Campbell Biology: Molecular Diversity of Life (DNA) & Gene Expression

Flashcards covering key vocabulary related to DNA structure, RNA, gene expression (transcription and translation), the genetic code, and mutations based on Campbell Biology notes.

DNA

Deoxyribonucleic acid, which serves as the fundamental genetic material for all known living organisms. It is often referred to as 'Life’s Blueprint' or 'Life’s Information System' due to its role in carrying the instructions needed for an organism to develop, survive, and reproduce.

Gene

A specific, locatable region within a genomic sequence that functions as a unit of inheritance. It comprises DNA sequences associated with regulatory regions, transcribed regions, and/or other functional areas, and can be expressed to produce a final functional product, which is either a polypeptide (protein) or an RNA molecule.

Phenotypes

Observable or measurable characteristics of an organism that result from the interaction of its genotype with the environment. These are heritable variations, ranging from physical traits like eye color to biochemical properties or behaviors.

Nucleic Acids

Biological polymers, specifically known as polynucleotides, that are essential for storing, transmitting, and expressing genetic information in living systems. The two main types are DNA and RNA.

Polynucleotides

Polymers composed of repeating monomeric units called nucleotides. These long chains form the structure of nucleic acids like DNA and RNA, which are crucial for genetic functions.

Nucleotide

The fundamental monomeric unit of a polynucleotide. Each nucleotide consists of three main components: a nitrogenous base, a pentose sugar (either deoxyribose in DNA or ribose in RNA), and one or more phosphate groups. These units are linked together to form nucleic acid strands.

Nitrogenous Bases

Heterocyclic compounds containing nitrogen, which are critical components of nucleotides and nucleic acids. They include five primary types: cytosine (C), thymine (T), uracil (U), adenine (A), and guanine (G). These bases are responsible for carrying genetic information through their specific pairing.

Thymine (T)

A pyrimidine nitrogenous base that is exclusively found in DNA molecules, where it forms complementary base pairs with adenine (A).

Uracil (U)

A pyrimidine nitrogenous base that is found exclusively in RNA molecules, replacing thymine. It forms complementary base pairs with adenine (A) during RNA synthesis and function.

Deoxyribose

A five-carbon (C_5) pentose sugar that is a characteristic component of DNA nucleotides, differing from ribose by the absence of a hydroxyl group at the 2' carbon.

Ribose

A five-carbon (C_5) pentose sugar that is a characteristic component of RNA nucleotides, containing a hydroxyl group at the 2' carbon, making RNA generally less stable than DNA.

Complementary Base Pairing

The specific and precise pairing of nitrogenous bases between two nucleic acid strands. In DNA, adenine (A) consistently pairs with thymine (T) via two hydrogen bonds, and guanine (G) always pairs with cytosine (C) via three hydrogen bonds. This specificity is crucial for DNA replication and transcription.

RNA

Ribonucleic acid, a versatile nucleic acid that acts as an intermediary (bridge) between DNA and protein synthesis. It typically contains ribose sugar, features uracil (U) instead of thymine (T), and is usually single-stranded, existing in various forms such as mRNA, tRNA, and rRNA.

Transcription

The biological process in which the genetic information encoded in DNA is copied into an RNA molecule. This synthesis of RNA, primarily messenger RNA (mRNA), occurs under the direction of RNA polymerase and serves as the initial step in gene expression.

Messenger RNA (mRNA)

A type of RNA produced during transcription that carries the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm. This genetic information, in the form of codons, dictates the sequence of amino acids for protein synthesis.

Translation

The biological process where the genetic information carried by messenger RNA (mRNA) is decoded to synthesize a polypeptide chain, which will fold into a functional protein. This process occurs at the ribosomes with the help of transfer RNA (tRNA).

Ribosomes

Complex cellular organelles responsible for protein synthesis (translation). They consist of ribosomal RNA (rRNA) and proteins, and they facilitate the accurate assembly of amino acids into polypeptide chains according to the mRNA template.

RNA Processing

A series of modifications that occur to the initial RNA transcript (primary transcript) in eukaryotic cells. These modifications, including splicing, 5' capping, and 3' polyadenylation, are necessary to yield the finished, functional messenger RNA (mRNA) before it is exported from the nucleus to the cytoplasm for translation.

Primary Transcript

The initial, unprocessed RNA molecule that is transcribed directly from a gene. In eukaryotes, this pre-mRNA undergoes extensive RNA processing before becoming a mature, functional RNA molecule.

Central Dogma

A fundamental concept in molecular biology describing the flow of genetic information within cells. It posits a cellular chain of command where information typically flows from DNA to RNA, and then from RNA to Protein (DNA \rightarrow RNA \rightarrow Protein).

Triplet Code

The fundamental basis for the flow of genetic information from a gene to a protein. It refers to the genetic instructions being written in DNA and mRNA as a series of nonoverlapping, three-nucleotide 'words' (codons), each specifying a particular amino acid or a stop signal.

Codons

Nonoverlapping sequences of three consecutive nucleotides in messenger RNA (mRNA) that specify a particular amino acid to be incorporated into a polypeptide chain during translation, or signal termination of protein synthesis. There are 64 possible codons.

Template Strand

One of the two DNA strands that serves as a guide or pattern for the synthesis of a complementary RNA molecule during transcription. For any given gene, the same strand is always used as the template, ensuring consistent gene expression.

Redundant Genetic Code

A characteristic of the genetic code where most amino acids are specified by more than one codon. This redundancy provides some protection against the effects of point mutations, as a change in a single nucleotide may not alter the amino acid sequence.

Non-ambiguous Genetic Code

A characteristic of the genetic code meaning that each specific codon codes for only one particular amino acid (or a stop signal). While multiple codons can specify the same amino acid (redundancy), no single codon ever specifies more than one amino acid, ensuring precise protein synthesis.

Mutations

Permanent changes in the nucleotide sequence of the genetic material (DNA or RNA) of a cell or virus. These changes can range from single base pair alterations to large-scale chromosomal rearrangements and can have various effects on an organism.

Point Mutations

Chemical changes that affect a single nucleotide pair within a gene or a very small number of nucleotide pairs. These include substitutions, insertions, or deletions of individual bases and can significantly alter the protein product depending on their location and nature.

Frameshift Mutations

Genetic mutations that occur when the insertion or deletion of nucleotides in a gene happens in a number that is not a multiple of three. This leads to a shift in the 'reading frame' during translation, causing all subsequent codons to be incorrectly read and typically resulting in a nonfunctional protein.

Primary Structure (of protein)

The unique, linear sequence of amino acids that make up a polypeptide chain. This sequence is determined by the genetic code of the gene and dictates the subsequent higher-order structures (secondary, tertiary, and quaternary) that a protein will assume.

Sickle-Cell Disease

An inherited genetic blood disorder caused by a single point mutation in the gene encoding the beta-globin subunit of hemoglobin. This mutation leads to an amino acid substitution (valine for glutamic acid) in the hemoglobin protein, causing red blood cells to become rigid, sticky, and sickle-shaped, which impairs their ability to carry oxygen and can lead to various health complications.

Rosalind Franklin

A highly accomplished British chemist whose pioneering work, particularly her high-quality X-ray diffraction images of DNA (most notably 'Photo 51'), was absolutely crucial in providing the key experimental evidence that led James Watson and Francis Crick to deduce the double helix structure of DNA.