Biology Part II

Cell Cycle

The life cycle of a cell, including its different stages of growth and division.

Interphase

The stage of the cell cycle where the cell grows and prepares for division, including G1, S, and G2 phases.

G1 (Gap 1) phase

The phase where the cell grows and performs its normal functions.

S (Synthesis) phase

The phase where the cell copies its DNA.

G2 (Gap 2) phase

The phase where the cell checks its copied DNA for mistakes and prepares to divide.

Mitosis

The process through which a cell divides its nucleus, consisting of four main phases: Prophase, Metaphase, Anaphase, and Telophase.

Cytokinesis

The process that follows mitosis, splitting the cytoplasm to form two daughter cells.

Prophase

The first phase of mitosis where DNA condenses and the nuclear membrane breaks down.

Metaphase

The second phase of mitosis where chromosomes line up in the middle of the cell.

Anaphase

The third phase of mitosis where sister chromatids are pulled apart to opposite sides of the cell.

Telophase

The fourth phase of mitosis where two nuclear membranes start to form around the split DNA.

Checkpoints

Regulatory points in the cell cycle where the cell assesses if it is ready to proceed with division.

Chromatin

Loose, stringy DNA present in the interphase of the cell cycle.

Chromosome

Tightly coiled DNA, shaped like an X, visible during cell division.

Chromatid

One half of a duplicated chromosome, with sister chromatids being identical copies.

Karyotype

A picture of all the chromosomes in a cell.

DNA (Deoxyribonucleic acid)

The molecule that carries genetic instructions; structurally resembles a twisted ladder.

Nucleotide

The building blocks of DNA consisting of a sugar, a phosphate group, and a nitrogenous base.

Nitrogenous Bases

The four types of bases (Adenine, Thymine, Cytosine, Guanine) that pair specifically A-T and C-G.

Semi-Conservative Replication

A method of DNA replication where each new DNA molecule consists of one old and one new strand.

Helicase

The enzyme that unwinds the DNA double helix during replication.

DNA Polymerase

The enzyme that adds nucleotides to form new DNA strands.

Okazaki Fragments

Small chunks of DNA produced on the lagging strand during replication.

Ligase

The enzyme that joins Okazaki fragments, creating a continuous DNA strand.

Telomeres

Protective caps at the end of DNA strands, preventing damage and fraying over time.

Stages of Mitosis

The stages of mitosis are Prophase, Metaphase, Anaphase, and Telophase, which result in the division of the cell's nucleus.

DNA Replication

The process by which a cell copies its DNA before cell division, ensuring each daughter cell receives an identical set of chromosomes.

Order of Mitosis

The correct order of phases in mitosis is: Prophase, Metaphase, Anaphase, and Telophase.

Role of Telomeres

Telomeres protect the ends of chromosomes from deterioration or from fusion with neighboring chromosomes during cell division.

Telomere Shortening

With each cell division, telomeres shorten, which is associated with aging and limits the number of times a cell can divide.

Telomerase

An enzyme that adds nucleotide sequences to telomeres, potentially extending the lifespan of cells by preventing telomere shortening.