Unit 4: DNA, Mitosis, Meiosis & Genetics VOCABULARY SHEET

A comprehensive set of flashcards covering key vocabulary in DNA, mitosis, meiosis, and genetics.

DNA (Deoxyribonucleic Acid)

The double-stranded molecule that stores genetic information using a sequence of nucleotides.

Nucleotide

The monomer of DNA/RNA; made of a phosphate group, sugar, and nitrogenous base.

Deoxyribose

The 5-carbon sugar found in DNA nucleotides (one fewer oxygen than ribose).

Ribose

The 5-carbon sugar found in RNA nucleotides.

Nitrogenous Base

The variable part of a nucleotide. DNA: A, T, G, C. RNA: A, U, G, C.

Adenine (A)

A purine base; pairs with Thymine (T) in DNA, or Uracil (U) in RNA.

Thymine (T)

A pyrimidine base found only in DNA; pairs with Adenine (A).

Guanine (G)

A purine base; pairs with Cytosine (C) in both DNA and RNA.

Cytosine (C)

A pyrimidine base; pairs with Guanine (G) in both DNA and RNA.

Uracil (U)

A pyrimidine base found only in RNA; replaces Thymine, pairs with Adenine.

Chargaff's Rules

In DNA, A = T and G = C in terms of amount. Also governs base pairing.

Double Helix

The twisted-ladder shape of the DNA molecule; two antiparallel strands connected by hydrogen bonds between base pairs.

Hydrogen Bond

The weak bond holding complementary bases together (A-T: 2 bonds; G-C: 3 bonds).

Complementary Base Pairing

A-T and G-C (DNA); A-U and G-C (RNA) — the rule that governs how strands pair.

DNA Replication

The process of copying DNA before cell division; occurs during S phase.

Helicase

Enzyme that unwinds and unzips the DNA double helix during replication.

DNA Polymerase

Enzyme that reads the template strand and synthesizes the new complementary DNA strand.

Gene

A specific sequence of DNA nucleotides that codes for a protein.

Chromosome

A tightly coiled structure of DNA and histone proteins; humans have 46 (23 pairs).

Homologous Chromosomes

Matching chromosome pairs (one maternal, one paternal) that carry genes for the same traits.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid; types include mRNA, tRNA, rRNA.

mRNA (Messenger RNA)

Carries the genetic code from DNA in the nucleus to the ribosome.

tRNA (Transfer RNA)

Carries specific amino acids to the ribosome; has an anticodon that matches mRNA codons.

rRNA (Ribosomal RNA)

Component of ribosomes; helps facilitate translation.

Transcription

The process of making mRNA from a DNA template; occurs in the nucleus.

Translation

The process of assembling a protein from an mRNA template at the ribosome.

Codon

A sequence of 3 mRNA bases that codes for one specific amino acid (or start/stop signal).

Anticodon

A sequence of 3 bases on tRNA complementary to an mRNA codon; delivers the correct amino acid.

Amino Acid

The monomer (building block) of proteins; joined by peptide bonds during translation.

Peptide Bond

The chemical bond that links two amino acids together in a polypeptide chain.

Start Codon

AUG — signals the beginning of translation and codes for methionine.

Stop Codon

UAA, UAG, or UGA — signals the end of translation; no amino acid is added.

Mitosis

Cell division producing 2 genetically identical diploid daughter cells; used for growth and repair.

Cell Cycle

The ordered series of events in a cell's life: G1 → S → G2 → Mitosis → Cytokinesis.

Interphase

The period of cell growth and DNA replication before mitosis (includes G1, S, G2).

Prophase

1st phase of mitosis; chromosomes condense, spindle forms, nuclear envelope breaks down.

Metaphase

2nd phase; chromosomes align at the cell's equator (metaphase plate).

Anaphase

3rd phase; sister chromatids are pulled to opposite poles by spindle fibers.

Telophase

4th phase; nuclear envelopes reform, chromosomes decondense.

Cytokinesis

Division of cytoplasm following mitosis; results in 2 separate daughter cells.

Sister Chromatids

Identical copies of a chromosome joined at the centromere (created during S phase).

Centromere

The region where sister chromatids are joined and where spindle fibers attach.

Spindle Fibers

Protein structures (microtubules) that move chromosomes during cell division.

Diploid (2n)

Cell containing two complete sets of chromosomes (e.g., human body cells: 2n = 46).

Binary Fission

Asexual reproduction in prokaryotes (bacteria); similar outcome to mitosis in single-celled organisms.

Meiosis

Cell division producing 4 genetically unique haploid gametes; occurs in reproductive organs.

Gamete

A sex cell (sperm or egg) with half the normal chromosome number (haploid, n).

Haploid (n)

Cell with one complete set of chromosomes (e.g., human gametes: n = 23).

Crossing Over

Exchange of DNA segments between homologous chromosomes during Prophase I; increases genetic variation.

Synapsis

The pairing of homologous chromosomes during Prophase I (forms a tetrad/bivalent).

Tetrad (Bivalent)

A pair of homologous chromosomes held together during Prophase I; contains 4 chromatids.

Independent Assortment

The random alignment of homologous pairs at Metaphase I leads to different possible chromosome combinations in gametes.

Karyotype

An organized image of an organism's chromosomes arranged in homologous pairs; used to detect chromosomal abnormalities.

Nondisjunction

Failure of chromosomes to separate properly during meiosis; can result in trisomy or monosomy.

Trisomy

Having an extra chromosome (3 instead of 2); e.g., Trisomy 21 = Down Syndrome.

Gregor Mendel

Father of genetics; discovered laws of inheritance using pea plant experiments in the 1800s.

Punnett Square

A diagram used to predict the possible genotypes and phenotypes of offspring from a cross.

Genotype

The genetic makeup of an organism; the actual alleles present (e.g., Bb, BB, bb).

Phenotype

The observable physical characteristics of an organism (expression of the genotype).

Allele

A variant (version) of a gene at a specific location on a chromosome.

Dominant Allele

The allele that is expressed when one or two copies are present; written as a capital letter (B).

Recessive Allele

The allele that is only expressed when two copies are present (homozygous recessive, bb).

Homozygous

Having two identical alleles for a trait (BB or bb).

Heterozygous

Having two different alleles for a trait (Bb).

Monohybrid Cross

A cross examining one trait (e.g., Bb x Bb).

Complete Dominance

One allele is fully dominant over the other; heterozygous looks like dominant homozygous.

Codominance

Both alleles are fully and simultaneously expressed in the heterozygote (e.g., blood type AB).

Incomplete Dominance

Neither allele is fully dominant; heterozygote shows a blend of both phenotypes (e.g., red + white = pink).

Multiple Alleles

When a gene has more than two possible alleles in a population (e.g., ABO blood type: I^A, I^B, i).

ABO Blood Type

A blood type system controlled by codominance and multiple alleles; types A, B, AB, O.

Antibody

A protein produced by the immune system that binds to a specific antigen; used in blood type testing.

Antigen

A molecule on the surface of red blood cells that determines blood type.

Epigenetics

The study of changes in gene expression that do not alter the DNA sequence itself.

Histone

Protein around which DNA coils to form chromatin; controls gene accessibility/expression.

Environmental Factors

Non-genetic influences (diet, stress, toxins, exercise) that can affect how genes are expressed.

Nature vs. Nurture

The debate over whether traits are determined by genetics (nature) or environment (nurture); most traits involve both.