MOLBIO LEC 1: INTRO TO MOLBIO

Watson-Crick DNA Double Helix Proposal Year

1953

Discovery by Tijo and Levan (1956)

Established that humans have 46 chromosomes.

Scientist Who Described Trisomy 21 (1959)

Jérôme Lejeune

Lyon Hypothesis (1961)

X-chromosome inactivation in females.

Year Genetic Code Was Deciphered

1966

Proteins That Cleave DNA at Specific Sequences

Restriction enzymes

Scientist Who Described DNA Blotting (1975)

Edwin Southern

1979 Medical Milestone Using Bacteria

Synthesis of human insulin by recombinant DNA technology.

Huntington Disease Gene Chromosome

Chromosome 4

Year CF Gene Was Cloned

1989

First Gene Therapy Trial Approval Year

1990

Major International Project Begun in 1991

Human Genome Project

Breast Cancer Gene Identified in 1994

BRCA1

Significance of Dolly (1997)

First mammal cloned from an adult somatic cell.

Human Genome Project Completion Publication Year

2003

Base Pairs in Human Genome

Approximately 3 billion base pairs.

Human DNA Sequence Variability Between Individuals

About 1%.

Base Pair with Adenine (DNA)

Thymine

Base Pair with Guanine (DNA)

Cytosine

Purine Bases

Adenine and Guanine

Pyrimidine Bases in DNA

Cytosine and Thymine

Hydrogen Bonds in A-T Pair

2

Hydrogen Bonds in G-C Pair

3

Purine Ring Structure

Double ring

Pyrimidine Ring Structure

Single ring

Stable pH Range of Double-Stranded DNA

pH 4-9

Temperature Where 50% DNA Denatures

Melting temperature (Tm)

Length of Fully Extended Human DNA

Approximately 3 meters

Appearance of Purified DNA

Stringy, viscous solution.

RNA Backbone Sugar

Ribose

Base Replacing Thymine in RNA

Uracil

RNA Stability in Alkaline Conditions

Labile; undergoes alkaline hydrolysis.

Enzyme That Degrades RNA

RNase

Enzyme That Degrades DNA

DNase

Primary Function of mRNA

Carries genetic code from nucleus to cytoplasm for protein synthesis.

Role of tRNA

Transports specific amino acids to ribosomes.

Location of rRNA

Component of ribosomes.

Direction Codons Are Read

5′ → 3′

Start Codon Sequence

AUG

Total Possible Codons

64

Universal Stop Codons

UAA, UAG, UGA

Mutation Passed from Parent to Child

Germline (hereditary) mutation

De Novo Mutation

New mutation arising in egg or sperm.

Mutation Common in Tumor Cells

Somatic mutation

Clinical Area Screening Blood for HBV/HIV

Infectious disease diagnostics

Missense Mutation

Nucleotide change causing substitution of one amino acid for another.

Nonsense Mutation

Nucleotide change creating a premature stop codon.

Most Common Genome Variation

Single nucleotide polymorphism (SNP)

Field Studying Drug Response Genetics

Pharmacogenetics

Why Molecular Diagnostics Is Highly Sensitive

Target amplification enables detection of very low amounts.

Turnaround Time vs Culture Methods

Molecular diagnostics are faster.

PCR Nobel Prize Recipient

Kary Mullis

PCR Denaturation Step

Heating to ~94-98 °C to separate DNA strands.

PCR Annealing Step

Primers bind complementary sequences (~50-68 °C).

PCR Elongation Temperature

72 °C

Gold Standard for Clinical Gene Detection

Real-time quantitative PCR (qPCR)

Mass Spectrometry Measurement

Mass-to-charge (m/z) ratio

Advantage of Capillary Electrophoresis

Reduced Joule heating; faster, sharper separations.

Sequencing Better Than Sanger for Outbreaks

Next-Generation Sequencing (NGS)

Most Common Cystic Fibrosis Mutation

ΔF508 deletion

CFTR Gene Chromosome

Chromosome 7

Mutation Predicting Anti-EGFR Therapy Failure

KRAS mutation

HIV Viral Load Measurement

HIV RNA copies per milliliter of blood.

Gene Inactivated in Retinoblastoma

RB1 gene

Technique Using Fluorescent Chromosome Probes

Fluorescence in situ hybridization (FISH)

Clinical Biomarker Definition

Measurable indicator of normal/abnormal processes or treatment response.

Primer Function in DNA Replication/PCR

Short nucleic acid sequence that initiates DNA synthesis.

Allele Definition

Alternative form of a gene at a specific locus.

Polymorphism Definition

Gene variant with frequency >1% in a population.

Instrument That Performs PCR

Thermocycler

Technology for High-Throughput Gene Screening

DNA microarray

Capillary Electrophoresis Feature Reducing Band Broadening

Narrow bore capillaries (≈2-100 µm).

Leading Preventable Cause Targeted by Pharmacogenetics

Adverse drug reactions.

Amino Acid Lost in ΔF508 CFTR Mutation

Phenylalanine

Anti-EGFR Drugs Ineffective with KRAS Mutation

Cetuximab and Panitumumab