Fundamentals of DNA, Genes and Protein Synthesis

Key Terms in Genetics

DNA: deoxyribonucleic acid, substance that carries genetic information in a cell.

Protein: organic compound that consists of long chains of molecules and is an essential part of living things.

Genetic code: set of instructions in a gene that tells a cell how to make a specific protein.

Genome: set of genes in an organism.

Genetic engineering: manipulation of genetic material to change the traits of an organism.

Biotechnology: biological techniques to create improved products for human consumption.

Genes and Their Role

Genes: are located in the chromosomes and are the basic unit of inheritance that carry genetic information. Genes consist of DNA, the molecule that gives cells and all organisms biological information.

Cell Cycle and Cytokinesis

Cytokinesis / Cell cycle phases:

• Phase G1: protein synthesis and cell growth.
• Phase S: replication of DNA and histones.
• Phase G2: preparation for cell division.
• Mitosis phase: division of the nucleus.

DNA Replication

Replication: process in which the DNA is duplicated.

1. The double helix of DNA opens up and two strands separate.
2. Free-floating nucleotides attach themselves to the separated DNA strands. Each nitrogenous base pairs with its complementary base.
3. The nucleotides join to the separated strands to form new strands.
4. At the end of the replication process there are two identical copies of DNA; each one has a strand from the original DNA and a new strand. The replication of DNA is called semiconservative replication.

Differences Between RNA and DNA

RNA consists of a single chain which has ribose nucleotides instead of deoxyribose nucleotides.

Types of RNA

mRNA: it is a copy of DNA that is needed to synthesize a protein.

rRNA (ribosomal RNA): this forms part of the ribosomes, where the amino acids join together to make protein chains.

tRNA (transfer RNA): this transports amino acids from the cytoplasm to the ribosomes. Its role is to attach specific amino acids to the protein chains that are being synthesized in the ribosomes.

Transcription

Transcription: it is a process in which the DNA copies its information into RNA so that it can be used to synthesize a protein.

1. The double helix of DNA opens up.
2. The complementary nucleotides position themselves opposite one of the two strands.
3. Only one of the DNA strands is copied.
4. An RNA strand is produced with a sequence of bases that is complementary to the DNA bases.

Genetic Code and Its Characteristics

Genetic code: it is the relationship between the nitrogenous bases and amino acids in mRNA that make proteins; it is used to synthesize proteins during translation. Characteristics:

• Universal: it is identical in all organisms, from the simplest bacteria to human beings.
• Degenerate: amino acids are associated with more than one codon.
• It has triplets (stop codons) which do not code for any amino acid.
• The AUG triplet acts as the start signal at the beginning of mRNA translation.