BIO Honors U5

DNA

A molecule that carries the genetic instructions.

Double helix

The structure of DNA, consisting of two intertwined strands.

Nucleotide

Basic building block of DNA, composed of deoxyribose sugar, phosphate group, and a nitrogen base.

Adenine

A nitrogen base that pairs with thymine in DNA.

Thymine

A nitrogen base that pairs with adenine in DNA.

Cytosine

A nitrogen base that pairs with guanine in DNA.

Guanine

A nitrogen base that pairs with cytosine in DNA.

Covalent bonds

Strong bonds that connect nucleotides in the DNA backbone.

Hydrogen bonds

Weak bonds that form between nitrogen bases in complementary DNA strands.

Chargaff’s rule

States that the amount of guanine equals cytosine and adenine equals thymine.

Purines

Nitrogen bases with a double-ring structure: adenine and guanine.

Pyrimidines

Nitrogen bases with a single-ring structure: cytosine and thymine.

Semiconservative replication

Type of DNA replication in which half of the original DNA strand is conserved.

Helicase

Enzyme responsible for unwinding and separating DNA strands during replication.

DNA Polymerase

Enzyme that adds complementary bases during DNA replication.

Ligase

Enzyme that connects the backbone of DNA by forming covalent bonds between sugars and phosphates.

Gene

A segment of DNA that codes for a particular trait.

Messenger RNA (mRNA)

RNA that carries the code from DNA to ribosomes for protein synthesis.

Transfer RNA (tRNA)

RNA that transfers amino acids to ribosomes during protein synthesis.

Ribosomal RNA (rRNA)

RNA that makes up ribosomes.

Transcription

Process of copying a gene from DNA to mRNA.

Translation

Process of converting mRNA into an amino acid chain (protein) on a ribosome.

Point mutation

Mutation that occurs at a single point/base pair in DNA.

Substitution mutation

Mutation where one nucleotide is replaced by another.

Frameshift mutation

Mutations that result from additions or deletions of nucleotides.

Cell cycle

Process by which a cell grows, replicates its DNA, and divides.

Binary Fission

A form of asexual reproduction in prokaryotes, resulting in two identical daughter cells.

Mitosis

Process of nuclear division in eukaryotic cells that results in two identical daughter cells.

Meiosis

Specialized form of cell division that produces haploid gametes from diploid cells.

Chromatin

Uncondensed form of DNA found in the nucleus during interphase.

Chromosome

Condensed form of DNA that is visible during cell division.

Diploid (2n)

Cells that contain two sets of chromosomes, one from each parent.

Haploid (n)

Cells that contain one set of chromosomes, typically found in gametes.

Autosomes

22 pairs of chromosomes that do not determine biological sex.

Sex chromosomes

23rd pair of chromosomes that determine biological sex.

Prophase

First stage of mitosis where chromosomes condense and spindle fibers form.

Metaphase

Stage of mitosis where chromosomes line up in the middle of the cell.

Anaphase

Stage of mitosis where sister chromatids are pulled apart to opposite ends of the cell.

Telophase

Final stage of mitosis where new nuclei form and chromosomes uncoil.

Karyotype

Visual display of an organism's chromosomes used to identify chromosomal abnormalities.

Gametes

Haploid sex cells produced by meiosis.

Oogenesis

Formation of egg cells in females during meiosis.

Spermatogenesis

Formation of sperm cells in males during meiosis.

Crossing over

Exchange of genetic material between homologous chromosomes during prophase I of meiosis.

Independent assortment

Process by which different genes independently separate from one another when reproductive cells develop.

Random fertilization

Concept that any sperm can fertilize any egg, contributing to genetic variation.