Biology Comprehensive Study Flashcards

Comprehensive vocabulary flashcards covering key topics in biology, including the scientific method, molecular biology, genetics, cell division, Mendelian inheritance, and evolutionary biology.

Theory

A well-tested, broad explanation for a wide range of phenomena that is supported by a large body of evidence.

Hypothesis

A testable proposed explanation for a specific observation or phenomenon.

Null hypothesis

A statement proposing that there is no relationship between variables.

Independent variable

The variable in an experiment that is deliberately changed or manipulated by the researcher.

Dependent variable

The variable that is measured or observed; it changes in response to the independent variable.

Control

A group or sample in an experiment kept under constant conditions to serve as a baseline for comparison.

Treatment groups

The test groups in an experiment that receive specific levels of the independent variable.

Correlation

A mutual relationship or connection between two or more variables (does NOT prove one causes the other).

Causation

A direct relationship where a change in one variable directly produces a change in another.

X-axis

The horizontal line on a graph, typically displaying the independent variable.

Y-axis

The vertical line on a graph, typically displaying the dependent variable.

DNA

Deoxyribonucleic Acid; the double-stranded molecule storing genetic information in organisms.

RNA

Ribonucleic Acid; a single-stranded nucleic acid involved in gene expression and protein synthesis.

Polymer

A large molecule (macromolecule) made up of many repeating smaller units called monomers.

Nucleotides

The monomer units of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base.

Nitrogenous base

A nitrogen-containing molecule that forms the 'rungs' of DNA/RNA (A, T, C, G, U).

Purine

A nitrogenous base with a double-ring structure: Adenine (A) and Guanine (G).

Pyrimidine

A nitrogenous base with a single-ring structure: Cytosine (C), Thymine (T), and Uracil (U).

Sugar-phosphate backbone

The structural frame of DNA/RNA formed by alternating sugar and phosphate molecules.

Complementary base pairing

Specific pairing of nitrogenous bases: A with T (or U in RNA), and C with G.

Phosphodiester linkage

The covalent bond that connects the sugar of one nucleotide to the phosphate group of the next.

Anti-parallel double helix

The structural arrangement of DNA where two strands run in opposite $5'$ to $3'$ directions.

Histone proteins

Proteins around which DNA wraps to form nucleosomes and package tightly inside chromosomes.

Chromosome

A thread-like structure of DNA and proteins containing genetic instructions.

Semi-conservative DNA replication

Mechanism of DNA copying where each new double helix consists of one original strand and one new strand.

Central Dogma

The directional flow of genetic information: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$.

Transcription

The process of copying a gene's DNA sequence into messenger RNA (mRNA).

Translation

The process of decoding mRNA at a ribosome to synthesize a specific protein.

mRNA

Messenger RNA; carries genetic instructions from DNA in the nucleus to the ribosome.

Ribosome

Cellular organelle made of rRNA and protein that acts as the site of protein synthesis.

Triplet

A sequence of three consecutive nucleotides on DNA that codes for a specific amino acid.

Codon

A three-nucleotide sequence on mRNA that specifies an amino acid or a start/stop signal.

Amino acid

The organic building-block monomer of proteins.

Protein

A functional macromolecule composed of one or more polypeptide chains folded into a specific shape.

Polypeptide

A polymer chain of amino acids linked together by peptide bonds.

Enzyme

A biological catalyst (usually a protein) that speeds up chemical reactions without being consumed.

Start codon

The specific codon (AUG) that signals the beginning of mRNA translation.

Stop codon

Codons (UAA, UAG, UGA) that signal the termination of translation.

Gene

A segment of DNA that contains instructions for building a specific RNA or protein product.

Loci / locus

The specific physical location of a gene on a chromosome.

Chromatin

The loose, uncoiled complex of DNA and histone proteins found during interphase.

Homologous chromosomes

A pair of chromosomes carrying the same genes at the same loci, one from each parent.

Sister chromatids

Identical copies of a chromosome formed during DNA replication and joined at the centromere.

Ploidy

The number of complete sets of chromosomes in a cell.

Diploid

Cell containing two full sets of chromosomes ($2n$), one set from each parent.

Haploid

Cell containing a single set of chromosomes ($n$), typical of gametes.

Gene expression

The process by which information from a gene is used to synthesize a functional product (protein/RNA).

Genotype

The actual genetic makeup or allele combination of an organism.

One-gene one-enzyme hypothesis

The idea that each gene produces a single specific enzyme (later broadened to 'one gene, one polypeptide').

Phenotype

The observable physical or biochemical characteristics of an organism, determined by genotype and environment.

Alleles

Different variant forms of the same gene.

Mutation

A change in the nucleotide sequence of DNA.

Point mutation

A mutation affecting a single nucleotide base pair in DNA.

Meiosis

A specialized cell division process that produces four genetically unique haploid gametes.

Meiosis 1

The first division in meiosis, separating homologous chromosome pairs.

Meiosis 2

The second division in meiosis, separating sister chromatids.

Daughter cell

A cell produced as a result of cell division (mitosis or meiosis).

Independent assortment of chromosomes

random placement of maternal and paternal chromosomes during meiosis.

Crossing over

The exchange of genetic material between non-sister homologous chromatids during prophase I of meiosis.

Random fertilization

The unpredictable combination of any sperm with any egg, increasing genetic diversity.

Genetic recombination

Production of offspring with combinations of traits that differ from either parent.

Gregor Mendel

Father of modern genetics who discovered patterns of inheritance using pea plants.

Blending inheritance

An outdated pre-Mendelian theory that parental traits mix together like paint in offspring.

Pure-breeding / true-breeding lines

Organisms that always produce offspring identical to themselves for a specific trait when self-pollinated.

Dominant allele

An allele that expresses its trait even when only one copy is present (masks recessive).

Recessive allele

An allele that is expressed only when two copies are present (masked by dominant).

Homozygous

Having two identical alleles for a given gene (e.g., AA or aa).

Heterozygous

Having two different alleles for a given gene (e.g., Aa).

Hybrids

Offspring resulting from a cross between parents with different traits or genetic backgrounds.

Parental generation

The original parent organisms (P generation) in a genetic cross experiment.

F1 generation

First filial generation; the offspring of the parental (P) generation.

F2 generation

Second filial generation; the offspring produced by crossing F1 individuals.

Monohybrid cross

A genetic cross between individuals focusing on a single trait.

Particulate inheritance

Mendel's concept that traits are passed down as discrete units (genes) that remain unchanged.

Principle of segregation

Mendel's rule stating that the two alleles for a gene separate during gamete formation.

Gamete

A haploid reproductive cell (sperm or egg).

Punnett square

A grid diagram used to predict the genotypes and phenotypes of offspring in a cross.

Independent assortment

Mendel's law stating that genes for different traits segregate independently of one another during gamete formation.

Dependent assortment

An outdated hypothesis that alleles for different traits are linked and inherited together as a unit.

Mendelian inheritance

Inheritance patterns that follow Mendel's laws of dominance, segregation, and independent assortment.

Dihybrid cross

A cross between individuals that examines the inheritance of two different traits.

Linked genes

Genes located close together on the same chromosome that tend to be inherited together.

Population

A group of individuals of the same species living in the same area at the same time.

Variation

Differences in physical or genetic traits among individuals of a population.

Gene pool

The complete set of all alleles for every gene present in a population.

Allele frequency

The proportion of a specific allele relative to all alleles for that gene in a population.

Hardy-Weinberg Equilibrium

A mathematical principle stating allele/genotypic frequencies remain constant in a non-evolving population.

Hardy-Weinberg variables (p, q, p2, 2pq, q2)

$p=\text{freq}(A)$, $q=\text{freq}(a)$, $p^2=AA$, $2pq=Aa$, $q^2=aa$; used to model allele and genotype proportions.

Typological thinking

The ancient belief that species are unchanging, ideal types created fixed in form.

Plato and the 'perfect essence'

Philosophical concept that individual organisms are imperfect variations of an ideal, static form.

Aristotle and the 'great chain of being'

Hierarchical organization of life from simple to complex, static and unchanging.

Jean-Baptiste Lamarck

Early evolutionary theorist who proposed species change over time through inherited acquired traits.

Use and disuse hypothesis

Lamarck's idea that body parts used frequently grow larger/stronger, while unused parts deteriorate.

Inheritance of acquired characteristics

Lamarckian idea that modifications acquired during an organism's lifetime can be passed to offspring.

Charles Darwin

Naturalist who proposed the theory of evolution by natural selection.

Artificial selection

Selective breeding of plants/animals by humans to favor desired traits.

Modern synthesis of evolution

The integration of Darwinian natural selection with Mendelian genetics and population biology.

Evolution

Change in the genetic composition (allele frequencies) of a population over generations.

Non-random mating

Mating system where individuals select mates based on phenotype or genetic relatedness.

Positive assortative mating

Mating between individuals with similar phenotypes.