UPSC Civil Services Model Paper 7

RNA:
RNA is the bridge between DNA and protein synthesis .
RNA is chemically similar to DNA but it contains ribose as its sugar and substitutes the nitrogenous base uracil for thymine.
Hence statement 2 is correct.
It is single-stranded rather than a double helix.
To get from DNA requires two major stages, transcription and translation.
The process from DNA to RNA is known as Transcription .
During transcription, a DNA strand provides a template for the synthesis of a complementary RNA strand.
Transcription of a gene produces a messenger RNA (mRNA) molecule .
During translation , the information contained in mRNA is used to determine the amino acid sequence of a polypeptide .
Translation occurs at ribosomes .
Chromosomes:
Chromosomes are thread-like structures present in the nucleus. Hence statement 1 is correct.
These are nothing but DNA tightly coiled around a protein called histone.
Chromosomes exist in pairs .
Human cells contain 23 such pairs or 46 chromosomes.
Each chromosome is comprised of one super-long DNA molecule.
The DNA is coiled around histones and then many such histones are packed together to form a chromosome.