ch.16/17 ap bio Flashcards
Who were watson and crick?
in 1953, they built models of a double helix and determined the base pairings (A w/ T, C w/ G)
Who was T.H Morgan?
in 1910, he identified genes were on chromosomes through breeding fruit flies.
Who was Griffith?
in 1928, he stained bacterium with S and R groups and discovered the transforming principle.
Who was Avery, McCarty, and MacLeod?
in 1944, they discovered that the transforming substance was DNA
Who were Hershey and Chase?
in 1952, they proved DNA was the genetic material because it entered an E. coli
Who was Chargaff?
in 1950, he found that DNA composition varies from one species to another in quantities of A,T,G and C.
Who were Franklin and Wilkins?
in 1950, studied the molecular structure of DNA using x-ray crystallography to take a picture of the structure.
What is the role of DNA polymerase?
to catalyze the elongation of new DNA in a 5’ to 3’ direction (pol III- leading strand) (poly I- replaces primer with DNA on lagging strand)
What is the role of DNA ligase?
joins the Okazaki fragments together.
What is the role of primase?
starts an RNA chain from scratch
What are telomeres?
postpone the erosion of genes near the ends of DNA strands.
describe the direction/complementary sequence from DNA all the way to amino acids.
DNA is read from 3’ to 5’ direction and the mRNA is made in a 5’ to 3’ direction (attaches at 3’ end) using complementary base pairing. Then the mRNA is coded into amino acids read from 5’ to 3’ direction.
What does RNA polymerase do?
used in RNA synthesis by prying the DNA strands apart and hooking the RNA nucleotides together
Whats a promoter
in transcription, the DNA sequence in which RNA polymerase attaches.
What are transcription factors?
they mediate the binding of RMA polymerase and the initiation of transcription.
what is a crucial promoter found in eukaryotes called?
the TATA box
what happens during the elongation of transcription?
RNA polymerase will move along the DNA, untwisting the double helix
how does termination work during transcription in prokaryotes?
the polymerase stops transcription at the end of the terminator (the stopping sequence of DNA)
how does termination work during transcription in eukaryotes?
the polymerase eventually falls off of the DNA
how is mRNA modified in eukaryotes?
introns are taken off and a modified nucleotide cap is added to the 5’ end and a poly-A tail is added to the 3’ end.
What are ribozymes and spliceosomes?
catalytic RNA molecules that can splice RNA
describe the structure of tRNA molecules
the top end carries a specific amino acid and on the bottom end is an anticodon whose base pairs with a complementary codon on mRNA.
what does aminoacyl-tRNA synthetase do?
helps to match a tRNA molecule to an amino acid
what are the three binding sites on ribosomes and what happens at each?
A site- holds the tRNA that carries the next amino acid
P site- holds the tRNA that carries the growing polypeptide chain
E site- exit site where tRNA’s leave
what happens during the initiation stage of translation?
an mRNA molecule and tRNA come together in the small ribosomal subunit and initiation factors bring in the large subunit so that the tRNA occupies the p site.
what happens during the elongation stage of translation?
amino acids are added one by one to an amino acid chain and each addition involves three steps: codon recognition, peptide bonding, and translocation.
what happens during termination in translation?
a stop codon is reached at the A site and it accepts a release factor, adding a water molecule
what are missense and nonsense mutations?
missense mutations use substitution and still code for an amino acid, but not the right one. nonsense mutations use substitution but code for a stop codon
what are mutagens?
physical or chemical agents that can cause mutations
