Understanding Genes, DNA, and the Human Genome

Genes and DNA

Genes are segments of DNA found in chromosomes. DNA is a molecule that stores genetic information.

DNA Replication

The process of copying the double helix of DNA. The helix opens like a zipper, and each strand is used as a template to create a complementary chain.

Genetic Function and Protein Synthesis

Genes serve to transmit genetic information. The genetic code provides instructions for making proteins from the nucleotide sequence of DNA. Nucleotides include: A, T, C, and G.

Understanding Mutations

A mutation is an error in the copying of DNA or RNA, or a protein involved in nucleotide exchange. Mutations can be:

• Neutral: No change in the protein; does not affect the individual.
• Beneficial: Changes the protein and provides a positive advantage.
• Harmful: Selected against.

Functions of DNA

• Store genetic information.
• Transmit genetic information to offspring.
• Encode proteins.

The Role of RNA

RNA acts as an intermediary between DNA and proteins because DNA cannot leave the nucleus. RNA is produced and moves outside the nucleus to facilitate protein synthesis. The DNA in the nucleus contains the message that is transcribed; the RNA then leaves the nucleus and binds to ribosomes, translating the genetic message into proteins.

The Human Genome

The genome is the complete set of genes in an organism.

The Human Genome Project

The Human Genome Project began in 1988 and concluded in 2003. Its goal was to sequence the entire human genome and determine the role of all genes. By 2003, full genome sequencing was achieved, identifying approximately 23,000 human genes. We currently understand the function of 50% of these genes.

DNA Composition

Only 2% of DNA consists of genes that encode proteins and various RNAs. The remaining 98% consists of non-coding regions, including introns. Within genes, there are coding fragments (exons) and non-coding pieces that are removed during RNA processing (introns).

Genomics and Proteomics

Genomics

The science that studies the genome. Notably, the size of a genome is not proportional to the complexity of the organism.

Proteomics

The science that studies the proteins encoded by the genome. A single gene with multiple exons can encode different proteins depending on how those exons are combined.