mRNA Grows Up
What are the similarities and differences between DNA and RNA?
Similarities: Both have 4 nitrogenous bases; both have Cytosine, Adenine, and Guanine; they both have a phosphate backbone.
Differences: RNA has Uracil whereas DNA has Thymine; DNA is double-stranded but RNA is single-stranded; DNA is more structurally stable than RNA and RNA is more flexible.
What is a codon? What is an anticodon?
A codon is the sequence of 3 nucleotides that, together, code for a specific amino acid.
An anticodon is a set of 3 nucleotides that corresponds to an mRNA codon.
What enzyme "unzips" the DNA strands?
Helicase
What is a ribosome? What is it made of?
A ribosome is a cellular organelle that is the site of protein synthesis. It is made of RNA and protein.
A codon consists of how many nucleotides?
3
What is added to the end of an mRNA strand in eukaryotes? To the front of the strand? What is the purpose of these additions?
A Poly-A Tail added to the end
A 5'-cap added to the front
The purpose of adding these is to protect the mRNA from RNase enzymes in the cytoplasm
Translate the mRNA codons into amino acids: GUA UGC AAG AGC CUU
Val- Cys- Lys- Ser- Leu
Describe the function of a spliceosome
It separates introns from mRNA strands
What is the difference between mRNA and tRNA?
The structure of mRNA is linear. It carries information copied from the original DNA sequence. The structure of tRNA is a 3D L shape. It's structure relies on a specific amino acid, and it carries that amino acid to the growing polypeptide chain inside of the ribosome.
What is a mutation? What could it lead to?
A mutation is a change in the nucleotide sequence of DNA. It can lead to genetic disorders or cancer. It can also have no effect at all.
What is the purpose of transcription and where does it occur?
The purpose is to make an RNA copy of the original DNA coding strand. This takes place in the nucleus.
What is the purpose of translation and where does it occur?
This process tells a cell how to link amino acids together in order to create proteins. This occurs in the ribosome.
Which enzyme builds a new DNA strand by adding complementary bases?
DNA Polymerase
What is an exon and what is an intron?
An exon is the part of the gene that is expressed in the protein. An intron is the part of the gene that is not expressed in the protein and they are found in-between the exons.
How is transcription different in prokaryotes and eukaryotes?
Eukaryotes had 3 types of RNA polymerases whereas prokaryotes only have one. Prokaryotic transcription occurs in the cytoplasm and occurs simultaneously with translation. Eukaryotic transcription is in the nucleus and it occurs before translation.
What is the role of the promotor AND the role of the TATA box?
Promotor:
1. When/where to start reading (it's the starting point)
2. Which strand to read (template strand)
3. Direction to read DNA (3' to 5')
TATA box: Indicates where a genetic sequence can be read. It specifies where transcription begins.
What is tRNA and what does it do? What is it's structure?
Transfer RNA is a type of RNA that helps decode a strand of mRNA into a protein.
Structure: Folded with 3 hairpin loops that create a three-leafed clover shape.
Describe DNA Primase
This enzyme initiates the synthesis of DNA by creating a short RNA segment at the replication fork.
Given the DNA coding strand AAT TGT AGG CGG, what is the corresponding mRNA sequence?
UUA ACA UCC GCC
Give 2 examples of diseases that can be a result of a mutation
1. Cystic Fibrosis
2. Sickle-cell Anemia
Describe the entire process of transcription (3 steps)
Initiation: The RNA polymerase binds to the promotor sequence on the DNA.
Elongation: The polymerase unwinds the DNA reading the 3' to 5' direction and builds in the 5' to 3' direction.
Termination: The RNA polymerase stops at the termination sequence, and the hairpin turn folds back on itself.
Describe the entire process of Translation
1. The ribosome binds to the mRNA strand.
2. The ribosome matches tRNA anticodons to the mRNA sequence
3. The tRNA is carrying a specific amino acid which gets added onto a polypeptide chain inside of the ribosome
4. The process stops when the ribosome reaches the stop sequence on the mRNA strand
5. The polypeptide chain is released from the ribosome, then it folds up and becomes a functioning protein.
What is an Okazaki Fragment AND what is the function the enzyme DNA Ligase?
An Okazaki Fragment is a fragment of copied DNA created by the lagging strand. DNA Ligase binds these fragments together.
What is the flow of information for the synthesis of proteins according to the central dogma?
DNA to mRNA to tRNA to protien
Who determined the first codon-amino acid match?
Nirenberg and Matthaei