division, where chromosoml division is necessary.