Molecular Basis of Inheritance Flashcards

Comprehensive vocabulary flashcards covering the molecular basis of inheritance including DNA structure, replication, transcription, and translation.

DNA (Deoxyribonucleic acid)

A long polymer of deoxyribonucleotides that acts as the genetic material for the majority of organisms.

Bacteriophage φ × 174

A virus known to have $5386$ nucleotides.

Escherichia coli (E. coli) DNA content

The DNA of this bacterium contains $4.6 \times 10^{6}$ base pairs ($bp$).

Haploid human DNA content

The DNA content in a haploid human cell is $3.3 \times 10^{9}$ base pairs ($bp$).

Nucleotide

A monomer consisting of three components: a nitrogenous base, a pentose sugar (ribose or deoxyribose), and a phosphate group.

Purines

A type of nitrogenous base that includes Adenine and Guanine.

Pyrimidines

A type of nitrogenous base that includes Cytosine, Uracil, and Thymine.

N-glycosidic linkage

The bond that links a nitrogenous base to the $OH$ of $1' C$ pentose sugar to form a nucleoside.

Phosphodiester linkage

A $3'-5'$ linkage that joins two nucleotides together to form a dinucleotide or polynucleotide chain.

Backbone of polynucleotide chain

The framework of the DNA or RNA polymer formed by the sugar and phosphate groups.

Nuclein

The name given to DNA as an acidic substance in the nucleus by Friedrich Meischer in $1869$.

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 to one.

Anti-parallel polarity

The arrangement of the two strands in a DNA helix where one chain runs $5'\rightarrow 3'$ and the other runs $3'\rightarrow 5'$.

Pitch of the DNA helix

The distance covered by one full turn of the DNA double helix, which is approximately $3.4\text{ nm}$.

Central Dogma

The principle proposed by Francis Crick stating that genetic information flows from $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$.

Nucleosome

A structure where negatively charged DNA is wrapped around a positively charged histone octamer, containing roughly $200$ base pairs.

Histone Octamer

A unit of eight molecules made of basic proteins rich in lysine and arginine amino acid residues.

Chromatin

Thread-like stained bodies in the nucleus composed of repeating units of nucleosomes, appearing as 'beads-on-string' under an electron microscope.

Euchromatin

Loosely packed, lightly stained regions of chromatin that are transcriptionally active.

Heterochromatin

Densely packed, dark-stained regions of chromatin that are transcriptionally inactive.

Transforming Principle

The substance identified by Frederick Griffith in $1928$ that enabled R strain bacteria to transform into virulent S strain bacteria.

Bacteriophages

Viruses that infect bacteria, used by Hershey and Chase to prove DNA is the genetic material.

Semiconservative DNA replication

The scheme where each DNA molecule produced after replication consists of one parental strand and one newly synthesised strand.

DNA-dependent DNA polymerase

The main enzyme that uses a DNA template to catalyse the polymerisation of deoxynucleotides during replication.

Replication Fork

A small opening of the DNA helix within which replication occurs, required because long DNA strands cannot be separated in their entire length.

Origin of replication

A definite region in DNA where the process of replication initiates.

Transcription

The process of copying genetic information from one strand of DNA into RNA governed by the principle of complementarity.

Coding Strand

The DNA strand with $5'\rightarrow 3'$ polarity that has the same sequence as RNA (except thymine is replaced by uracil) and does not code for anything.

Cistron

A segment of DNA coding for a polypeptide; can be monocistronic in eukaryotes or polycistronic in bacteria.

Exons

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

Introns

The intervening, non-coding sequences that interrupt exons and do not appear in mature or processed RNA.

Splicing

The eukaryotic process of removing introns and joining exons together in a defined order.

Genetic Code

The triplet-based system of nucleotides that directs the sequence of amino acids during protein synthesis.

Degenerate Code

A property of the genetic code where some amino acids are coded by more than one codon.

Initiator Codon

The codon $AUG$, which codes for Methionine and signifies the start of translation.

tRNA (Transfer RNA)

An adapter molecule with an anticodon loop and an amino acid acceptor end that links mRNA codons to specific amino acids.

Translation

The process of polymerisation of amino acids to form a polypeptide, defined by the sequence of bases in mRNA.

Aminoacylation (Charging of tRNA)

The process of activating amino acids in the presence of $ATP$ and linking them to their cognate tRNA.

Ribozyme

A catalytic RNA molecule, such as the $23S\text{ rRNA}$ in bacteria, which acts as an enzyme for peptide bond formation.

Untranslated Regions (UTR)

Sequences of RNA present at both $5'$ and $3'$ ends that are not translated but are required for efficient translation.