Molecular Biology Flashcards
Griffith and his experiment
He discovered that genetic information could be transferred from dead bacteria to live bacteria (injecting mice w live vs dead vs noninfectey + dead)
Watson, Crick, Wilkins, and Franklin and their experiments
They discovered the structure of DNA
Semiconservative Replication
DNA replication where one double helix is unzipped, and then a correspondey strand is woven for each side. One part of each new helix was conserved, but one part of it is new
Which enzyme unwinds the DNA helix?
Helicase
Which proteins attach to each strand of uncoiled DNA to keep them seperate?
single-strand-binding-proteins
Which direction does DNA polymerase move?
3 prime 5 prime. DNA polymerase tags on the corresponding bases, which go in the 5 prime 3 prime direction. This strand (the corresponding one) is the leading strand
Which way does the lagging strand go?
the 3 prime 5 prime direction, but it’s corresponding section of old DNA goes in the 5 prime 3 prime direction.
How does DNA polymerase assemble DNA in the 5 prime 3 prime DNA strand?
It goes back then forwards then back creating little fragments of complementary DNA called Okazaki fragments. These fragments are connected by DNA ligase. This is the lagging strand
Explain how RNA primers work and why they exist
DNA polymerase can only attach nucleotides to an already existing complementary strand. This means that for the creation of the lagging strand an enzyme called primase has to create fake little strands of RNA to make the DNA polymerase work and make okazaki fragments. These strands of RNA are called RNA primers.
How are prokaryotes and eukaryotes different in terms of DNA replication?
Prokaryotes have circular chromosomes (euks have linear ones), and they only have one origin of replication (euks have many)
What are telomeres?
Basically, aglets for our chromosomes
What does the enzyme telomerase do?
It makes sure that telomeres exist on the ends of the lagging strand (since DNA polymerase can only function in the 3 prime 5 prime direction).
DNA repair methods
Proofreading: DNA polymerase proofreads.
Mismatch repair proteins repair stuff that DNA polymerase doesn’t catch
Excision repair proteins repair nucleotides that change because of external factors like radiation
What are the three steps of protein synthesis?
transcription (think music), RNA processing, translation
Messenger RNA
A single strand of RNA that provides the information for which amino acids to assemble and in what order. Each three-base codon codes for one or more amino acids
Transfer RNA
RNA dedicated to transporting amino acids to the ribosomes where they are assembled into proteins. They contain anticodons, which is what the strands from mRNA actually bond to.
Ribosomal RNA
These molecules are transcribed in the nucleus. Make up ribosomes, which coordinate the activities of mRNA and tRNA.
Three stages of transcription
initiation, elongation, termination
Initiation (transcription)
An RNA polymerase attaches to a promoter region (for RNA, often includes TATA) on the DNA and begins to unzip it.
Elongation (transcription)
mRNA is transcribed. The RNA strand goes in the 5 prime 3 prime direction
Termination (transcription)
When the RNA polymerase reaches a termination point (a “stop” set of nucleotides)
mRNA processing
Introns are cut away, and exons are left. Exons are sequences that EXpress a code for a polypeptide, while introns are INtervening, non-coding sequences. snRNPs are the ones that do this cutting
Translation
mRNA attaches to the ribosome, where tRNAs bring amino acids to the ribosome such that their codon-anticodon things match. The new amino acids is then attached to other amino acids that are already present with a peptide bond. This process is repeated until a “stop” codon is reached.
Mutagens
A chemical or radiation that causes mutation. Carcinogens are chemicals that cause uncontrolled cell growth (cancer)
What are the different kinds of point mutations?
Substitution, deletion, insertion, frameshift (as a result of deletion of insertion)
Silent Mutation
A mutation that when transformed to mRNA still codes for the same amino acid that it would have coded for had it not been mutated
Missense mutation
A mutation that, when transformed into mRNA, codes for a different amino acid than it would have otherwise
Nonsense mutation
A mutation that makes its codon code for stop
five kinds of chromosomal aberrations
Deletion, duplication, inversion, translocation, transposons
Deletion (chromosomal)
When significant amounts of chromosomal DNA are lost. Usually fatal.
Duplications (chromosomal)
Can either be bad, since frameshifts can be fatal; or good, since some processes are in high demand. Good ones include hemoglobin and antifreeze genes in fish.
Inversion (chromosomal)
When a DNA segment is reversed. Doesn’t necessarily have a huge effect.
Translocations (chromosomal)
When sections of chromosomes are deleted and inserted somewhere else.
Transposons (chromosomal)
Naturally occurring mutations that insert themselves throughout the genome after copying or deleting themselves from another area.
Describe the structure of a virus
A virus consists of a nucleic acid (either single or double stranded RNA or DNA), a protein coat, and, sometimes, another enveloping layer
The lytic cycle
A virus penetrates a cell and uses its machinery to create copies of itself. When all of these copies are released, it lyses the cell (hence lytic)
The lysogenic cycle
A virus infiltrates a cell and lies in wait until some trigger causes it to wake up and begin the lyric cycle.
Revtrovirus
A single strand RNA virus that uses an enzyme called reverse transcriptase to create a DNA complement that is then used to manufacture mRNA and begin the lytic cycle. Retroviruses can also be in the lysogenic cycle, and their viral DNA can be inserted almost anywhere in the cell’s DNA. HIV is a retrovirus. Retroviruses also evolve very quickly bc there is no spellcheck for them.
How do prokaryotes reproduce?
Binary fission. They split themselves in two with each half containing one circular chromosome.
Plasmid
A bit of double strand DNA that prokaryotes carry a little outside of their chromosomes. They carry genes that are beneficial but not essential to the survival of the prokaryote. Plasmids replicate independently of the chromosome.
How is genetic variation introduced to prokaryotes?
Horizontal gene transfer. Conjugation, transduction, or transformation.
Conjugation (Prokaryote gene transfer)
One prokaryote sends a tube (pilus) to another, and then proceeds to transfer plasmid or chromosomal DNA.
Transduction (prokaryote genetic variation)
When a virus is duplicated along with some bacterial DNA inside of it, which it then passes on to the next bacteria it infects
Transformation (prokaryote genetic variation)
When bacteria absorb DNA from their surroundings and take it in.
Promoter region
A sequence of DNA to which RNA polymerase attaches to begin transcription.
Operator
A region engaged by a regulatory protein to either block or promote the action of the RNA polymerase.
Structural genes
contain coding DNA that codes for related enzymes (end products)
Regulatory gene
Produces a regulatory protein that engages the operator region. Regulatory proteins turn on or off based on other substrate proteins. They can either be repressor proteins, which block the attachment of RNA poly and must be inactive for transcription to occur; or activator proteins, which promotes attachment of RNA poly and must be active to transcription to occur
Give at least 2 examples of gene regulation
the trp operon, the lac operon, and glucose repression are possible answers.
The trp operon
In E. coli, a regulatory gene produces an inactive repressor., which allows the RNA polymerase to proceed and tryptophan to be produced. If E. coli can get trypt from its surroundings, some trypt will react with the repressor, activating it, and blocking the RNA poly from synthesizing more trypt.
The lac operon
In E. coli, a regulatory gene produces an active repressor that binds to the operator region. When this occurs, no lactase is produced. However, once lactose is available, it binds with the repressor to make it inactive.
Why is gene expression more complicated in eukaryotes?
Multicellularity, chromosome complexity, and uncoupling of transcription and translation.
DNA methylation
When methyl groups attach to DNA bases, making it more difficult to get to them. Seems to be related to long term inactivation of genes.
Histone modification
When histones change how tightly they grab their DNA segments in order to make it easier or harder to express certain DNA segments.
General transcription factors
Proteins required by all transcription events to successfully initiate transcription
Specific transcription factors
Regulatory proteins that attach to enhancers, DNA binding sites that can be very far away from the transcription site. The DNA then folds to allow the specific transcription factors to be w/ the general ones.
Coactivators and mediators
Additional proteins that contribute to the binding of transcription complexes
RNA interference
Gene silencing caused by short sequences of RNA that bind to the mRNAs in the cytoplasm and block their translation.
Cell determination
The process that fixes what the cell is gonna be when it grows up
Recombinant DNA
DNA that contains DNA segments or genes from different sources.
Gel electrophoresis
A procedure in which DNA fragments of different lengths are separated as they diffuse across a gelatinous material under the influence of an electric field.
