Bio Lab Refresher Quiz

Nucleotide

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

DNA (deoxyribonucleic acid)

The molecule that stores hereditary genetic information, structured as a double helix composed of two nucleotide strands.

Gene

A segment of DNA that codes for a specific protein or functional RNA, acting as an instruction unit.

Chromosome

A long, tightly coiled structure of DNA wrapped around histone proteins; human body cells typically contain $46$ ($23$ pairs).

Genome

The complete set of genetic material in an organism, encompassing all of its DNA and genes.

Nitrogenous bases

The information-carrying chemical units in nucleic acids: adenine (A), thymine (T), guanine (G), and cytosine (C) in DNA, with uracil (U) substituting for thymine in RNA.

Base pairing rules

The complementary pairing mechanism in DNA where adenine pairs with thymine via hydrogen bonds, and guanine pairs with cytosine.

Double helix

The twisted-ladder shape of DNA, featuring a sugar-phosphate backbone along the outer edges and paired bases forming the rungs.

Complementary strands

The two matching strands of DNA in which the sequence of bases on one strand directly dictates the opposing sequence on the other strand.

Transcription

The process taking place in the nucleus where a DNA sequence is copied into a messenger RNA (mRNA) transcript.

Translation

The process where an mRNA transcript is decoded by a ribosome to assemble a polypeptide chain of amino acids.

mRNA (messenger RNA)

The RNA molecule that carries genetic instructions from genomic DNA in the nucleus to the ribosome for protein synthesis.

Codon

A sequence of three consecutive nucleotides in mRNA that specifies a particular amino acid or translation stop signal.

Amino acid

The organic monomer subunit that links together in chains to build proteins.

Protein

A macromolecule composed of amino acid chains that carries out most cellular functions and structural roles.

Central dogma

The principle describing the directional flow of genetic information: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{protein}$.

Allele

A specific variant or alternative version of a given gene.

Genotype

The underlying genetic makeup of an organism, representing the specific set of alleles it carries (such as Bb).

Phenotype

The observable physical or physiological traits of an organism produced by its genetic composition and environmental influences.

Dominant allele

An allele whose associated trait is expressed in the phenotype even when only a single copy is inherited.

Recessive allele

An allele whose associated trait is observed in the phenotype only when two identical copies are present.

Homozygous

Possessing two identical alleles for a specific gene locus (such as BB or bb).

Heterozygous

Possessing two different alleles for a specific gene locus (such as Bb).

Locus

The specific physical site or coordinate of a gene on a chromosome.

Mutation

Any permanent change or alteration in a nucleotide sequence of DNA.

Point mutation

A genetic alteration resulting from a change in a single nucleotide base pair.

Silent mutation

A point mutation that changes a codon without changing the resulting amino acid, producing no functional effect.

Missense mutation

A point mutation that substitutes one nucleotide for another, resulting in a codon that codes for a different amino acid.

Nonsense mutation

A point mutation that introduces a premature stop codon, causing translation to terminate early and truncating the protein.

Frameshift mutation

An insertion or deletion of nucleotides not divisible by $3$, shifting the reading frame and altering all subsequent amino acids.

Insertion mutation

A sequence change involving the addition of one or more extra nucleotide bases into a DNA strand.

Deletion mutation

A sequence change involving the removal or loss of one or more nucleotide bases from a DNA strand.

Substitution mutation

A sequence change in which one nucleotide base is swapped with a different base.

Mutagen

An environmental agent, such as UV radiation or specific chemicals, that increases the frequency of genetic alterations.

Somatic vs. germline mutations

Somatic mutations arise in non-reproductive body cells and are not inherited, while germline mutations occur in gametes and can be passed to offspring.

DNA replication

The biological process in which a cell synthesizes an exact copy of its DNA genome prior to cell division.

Semiconservative replication

The mode of DNA copying where each newly formed double-stranded molecule consists of one original template strand and one newly synthesized strand.

Nucleus

The membrane-enclosed organelle in eukaryotic cells that houses and protects genomic DNA.

Homologous chromosomes

A matching pair of maternal and paternal chromosomes carrying the same genes at the same loci.

Diploid ($2n$)

A cell or organism containing two complete sets of chromosomes.

Haploid ($n$)

A cell or organism containing only a single complete set of unpaired chromosomes, typical of gametes.