Following are the steps involved in the conversion of a nucleotide sequence to amino acid sequence.
1. Write the complementary bases for the given nucleotide sequence in order to complete the DNA sequence.
5' GGTTTCTTCAAGAGA 3'
3' CCAAAGAAGTTCTCT 5' (complementary base sequence)
2. Now consider previous half of the DNA sequence and replace its bases as per the bases couples involved in mRNA. (G-C/A-U)
5' GGTTTCTTCAAGAGA 3'
3' CCAAAGAAGUUCUCU 5' (mRNA)
3. Below given mRNA sequence enters the ribosome and then further band into transfer RNA sequence.
5' GGUUUCUUCAAGAGA 3' (mRNA)
3' CCAAAGAAGTTCUCU 5' (tRNA)
4. Through tRNA sequence we can easily decode the amino acid sequence (codon), because it is responsible for carrying the amino acids to the ribosome. Here, each pair of three bases in the tRNA sequence carries an amino acid that codes for a particular amino acid. After pairing them, we make use of a codon table in order to identify the codons and produce an amino acid sequence.
5' GGU UUC UUC AAG AGA 3' (mRNA)
3' CCA AAG AAG TTC UCU 5' (tRNA)
(Amino acid sequence)
5. Therefore, the above sequence represent amino acid sequence and the codons present in the amino acid sequence are glycine (G), phenylalanine (F), phenylalanine (F), lysine (K) and arginine (R).
Antisense drugs are made up of synthetic compounds that interact with other natural genetic material in order to retain the information for the production of proteins. These are usually short strands complementary to their target mRNAs. When they bind with each other, it forms a DNA/RNA hybrid which is further degraded by RNAase-H enzyme. This enzyme catalyzes the cleavage of RNA by means of hydrolytic mechanism resulting in the cleavage of phosphodiester bonds. This event makes mRNA unavailable for translation and would lead to methylation of promoter and coding regions of normal gene resulting in silencing of that particular gene. That is how such drugs help in fighting against various contagious diseases.
Cigarette smoking is main cause of lip cancer and lung cancer. Smokers are more prone to mouth cancer. It is also a cause of laryngeal, oral, oesophageal and gall bladder cancer in men and women. It is important contributory factor for the development of kidney and pancreatic cancer. It is also associated with cancer of stomach and uterine cervix.
There are various chemicals such as benzopyrene and many other substances present in cigarette smoke which are carcinogenic. Reverse smoking cause's oral cancer. In reverse smoking the burning end of cigarette is kept in mouth. Lip cancer is caused by constant irritation by cigarette and pipes. Cigarette smoking mutates and inactivates P53 (tumour suppressor gene) which checks cancer growth. Loss of these suppressor genes can lead to cancer which is regarded as an uncontrolled cell growth. In healthy cells, cell growth is regulated by proto-oncogenes and tumour suppressor proteins. Mutation can be caused by variety of factors that stimulate the development of proto-oncogenes into oncogenes and can affect the availability of tumour suppressor proteins. This is how; many other chemicals in cigarette can lead to cancer.