Biology Basics: Genetics and Nucleotides

Study Notes

Chromosome: A thread of DNA, containing genes, located within a cell nucleus. A nucleus can have one set of unpaired chromosomes or two sets of paired chromosomes.
Homologous Chromosomes: Paired chromosomes that carry the same genes but may have different versions (alleles) of those genes. Most body cells have homologous chromosomes.
Gene: A specific length of DNA that acts as a unit of heredity.
Nucleotide: The basic building blocks of nucleic acids (DNA and RNA). Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base.
Bonds in Nucleotides: The components of a nucleotide are connected by different types of bonds.
Nitrogenous Bases (DNA): Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
Nitrogenous Bases (RNA): Adenine (A), Uracil (U), Cytosine (C), Guanine (G)
Differences between DNA and RNA: DNA contains deoxyribose sugar, RNA contains ribose sugar; DNA is double-stranded, RNA is single-stranded. The difference between ribose and deoxyribose is a single oxygen atom.
Mitosis: A type of cell division that produces two genetically identical daughter cells. Mitosis results in genetically identical cells.

Interphase: The stage of the cell cycle prior to mitosis that consists of three phases:
- G1 Phase: Cell growth and normal functions. This is the first stage of growth in the cell.
- S Phase: DNA replication
- G2 Phase: Cell continues to grow after synthesis until mitosis begins.
Mitosis Phases:
- Prophase: Chromosomes condense, spindle fibers form, nuclear envelope breaks down.
- Metaphase: Chromosomes align at the cell's center. Spindle fibers attach to chromosomes.
- Anaphase: Sister chromatids are pulled apart to opposite poles.
- Telophase: The cell develops a cleavage furrow, nuclear membranes reform, chromosomes uncoil; the cytoplasm splits into two, and the cell divides.
Crossing Over: Crossing over occurs during meiosis, not mitosis.
Chromosome Duplication: When a chromosome replicates, it forms two identical halves called sister chromatids. These are held together at the centromere
Number of Cell Divisions in Mitosis: One cell division.
Ploidy of Daughter Cells in Mitosis: Diploid
Number of Daughter Cells in Mitosis: Two