What is translation?
The RNA directed synthesis of a polypeptide
What interprets the code on an mRNA molecule?
tRNA
What is the function of tRNA?
transfer amino acids from the cytoplasm to a ribosome
How many amino acids are there?
20
Are all tRNA molecules identical?
No, each codes for a particular mRNA codon in a particular amino acid
On one end of the tRNA is the amino acid, what is at the other end?
Nucleotide triplet called an anticodon that base pairs with complementary codon of mRNA
Where is tRNA transcribed?
From DNA in the nucleus
What happens to the tRNA molecule once it has dropped an amino acid at the ribosome?
Recycled, goes to get another one
What is a tRNA made of?
Single RNA strand, about 80 nucleotides long
How does tRNA get its structure?
complementary stretches in the polypeptide can hydrogen bond
Which end of the molecule does amino acid attach to?
3’ end
What shape is tRNA?
3D Structure, 3 loops, l shaped
What are the two recognition stages required for accurate translation?
Correct match between amino acid and tRNA and a correct match between the tRNA anticodon and mRNA codon.
What enzyme is required to match up tRNA and amino acid?
Aminoacyl-tRNA synthetase
How does the enzyme Aminoacyl-tRNA synthetase attach the tRNA and amino acid
active site of enzyme fits only a specific amino acid and tRNA combination, joins together by covalent bond using ATP hydrolysis
How many different types of Aminoacyl-tRNA synthetase enzymes are there?
20
How many different codons are there for amino acids?
61 different codons
What can be seen from the fact that there are 61 different codons but 20 amino acids?
tRNA is able to bind to more than one different codon, wobbly base pairings, the third base pair rule is more relaxed
What I the function of a ribosome?
Facilitates the specific coupling of tRNA anticodons with mRNA codons during protein synthesis
What is a ribosome built from?
rRNA, Small and large subunits
Where is rRNA made?
In the nucleus from chromosomal DNA
When do the large and small subunits attach?
Only join to form a functional ribosome when they attach to mRNA in the cytoplasm
What is the most abundant type of cellular RNA?
rRNA
What are the components of a nucleotide monomer?
nitrogenous base, sugar molecule, phosphate group
What are the two families of nitrogenous bases?
pyrimidines and purines
Which bases are pyrimidines?
Cytosine and Thymine and Uracil
Which bases are purines?
guanine and adenine
How do you differentiate between purines and pyrimidines?
Purines are larger, with 6 carbon ring fused to a five carbon ring, as opposed to a single six carbon ring
What sugar is found in RNA?
Ribose
What sugar is found in DNA?
Deoxyribose
What is the difference between the sugar in DNA and RNA?
presence and absence of oxygen
Which carbon is the phosphate group added to in the sugar of a nucleotide?
5’ carbon
How are adjacent nucleotides joined?
Phosophodiester linkage
What is a phosphodiester bond?
Phosphate group that links sugars of two nucleotides, one has a phosphate attached to the 5’ carbon, the other has a hydroxyl group on a 3’ carbon
What specifies the sequence of a gene?
linear order of bases on a chromosome
How is cellular DNA structured
Two polynucleotide chains, two sugar phosphate backbones run in antiparallel directions in a double helix, joined together by hydrogen bonds between bases
What is the semi conservative model of replication?
New DNA molecule contains one parent strand and one daughter strand
What is a nucleoside triphosphate?
A molecule with three phosphate groups
Which end are nucleotides added to?
3’ end
Where does replication begin?
Origin of replication