Chapter 9: Molecular Biology Flashcards
Transformation
The ability of bacteria to absorb and express genetic information obtained from their surroundings.
Griffith’s DNA Discoveries
Genetic information can be transferred from dead bacteria to living bacteria.
Avery, Macleod, McCarth
Identify DNA as the heredity information of a cell.
Hershey and Chase
Establish that DNA was the genetic material of phages.
Watson, Crick, Wilkins and Franklin
Determine the structure of DNA
Phages
Viruses that infect bacteria
One-gene-one-enzyme
The theory that the gene was defined as the segment of DNA that codes for a particular enzyme.
one-gene-one-polypeptide hypothesis
Each DNA segment codes for a particular polypeptide.
DNA replication
Involves separating (unzipping) the double-stranded DNA molecule into two strands, each of which serves as a template to assemble a new, complementary strand.
Semiconservative Replication
Each DNA contains one old strand, and one new strand.
Helicase
The enzyme that unwinds the DNA helix
Single-strand binding proteins
Proteins that attach to each strand of the uncoiled DNA to keep them separate.
DNA Polymerase
The enzyme that assembles the new DNA strand
Okazaki Fragments
DNA fragments in the 5’—>3’ template strand that are in segments because they can’t be connected as created when the DNA polymerase is working in the 5’–3’ direction.
DNA ligase
The thing that that connects the Okazaki fragments
Lagging Strand
The strand that takes more time to assemble than the complementary strand.
Chromosome Structure of Prokaryotes and Eukaryotes
Prokaryotes- Circular
Eukaryotes- Linear with ends called telomeres
Proofreading
DNA Polymerase checks to make sure that each newly added nucleotide correctly base-pairs with the template strand.
Mismatch repair problems
Repair errors that escape the proofreading ability of DNA polymerase.
Excision Repair Proteins
Identify and remove damaged nucleotides caused by environmental factors, such as toxins or radiation.
Protein Synthesis
The process that describes how enzymes and other proteins are made from DNA.
Polypeptides
DNA holds the codes for polypeptides.
Polypeptides are enzymes that regulate chemical reactions.
3 Steps in Proteins Synthesis
- Transcription
- RNA processing
- Translation
mRNA
Messenger RNA
A single strand of RNA that provides the template used for sequencing amino acids into a polypeptide.
Codon
A triplet group of three adjacent nucleotides on the mRNA
tRNA
A short RNA molecule (80 nucleotides) that is used for transporting amino acids to their proper place on the mRNA.
rRNA
Molecules that combine with various proteins to form ribosomes.
3 stages of Transcription
- Initiation
- Elongation
- Termination
- Initiation
Stage 1 of Transcription
The RNA polymerase attaches to a promoter region on the DNA and begins to unzip the DNA into two strands.
- Elongation
Second stage of transcription
Occurs as the RNA polymerase unzips the DNA and assembles RNA nucleotides using one strand of the DNA as a template.
- Termination
Occurs when the RNA polymerase reaches a special sequence of nucleotides that serve as a termination point.
5’ Cap
A guanine nucleotide with two additional phosphate groups that is added to the 5’ end of mRNA.
Provides stability to the mRNA and a point of attachment for the small subunit of the ribosome
Poly- A tail
Attached to the 3’ end of the mRNA
Provides stability to the mRNA, and also controls the movement of mRNA across the nuclear envelope
RNA splicing
Removes nucleotide segments from mRNA.
Exons
Sequences that EXpress a code for a polypeptide
Introns
INtervening sequences that are noncoding
snRNPs
Small Nuclear Ribonucleoproteins
Delete the introns and splice the exons
Alternative Splicing
Allows different mRNAs to be generated from the same RNA transcript.
By selectively removing different parts of an RNA transcript, different mRNAs can be produced, each coding for a different protein product.
Mutation
Any sequence of nucleotides in a DNA molecule that does not exactly match the original DNA molecule from which it was copied.
Mutagens
Radiation or chemicals that cause mutations
Carcinogens
Mutagens that activate uncontrolled cell growth.
Point Mutation
A single nucleotide error.
Ex. Substitution, Deletion, Insertion, Frameshift
Silent Mutation
Occurs when the new codon still codes for the SAMe amino acid
Wobble Pairing
The relaxed requirement for the nucleotide in the third position
Missense Mutation
Occurs when the new codon codes for a new amino acid
Ex. Haemoglobin Protein—> Sickle Cell Disease
Nonsense Mutation
Occurs when when the new codon codes for a stop codon.
Transposons
“Jumping Genes”
DNA segments that insert themselves throughout the genome after copying or deleting themselves from another area.
Bacteriophages
Viruses that attack only bacteria
Virus
Parasite of cells
Lytic Cycle
A virus penetrates the cell membrane of the host and uses the enzymes of the host to produce viral nucleic acids and viral proteins.
Lysogenic Cycle
The viral DNA is temporarily incorporated into the DNA of the host cell.
Eventually, a trigger, often an external environmental stimulus, causes the virus to begin the lytic cycle.
A virus in its dormant state
Provirus
Retroviruses
ssRNA viruses that use an enzyme called reverse transcriptase to make a DNA complement of their RNA.
Binary Fission
How prokaryotes reproduce.
The chromosome replicates and the cell divides into two cells, each cell bearing one chromosome.
Plasmids
Short, circular dsDNA molecules outside the chromosome.
Replicate independent of the chromosome.
Conjugation
The process of DNA exchange between bacteria.
Transduction
Occurs when new DNA is introduced into the genome of a bacterium by a virus.
Horizontal Gene Transfer
How genetic variation is introduced into the genome of a bacterium by a virus.
Transformation
Occurs when bacteria absorb DNA from their surroundings and incorporate it into their genome.
Operon
A unit of DNA that contains multiple genes whose products work together to direct a single metabolic pathway.
Operator Region
The region that is engaged by a regulatory protein to either block or promote the action of the RNA polymerase.
Promoter Region
A sequence of DNA to which the RNA polymerase attaches to begin transcription.
Structural Genes
Contain coding DNA. DNA sequences that code for various related enzymes that direct the production of some particular end product.
Regulatory Gene
Lies outside the operon region, and produces a regulatory protein that engages the operator region and governs whether RNA polymerase can attach to the promoter region and begin transcription.
Repressor Protein
BLOCKS the attachment of RNA polymerase to the promoter region.
Must be inactive for transcription to occur.
Activator Protein
Promotes the attachment of RNA polymerase to the promoter region.
Must be active for transcription to occur.
3 Examples of Gene Regulation in Bacteria
trp operon— E. coli
lac operon— E. Coli
Glucose repression— E. Coli
trp operon
Produces enzymes for the synthesis of the amino acid tryptophan. A regulatory gene produces an inactive repressor that does not bind to the operator.
When levels of tryptophan rise to a certain level, the repressor becomes active.
lac operon
Controls the breakdown of lactose.
Regulatory gene produces an active repressor that binds to the operator region.
When lactose is available, some binds to repressor making it inactive.
Glucose Repression
A second regulatory process that influences the lac operon.
Glucose is preferred over lactose for energy.
When only lactose is present, this process enhances the breakdown of lactose.
Positive Regulation
3 things that make regulation of gene expression in eukaryotic cells more complicated
- Multicellularity
- Chromosome Complexity
- Uncoupling of Transcription and Translation
DNA methylation
Occurs when methyl groups (-CH2) attach to DNA bases.
Makes it difficult to access genes
Histone Modification
Changes in the organization of histone proteins with DNA.
DNA arranged in tight nucleosomes
Access to DNA for transcription can by increased by Acetylation and Methylation
Acetylation
Histone molecules loosen their grip on the DNA molecule when they are acetylated.
Associated with activated transcription.
Methylation
Histones are methylated when a methyl group is attached. In most cases, methylated histones are associated with repressed transcription.
Transcription Complex
A group of various proteins that are associated with RNA polymerase activity
General Transcription Factors
Proteins that are required by ALL transcription events to successfully initiate transcription by RNA polymerase.
Specific Transcription Factors
Additional proteins associated with regulating SPECIFIC transcription activities.– SPecific to cell type, specific to the particular genes, or specific to the timing of the transcription.
Co-activatiors and Mediators
Additional proteins that contribute to the binding of transcription complex components.
Cell Determination
The process that fixes a cell’s fate
Reproductive Cloning
The process of making an individual with the same nuclear DNA as another animal.
Recombinant DNA
Contains DNA segments or genes from different sources.
Biotechnology
The use of biological systems to modify organisms or produce desired products.
DNA Cloning
A procedure that allows DNA fragments or genes to be copied
Genomic Library
A collection of bacteria, each of which contain a fragment of the genome of the foreign DNA but together contain the entire genome of the foreign DNA.
Polymerase Chain Reaction
A technique that makes large numbers of DNA copies faster than the DNA cloning process previously described.
