Molecular Basis of Inheritance Lecture Notes

These flashcards cover the molecular basis of inheritance including DNA structure, packaging, historical experiments (Griffith, Hershey-Chase, Meselson-Stahl), the processes of transcription and translation, gene regulation via the lac operon, the Human Genome Project, and DNA fingerprinting.

DNA (Deoxyribonucleic acid)

A long polymer of deoxyribonucleotides that acts as the genetic material in most organisms.

Nucleoside

A structure formed when a nitrogenous base is linked to the OH of $1'$ C pentose sugar through an N-glycosidic linkage.

Nucleotide

A molecule formed when a phosphate group is linked to the OH of $5'$ C of a nucleoside through a phosphoester linkage.

3'-5' phosphodiester linkage

The chemical bond that joins two nucleotides to form a dinucleotide or a polynucleotide chain.

Chargaff's Rule

The observation that for a double-stranded DNA, the ratios between Adenine and Thymine and Guanine and Cytosine are constant and equal one.

Central Dogma

The proposition by Francis Crick stating that genetic information flows from $DNA \rightarrow RNA \rightarrow Protein$.

Nucleosome

The repeating unit of chromatin consisting of negatively charged DNA wrapped around a positively charged histone octamer, typically containing $200$ bp of DNA helix.

Euchromatin

Loosely packed regions of chromatin that stain light and are considered transcriptionally active.

Heterochromatin

Densely packed regions of chromatin that stain dark and are transcriptionally inactive.

Transforming Principle

The concept derived from Frederick Griffith's experiments with Streptococcus pneumoniae, where heat-killed S strain bacteria enabled live R strain bacteria to become virulent.

Bacteriophage

A virus that infects bacteria, used by Hershey and Chase to prove that DNA is the genetic material.

Semiconservative replication

A DNA copying mechanism where each resulting DNA molecule contains one parental and one newly synthesized strand.

DNA-dependent DNA polymerase

The main enzyme that uses a DNA template to catalyze the polymerization of deoxynucleotides in the $5' \rightarrow 3'$ direction.

Replication Fork

The small opening of the DNA helix where replication occurs, necessitated by the high energy requirement of separating long DNA strands.

Transcription

The process of copying genetic information from one strand of the DNA into RNA.

Cistron

A segment of DNA coding for a polypeptide.

Exons

The coding or expressed sequences in eukaryotes that appear in mature or processed RNA.

Introns

The intervening sequences in eukaryotic genes that are removed and do not appear in mature RNA.

Splicing

The eukaryotic process where introns are removed and exons are joined together in a defined order.

Genetic Code

The sequence of triplets (codons) of nucleotides that determines the sequence of amino acids in proteins.

Lac Operon

A transcriptionally regulated system in bacteria where a polycistronic structural gene is controlled by a common promoter and regulatory genes (i, z, y, and a).

Expressed Sequence Tags (ESTs)

An approach in the Human Genome Project focused on identifying all the genes that are expressed as RNA.

Sequence Annotation

The blind approach of sequencing the entire genome (coding and non-coding) and subsequently assigning functions to different regions.

Variable Number of Tandem Repeats (VNTR)

A class of mini-satellite DNA used as a probe in DNA fingerprinting that shows high degrees of polymorphism.