In bacteria, both transcription and translation processes occur in the cytoplasm as nucleus is not present in bacteria. In eukaryotes, transcription occurs in nucleus, while translation occurs in the cytoplasm.

A segment of DNA that codes for a polypeptide.

A-Continuous synthesis,
B-Discontinuous synthesis

A-B is 3'\(\rightarrow \)5' and C-D is 5'\(\rightarrow \)3'.

Futher polymerisation would not occur, as the 3'OH on sugar is not there to add a new nucleotide for forming ester bond.

DNA polymerase enzyme is highly specific to recognise only deoxyribonucleoside triphosphates(dNTPs). Therefore, it cannot hold ribo nucleosides.

Histones are a set of positively charged basic proteins associated with DNA helix

Deoxyribonucleoside monophosphates

Tabacco mosaic virus, (TMV), human immunodeficiency virus (HIV), wound tumour virus

A single codon mutation from GAG to GUG at sixth position of haemoglobin -\(\beta \) chain gene changes the amino acid, glutamic acid to valine. change in the nucleotide type and sequence results in the formation of changed haemoglobin, e.g., sickle cell anaemia. valine builds hydrophobic bonds under the condition of oxygen stress. This causes distortion of haemoglobin structure that is lethal in homozygous state and produces sickle cell anaemia in heterozygous condition

a) 5'-TTACGTCGATAATCC-3'
B) 3'-AAUGCAGCUAUAGG-5'

(i) The DNA polymerase catalyses the addition of nucleotides, i.e. polymerization of nucleotides to form a DNA strand in the 5' -3' direction only
(ii) In prokaryotes, It removes any wrong base added to the DNA strand being synthesised.

Eight molecules of histones (paired \({ H }_{ 2 }A{ ,\quad H }_{ 2 }B,\quad { H }_{ 3 },\quad { H }_{ 4 }\) ) join to form an octamer, on which the negatively charged DNA becomes wrapped around to form a nucleosome: Thus very long DNA molecules can be accommodated within the nucleus. \({ H }_{ 1 }\) protein acts as a linker between two adjacent nucleosomes.

¹⁵N/¹⁵N O :¹⁵N/¹⁴N 2 : ¹⁴N/¹⁴N 14