Molecular Biology and Genetics Review

These flashcards cover key vocabulary and concepts in molecular biology and genetics, helping students review essential terms and definitions.

DNA

Deoxyribonucleic acid; a molecule composed of two strands forming a double helix, containing genetic information.

Nucleotide

The basic building block of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base.

Double helix

The structure of DNA, where two antiparallel strands of nucleotides twist around each other.

Semiconservative replication

A method of DNA replication where each new molecule contains one original strand and one new strand.

Helicase

An enzyme that unwinds the DNA double helix during replication.

DNA polymerase

An enzyme that adds complementary nucleotides during DNA replication.

Okazaki fragments

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

mRNA

Messenger RNA; carries the genetic code from DNA to ribosomes for protein synthesis.

tRNA

Transfer RNA; brings amino acids to ribosomes during translation, matching anticodons to codons.

rRNA

Ribosomal RNA; combines with proteins to form ribosomes, the site of protein synthesis.

Transcription

The process by which DNA is transcribed into mRNA.

Translation

The process by which the ribosome translates mRNA into a polypeptide chain.

Amino acids

Building blocks of proteins, brought to the ribosome by tRNA.

Peptide bonds

Covalent bonds formed between amino acids during protein synthesis.

Gene mutations

Changes in the DNA sequence that can lead to altered or nonfunctional proteins.

Point mutation

A genetic mutation where a single base pair is altered.

Silent mutation

A mutation that does not change the amino acid sequence of a protein.

Missense mutation

A mutation that results in a different amino acid being incorporated into a protein.

Nonsense mutation

A mutation that introduces a premature stop codon in a protein sequence.

Frameshift mutation

A mutation caused by insertions or deletions of bases that alter the reading frame.

Apoptosis

Programmed cell death that removes damaged or unnecessary cells.

Cell cycle

The series of stages that a cell goes through to divide and replicate its DNA.

G₁ phase

The first phase of the cell cycle where the cell grows and prepares to replicate DNA.

S phase

The synthesis phase of the cell cycle where DNA replication occurs.

G₂ phase

The second growth phase of the cell cycle before mitosis.

M phase

The mitotic phase where the cell divides its nucleus and cytoplasm.

Proto-oncogenes

Normal genes that regulate cell division; mutations can convert them to oncogenes.

Tumor suppressor genes

Genes that inhibit cell division and trigger apoptosis; mutations can inactivate them.

Mitosis

The process of nuclear division that results in two identical daughter cells.

Cytokinesis

The division of the cytoplasm, resulting in two separate cells.

Haploid

A cell with half the original number of chromosomes (n); gametes are haploid.

Diploid

A cell with the full set of chromosomes (2n); somatic cells are diploid.

Crossing over

The exchange of genetic material between homologous chromosomes during prophase I of meiosis.

Independent assortment

The random orientation of chromosome pairs during meiosis, leading to genetic variation.

Nondisjunction

The failure of chromosomes to separate properly during meiosis, leading to abnormal chromosome numbers.

Genotype

The genetic makeup of an organism (e.g., BB or Bb).

Phenotype

The physical expression or trait of a genotype (e.g., brown eyes).

Homozygous

An organism with two identical alleles for a trait (e.g., AA or aa).

Heterozygous

An organism with two different alleles for a trait (e.g., Aa).

Punnett square

A diagram used to predict the genotypic and phenotypic ratios of offspring from genetic crosses.

Dominant allele

An allele that is expressed when present (e.g., A).

Recessive allele

An allele that is expressed only when two copies are present (e.g., aa).

Speciation

The process by which new species arise from existing species.

Allopatric speciation

Speciation that occurs due to geographic separation of populations.

Sympatric speciation

Speciation that occurs without geographic separation, often through polyploidy.

Microevolution

Small evolutionary changes within a population over time.

Hardy-Weinberg equilibrium

A state where allele frequencies in a population remain constant from generation to generation.

Natural selection

The process by which individuals with advantageous traits survive and reproduce more successfully.

Gene flow

The transfer of alleles or genes from one population to another.

Genetic drift

Random changes in allele frequencies in a population, often due to small population size.

Isolation mechanisms

Forces that prevent mating and reproduction between different species.

Phylogenetics

The study of evolutionary relationships among biological entities.

Cladistics

A classification method based on common ancestry and shared derived traits.