Online Learning 4

DNA

Key molecule in living cells that is a polymer of individual building blocks, enabling it to store information required to make living cells.

Nucleotide

The monomer of nucleic acids, consisting of a phosphate group, a five-carbon sugar, and a nitrogenous base.

Phosphodiester bond

The bond that links nucleotides in a DNA or RNA strand, formed between the 5' phosphate group of one nucleotide and the 3' hydroxyl group of another.

Leading strand

The strand of DNA that is synthesized continuously in the 5' to 3' direction during DNA replication.

Lagging strand

The strand of DNA that is synthesized in short segments (Okazaki fragments) in the 3' to 5' direction, which is more complicated in the replication process.

Okazaki fragments

Short sequences of DNA nucleotides synthesized discontinuously and later connected by DNA ligase during DNA replication.

Replicaton fork

The area where the DNA double helix is unwound and separated into single strands for replication.

Cyclin-dependent kinases (CDK)

Enzymes that, when activated through binding with cyclin, regulate the cell cycle and progression through checkpoints.

Proto-oncogenes

Genes that normally promote cell division; if mutated or expressed abnormally, they can become oncogenes and contribute to cancer.

Tumor suppressor genes

Genes that inhibit cell division; their inactivation can lead to uncontrolled cell growth and cancer.

Cell cycle

The series of phases (G1, S, G2, and M) that cells go through to divide and replicate.

Checkpoints in the cell cycle

Control points in the cell cycle (G1, G2, and M) that ensure cells do not proceed to the next phase until specific criteria are met.

Mitosis

The process of nuclear division that results in two daughter nuclei, each with the same number of chromosomes as the parent nucleus.

Cytokinesis

The division of the cytoplasm that follows mitosis, resulting in two separate daughter cells.

Apoptosis

Programmed cell death, a mechanism that can eliminate damaged or unwanted cells.