Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Chapter 17 review
| Question | Answer |
|---|---|
| What are three ways in which RNA differs from DNA? | Contains ribose instead of deoxyribose, uses uracil as a nucleotide in place of thymine and is single stranded |
| What are the monomers of DNA and RNA? | nucleotides |
| Monomers of proteins? | amino acids |
| What is transcription? | The synthesis of RNA using information in the DNA. Performed in the nucleus. Pre-mRNA is made first before final mRNA. |
| What is translation? | The synthesis of polypeptides using the information from mRNA |
| Describe transcription: | DNA strand is template, product synthesized is mRNA and it is located in the nucleus of eukaryotes. |
| Describe translation: | Nucleotides of mRNA strand are template, product synthesized is amino acids, and location is cytoplasm in ribosomes for eukaryotes. |
| What is pre-mRNA called? | Primary transcript |
| What is the central dogma? | DNA to RNA to Proteins |
| How many unique triplets exist? | 64 |
| What is the coding strand called? | The template strand |
| How did nirenberg find the first codon? | He synthesized an artificial mRNA by linking identical RNA nucleotides containing uracil as their base. It could only contain one base in repetition: UUU. He added this codon to a mixture of other materials needed for protein formation. |
| What was the first codon pair to be identified? | UUU (Phe) |
| How many triplets code for amino acids? | 61 |
| What event is coded for by UAG, UGA and UAA | Stop |
| What is the start codon? | AUG |
| Why is the genetic code said to be redundant but not ambiguous? | More than one codon can code for a specific amino acid, but those specific codons cannot code for more than one amino acid. |
| What is the reading frame? | Codons must be read from the 5 prime to 3 prime direction (left to right). |
| What is the enzyme that uses the DNA template strand to transcribe a new mRNA strand? | RNA polymerase |
| Which enzyme, DNA polymerase or RNA polymerase does not require a primer to start transcription? | RNA polymerase |
| What is a transcription unit? | The stretch of DNA that is transcribed into an RNA molecule. |
| What is the first step of transcription? | Initiation: RNA polymerase binds to the promoter and the DNA strands unwind. RNA synthesis begins. |
| What is the second step of transcription? | Elongation: Polymerase moves towards the five prime end, RNA is elongated and DNA begins to rewind. |
| What is the third step of transcription? | Termination: Polymerase moves downstream. RNA transcript is released and polymerase detaches from the DNA. |
| What are three important facts regarding the promoter? | Transcription factors mediate the binding of RNA poly. and the initiation of transcription, TATA box forms the initiation complex at a eukaryotic promoter and RNA poly. binds at a precise location where transcription begins |
| Describe the process by which the promoter for transcription is activated: | 1.) Eukaryotic promoter: TATA box (nucleotide sequence containing thymine and adenine) determine the start |
| Description continued: | 2.) Several transcription factors must bind to DNA before RNA polymerase II can bind in correct position. |
| Description continued: | 3.) Additional transcription factors bind to DNA along with RNA poly. II creating transcription initiation complex. RNA poly. II unwinds DNA and synthesis begins. |
| What is a TATA box? | A crucial promoter DNA sequence that forms the initiation complex. It got it's name based on its nucleotide sequence (a,t). They recognize this, so RNA can begin. |
| What comprises the transcription initiation complex? | Whole complex of transcription factors, RNA polymerase II, proteins, TATA box, etc. |
| What happens at the five prime end? | A five prime cap is attached, which is a modified guanine nucleotide sequence added after the first 20-40 nucleotides. |
| What happens at the three prime end? | A poly-A tail is added. 50-250 more adenine nucleotides are added to the end by enzymes. |
| What are three important functions of the five prime cap and a poly a tail? | They facilitate in the transfer of mature mRNA from the nucleus, help protect mRNA from degradation and help ribosomes attach to the five prime end of mRNA when it reaches the cytoplasm |
| What is the difference between introns and exons? | Exons are expressed, introns are cut out and not expressed in the mRNA sequence that is to be translated |
| What is a ribozyme? | RNA molecules that function as enzymes (don't have to be proteins to catalyze reactions). |
| What is the consequence of alternative splicing of identical mRNA transcripts? | A single gene can encode more than one kind of polypeptide. This depends on which segments of the RNA are treated as exons (expressed). |
| What does mRNA do? | messenger RNA, transcribed into amino acids, and creates them. |
| What does tRNA do? | transfer RNA, transfer certain amino acids to and from ribosomes, and transfers amino acids |
| What does rRNA do? | ribosomal RNA, makes up ribosomes, and creates the ribosomes for translation |
| What is an anticodon? | A sequence of three nucleotides on the end of tRNA that base pairs to a complementary sequence on an mRNA molecule. |
| tRNA has two attachment sites. What attaches to these? | Amino acids attach to the top and the anticodon is read by the bottom. |
| How many different aminoacyl-tRNA synthetases are there? | 20 (1 for each amino acid) |
| How does wobble explain the fact that far fewer aminoacyl-tRNA synthetases exist? | A wobble is a flexible base pairing at a codon position. Most codons differ in their third nucleotide base, but not in the other bases. UCU can either pair with the mRNA codon AGA or AGG, which both code for arginine. |
| What is the process of specific amino acids being joined to a tRNA? | 1.) Active site binds to the amino acid and ATP. 2.) ATP loses two phosphate groups and binds to the amino acid and amp. 3.) Appropriate tRNA covalently bonds to amino acid, displacing amp. 4.) tRNA is charged and released by enzyme |
| What is the structure of a eukaryotic ribosome? | Consists of a large subunit and smaller one, each made of RNA's and proteins. Subunits are made in the nucleolus. Ribosomes are assembled by rRNA's and proteins from the cytoplasm. |
| How does a prokaryotic ribosome differ from a eukaryotic ribosome? | Eukaryotic ribosomes are larger and more complex in their molecular composition. |
| What does the A site do? | Holds the next tRNA carrying the amino acid to be added to the chain. |
| What does the P site do? | Holds the tRNA carrying the growing polypeptide chain. |
| What does the E site do? | Discharged tRNAs leave the ribosome from here. |
| What is the first step of translation? | Initiation: brings together mRNA, tRNA and the two subunits of ribosomes to start translation. |
| What is the second step of translation? | Elongation: Amino acids are added one by one to the previous amino acid at the c terminus of the growing chain |
| What is the third step of translation? | Termination: elongation continues until it reaches the stop codon. Polypeptide chain is released. |
| What happens during initiation? | 1.) Small subunit binds to a molecule of mRNA. Recognizes the start codon and initiator tRNA carrying UAC base pairs with AUG. 2.) Large ribosomal complex completes complex. Initiation factors plus GTP required. initiator tRNA in P site; A site open |
| What is always the first amino acid in the new polypeptide? | Methionine |
| What is the first step of elongation? | 1.) Codon recognition: anticodon of tRNA pairs with complementary mRNA codon. GTP helps this process. |
| What is the second step of elongation? | Peptide bond formation: rRNA molecule catalyzes the formation of peptide bond between amino group of new amino acid and carboxyl group of P site amino acid. |
| What is the third step of elongation? | Translocation: the ribosome translocates the tRNA in the A site to the P site. tRNA is moved from p to E. mRNA moves along and brings the next amino acid to the translated into the A site |
| What is a release factor? | A protein shaped like an aminoacyl-tRNA, binds directly to the stop codon in the A site and releases water. The reaction breaks the bond between amino acids and releases new chain. |
| What is a polyribosome? | Multiple ribosomes bind to a single mRNA strand translate at the same time, making multiple polypeptides. |
| What are some of the things that will result in a final-form functional protein? | A protein will coil and fold spontaneously because of its amino acid sequence, which gives it a specific shape. |
| Define mutation in terms of molecular biology: | Mutations occur when nucleotide pairs are changed in a way where the genotype or phenotype of the organism is altered, or not. |
| What are frameshift mutations? | Insertion or deletion of nucleotides may alter the reading frame of the genetic message, the triplets read during mRNA translation. |
| Identify two mechanisms by which frameshifts may occur: | Insertion or deletion of nucleotides |
| What is a nonsense mutation? | Changes a codon for an amino acid into a stop codon |
| What is a missense mutation? | Change one amino acid into another |
| How can a nucleotide-pair substitution result in a silent mutation | Can transform one codon into another, but they both code for the same one. |
| What are the two categories of mutagens? | Nucleotide analogs and chemical mutagens |
Created by:
mbuch