Copy of Unit 5 & 6.1 Review - 2025

Biology Honors

DNA (Deoxyribonucleic Acid)

A molecule that carries the genetic instructions for the development, functioning, growth and reproduction of all known living organisms.

Nucleotide

The basic structural unit of DNA, composed of a phosphate group, a deoxyribose sugar, and a nitrogenous base.

Nitrogen Bases

The four components of nucleotides in DNA: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

Chargaff's Rule

A rule stating that in DNA, the amount of Adenine equals Thymine and the amount of Guanine equals Cytosine.

Semi-conservative replication

The process of DNA replication where each new DNA molecule consists of one original strand and one new strand.

Helicase

An enzyme that unwinds the DNA double helix by breaking the hydrogen bonds between the nitrogen bases.

DNA polymerase

An enzyme that synthesizes new DNA strands by adding nucleotides to the growing chain during DNA replication.

Ligase

An enzyme that seals gaps between Okazaki fragments on the lagging strand during DNA replication.

Leading Strand

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

Lagging Strand

The DNA strand that is synthesized discontinuously in fragments called Okazaki fragments, running in the 3' to 5' direction.

Okazaki Fragments

Short sequences of DNA nucleotides synthesized on the lagging strand during DNA replication.

Cell Cycle

The series of events that take place in a cell leading to its division and replication, consisting of Interphase, Mitosis, and Cytokinesis.

Interphase

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

Cytokinesis

The process of cytoplasmic division that occurs after mitosis, resulting in two daughter cells.

Cyclins

Proteins that regulate the cell cycle by activating cyclin-dependent kinases (Cdks) to progress through the stages of the cycle.

Kinases

Enzymes that act as key regulators in cell cycle progression, activating proteins to move the cell through its cycle.

Surface Area to Volume Ratio

A measurement that describes how the surface area of a cell compares to its volume, which decreases as cell size increases.

Cell Differentiation

The process by which a cell transitions from one cell type to another, involving changes in gene expression.

Cell Specialization

The process that allows cells to develop unique structures and functions tailored to their specific roles in a multicellular organism.

Double Helix

The structural shape of DNA, consisting of two elongated strands wound around each other, holding the genetic information.

Antiparallel Strands

The orientation of the two strands of DNA, running in opposite directions (5' to 3' and 3' to 5').

Backbone of DNA

The sugar-phosphate backbone of DNA, formed by alternating deoxyribose sugars and phosphate groups.

Hydrogen Bonds

The weak bonds between nitrogenous bases (A-T and G-C) that hold the two DNA strands together.

Base Pairing Rules

The rules that determine how nitrogenous bases pair in DNA: Adenine pairs with Thymine, and Guanine pairs with Cytosine.

Major and Minor Grooves

The indentations on the DNA double helix where proteins can bind, playing crucial roles in gene regulation.

Chromatin

The complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells, allowing for DNA packaging.

Telomeres

The protective end caps on linear chromosomes that prevent degradation and loss of important genetic information during replication.

Histones

Proteins around which DNA is coiled to form nucleosomes, enabling DNA packaging and regulation in chromatin.

Nucleosome

The fundamental unit of DNA packaging, consisting of a segment of DNA wound around a core of histone proteins.

G1 Phase

The first phase of Interphase in the cell cycle, where the cell grows and synthesizes proteins necessary for DNA replication.

S Phase

The phase of the cell cycle during Interphase where DNA is replicated, resulting in two sister chromatids for each chromosome.

G2 Phase

The second growth phase in Interphase, where the cell prepares for mitosis and continues to grow and produce proteins.

Mitosis

The process of nuclear division in the cell cycle, consisting of prophase, metaphase, anaphase, and telophase, leading to the formation of two daughter nuclei.

Prophase

The first stage of mitosis, where chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and spindle fibers begin to form.

Metaphase

The stage of mitosis where chromosomes align at the cell's equatorial plate and spindle fibers attach to their centromeres.

Anaphase

The stage of mitosis where sister chromatids separate and are pulled to opposite poles of the cell.

Telophase

The final stage of mitosis where chromosomes de-condense, nuclear envelopes reform, and the cell prepares for cytokinesis.

Centriole

A structure that helps organize the spindle fibers during cell division, crucial for proper chromosome separation.

Cytoplasmic Division

The process that occurs during cytokinesis, resulting in the physical separation of the cytoplasm into two daughter cells.

Checkpoints

Control mechanisms in the cell cycle that ensure proper division and prevent errors; major checkpoints occur at G1, G2, and M phases.

Apoptosis

The process of programmed cell death that eliminates unnecessary or damaged cells during development and maintenance.

Telophase and Cytokinesis

Telophase is the final stage of mitosis followed by cytokinesis, which completes the division of the cytoplasm into two separate daughter cells.

M Phase

The period of the cell cycle that includes mitosis and cytokinesis; during this phase, the cell divides to produce two daughter cells.

G0 Phase

A phase where cells exit the cell cycle and enter a state of dormancy, remaining metabolically active but not actively dividing.

Checkpoints in the Cell Cycle

Regulatory points in the cell cycle (G1, G2, and M checkpoints) that assess if the cell is ready to proceed with division.

Role of Cyclins and Cdks

Cyclins bind to cyclin-dependent kinases (Cdks) to activate them; this complex regulates the progression of the cell cycle.

Apoptosis in the Cell Cycle

A controlled process of programmed cell death that can occur if a cell does not meet necessary conditions for division.