biology: DNA, RNA, and Protein Synthesis Flashcards
purpose of Griffith’s Experiments with Streptococcus pnuemoniae (bacteria)
find a cure for pnuemonia
S strain
Bad, causes pnuemonia
R strain
not bad, does not cause pnuemonia
inject mouse with S strain
mouse lives
inject mouse with R strain
mouse dies
inject mouse with killed S strain
mouse lives
inject mouse with R strain+ killed S strain
mouse dies
conclusion of Griffith’s Experiments with Streptococcus pnuemoniae (bacteria)
killed S strain transformed live R strain into live S strain
purpose of Avery-MacLeod-McCarty Experiments with Streptococcus pneumonia
What causes transformation? Protein or DNA or RNA?
injected mice with: R strain + killed S strain with no protein
dead mouse
injected mice with: R strain + killed S Strain with no RNA
dead mouse
injected mice with: R strain + killed S Strain with no DNA
live mouse
conclusion: Avery-MacLeod-McCarty Experiments with Streptococcus pneumonia
DNA is responsible for transformation
purpose: Hershey-Chase Experiments
Is DNA or protein hereditary material in viruses?
bacteriophage
Virus that infects bacteria
result:Bacteriophage with radioactive protein+ bacteria
bacteria not radioactive
Purpose of Watson and Crick experiment
What does DNA molecule look like?
result of watson and crick experiment
Used models to figure out that DNA made of two chains in a double helix
Franklin X-ray diffraction photographs critical to “helix” idea
where is DNA located in a Eukaryote cell?
nucleus
Where is DNA located in a prokaryote cell?
not in nucleus
what makes up DNA?
nucleotides
what makes up nucleotides?
five carbon sugar (deoxyribose) + phosphate + nitrogenous base
sugar and phosphate identical
different nitrogenous bases
what are the purine nitrogenous bases?
Adenine and Guanine
double ring of carbon
what are the pyrimidines of DNA
Thymine and Cytosine
single ring of Carbon
How many hydrogen bonds between A and T
2
How many hydrogen bonds between C and G
3
What is the structure of DNA?
double-stranded helix; antiparallel; joined by hydrogen bonds
polymer of nucleotides
how are nucleotides joined together?
dehydration reaction
when does DNA replication take place?
S phase
semi-conservative replication
one original copy of DNA strand and one new strand of DNA form new double helix strand
how is DNA replicated?
- the enzyme helicase unwinds and separates strands
- replication fork forms- Y shaped region where new DNA strands elongate
- The enzyme polymerase adds complementary nucleotides to each strand
- DNA Polymerase finishes replication and falls off DNA strand
leading strand
synthesis of one strand that moves towards replication fork
polymerase moves from 5’ to 3’
lagging strand
synthesis of other strand moves away from replication fork
DNA replicated as short Okazaki fragments
DNA ligase (enzyme) will connect Okazaki fragments together
polymerase moves from 5’ to 3’
telomeres
tips of chromosomes get shorter and shorter every cell division
eventually cause cell death
repetitive base pairs on ends lost at each replication
do not code for anything so no problem if lost
eventually totally removed, cause cell death
how do prokaryotes replicate DNA?
single circular DNA
replication begins in one place
How do Eukaryotes replicate DNA?
numerous strands of DNA
replication begins in hundreds of places
mutation
change in nucleotide sequence due to error in DNA dupliaction
what happens to mutations?
usually caught and corrected by “proofreading” polymerase
if not corrected can cause cancer or malfunction or beneficial, which leads to evolution
why is DNA important?
DNA stores and transmits genetic information of organisms
DNA transcribed as RNA which is translated into proteins
What is RNA?
ribonucleic acid single stranded molecule, contains ribose sugar
uracil instead of thymine A-U G-C
three main types- mRNA tRNA rRNA
made in nucleus
rRNA
ribosomal RNA
combines with proteins to form ribosome
mRNA
messenger RNA
DNA instructions for making protein located here
DNA to mRNA to protein
mRNA binds with ribosome to create polypeptide (protein)
codon
sequence of three nucleotides that code for a specific amino acid
tRNA
transfer RNA
carries amino acids to ribosome to make protein
Anticodon
sequence of three nucleotides complementary to mRNA’s codon
how do they use DNA to make a protein
- Transcription
make a copy of DNA using mRNA - Translation
make polypeptide using mRNA tRNA and rRNA
Transcription in the nucleus
- initiation
- elongation
- termination
initiation (transcription)
RNA polymerase attaches to promoter region
once polymerase binds DNA unwinds
Elongation (transcription)
RNA polymerase transcribes DNA into mRNA
new nucleotides are RNA nucleotides (A,U,G,C)
termination (transcription)
RNA polymerase reaches termination sequence
before RNA leaves the nucleus: add cap and poly-A tail for protection and stability
mRNA contains introns and exons
introns are removed and exons spliced together
promoter region
nucleotide sequence on DNA that attracts RNA polymerase
termination sequence
Nucleotide sequence on DNA that repels RNA polymerase; releases RNA polymerase and mRNA
exon
sequences that express polypeptide code
introns
non-coding sequence
what does translation do?
makes polypeptide- string of amino acids
initiation (translation)
small ribosome unit attaches to mRNA
tRNA anticodon pairs with mRNA at start codon (AUG)
Large ribosome unit attaches to small ribosome unit
elongation (translation)
ribosome moves along mRNA; exposes next codon
new tRNA anticodon pairs with next mRNA codon
new amino acids attach to chain via peptide bonds
old tRNA detaches
process is repeated
termination (translation)
ribosome reads STOP codon
polypeptide and ribosomal subunits detach from mRNA
ribosomal subunits can now attach to same or another mRNA and repeat
What is the human genome
complete gene sequence of human DNA
may help diagnose treat and prevent genetic disorders cancer and infectious diseases
