Microbial Genetics and Biotechnology Overview

Genetics

The study of genes, how they carry information, how information is expressed, and how genes are replicated.

Chromosomes

Structures containing DNA that physically carry hereditary information.

Genes

Segments of DNA that encode functional products (polypeptides or RNA).

Locus

The location of a gene on a chromosome.

Genome

All the genetic information in a cell.

Central Dogma

Explains the flow of information moving from DNA to protein.

Transcription

The process of synthesizing RNA from a DNA template.

Translation

The process of synthesizing proteins from mRNA.

Alleles

Different versions of a gene.

Mutation

A change in a gene that can result in a different protein.

Blood Type Alleles

There are 3 alleles for blood type: A, B, and O.

Deoxyribonucleic Acid (DNA)

A nucleic acid that is a macromolecule storing information.

Nucleotides

Individual units that make up DNA, consisting of a phosphate group, a sugar, and a nitrogen-containing base.

Double Helix

The physical structure of DNA, described as having two distinct strands.

Backbone of DNA

Made from two alternating molecules: a sugar and a phosphate group.

Nitrogen-containing Bases

The four types of bases in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C).

Covalent Bond

A strong bond in the backbone of DNA.

Hydrogen Bonds

Weak bonds between base pairs in DNA that allow the strands to open and close.

Non-Coding DNA

Regions of DNA that do not code for proteins; more prevalent in eukaryotes.

Introns

Non-coding portions of a gene that are removed during RNA processing.

Exons

Coding portions of a gene that are retained during RNA processing.

Semiconservative Model

The model of DNA replication where each offspring cell receives one copy of the DNA molecule.

DNA Replication

The process by which DNA makes a copy of itself, typically bidirectional in bacteria.

DNA Polymerase

An enzyme that proofreads DNA during replication to ensure accuracy.

Transcription

Copy of a gene's base sequence is made.

Translation

The copy is then used to direct polypeptide sequence.

Polypeptide

Occurs in the ribosomes.

RNA Molecule

Ribonucleic acid that is single-stranded and contains uracil (U) instead of thymine (T).

Messenger RNA (mRNA)

Carries coded information from DNA to ribosomes.

Ribosomal RNA (rRNA)

Integral part of ribosomes.

Transfer RNA (tRNA)

Transports amino acids during protein synthesis.

DNA Gyrase

Relaxes supercoiling ahead of the replication fork.

DNA Ligase

Makes covalent bonds to join DNA strands; Okazaki fragments, and new segments in excision repair.

DNA Polymerases

Synthesizes DNA; proofreads and repairs DNA.

Endonucleases

Cut DNA backbone in a strand of DNA; facilitate repair and insertions.

Exonucleases

Cut DNA from an exposed end of DNA; facilitate repair.

Helicase

Unwinds double-stranded DNA.

Methylase

Adds methyl group to selected bases in newly made DNA.

Photolyase

Uses visible light energy to separate UV-induced pyrimidine dimers.

Primase

An RNA polymerase that makes RNA primers from a DNA template.

Ribozyme

RNA enzyme that removes introns and splices exons together.

RNA Polymerase

Copies RNA from a DNA template.

snRNP

RNA-protein complex that removes introns and splices exons together.

Topoisomerase

Relaxes supercoiling ahead of the replication fork; separates DNA circles at the end of DNA replication.

Transposase

Cuts DNA backbone, leaving single-stranded 'sticky ends'.

Leading strand

Template strand where nucleotides are added from 5' to 3' and moves toward replication fork.

Lagging strand

At replication fork, primase adds RNA primer; builds DNA strand in 5' to 3' direction and moves away from replication fork.

Okazaki fragments

Fragments made on the lagging strand during DNA replication.

RNA primer

A starting line required by DNA polymerase to initiate DNA synthesis.

DNA ligase

The connecting enzyme that connects the fragments of DNA.

Nucleoside triphosphate

Building blocks of nucleic acids; when two phosphates are removed, energy is released for DNA synthesis.

Nucleotide

The basic building block of DNA and RNA, produced from nucleoside triphosphate.

DNA Replication

The process by which DNA is copied to produce two identical DNA molecules.

Energy for replication

Supplied by nucleotides; specifically, the hydrolysis of two phosphate groups on ATP.

Pyrophosphate

Released during the removal of a phosphate from triphosphate, providing energy for DNA replication.

Transcription

The synthesis of a complementary mRNA strand from a DNA template.

RNA polymerase

The main enzyme in transcription that synthesizes RNA from a DNA template.

Promoter sequence

The specific DNA sequence where RNA polymerase binds to initiate transcription.

Terminator sequence

The DNA sequence that signals the end of transcription.

Translation

The process of reading mRNA to synthesize proteins.

Codons

Groups of three mRNA nucleotides that code for a particular amino acid.

Sense codons

61 codons that encode the 20 amino acids.

Degeneracy

The genetic code property where multiple codons can encode the same amino acid.

Start codon

The codon AUG that signals the beginning of translation.

Nonsense codons

Codons that signal the termination of translation: UAA, UAG, UGA.

tRNA

Molecules that transport amino acids to the ribosome during translation.

Anticodon

A sequence on tRNA that base-pairs with the corresponding codon on mRNA.

Peptide bonds

The bonds that join amino acids together in a protein.

Ribosome

The cellular structure where translation occurs.

mRNA

Messenger RNA that carries genetic information from DNA for protein synthesis.

Amino acids

The building blocks of proteins, brought to the ribosome by tRNA.

5' to 3' direction

The direction in which RNA polymerase synthesizes RNA during transcription.

Gene replication

The combined processes of transcription and translation.

Anticodon

The reading device that corresponds to the codon of the mRNA molecule.

tRNA

Transfer RNA that carries amino acids to the ribosome during translation.

Peptide Bonds

Individual bonds that link amino acids together in a protein.

P Site

The site in the ribosome where the first tRNA molecule enters.

A Site

The site in the ribosome where other tRNA molecules enter.

E Site

The exit site where uncharged tRNA is released from the ribosome.

Start Codon

The codon that initiates translation, typically AUG.

Stop Codon

The codon that signals the end of translation.

Simultaneous Transcription and Translation

The process in bacteria where translation begins before transcription is complete.

Eukaryotic Transcription

Occurs in the nucleus of a eukaryotic cell.

Eukaryotic Translation

Occurs in the ribosomes in the cytoplasm.

Exons

Regions of DNA that code for proteins.

Introns

Regions of DNA that do not code for proteins.

snRNPs

Small nuclear ribonucleoproteins that remove introns and splice exons together.

Constitutive Genes

Genes that are expressed at a fixed rate.

Inducible Genes

Genes that are expressed only when needed.

Repressible Genes

Genes that are typically on but can be turned off.

Repression

The process that inhibits gene expression and decreases enzyme synthesis.

Induction

The process that turns on gene expression.

Repressors

Proteins that block transcription.

Default Position of a Repressible Gene

Typically on, but can be turned off.

Default Position of an Inducible Gene

Typically off, but can be turned on.

Inducible operon

Structural genes are not transcribed unless an inducer is present.

Repressor

A protein that binds to the operator, preventing transcription.

Operator

Segment of DNA that controls transcription of structural genes.

Promoter

Segment of DNA where RNA polymerase initiates transcription of structural genes.

Operon

Set of operator and promoter sites and the structural genes they control.