Nucleicacid Dna

Question 1

Replication

Answer 1

DNA synthesis by copying of existing DNA

Question 2

Transcription

Answer 2

RNA synthesis by copying of DNA

Question 3

RNA processing

Answer 3

Modification of RNA in the nucleus

Question 4

Translation

Answer 4

Protein synthesis by decoding of RNA

Question 5

Nucleic acid are composed of what

Answer 5

Monomeric units made up of an ‘information coding’ nitrogen base (purines and pyrimidines)
Adenine, Guanine
Thymine, Cytosine, Uracil

A sugar scaffold to hold the bases
Ribose in RNA
Deoxyribose in DNA

A phosphate connector

Question 6

five principal bases in nucleic acids

Answer 6

A, G, T, C are present in DNA

A, G, U, C are present in RNA

Each have H bond donors and acceptors

Question 7

The sugar forms the backbone on the outside of the molecule and has anti-parallel 5’ to 3’ directionality

Question 8

DNA properties

Answer 8

Native DNA is a double helix of complementary antiparallel chains

Hydrogen bonding between complementary base pairs (A-T or G-C) holds the two strands together

As the nucleotides stack, phosphodiester bonds between the phosphates above and below create the strand backbone

DNA helix is right handed (B, A, and Z forms exist, but B is the common form)

The two strands are slightly asymmetrically aligned, which results in the major and minor grooves along the double helix structure

The grooves enable factors to interact with the bases during DNA replication and transcription

The unit of length of DNA is the base pair (bp) and there are around 3 billion bp in the human genome and around 20,000-25,000 genes

Question 9

Eukaryotic DNA

Answer 9

packaged into chromatin (forms 23 pairs of individual chromosomes)

Question 10

What is the nucleo some

Answer 10

The basic building unit of chromatin is the nucleosome

Question 11

Nucleosome are composed of what

Answer 11

8 highly basic protein called histone

Question 12

Dna

Answer 12

‘DNA is wound around the nucleosome with spacing between nucleosomes
DNA follows a hierarchical pathway of folding to form the chromosome. The centromere is a constricted region of the chromosome involved in segregation of chromosomes to daughter cells during DNA replication and cell division
Ends of chromosomes have a highly repetitive G-C rich sequence called the telomere - this non-coding region helps protect the structure of chromosome. Telomeres shorten with successive replications and eventually prevent further replication causing cellular senescence

Question 13

Nucleoside role

Answer 13

regulation of gene expression, or activity, by determining whether the DNA sequences can be accessed by transcription factors (gene expression)

Question 14

Enzymatic modification of theamino-terminaltails of histones (e.g. acetylation, methylation, or phosphorylation) modifies the electrical charge and shape

These modifications are physiologically reversible and may prepare the chromatin for DNA replication and transcription

Question 15

Ribose nuclei’s acid (RNA)

Answer 15

Like DNA is composed of nucleotides, but differs from DNA;
Uracil, adenine and guanine and cytosine
Polymer joined by 3’ to 5’ phosphodiester bonds, but usually single stranded
Can form secondary and tertiary structuters by folding and base-pairing with itself
Some RNAs are capable of catalyzing reactions e.g. peptidyl transferase (involved in translation)

Question 16

Messenger RNA (mRNA)

Answer 16

Carries genetic information from DNA to the cytoplasm for translation into proteins

Question 17

Transfer RNA((tRNA)

Answer 17

Has a ‘cloverleaf’ secondary structure and carries individual amino acids for assembly into proteins
Inosine, which is nucleoside modified from adenine is important in tRNA function

Question 18

Ribosomal RNA (rRNA)

Answer 18

Several rRNAs (5S, 5.8S, 18S, 28S) and accounts for the majority of total RNA in a cell

Question 19

Intracellular communication:

Answer 19

Cyclic adenosine monophosphate (cAMP) and guanosine monophosphate (cGMP) are intracellular common chemical signalling molecules.

Question 20

Energy

Answer 20

Adenosine triphosphate (ATP) is a key energy currency of the cell. Guanosine triphosphate (GTP) is also as an energy source in many cellular activities
Energy is stored in the covalent bonds which link the three phosphates

Question 21

differences between RNA and DNA

Answer 21

Nucleotides in DNA have a 2’ deoxyribose sugar, while nucleotides in RNA have a ribose sugar

RNA has uridine (base: uracil) instead of deoxythymidine (base:thymine) phosphate residues

DNA is usually a double helix, usually in the B form, while RNA is usually single stranded,

Single stranded RNA can fold into diverse structures through regions of internal base pairing and perform similar functions to proteins, including catalysis

Several types of RNA e.g. messenger RNA (transcription), transfer RNA (translation), ribosomal RNA (ribosomes/translation) and others