Molecular Biology

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A series of free High School Biology Video Lessons.

What is the DNA Structure?
DNA structure is what is called a double helix. DNA consists of two strands of nuclotides connected by pairs of bases. These strands "point" in opposite directions and are twisted into a helix shape. Each nucleotide subunit contains a phosphate group, a pentose sugar and a nitrogenous base. The four nitrogenous bases in DNA are adenine, thymine, guanine and cytosine.
An introduction to the structure of DNA.
What is the RNA Structure?
RNA Structure is a single strand composed of nucleotides. Unlike DNA it does not form a double helix shape, but it does contain a series of nitrogenous bases (adenine, uracil, guanine and cytosine). RNA can temporarily form hydrogen bonds between bases of two strands.
An introduction to the structure of RNA.
What is DNA Replication
Immediately before cell division, DNA copies itself in a process called DNA replication. First, an enzyme called helicase "unzips" the two strands in the double helix. Then DNA polymerase adds new nucleotides to the new strands. Finally, ligase rejoins the strands and they twist into a helix.
The process of DNA replication.
Protein Synthesis
Protein synthesis begins with a process called translation which occurs in the ribosomes, located in the endoplasmic reticulum. mRNA copies genetic information from the nucleus in a process called transcription. Then the mRNA brings that information to the ribosome and the tRNA brings amino acids which are arranged according to the information on the mRNA.
The synthesis of proteins.