DNA and RNA Structure, Function, and Mutations Review

This set explores the structural components of nucleic acids, the mechanisms of the Central Dogma including replication and protein synthesis, and the various classifications and effects of genetic mutations.

Molecular Biology

The study of biology at a molecular level, focusing on the structure and function of macromolecules like DNA, RNA, and proteins essential to life.

Diagnostic Molecular Biology

The integration of knowledge and technology in molecular biology with clinical laboratory techniques.

Nucleotides

The fundamental building block of all nucleic acid molecules.

2-Deoxyribose

The pentose sugar component of DNA that lacks an $-\text{OH}$ group at the $C2'$ position.

Ribose

The pentose sugar component of RNA that contains a reactive $-\text{OH}$ group at the $C2'$ position.

Purines

Nitrogenous bases including Adenine (A) and Guanine (G), characterized by a double-ring structure.

Pyrimidines

Nitrogenous bases including Cytosine (C), Thymine (T), and Uracil (U), characterized by a single-ring structure.

DNA (Deoxyribonucleic Acid)

A highly stable, double-stranded antiparallel helix configured for long-term archival storage and transmission of total genetic information.

RNA (Ribonucleic Acid)

A typically single-stranded, transient/labile polynucleotide used for direct execution, encoding, decoding, and regulation of protein translation.

DNA Complementary Pairing

$A=T$ ($2$ Hydrogen bonds) and $G=C$ ($3$ Hydrogen bonds).

RNA Complementary Pairing

$A=U$ ($2$ Hydrogen bonds) and $G=C$ ($3$ Hydrogen bonds).

mRNA (Messenger RNA)

The type of RNA that encodes proteins.

tRNA (Transfer RNA)

Acts as an adaptor between mRNA and amino acids.

rRNA (Ribosomal RNA)

The type of RNA that forms the ribosome.

snRNA (Small Nuclear RNA)

RNA that functions in various nuclear processes such as splicing.

snoRNA (Small Nucleolar RNA)

RNA that facilitates chemical modification of other RNAs.

miRNA and siRNA

RNA types that regulate or silence gene expression.

The Central Dogma

The flow of genetic information within a cell, described as DNA to RNA to Proteins.

Transcription

The process where one strand of DNA is copied into messenger RNA (mRNA) by RNA polymerase II.

Translation

The process where a molecule of mRNA is read by ribosomal machinery in the cytoplasm to produce proteins.

DNA Replication

The process that synthesizes DNA by copying existing DNA before cell division.

Replication Bubble

A structure created as replication moves away from the origin of replication in both directions.

Replication Forks

Single-stranded regions created when DNA helicase unwinds the double helix by breaking hydrogen bonds.

Primase

An enzyme that synthesizes short RNA sequences ($6$ to $11$ base pairs) called primers that mark the starting point for elongation.

DNA Polymerase

The primary enzyme that adds complementary DNA nucleotides to the template in the $5'$ to $3'$ direction.

Leading Strand

The DNA strand where replication proceeds in a continuous, uninterrupted manner.

Lagging Strand

The DNA strand where replication is discontinuous, requiring the apparatus to jump ahead and work backwards.

Okazaki Fragments

Small DNA segments created on the lagging strand during discontinuous replication.

DNA Ligase

An enzyme that acts as 'molecular glue' to link Okazaki fragments together into a single strand.

Nucleases

Enzymes that scan the newly formed double helix to remove and correct incorrectly paired bases during proofreading.

Mutation

Any permanent alteration in the base sequence of a DNA molecule.

Hereditary Mutations

Also known as germline mutations; they are present throughout a person's life in every cell in the body.

Acquired Mutations

Also known as somatic mutations; they occur at a certain time in certain cells and are not passed down.

Point Mutation

A single base pair change, also known as a Single Nucleotide Polymorphism (SNP).

Transitions

A point mutation where a base changes from a purine to a purine ($A \rightleftharpoons G$) or a pyrimidine to a pyrimidine ($T \rightleftharpoons C$).

Transversions

A point mutation where a purine is replaced by a pyrimidine, or vice versa (e.g., $A \rightarrow T$, or $C \rightarrow G$).

Silent Mutation

A single base alteration causing little or no change in the amino acid sequence, resulting in normal protein expression.

Missense Mutation (Non-conservative)

A single nucleotide change that codes for a different amino acid with different properties, such as the $GAG \rightarrow GTG$ change in Sickle cell anemia.

Nonsense Mutation

A single nucleotide change that leads to a premature STOP codon ($UAA$, $UAG$, or $UGA$), resulting in a truncated protein.

Frameshift Mutation

The addition or subtraction of codons in non-multiples of three, shifting the reading frame and creating a garbled amino acid sequence.

Translocation

An interchromosomal exchange of large chromosome segments, such as the Philadelphia Chromosome in leukemia.