Chapter 6 Flashcards
Plasmids
Small extra chromosomal, double stranded, circular DNA molecules and it is found in the mitochondria. Prokaryotes and eukaryotes have it.
Fredrich Meicher
He was the first to identify DNA as a unique molecule in a cell in 1869
Robert Feulgen
He did a staining technique that stained more or less based on the amount of DNA present. He found that all cells had the same amount of DNA, except gametes which had half the amount in 1914
Fred Griffith
He mentioned that the bacteria in his experiment had transformative characteristics.
Griffiths experiment
Fred Griffith showed that the bacteria could be transformed from one strain to another by transferring genetic factor from one organism to another. Bacterial transformation- dead R-strained turned into S- strained living
Valent strain
Caused death
Avalent strain
Did not cause death
Avery, MacLeod, and Mc Carty
In their experiment they used various molecules such as RNA, protein, DNA, lipid, and carbohydrate that are found in the S- strain cells to prove that DNA was responsible for the transformation of the bacterial cells.
Experiment Chargaff
Nitrogenous bases were present about the same amount. One strand of DNA had 50% nitrogenous bases.
Rosalind Franklin
She used an x-ray crystallography to determine that DNA is double stranded, a helix, and that phosphates were on the outside and three distances which were, 2.0 nm, 0.34 nm, 3.4 nm showed up in a pattern constantly. These distances were between the nitrogenous bases and complete turn of a helix.
James Watson and Francis Crick
They used Chargaff’s and Franklins work in order to determine the structure of DNA by making models.
DNA replication
It happens at the same time in many locations along very long eukaryotic chromosomes. Replication bubbles are common.
Helicases
They are enzymes responsible for the unwinding of the DNA molecule in both directions. They form bubbles to release tension and break hydrogen bonds.
Topoisomerase I and II
They come in when there is tension in the DNA strand that causes it to tangle as it is unwound by the helicase. They are responsible for relieving that stress by clipping one or two strands of the DNA in front of the replication fork.
Nucleotides as triphosphates
Nucleotides are always added on as triphosphates. Once they are added then two phosphates are divided off making a pyrophosphate. DNA is always added to the 3-prime end of the growing strand not the parent template strand.
DNA polymerase
Is an enzyme responsible for the base pairing the correct nucleotides to the template. It creates the formation of hydrogen bonds. DNA synthesis (grows in length) happens only in the 3 -prime direction.
What are proteins useful for?
Carrying gases, Enzymes, structure, storage of protein, movement, and antibodies
The central dogma
Transcription and translation
Where does transcription occur?
In the nucleus
Where does translation occur?
In the cytoplasm
polynucleotide
A series of nucleotides linked together
Nucleotide contains 3 parts what are they?
A pentose sugar, nitrogenous base, and a phosphate group.
What are the three main types of RNA
mRNA, tRNA, rRNA
mRNA
Carries the information from the DNA gene to the cytoplasm. Determines the sequence of amino acids for a protein.
tRNA
Brings the correct amino acid to the ribosome and mRNA in translation.
rRNA
Found on ribosomes and used to “connect” the tRNA to the mRNA.
How many naturally occurring codons do we have?
We have 20 and there are multiple codons that code the same amino acid.
Codon
3 nucleotides.
Difference in prokaryotic cells in protein synthesis
Prokaryotes do not have introns like eukaryotes. RNA does not have to be processed. Transcription and translation can happen at the same time.
How many codons are there? and how many code for amino acids?
There and 64 codons and only 61 code for amino acids and only one is also a start codon.
What happens if there is a mutation in the codon?
It is possible for another codon to replace it bc it could be code for the same amino acid.
What genetic code does every polypeptide start with?
MET
The wobble effect
A mutation at letter 3 the amino acid will most likely not change.
Promoter region
Determines which side of the gene will be transcribed. To encourage replication.
TATA nucleotides
This is located within the promoter region and it is also called the “TATA box”. It helps to identify where the RNA polymerase should bind.
Elongation
RNA polymerase unwinds the DNA and the base pairs RNA nucleotides to the DNA gene. RNA is made 5 prime to 3 prime so that way DNA gene is read 3 prime to 5 prime.
Termination
RNA sequence will stop and fall off after reading the “STOP” sequence.
RNA processing
You now have a complete mRNA and it will function as a telomere. 5 prime cap is added- to move through nuclear pores. At the 3 prime end 30-200 adenine nucleotides are added (poly-A tail). Introns are removed.
Removing introns
A series of nucleotides that don’t code for anything. SNRP cuts off introns.
Spliceosomes
They remove the introns and they are composed of snRNP (made of proteins and sRNA). It will excise the intron at a specific RNA sequence releasing a “lariat” and splice the exons.
Alternative splicing
Excision of introns and splicing and retention of exons can generate different verisons of the resulting mRNA molecule.
Exon shuffling
Results in the evolution of new proteins
Things needed for translation
It involves mRNA protein polypeptide. You need ribosomes, tRNAs, and mature mRNA.
What are the 3 sites where tRNA attaches on a ribosome?
The A site where the tRNA arrives with the amino acid.
The P site has a second tRNA that attaches to the tRNA at the A site.
The E site is where tRNA exits without an amino acid
Initiation of translation
The small subunits attach to the mRNA at AUG (start). Now the tRNA with the anticodon UAC will attach to the P site. Then the large subunit will attach to the small subunit.
Elongation of translation
The second tRNA arrives and attaches at the A site, with the correct anticodon and the correct amino acid. A peptide bond is formed between the amino acids and water is removed.
Gene Regulator
can inhibit the transcription of one biochemical pathway enzymes.
Regulating biochemical pathway
- produce something that will interfere with the function of the enzyme in the pathway.
- Produce a gene regulator that can inhibit the transcription of one biochemical pathway.
Prokaryotic gene regulation
It tends to be negative. Meaning that the gene is usually activated unless some regulator deactivates it. “Turns genes off”
Eukaryotic gene regulation
It is usually positive, meaning that then gene is usually deactivated unless a regulator turns it “on”.
Operon
A group of prokaryotic genes with a related function that are often grouped and transcribed together. The operon only has one promoter region for the entire operon.
What is operon composed of?
Structural genes, promoter, and operator
Structural genes
Genes that are related and used in a biochemical pathway.
Promoter
The nucleotide sequence that can bind with RNA polymerase to start transcription. This sequence also contains the operator region.
Operator
The nucleotide sequence that can bind with repressor protein to inhibit transcription.
Regulator gene
Produces a gene called a repressor. This is close to the operon, and they are expressed together.
Repressor
Inhibits the transcription of an operon by attaching to the operator. They have allosteric properties.
Lac operon
This is an example of inducible operon. An operon that is an induced, or turned on, by a particular modulator that inhibits the repressor.
Modulators
They can bind to the repressor at an allosteric site by changing the conformation of the repressor.
What happens if there is no lactose and the lac operon?
The repressor protein is active, binding to the operator site. This prohibits the RNA polymerase from transcribing the operon.
trp operon
Synthesizes the amino acid tryptophan when needed. Tryptophan acts as a repressor
Repressible operon
They are “on” unless the presence of something actively turns them “off” - represses them to make them inactive. EX: when tryptophan is present, the transcription of the operon is stopped
Lac and tryp operons
Examples of negative gene regulation as the repressor protein inhibit transcription of the operons.
