Molecular Bio Exam #1

Meischer

Discovered nuclein, now known as DNA.

Morgan

Linked genes to chromosomes using fruit flies.

Beadle & Tatum

Proposed the "one gene, one enzyme" hypothesis.

Griffith

Demonstrated bacterial transformation in mice

Avery, McCarty & MacLeod

Proved DNA as the transforming principle.

Hershey-Chase

Showed that DNA is the genetic material in viruses.

Watson & Crick

Developed the double helix model of DNA.

Characteristics of Living Systems

Require energy, maintain homeostasis, exhibit growth and reproduction, made of cells, and have genetic material (DNA or RNA).

Central Dogma

DNA → RNA → Protein.

Retroviruses

Use reverse transcription (RNA → DNA).

Rosalind Franklin

Used X-ray diffraction to image DNA.

Crick

Coined "central dogma" and proposed the flow of genetic information.

Nirenberg & Matthaei

Cracked the genetic code.
Deciphered how nucleotides encode amino acids.

RNA World Hypothesis

RNA was the original molecule for storing genetic information and catalysis.

Catalysis

The process of speeding up a reaction.

Enzyme

Proteins that act as biological catalysts.

Horizontal Gene Transfer

Transfer of genes between organisms (not parent to offspring).

Last Universal Common Ancestor (LUCA)

Hypothetical early cell from which all life descends.

Scientific Method

Systematic process involving hypothesis generation, experimentation, observation, and conclusion.

Model Organisms

Organisms used for studying biological processes due to shared characteristics with humans.

Homozygous

Having two identical alleles.

Heterozygous

Two different alleles.

Genotype

Genetic makeup.

Phenotype

Observable traits.

Alleles

Variations of a gene.

Diploid

Two sets of chromosomes.

Haploid

One set of chromosomes.

autosomal vs. sex-linked trait

Autosomal passed down from parent to offspring
Sex-linked trait: passed down from one parent the offspring of the same sex

Law of Segregation

Alleles segregate during gamete formation.

Law of Independent Assortment

Genes for different traits are inherited independently (for unlinked genes).

Incomplete Dominance

Intermediate phenotype (e.g., red and white flowers produce pink offspring).

Codominance

Both alleles expressed (e.g., AB blood type).

Polygenic Inheritance

Traits controlled by multiple genes (e.g., skin color).

Mitosis

Produces two identical diploid cells.

Meiosis

Produces four genetically unique haploid cells; involves crossing over and independent assortment.

Gene Linkage

Genes close together on the same chromosome are inherited together.

X-linked Traits

Traits associated with genes on the X chromosome.

Crossing Over

Exchange of genetic material between homologous chromosomes.

Genetic Markers

Help identify locations of genes on a chromosome.

Mutation

A change in DNA sequence that can lead to genetic variability.

Recombination

The rearrangement of genetic material.

Sickle Cell Anemia

Caused by a mutation in hemoglobin gene.

Huntington’s Disease

Caused by expansion of CAG repeats in a gene.

Covalent Bonds

Strong bonds where electrons are shared.

Hydrogen Bonds

Weak interactions, important in DNA and protein structures.

Van der Waals Forces

Weak, non-covalent interactions.

Gibbs Free Energy (ΔG)

Determines if a reaction is spontaneous.

Exergonic Reaction

ΔG < 0, spontaneous.

Endergonic Reaction

ΔG > 0, non-spontaneous.

First Law of Thermodynamics

Energy cannot be created or destroyed.

Second Law of Thermodynamics

Entropy (disorder) increases in an isolated system.

Enzymes

Lower the activation energy of reactions, speeding them up.

ATP Hydrolysis

Releases energy used to drive cellular processes (e.g., protein synthesis, DNA replication).

Negative ΔG

Spontaneous.

Positive ΔG

Non-spontaneous.

Valence

Atom’s capacity to bond.

Free Energy Equation

ΔG = ΔH – TΔS, where ΔH is enthalpy, T is temperature, and ΔS is entropy

Standard Free Energy (ΔG°)

he free energy change under standard conditions (1M, 1 atm, 25°C).

Equilibrium Constant (Keq)

When Keq > 1, products are favored; when Keq < 1, reactants are favored.

Chiral

A molecule that has a non-superimposable mirror image

Polar

refers to molecules with unequal distribution of charges

Chemical Bond

Attraction holding atoms together.

Peptide Bond:

Covalent bond linking amino acids in proteins

Energy in Bonds

Different types of bonds store different amounts of energy, with high-energy phosphate bonds in ATP being crucial for cellular work.

Jacob & Meselson

Showed that ribosomes are the sites of protein synthesis.

Brenner

Identified messenger RNA (mRNA).

Khorana

Synthesized artificial RNA sequences to crack the genetic code

Sutton’s Chromosomal Theory of Inheritance

Chromosomes pass from one generation to another

McClintock’s Non-Crossove

Some genes are inherited together without exchanging genetic material during meiosis

McClintock’s Crossover

Crossover occurs when homologous chromosomes exchange genetic material, leading to genetic diversity

Transcription

5' to 3'

Translation

5' to 3' (mRNA) and N-terminus to C-terminus (polypeptide)

Transcription Phase: Initiation

RNA polymerase binds to the promoter region of DNA, unwinding the DNA strands

Transcription Phase: Elongation

RNA polymerase synthesizes RNA by adding complementary RNA nucleotides in the 5' to 3' direction.

Transcription Phase: Termination

RNA polymerase reaches a termination signal, releasing the newly synthesized RNA strand.

Translation Phases: Initiation

The ribosome assembles around the mRNA, and the first tRNA binds to the start codon.

Translation Phases: Elongation

tRNAs bring amino acids to the ribosome, forming a polypeptide chain in the 5' to 3' direction of mRNA.

Translation Phases: Termination

The ribosome reaches a stop codon, releasing the completed polypeptide

Cystic fibrosis

A genetic disorder caused by a mutation in the CFTR gene

Entropy (ΔS)f

the amount of energy in a physical system that is not available to do work.

Enthalpy (ΔH)

The total heat content of a system.

Ionic Bonds

Occur between oppositely charged groups in molecules, such as between ions in a salt bridge.

Hydrophobic Interactions

Occur when non-polar molecules aggregate to avoid water.

Phosphoanhydride Bonds in ATP

High-energy bonds that release energy when hydrolyzed.

ATP

the primary energy currency of the cell.

Hydrolysis of ATP Formula

TP + H₂O → ADP + Pi + energy.

Protein Synthesis

ATP provides energy for ribosome function during the translation of mRNA

Amino Acid Activation

ATP is used to attach amino acids to tRNA molecules.

DNA Synthesis

ATP powers helicase and other enzymes during replication.

ATP Synthesis

During cellular respiration, ATP is regenerated from ADP in the mitochondria.

Actomyosin Cycle

ATP powers muscle contraction by interacting with actin and myosin.