Biology Gene Expression and Cell Division

Study Notes

Each cell type uses only the genes that are relevant to its function, despite all nucleated cells having the same genes.
Red blood cells are the only cells that contain hemoglobin, though all body cells have the hemoglobin gene.
Regulatory substances control selective gene expression.
Genes are kept switched off when they are not needed by a cell.

The complementary RNA base sequence for ATTGAC is UAACUG.
A codon is a sequence of three bases on an RNA molecule that codes for a specific amino acid.

Most body cells can divide, even in adulthood.
Mitosis produces two identical diploid daughter cells and is critical for growth and repair.
Gametes are produced by meiosis, which results in daughter cells with half the number of chromosomes.
Gametes are haploid, containing 23 chromosomes instead of 46.

DNA replication is the process by which DNA makes an identical copy of itself.
Mistakes in DNA replication can lead to non-functional cells, poorly functioning cells, or cells that ignore cell controls, potentially leading to tumor development.
During DNA replication, the double helix unfolds and the two strands unzip to expose the bases.
The enzyme responsible for DNA replication moves along the base sequence, reading the genetic code and adding the complementary base to the new chain.
Two identical DNA molecules are formed as each strand of exposed bases becomes a double strand.
Other enzymes cause the new double strands to twist and coil back into their highly folded form.

Mitosis is a type of cell division that produces two daughter cells that are genetically identical to the parent cell.

Meiosis is the final step in gamete production.
When a sperm cell and an ovum unite, the resulting zygote is diploid since each gamete was haploid.
Meiosis involves two distinct cell divisions, unlike mitosis.
Meiosis produces four daughter cells, all different from the parent cells and from each other.
Genetic diversity and the unique character of each human are determined by meiosis.