Molecular Biology and Genetics

RNA contains the sugar ribose, while DNA contains deoxyribose. This is a fundamental biochemical difference - the 'deoxy' in DNA means it lacks one oxygen atom that ribose has. RNA is found in both nucleus and cytoplasm, not only nucleus. DNA uses thymine and RNA uses uracil, not the reverse. Both RNA and DNA can form helical structures (RNA can be single-stranded but also forms helices like in tRNA).

Restriction enzymes like EcoRI are called 'molecular scissors' because they cut DNA at specific recognition sequences (EcoRI cuts at GAATTC). This ability to precisely cleave DNA makes them essential tools in genetic engineering for creating recombinant DNA. Glucose oxidase, isocitrate dehydrogenase, and homoserine dehydrogenase are metabolic enzymes, not nucleases.

In the year 1963, the two enzymes, restriction exonuclease and restriction endonuclease, responsible for restricting the growth of bacteriophage in Escherichia coli were isolated. One of these enzyme (exonuclease) added methyl groups to DNA, while the other cut DNA (endonuclease). Restriction exonuclease removes nucleotides from the ends of the DNA, whereas restriction endonuclease makes cuttings at specific positions within the DNA.

(continuous fragments ) are clones containing neighbouring DNA fragment having an overlapping regions. Contigs greatly facilitate mapping and ultimately the correct alignment of base sequence data.

About 1% of human chromosomal DNA is stably unmethylated, these regions are called CpG islands, since they contain more than 50% of C+G. These sequences are used as powerful markers for genome mapping.

Streptomyces coelicolor has G-C content of 72%. It has the highest G-C content.

Uracil is present only in RNA. In DNA, Thymine is present in place of Uracil.

Replication is the formation of new DNA molecules from parent DNA during cell division.

In genetics, an enhancer is a short (50 - 1500 bp) region of DNA that can be bound with proteins to activate transcription of a gene or genes.

Repetitive DNA will renature at low C₀t values. The fast renaturation of the repetitive DNA is because of the avalability of numerous complementary sequences.

Ethidium bromide is the most commonly used dye for DNA and RNA detection in gels. Ethidium bromide is a DNA intercalating agent, inserting itself between the base pairs.

Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome.

The basic repeating structural (and functional) unit of chromatin is the nucleosome, which contains nine histone proteins and about 166 base pairs of DNA.