Test 3 Flashcards
DNA structure
-Nucleotide pairs are bound together by hydrogen bonds.
-Sugar in DNA is Deoxyribose
-Nitrogenous based (ACTG)
-More hydrogen bonds in G,C than T,A so harder to pull
-The origin of DNA replication contains lots of A + T.
-The strands are antiparallel. (Sugars are pointed in opposite direction) 5’ (prime) end and 3’ end.
-DNA are instructions for making proteins
-Gene, instructions for a particular protein (amylase)
Seperates the two strands of DNA?
Helicase
Creates a complementary strand of DNA?
DNA polymerase
-reads from 3’ to 5”
-creates from 5’ to 3’
Primase adds a primer (piece of RNA), since it can only add nucleotides to existing strand.
Leading strand? Lagging strand?
-DNA polymerase follows helicase getting long new strand of DNA.
-Lagging——- where DNA polymerase move away from helicase. This is where pieces of fragments are made (Okazaki fragments).
Lagging strand? Enzymes………. RNASE H? LIGASE?
-Lagging——- where DNA polymerase move away from helicase. This is where pieces of fragments are made (Okazaki fragments).
—-WHEN REPLICATION COMPLETED—-
–RNASE H … removes primers and get replaced by DNA
–Ligase.. joins the fragments
Semiconservative
Each strand contains one old and one new strand
- Eukaryotes these are sister chromatids seperated by Anaphase 1 (mitosis) and Anaphase II (meiosis)
- Prokaryotes , separated by Binary Fission.
DNA replication Thermodynamically unfavorable (creating larger molecules)
-made to occur by coupling it by phosphate removal.
-each nucleotide is brought in as tri-phosphate so 2 phosphates are removed to link together.
PCR (polymerase chain reaction) check list
-Thermocycle (applies heat to denature DNA, breaks hydrogen bonds)
-Starting DNA
-Primers specific to DNA
-DNA polymerase (from thermophile)
-Nucleotides (triphosphates)
- This is useful for
– genetic engineering
–DNA fingerprinting
–DNA sequencing
DNA sequencing
-Determines the sequence of nucleotides.
-Identifies microorganisms
-uses a mix of dideoxy + regular DNA nucleotides
-Starts with a primer then it either adds a regular nucleotide or dideoxynucleotide in which it would stop.
-it ends up with fragments of different length with fluorescent end.
-DNA is negatively charged-pulled towards + electrode
-Smaller fragments travel faster
- Fragments get read by fluorescent detector.
Dideoxynucleotide
-No hydroxyl group -OH in carbon 2 and 3
-No -OH in carbon 3, no new nucleotides added.
-Fluorescent components are added to identify them
Proteins are made?
On ribosomes
Transcription
-Makes a temporary RNA copy of a gene
-Only one strand gets copied, the coding strand
-Promoter makes the start of a gene, and the end of the gene is called the termination sequence.
-RNA polymerase reads 3’ to 5’ makes a complimentary RNA copy (messenger RNA)
-Prokaryotes, messenger RNA immediately ready for translation
-Eukaryotes, RNA need to be processed, INTRONS (extra letters of DNA not necessary for making protein)
Translation
-Reading instructions to make protein.
-mRNA (messenger RNA) bind with ribosome
-2 tRNA (transfer RNA) molecules bring in the first amino acids
-Ribosome catalyzes dehydration transferring amino acid from 1st tRNA to second tRNA.
- Ribosome moves down one codon -empty tRNA falls off, next tRNA brings in next amino acid.
-Ribosome catalyzes dehydration synthesisk repeating step 3 and 4 until it reaches a stop codon (UAG)
—————mRNA can be reused, ribosome units find another mRNA to translate, tRNA needs another amino acid.
– In prokaryotes translation can start before transcription is finished.
Codon chart
-Each codon codes for a particular amino acid
-It is for messenger RNA and not for the anticodon
Mutation
change in DNA due to
—-DNA polymerase errors
—-DNA demage
1.Silent mutations
1.missense mutations
2.nonsense mutations
3.frameshift mutation
- when DNA changes but polypeptide doesn’t
- change in amino acid
- stop codon forms
- addition or deletion of bases.
Ames test
Whether a compound causes mutations (mutagens).
-Mutations are often carcinogens in humans.
Add chemical to be tested + liver enzymes (liver breaks down chemical and sometimes into worse products) this allows all chemical components.
carcinogen
substance capable of causing cancer.
Gene regulation
Process of controlling which genes are being transcribed (on)
Constitutive Genes
not regulated, expressed constantly (ex, glycolysis enzymes)
Inducible genes
Usually off but can be turned on (ex for catabolism)
the repressor protein is active
Operon (in prokaryotes)
All genes regulated/transcribed together
gene regulation when ex (lactose present)
lactose binds to represent. letting RNA polymerase bind to promoter so that transcription can occur.
cAMP
-starvation signal
- binds to cAMP receptor protein
-which they both bind to promoter acting as transcription factor (increases transcription). it encourages RNA polymerase to bind so more genes for certain molecules can be made more.
Repressible genes
usually on, can be turned off (Most genes for anabolism)
Repressor is inactive.
When there is enough of that certain molecule, that certain molecule binds to repressor activating it so that RNA polymerase can’t bind to promoter.
In Eukaryotes there is no operons
All genes have their own promoter.
–if there is an enhancer away from the promoter, transcription factors bind to the enhancer which encourages RNA polymerase to bind to the promoter.
