REVIEW SHEET FOR RNA AND PROTEIN SYNTHESIS
TERMS:
Gene: A section of DNA that codes for a protein (polypeptide)
Codon (including start and stop): Three sequential bases of mRNA (usually codes for an amino acid)- Start=AUGStop=UAA, UAG, UGA- 64 possibilities
-Group of 3 nucleotides in mRNA that specifies an amino acid
-Group that can be thought of as one of the words of the genetic message
-The sequence of 3 nitrogenous bases in mRNA
Anticodon: Three sequential bases on tRNA that is complementary to the codon
-The 3-base sequence found on tRNA that binds to a complementary piece of mRNA during protein synthesis
Genetic Code: DNA codes for all the different patterns in an organism- determined by the sequence of nitrogen
bases/nucleotides
-Consists of 64 codons along with their corresponding amino acids
Intron: A section of DNA (or RNA) that does not code for a part of a protein
-Section of DNA or RNA that does not code for proteins
Exon: A section of DNA (or RNA) that codes for a part of a protein
-Section of DNA or RNA that codes for part of a protein
Expressed Gene: A gene that is being actively transcribed (the process of protein synthesis is taking place)
RNA Polymerase: Enzyme that directs transcription by matching RNA bases to complementary DNA base
-Enzyme that binds directly to a DNA molecule during transcription
Initiation and Elongation: Initiation begins with the building of mRNA to the small subunit of a ribosome. The first
tRNA, with its amino acid binds to the complementary part of mRNA. The large subunit of the ribosome binds to the
small subunit so that the first tRNA is positioned in the P site. The second tRNA enters and binds to the A site of a
ribosome. The amino acid from the first tRNA detaches and forms a peptide bond with the second amino acid at the A
site. The first tRNA is released, the ribosome moves 3 bases along the mRNA, and a new tRNA moves into the A site.
The tRNA that had been in the A site moves into the P site.
-Elongation is the lengthening of the amino acid chain during protein synthesis
Parts of a ribosome (large, subunit, small subunit, P site, A site):
Large subunit- catalyzes the reactions that combine the amino acids into a polypeptide chain- 50S
Small subunit- Binds to a mRNA molecule and reads its genetic codes- 30S
P site- Donates the amino acid used to form the polypeptide chain
A site- The amino acid located here accepts the released amino acid from the P site. It also accepts the next
tRNA from the cytoplasm
Compare structure of DNA to that of RNA:
1. The sugar in RNA is ribose instead of deoxyribose
2. RNA is generally single stranded, not double
3. RNA contains Uracil in place of Thymine
- RNA is also made from nucleotides
- Phosphate group
Understand process of transcription, RNA splicing, translation:
Transcription- process where information stored in DNA is transferred to mRNA (mRNA is made) (occurs in
the nucleus)
- Process by which RNA is made
- Process by which part of the nucleotide sequence of a DNA molecule is copied into RNA
- The process of transferring information from DNA to a strand of RNA
RNA splicing (RNA editing)- Process where introns are removed from pre-mRNA and exons are joined
together to form mRNA
Translation- (occurs at the ribosomes in the cytoplasm) Process where the code in mRNA is converted into an
amino acid sequence (building a protein)
-Process by which nucleotide in mRNA are decoded into a sequence of amino acids in a polypeptide
-Formation of an amino chain from the information provided by mRNA
Roles of:
mRNA- type of RNA that carries the instruction for protein production to the ribosome- messenger
-Serves as a template for the assembly of amino acids during protein synthesis
-Form of RNA that serves as a messenger from DNA to the rest of the cell
-RNA that carries the genetic instructions for protein production
tRNA- type of RNA that transports amino acids to the ribosome
-Form of RNA that transfers amino acids to the ribosome during the assembly of a protein
-RNA that carries amino acids to the ribosome during protein synthesis
rRNA- type of RNA that is a major component of the ribosome
-Form of RNA that is part of the structure of ribosomes
Transcribe section of DNA and use table to find associated amino acids---------------------------
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Translation diagram:
1. The cell gets a message to make a certain quantity of a specific protein
2. A portion of the DNA molecule unwinds, exposing the gene responsible for that protein
3. Nucleotides, with the help of enzymes, move along one strand of the exposed gene and forms a molecule of
mRNA (U pairs with A)
4. Multiple copies of mRNA are made according to the quantity of the order. They leave the nucleus and enter
the cytoplasm via nuclear pairs.
5. An mRNA binds with a ribosome so that the mRNA can be decoded (read) by the ribosome. The message is
read 3 nucleotide bases (codon) at a time
6. Each codon code strands for a specific amino acid. When the codon is read, the corresponding amino acid is
activated by an enzyme
7. A tRNA molecule has 2 ends. One end has a specific binding site for a particular amino acid. The other end
has an anticodon that can pair with a codon
8. The appropriate molecule of tRNA attaches to and carries the activated amino acid to the ribosome.
Anticodon bases pair with codon in order to bring the specific amino acid to the correct place
9. A 2nd tRNA molecule picks up another activated amino acid and brings it to the ribosome, matching
anticodon to codon
10. The 1st tRNA releases its amino acid to the 2nd tRNA and leaves the site. The 2 amino acids from a peptide
bond using ATP as its energy source
11. The ribosomes read the next codon. Corresponding tRNA brings the activated amino acid to the ribosome
12. The 2nd tRNA releases its load of amino acids to the 3rd tRNA and leaves the site. Amino acids link up
forming peptide bonds using ATP
13. The process repeats itself until the entire message is read and all amino acids are brought in sequence,
forming a polypeptide chain
14. The polypeptide chain folds into its final conformation and is completed and released
15. Multiple copies of proteins are made as other ribosomes follow the 1st ribosome