What Genes Do

Lecture 7

Gene

A segment of DNA that contains instructions to produce a functional protein or RNA

Allele

A version of a gene that may result in different traits.

Protein

linear strings of covalently joined amino acids that performs various functions in the body.

Amino Acids

The building block of proteins

20

how many versions of amino acids found in proteins

Peptide Bond

A covalent bond that links amino acids together in a protein

Primary Structure

The linear sequence of amino acids in a protein.

Secondary Structure

Local structures formed by hydrogen bonding

Secondary Structure

alpha-helices and beta-sheets

Tertiary Structure

The overall 3D shape of a single polypeptide chain, stabilized by various interactions.

Quaternary Structure

The arrangement of multiple polypeptide subunits into a functional protein

Quaternary Structure

hemoglobin

Hydrophobic Amino Acid

An amino acid with a nonpolar side chain, typically found inside proteins

Hydrophobic Amino Acid

valine and leucine

Hydrophilic Amino Acid

An amino acid with a polar or charged side chain, usually found on the surface of proteins.

Enzyme

A protein that catalyzes (speeds up) chemical reactions.

Substrate

molecule that an enzyme acts upon.

Active Site

The region on an enzyme where the substrate binds and the reaction occurs.

Biochemical Pathway

A sequence of enzyme-catalyzed reactions that produce a final product.

Metabolic Disorder

A disease caused by a defect in an enzyme within a biochemical pathway.

Alkaptonuria

A genetic disorder caused by a defective enzyme that leads to black urine and arthritis.

Phenylketonuria

A disorder where a mutation in the PAH gene prevents the breakdown of phenylalanine, leading to brain damage.

Tay-Sachs Disease

A fatal disorder caused by a defective enzyme (HEXA) that leads to the accumulation of toxic substances in neurons.

Sickle Cell Anemia

A disorder caused by a single amino acid change in beta-hemoglobin, leading to misshaped red blood cells.

Central Dogma

flow of genetic information

Central Dogma

DNA → RNA → Protein

Transcription

process where DNA is copied into RNA.

Translation

process where RNA is used to build a protein.

Codon

set of three nucleotides in mRNA that codes for a specific amino acid.

Mutation

change in the DNA sequence that can affect protein function.

One Gene–One Enzyme Hypothesis

idea that each gene encodes a specific enzyme, proposed by Beadle and Tatum.

Neurospora crassa

bread mold used by Beadle and Tatum to study gene-enzyme relationships.

Prototroph

strain that can grow on minimal media because it synthesizes all essential nutrients.

Auxotroph

mutant strain that cannot grow on minimal media and requires a specific nutrient.

Gel Electrophoresis

technique used to separate proteins or DNA fragments based on size and charge.

Linus Pauling

discovered that sickle cell hemoglobin has a different shape and charge than normal hemoglobin.

Malaria

disease caused by the parasite Plasmodium falciparum, which infects red blood cells.

Heterozygote Advantage

When carriers of a genetic mutation (e.g., sickle cell) have a survival benefit in a certain environment.

peptide

two or more amino acids joined together

amino terminus

free amino group at the beginning of
polypeptide chain

carboxyl terminus

free carboxyl group at the end of
polypeptide chain

diseases

caused by mutations that alter the
activity of a single enzyme in a biochemical pathway