Injected strain 1 to mouse 1 and the mouse died-Expected
Injected strain 2 to mouse 2 and the mouse was healthy-Expected
Injected heated strain 1 to mouse 3 and the mouse was healthy-Expected
Injected a mix of strain 2 and heated strain 1 and the mouse died-Surprise
Used enzyme destroying proteins on the 2 strains of bacteria used in Griffith's experiments. Nothing changed and bacteria was still transformed. Second, he used enzyme destroying DNA and the transformation did not happen.
Hershey and Chase
Used bacteriophage. No radioactivity entered the cell when protein coats were radioactively labeled. Radioactivity entered the cell when DNA was radioactively labeled.
found that the amount of adenine is always equal to the amount of thymine and the amount of guanine is always equal to the amount of cytosine in a DNA molecule
Watson and Crick
Modeled the DNA molecule as two chains of sugar-phosphate groups running parallel to each and connected by "rungs" of paired nitrogenous bases. Discovered the double helix shape.
Wilkins and Franklin
Used x-ray crystallography to investigate the chemical structure of DNA
"one gene-one polypeptide" hypothesis
Scientist have learned that some genes dictate the production of a single polypeptide which may make up a part of an enzyme or an other kind of protein.
Beadle and Tatum
Studies mutant strains of bread mold that were unable to grow on the usual nutrient medium. Each mutant strain lacked a single enzyme needed to produce some molecule. They came up with the "one gene-one enzyme" hypothesis that states that the function of an individual gene is to dictate the production of a specific enzyme.
In the first stage of DNA replication, DNA is unwinded at its replication fork. Helicase unwinds the parental strands and DNA gyrase cuts, winds, and rejoins the DNA strand. The new DNA strands are made in the next step. DNA polymerase III adds a nucleotide to the 3 foot end of a pre-existing chain of nucleotides. Two phosphates come off of the nucleoside triphosphate and it goes into the DNA strant. RNA polymerase makes an RNA primer, a sequence of about 10 nucleotides that is complementary to the parent DNA. DNA polymerase III can now add deoxyribonucleotides to synthesize the new complementary strand of DNA. DNA polymerase I replaces DNA polymerase III and removes the RNA at the RNA primer and replaces it with DNA. DNA ligase then attaches and forms phosphodiester bonds. Finally, the two DNA molecules rewind into their double helix shape.
First is transcription. mRNA is transcribed from a DNA template. After the DNA strands separate, RNA bases pair with complementary DNA bases. Its base uracil pairs with adenine. RNA polymerase links the RNA nucleotides together. This takes place in the nucleus. Before RNA exits the nucleus, RNA splicing takes place. The introns, noncoding regions, are removed and the exons, coding regions, are joined together. The the mRNA moves to the cytoplasm. Translation then occurs. During translation, the anticodon on tRNA recognizes a particular codon on mRNA. At the other end of tRNA, there is a site where a particular amino acid can attach. An enzyme links to tRNA and the amino acid with energy from ATP. Finally, in the ribosome made of rRNA has a binding site for mRNA and two for tRNA. The tRNA binding sites are the "P" site and the "A" site. The "P" site holds the tRNA carrying the growing plypeptide chain. The "A" site holds a tRNA carrying the next amino acid to be added to the chain. The ribosome connects the amino acids to the growing polypeptide chain.
Characteristics of DNA and RNA
-RNA has the sugar ribose and DNA has deoxyribose.
-RNA contains the nitrogenous base called uracil instead of thymine in DNA.
-RNA forms a single, sometimes twisted strand, not a double helix like DNA.
-RNA is shorter than DNA
package of nucleic acid wrapped in a protein coat
a virus that infects bacteria
the monomers of nucleic acid polymers
A single of double ring of carbon and nitrogen atoms with functional groups. The four nitrogenous bases are thymine which pairs with adenine and cytosine which pairs with guanine.
single-ring structures (Bases thymine and cytosine)
double-ring structures (Bases adenine and guanine)
twisting shape of DNA
complementary base pairing
A pairs with T and is complementary to T. G pairs with C and is complementary to C.
new DNA stran formed when enzymes link the nucleotides together in DNA replication
when DNA replicates, the two strands separate and each strand acts as a "negative" or template to produce a new strand
Enzymes that make the covalent bonds between the nucleotides of the new DNA strand.
origins of replication
A sequence of nucleotides where the replication of DNA begins
A sequence of nucleotides where the replication of DNA begins
The DNA sequence is converted to the form of a single-stranded RNA molecule. Occurs in the nucleus.
Converts the nucleic acid sequence into a sequence of amino acids. Occurs in the cytoplasm.
a three-base sequence that codes for one amino acid
A sequence that is complementary to a codon in the mRNA. On one end of tRNA
Joins the RNA nucleotides together during transcription.
Introns are removed from mRNA and the coding regions called exons are joined.
noncoding regions of RNA/DNA and are removed during RNA splicing
Coding regions of mRNA joined during RNA splicing
mRNA (messenger RNA)
An RNA molecule transcribed from a DNA template during transcription. Carries the message of DNA from nucleus to cytoplasm.
tRNA (transfer RNA)
A molecule with an amino acid binding site at one end and a three-base anticodon at the other end. The tRNA anticodon bonds to the mRNA codon, bringing an amino acid into a position to be added to the polypeptide. Translates letters into amino acids.
rRNA (ribosomal RNA)
RNA that makes up a ribosome where the tRNA anticodon bonds to the mRNA codon.
a change in the nucleotide sequence of DNA
the replacement of one base or nucleotide with another
deletion of one or more nucleotides in a gene. Effects are more disastrous than that of a base substitution
substitution where the new base codes for the same base
delete one letter as a substitution but the new base codes for a different amino acid so the protein may not function
delete or insert a base and all the rest of the amino acids are affected
What are the three building blocks of a nucleotide?
a sugar, a phosphate group, and a nitrogenous base
Describe the structure of a DNA molecule.
DNA has a sugar phosphate backbone of nucleotides and a double helix where two strands twist with the sugar-phosphate backbone on the outside and a nitrogenous bases on the inside.
Where in a cell is DNA transcribed? Where is it translated?
DNA is transcribed in the nucleus. It is translated in the cytoplasm.
What is the role of tRNA in translation?
tRNA has an anticodon that binds to the mRNA codon, bringing an amino acid into position to be added to the polypeptide.
segment of DNA that directs the formation of RNA which in turn directs formation of a protein