Cell Cycle

Cell Cycle

The ordered sequence of events by which a cell grows, replicates its DNA, and divides into daughter cells.

Genome

The entire set of genetic information contained in an organism's DNA.

Chromosome

A DNA molecule packaged with proteins that carries genes.

Chromatin

Loose, uncondensed form of DNA found when a cell is not dividing.

Sister Chromatids

Two identical copies of a chromosome that remain attached at the centromere.

Homologous Chromosomes

Pairs of chromosomes that are similar in size, carry the same genes, and have genes in the same locations.

Alleles

Different versions of the same gene.

Haploid

A cell containing one set of chromosomes (n). In humans, haploid cells have 23 chromosomes.

Diploid

A cell containing two sets of chromosomes (2n). In humans, diploid cells have 46 chromosomes.

Interphase

The first three stages (G1, S, G2) of the cell cycle where the cell grows, duplicates organelles, and replicates DNA.

S phase

The phase of the cell cycle where DNA replication occurs.

Semi-Conservative Replication

DNA replication method where each new DNA molecule contains one original strand and one newly synthesized strand.

Origin of Replication

Specific DNA sequence where DNA replication begins.

Leading Strand

The DNA strand that is synthesized continuously during replication.

Lagging Strand

The DNA strand that is synthesized in fragments during replication.

Okazaki Fragments

Short DNA segments produced on the lagging strand during replication.

DNA Ligase

Enzyme that seals breaks in the sugar-phosphate backbone of DNA and connects Okazaki fragments.

Mitosis

The process of nuclear division that produces two genetically identical nuclei.

Cytokinesis

Division of the cytoplasm into two separate daughter cells after mitosis.

Meiosis

A specialized form of cell division that produces haploid gametes.

Gametes

Haploid reproductive cells, such as sperm and eggs.

Crossing Over

Exchange of segments of DNA between homologous chromosomes during Prophase I of meiosis.

Independent Assortment

Random alignment of homologous chromosome pairs during Metaphase I of meiosis.

Genetic Diversity

Increase in genetic combinations resulting from crossing over and independent assortment.

Nondisjunction

An error in chromosome separation during meiosis, resulting in gametes with abnormal chromosome numbers.