DNA Biology and Technology chapter 22

Vocabulary and key concepts regarding DNA structure, replication, protein synthesis, biotechnology, and genomics.

DNA (deoxyribonucleic acid)

The genetic material of the cell that contains genes, organized into chromosomes, and is located primarily in the nucleus of eukaryotic cells.

Genes

Short segments of DNA that contain instructions for a specific trait.

Nucleotides

The subunits of DNA composed of three parts: a phosphate, a pentose sugar (deoxyribose), and a nitrogen-containing base.

Purines

Nitrogen-containing bases with two rings; in DNA, these are adenine ($A$) and guanine ($G$).

Pyrimidines

Nitrogen-containing bases with one ring; in DNA, these are cytosine ($C$) and thymine ($T$).

Complementary base pair rules

The standard pairing in DNA where $A$ pairs with $T$ via two hydrogen bonds, and $G$ pairs with $C$ via three hydrogen bonds.

Antiparallel

The characteristic of the two DNA strands running in opposite directions, determined by the position of the $5'$ and $3'$ carbon molecules on the deoxyribose sugars.

DNA replication

The process of copying DNA during the $S$ phase of interphase, described as semiconservative because each new double helix contains one original and one new strand.

DNA helicase

The enzyme that unwinds and 'unzips' DNA by breaking the hydrogen bonds between the bases.

DNA polymerase

The enzyme that adds new DNA nucleotides to a template strand using complementary base pairing rules.

Leading strand

The strand of DNA that is synthesized continuously, following the helicase enzyme.

Lagging strand

The strand of DNA synthesized in short segments called Okazaki fragments.

DNA ligase

The enzyme that seals breaks in the sugar-phosphate backbone during replication or gene cloning.

Mutation

An error in replication that results in a base sequence different from the parental strand, potentially introducing genetic variability.

RNA (ribonucleic acid)

A nucleic acid containing the sugar ribose and the base uracil ($U$) instead of thymine, usually existing as a single strand.

Messenger RNA (mRNA)

RNA produced in the nucleus that carries genetic information from DNA to the ribosomes in the cytoplasm.

Ribosomal RNA (rRNA)

RNA produced in the nucleolus that joins with proteins to form the large and small subunits of ribosomes.

Transfer RNA (tRNA)

RNA that transfers amino acids to the ribosomes during protein synthesis, with each of the $20$ different types carrying a specific amino acid.

Transcription

The first step of gene expression where a DNA sequence is copied into a sequence of nucleotides in mRNA.

Translation

The second step of gene expression where mRNA is translated into a sequence of amino acids to form a protein.

Codon

A three-base sequence in mRNA that represents a specific amino acid; there are $64$ possible codons, including $3$ stop codons and $1$ start codon ($AUG$).

Introns

Segments of DNA that interrupt genes and do not code for a functional protein; they are removed during mRNA processing.

Exons

The portions of a gene that are expressed and result in a protein product.

Spliceosome

A complex of RNA and protein that removes introns and joins exons; the RNA portion is called a ribozyme when it acts as an enzyme.

Anticodon

A three-base sequence on tRNA that complementary base pairs with a codon in mRNA.

Polyribosome

The structure formed by multiple ribosomes moving along one mRNA molecule simultaneously, synthesizing several identical polypeptides.

Transcription factors

DNA-binding proteins that initiate transcription by helping RNA polymerase attach to the DNA.

Biotechnology

The use of natural biological systems to create a product or achieve an end desired by humans.

Polymerase chain reaction (PCR)

A technique using DNA polymerase to rapidly copy DNA segments through cycles of denaturation, annealing, and extension.

Plasmid

A small ring of DNA in bacteria, not part of the bacterial chromosome, often used as a vector for gene cloning.

Restriction enzyme

An enzyme used to cleave human and plasmid DNA at specific sequences to create gaps for foreign DNA insertion.

Reverse transcriptase

An enzyme used to copy mRNA into complementary DNA ($cDNA$) that lacks introns.

CRISPR

A genome editing system that uses the Cas9 enzyme and a guide RNA to target and cut specific DNA sequences for removal or replacement.

Transgenic organisms

Organisms, such as bacteria, plants, or animals, that have had a foreign gene inserted into their genome.

Genomics

The study of genomes, including functional genomics (how genes function) and comparative genomics (comparing genomes across species).

Proteomics

The study of the structure, function, and interaction of cellular proteins resulting from the translation of coding genes.

Bioinformatics

The use of computers and statistical analysis to find significant patterns in genomic and proteomic data.

Gene therapy

The insertion of genetic material into cells to treat a disorder; categorized as ex vivo (outside the body) or in vivo (inside the body).

Xenotransplantation

The transplantation of animal organs into humans instead of using human organs.