PROTEIN SYNTHESIS. DNA vs. RNA. I. DNA vs. RNA. A . Differences 1. # of Strands: DNA = 2 RNA = 1 2. Sugars: Deoxyribose in DNA, ribose in RNA 3 . Bases: DNA (A, C, T, G), RNA (A, C, U , G). RNA replaces thymine with uracil. B. Similarities 1. Both are Nucleic Acids
1. # of Strands: DNA = 2 RNA = 1
2. Sugars: Deoxyribose in DNA,
3. Bases: DNA (A, C, T, G), RNA (A, C, U, G). RNA replaces thymine with uracil
1. Both are Nucleic Acids
2. Both are made of units called nucleotides
DNA RNA Protein
Occurs in the nucleus Occurs in the cytoplasm
B. The Process:
1. DNA “puffs” in the region of the needed gene
2. 1 DNA strand serves as the template, directing the sequence of mRNA nucleotides
3. RNApolymerase matches RNA bases with their complementary bases on the DNA
4. The mRNA strand leaves the nucleus and attaches to a ribosome in the cytoplasm to be translated
Example : DNA= A T C G A
1. Long non-coding stretches of nucleotides called intronsare cut out of the pre-mRNA and the remaining nucleotides called exonsare glued back together. Exons"exit" the nucleus.
1. A polyAtail is attached to one end of the mRNA strand to help it leave the nucleus through a pore and to determine it's lifetime in the cytoplasm.
2. An mcapprotects the RNA from wandering enzymes and help the mRNA attach to a ribosome.
A. Definition- The process of translating mRNA to proteins
B. Proteins are made of chains of amino acids. (Chains = polymers)
1. tRNAbrings amino acids to mRNA at ribosomes
a. On one side of a tRNA are 3 bases known as an anticodon
b. On the other side of a tRNA is a specific amino acid
c. Anticodons line up across from complementary mRNA codons
2. Amino acids bond together to form a protein
3. tRNAreleases amino acid and returns to the cytoplasm
D. The details
a. Enzymes match individual tRNA molecules with a specific amino acid.
2. The code may be redundantbut it is never ambiguous.
1. A, P, and E sites exist on ribosomes
a. A site - where new tRNAattach
b. P site - where the two amino acids next to each other form peptide bonds
c. E site - where the tRNAexitfrom the ribosome
2. polyribosomes- more than one ribosome can work on the same mRNA strand at a time.
A. Base-Pair substitutionUsually not a big deal.
1. missense--> one altered codon --> one different amino acid
2. nonsense --> one altered codon changes amino acid to "STOP"
3. Disease example: ________________
B. Base-Pair Insertions and Deletions...some are disasterous
1. Alters reading frame = __________ mutations (all codons and resulting amino acids will be different after the insertion or deletion.
2. Disease example: ____________________