DNA and protein synthesis
 mRNA, tRNA, rRNA – jobs, differences, locations
o mRNA is a copy of the DNA code that can leave the nucleus and go to the
ribosome to direct the making of a protein. It can be found in the
nucleus and the cytoplasm
o tRNA is found in the cytoplasm, and brings amino acids to the ribosome
o rRNA is produced in the nucleolus and makes up the ribosomes, found in
the cytoplasm
 How does DNA replication work?
o DNA unzips when helicase breaks hydrogen bonds between the bases.
o DN polymerase pairs complementary bases to those on the original or
parent strand. This produces the daughter strand.
o DNA replication ensures that each new cell has its own copy of DNA.
DNA replication occurs every time a new cell is produced, such as for
growth, repair, and fighting disease.
 Translation v. transcription
o Transcription makes mRNA from DNA. Since DNA can’t leave the
nucleus, proteins are made outside the nucleus, and a copy of the DNA
code is needed outside the nucleus, mRNA must be produced. This
process happens inside the nucleus.
o Translation uses the mRNA that was produced during transcription to
produce a protein. mRNA has sequences of bases called codons, and it
meets with tRNA, having sequences of anticodons. Codon and anticodon
are complementary. tRNA brings amino acids to the ribosome, and
those amino acids are linked together by peptide bonds to produce a
protein.
 Labels of models of transcription and translation
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When does protein synthesis occur (in comparison with mitosis)
o Protein synthesis occurs anytime the body needs to make new body
tissue, new organelles, new enzymes, new antibodies, etc. It happens
during the G1 stage of interphase. Then, when new cells are created
during cell division, there are enough materials to divide the cytoplasm
in two to make a new cell.
What is a nucleotide
o A nucleotide is made of a phosphate, sugar, and a base. DNA and RNA
are both made of nucleotides – DNA has two strands of them, and RNA
has one strand.
Sequence of genes to proteins
o DNA is copied into mRNA through the process of transcription, which is
followed by translation, during which the mRNA code is converted into a
protein
Codon v. anticodon
o Codons are found on mRNA, anticodons are found on tRNA. Codons and
anticodons are complementary
Hershey chase experiment
o They set up 2 experiments – one in which DNA was labeled with
radioactive phosphorous, the other in which the protein was labeled
with radioactive sulfur. The DNA or protein of the virus was labeled,
then allowed to infect the bacteria (viruses infect bacteria by injecting
their genetic information into a bacteria cell). Once the viruses had
infected the bacteria, they separated the viruses and bacteria, and
looked to see whether there was radioactive phosphorous or sulfur
inside the bacteria. Since they found radioactive phosphorous inside,
they concluded that DNA, and not protein, was the genetic material
found in chromosomes.