Genetic Bases of Development - Genes

DNA stands for Deoxyribonucleic Acid. It is the genetic material in most living organisms, except some viruses, which have RNA instead.​ DNA stores instructions for making proteins that determine traits such as eye color, hair type, and height.​

• DNA looks like a twisted ladder, called a double helix.
• Each “step” of the ladder is made up of base pairs.
• Adenine (A) pairs with Thymine (T).
• Guanine (G) pairs with Cytosine (C).
• Each side of the ladder is made of sugar (deoxyribose) and phosphate groups.
• The unit of DNA is called a nucleotide.
• A nucleotide contains a nitrogenous base (A, T, G, or C).
• A nucleotide also contains a sugar molecule.
• A nucleotide contains a phosphate group.

• Genes are small sections of DNA that contain instructions to make a protein.​
• Chromosomes are long, coiled DNA molecules found in the cell nucleus.
• Humans have 23 pairs (46 total) of chromosomes.
• Each gene has a specific place on a chromosome, called its locus.

Genes express themselves through two steps:

1. Transcription: DNA makes a working copy called mRNA.
2. Translation: mRNA is used to make proteins inside ribosomes.
   These proteins decide how traits appear (e.g., hair color).

• Stores genetic information.
• Copies itself during cell division.
• Passes hereditary information from parents to offspring.​
• Controls the synthesis of proteins that govern body structure and function.

• Melanin gene: Controls skin color.
• Hemoglobin gene: A Mutation in this gene can cause Sickle Cell Anemia.
• Height gene: Controlled by many DNA segments (polygenic inheritance).

• DNA is the molecule of heredity.
• Genes are short sections of DNA that code for proteins.
• DNA has a double helix shape made of nucleotides.
• Base pairs: A–T and G–C.
• Genes control traits through the process of transcription and translation.
• Humans have 23 pairs of chromosomes carrying genetic information.