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What are polypeptide chains?
A number of amino acids put together, which folds up in a specific three-dimensional manner, resulting in a protein.
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How are proteins created?
- DNA is contained in the nucleus of the cell.
- 1. A stretch of it unwinds in the nucleus & its message - the order of a string of A's, T's, C's, 7 G's - is copied onto mRNA, then exits the nucleus.
- 2. mRNA goes into the ribosome, a molecular workbench in the cytoplasm; site of protein synthesis
- 3. Once the chain is finished & folded up, a protein has come into existence
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What is a ribosome?
Organelle, located int the cell's cytoplasm, that's the site of protein synthesis.
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What is transcription?
Process by which genetic info encoded in DNA is copied onto mRNA.
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What are the steps of transcription?
- 1. A section of DNA unwinds & nucleotides on it form base pairs with nucleotides of mRNA, creating an mRNA chain.
- 2. mRNA leaves nucleus & enters ribosome where translation takes place.
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What is translation/
Process by which info encoded in mRNA is sued to assemble a protein at a ribosome.
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What are the steps of translation?
- Joining the mRNA chain at the ribosome are amino acids, brought there by tRNA molecules. The length of mRNA is then "read" within the ribosome. The result is a chain of amino acids linked together in order specified by the mRNA sequences.
- 2. When the chain's finished & folded up, a protein's come into existence.
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What is RNA polymerase? What are its two functions?
Enzyme that unwinds the DNA sequence & then strings together the chain of RNA nucleotides that's complementary to it, thus producing the initial RNA chain.
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What's mRNA?
Type of RNA that encodes, & carries to ribosomes, info for the synthesis of proteins.
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What's the difference between the structures DNA & RNA?
- 1. RNA is usually single stranded, while DNA has a "double helix"
- 2. DNA has bases of "A,G,C,T"
- 3. RNA uses the first three of these, but subs U for T
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What's a codon?
- Each coding triplet of mRNA base
- Ex: CGU//UCA//UGG//ACU
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What's the genetic code?
The inventory of linkages between the nucleotide triplets & the amino acids they code for.
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What's tRNA?
Form of RNA that, in protein synthesis, binds with amino acids, transfers them to ribosomes, & then binds with mRNA.
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What are the functions of tRNA?
Binds with amino acids and nucleic acids
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What's an anticodon?
An mRNA codon by means of three bases it possesses.
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What's rRNA?
Structural component of ribosomes.
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What are the steps of translation?
- 1. mRNA transcript binds the small subunit of a ribosome as the first tRNA's arriving. the mRNA codon AUG is the "start" sequence for most polypeptide chaines. The tRNA, with its (MET) amino acid attached, then binds this AUG codon.
- 2. The large ribosomal subunit joines the ribosome, as a second tRNA arrives, bearing a (LEU) amino acid. The second tRNA binds to the mRNA chain, within the ribosome's A site.
- 3. A polypeptide chain's formed. The ribosome now shifts one codon to the right, relocating the original P site tRNA to the E site, the A site tRNA to the P site, & moving a new mRNA codon into the A site.
- 4. The E site tRNA leaves the ribosome, even as a new tRNA binds with the A site mRNA codon, & the process of elongation continues.
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What's the start amino acid of any sequence?
Methionine
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How many amino acids exist?
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What's the purpose of the promoter sequence?
In order for transcription to take place in any gene, a multipart complex must bind with the promoter sequence to help RNA polymerase align with it.
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What's alternative splicing?
Process in which a single primary transcript can be edited in different ways to yield multiple mRNAs. This is how we do so much with our relatively small number of genes.
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Though there are hundrds of thousands of proteins active in living things, all of them are put together from a starting set of __________ of the building blocks known as __________.
20; amino acids
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The info for building proteins encoded in DNA is passed on first to __________, which then migrates to an organelle called a __________, where the protein's put together.
mRNA; ribosome
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Amino acids are brough to the __________ by another form of RNA called, __________.
ribosome; tRNA
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DNA passes on its info to mRNA by means of __________.
complementary base pairing
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Each __________ DNA bases code for _________ RNA bases, which code for __________ amino acid(s).
three; three; one
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A tRNA molecule attaches to an __________ on one end & a __________ on the other.
amino acid; mRNA codon (triplet)
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True or False. Most of the DNA in the human genome codes for proteins
False; Less than 1.2% of the human genome codes for proteins
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In eukaryotic organisms such as ourselves, the RNA chains, called primary transcripts, that code for proteins must undergo __________ on their way to becoming __________. The segments of the primary transcripts that are removed in this process are called __________, while the segments that are retained are called __________.
editing; mRNA; introns; exons
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Small lengths of RNA called __________ have the effect of "silencing" genes in the genome by means of targeting their __________ for destruction.
micro-RNA's; mRNAs
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