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Biology Chapter 15
Genes and Proteins part 1 (15.1-15.2)
| Question | Answer |
|---|---|
| What is messenger RNA? | A mobile copy of one or more genes with an alphabet of A,C,G,U. This molecule is generated by transcription. |
| What happens in the translation of the mRNA? | The template on the ribosomes converts nucleotide-based genetic info into a protein product. |
| What is responsible for the variation in protein structure and function? | The variation in amino acid sequence. (There are 20 common amino acids known as "letters.") |
| What are the components of an amino acid? | An amino group (NH3+), a carboxyl group (COO-), and a side chain. |
| What is the Central Dogma? | It states that genes specify the sequence of mRNAs, which in turn specify the sequence of all proteins. |
| Define colinear. | In terms of RNA and protein, three "units" of RNA (nucleotides) specify one "unit" of protein (amino acid) in a consecutive fashion. |
| What molecule are the instructions on DNA transcribed onto? | They are copied onto messenger RNA. |
| What reads the genetic info inscribed on strand of mRNA? | Ribosomes read the instructions on the mRNA. |
| What is a triplet codon? | This is the three-nucleotide sequence of amino acids. |
| What is degeneracy of a genetic code? | This describes that a given amino acid can be encoded by more than one nucleotide triplet' the code is degenerate, but not ambiguous. |
| What is a codon? | The three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation. |
| What is the reading frame? | Sequence of triplet codons in mRNA that specify a particular protein. A ribosome shift of 1 or 2 nucleotides could completely destroy synthesis of that protein. |
| How many of the total 63 codons terminate protein synthesis and release the polypeptide from the translation machinery? | Three of the 64 codons. These are called stop or nonsense codons. (UAA, UAG, UGA) |
| What specific codon serves as the start codon to start translation? | AUG, which codes for methionine (eukaryotes). |
| How is the mRNA read? | Starting near the 5' end of the mRNA, after the start codon, it is read in chunks of 3 until a stop codon is detected. |
| What is a pyrimidine half? | When the codon triplet ends in U or C. |
| What is a purine half? | When the codon triplet ends in A or G. |
| What is a plasmid? | This is found in prokaryotes. It is circular DNA molecules that may only have 1 or a few genes. |
| What is a transcription bubble? | The region of the unwinding of DNA. |
| Define the template strand. | The strand of DNA that specifies the complementary mRNA molecule. This is the strand where transcription always goes from. |
| Define the non-template strand. | The strand of DNA that is not used to transcribe mRNA. It is identical to the mRNA except that T nucleotides in the DNA are replaced by U in nucleotides of mRNA. |
| What is the initiation site? | The nucleotide where mRNA synthesis proceeds in the 5' to 3' direction. Denoted with a "+1." |
| What nucleotides are denoted with a "-" sign? | These are the nucleotides preceding the initiation site. (upstream nucleotides) |
| What is a cistron? | It is the coding sequence for a single protein. |
| What is the core enzyme (prokaryotes)? | This RNA polymerase consists of greek a, greek a, greek B, and greek B' but lacks greek o. This complex performs elongation. |
| What does the two greek a subunits do in the core enzyme? | They are necessary to assemble the polymerase on the DNA. |
| What does the the greek B and the greek B' subunits do in the core enzyme? | Greek B binds to the ribonucleoside triphosphate that becomes part of the nascent mRNA molecule. The greek B' binds the DNA template strand. |
| What does the greek o do? | This is the fifth subunit of the polymerase. It is involved only in transcription initiation. |
| What is a holoenzyme? | The polymerase made of ALL 5 polypeptide subunits. (Greek a, greek a, greek B, greek B', and greek o.) |
| What is a promotor? | It is a DNA sequence onto which which the transcription machinery (including RNA polymerase) binds and initiates transcription. They exist upstream of the genes they regulate. |
| What does the specific sequence of a promotor control? | It determines if the corresponding gene is transcribed all of the time, some of the time, or infrequently. |
| Where are the two promotor consensus sequences (regions similar across all promotors) located and what are their sequences? | One is located at the -10 region and has a sequence of TATAAT. The other is located at -35 region and has a sequence of TTGACG |
| What are the4 two promotor consensus sequences bound by? | By the greek o polypeptide subunit of an RNA polymerase. |
| What begins the transcription elongation phase? | The release of the greek o subunit from the polymerase. This allows the core enzyme to proceed along the DNA template. |
| What are the 2 kinds of termination signals (prokaryotes)? | 1) Protein-based Rho-dependent termination and 2) rho-independent termination. |
| What causes rho-dependent termination signal to be released? | Rho-dependent is released when an interaction between RNA pol and rho protein contact a run of G nucleotides on the DNA template. |
| What causes the rho-independent termination signal to be released? | This is caused by hairpin formation in the mRNA that stalls the polymerase action. |
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tali_Alley
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