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showed that DNA is located on chromosomes


studied bacteria (pathogenic versus nonpathogenic)


change in genotype and phenotype due to the assimilation of external DNA by a cell

Avery, McCarty, and MacLeod

showed the DNA is the transforming factor

bacteriophages/ phages

bacteria eaters

Hershey and Chase

grew bacteriophages on the radioisotopes of Phosphate and Sulfur


discovered nucleic acids


DNA tetranucleotide hypothesis


% of DNA varies per organism

Wilkins and Franklin

made x-ray defraction of DNA

Watson and Crick

discovered that DNA is a double helix

A pairs with (on DNA)


G pairs with


A pairs with (on RNA)


semiconservative model

each of the two new double helices of DNA will have one new strand and one old strand of DNA

Meselson and Stahl

found that the semiconservative DNA model was correct

origins of replication

where the replication of DNA begins

replication fork

y-shaped region where the new strands of DNA are elongating

What are the bases of DNA?

Adenine, Thymine, Guanine, Cytosine

What are the bases of RNA?

Adenine, Uracil, Guanine, Cytosine

leading strand

the strand created by DNA polymerase III adding nucleotides to the complementary strand

DNA nucleotides are added from what end to what end?

5' prime to 3' prime

lagging strand

the direction that DNA is synthesized in

Okazaki Fragments

the segments of the lagging strand

DNA ligase

an enzyme that eventually joins the backbones of the Okazaki fragments


the initial nucleotide chain


starts RNA chain from scratch


enzyme that untwists the double helix at the replication fork, separating the two parental strands and making them available as template strands


helps the relive the strain ahead of the replication fork

single-strand binding protein

after the helicase separates the two parental DNA strands, this binds to the unpaired DNA strands, stabilizing themuntil they serve as templates

DNA polymerase I

removes the primer from the 5' end of the second fragment, replacing it with DNA nucleotides that it adds one by one to the 3' end of the third fragment

mismatch repair

cells use special enzymes to fix incorrectly paired nucleotides


DNA cutting enzyme

nucleotide excision repair

when DNA is repaired through the usage of the enzymes DNA polymerase and ligase


nucleotide sequences at the end of DNA molecules to prevent the genes from being damaged


an enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells, thus restoring their original length

Which way is DNA read?

3' prime to 5' prime


showed that genes act by influencing enzymes

Beadle and Ephrussi

examined fruit flies' eyes and saw that enzymes cause changes in eye color

Beadle and Tatum

looked at neospora (bread mold) and deduced the one gene- one enzyme hypothesis (now false)

What was the hypothesis that expanded the one gene- one enzyme hypothesis?

one gene- one polypeptide hypothesis


synthesis of RNA under the direction of DNA


discovered poly- U (phenyalanine)


synthesis of a polypeptide which occurs under mRNA in ribosomes

RNA processing

yields finished RNA

primary transcript

initial transcript

triplet code

genetic instructions for a polypeptide chain that are written on DNA in a series of 3 nucleotide words

template strand

provides template for ordering the sequence of nucleotides in RNA transcript


mRNA's base triplets (read 5' to 3')

RNA polymerase

pries 2 DNA strands apart and hooks together the RNA nucleotides as they base pair along the DNA template


where RNA polymerase attaches/ initiates transcription


sequence that ends transcription

transcription unit

stretch of DNA that is transcribed into an RNA molecule

transcription factors

collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription

transcription initiation complex

assembly of transcription factors/ RNA polymerase II is bound to the promoter

TATA box

crucial promoter DNA sequence

5' cap

guanine after first 20-40 nucleotides

poly- A tail

at the 3' end consisting of 50-250 adenine nucleotides

RNA splicing

when a chunk of synthesized RNA is removed


noncoding segments of nucleic acid that lie between coding regions


other regions usually translated into amino acids


when several snRNPs join with other proteins to form an even larger assembly


RNA molecules that function as enzymes

alternative RNA splicing

a number of genes are known to give rise to 2 or more different polypeptides


structural/ functional regions on proteins


base pair of reflected codons on mRNA

aminoacyl- tRNA synthase

each amino acid is joined to a correct enzyme


relaxation of base pairing rules

P site

holds tRNA carrying the growing polypeptide chain

A site

holds tRNA carrying the next amino acid to be added to the chain

E site

tRNA leaves the ribosome here

polyribosomes/ polysomes

strings of ribosomes

post- translational modifications

additional steps after folding

signal peptide

targets proteins to the endoplasmic reticulum

signal recognition particle

emerges from the ribosome by this protein- RNA complex

messenger RNA (mRNA)

carries information specifying amino acid sequences of proteins from DNA to the ribosomes

transfer RNA (tRNA)

adapter molecule in protein synthesis/ translates mRNA codons to amino acids

ribosomal RNA (rRNA)

plays catalytic (ribozyme) roles and structured roles in spliceosomes

signal recognition particle RNA (SRP RNA)

component of signal recognition particle, the protein- RNA complex that recognizes the signal peptides of polypeptides to the endoplasmic reticulum

small nuclear RNA (snoRNA)

aids in processing of pre-RNA transcripts for ribosome subunit formation in the nucleolous

siRNA/ miRNA

regulation of gene expression


changes in the genetic information of a cell

point mutations

chemical mutations in the one base pair of a gene

base pair substitution

replacement of one nucleotide and its partner with another pair of nucleotides

missense mutation

substitution mutation

nonsense mutation

codon changes into a STOP codon

frameshift mutation

alters the reading frame of the genetic code


physical/ chemical agents that interact with DNA in ways that cause mutations


showed that x-rays cause genetic changes in fruit flies


region of DNA whose final product is either a polypeptide or an RNA molecule

What is the start codon?

AUG/ methionine

What is an example of a stop codon for RNA?


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