Chapter 13 Flashcards
What are auxotrophs?
Mutant strains that are unable to grow on Minimal mediums (MM)
What did Tatum and Beadle discover with their experiments?
They showed the direct relationship between genes and enzymes which they put forest as the one gene-one (enzyme) hypothesis
What are the two steps on he pathway from gene to polypeptide?
Transcription- the mechanism in which the information encoded in DNA is made into a complementary RNA copy.
Information in one nucleic acid type is transferred to another nucleic acid type
Translation- the use of the information coded in the RNA to assemble amino acids into a polypeptide
What is the enzyme used in transcription?
RNA polymerase creates an RNA sequence complementary to the DNA sequence
Where does transcription and translation take place in prokaryotes? Eukaryotes?
Eukaryotes- transcription- nucleus
Translation- cytoplasm before ribosome
Prokaryotes- transcription- cytoplasm
Translation- throughout the cell
What is a codon?
The three letter word of the genetic code
How do you transfer the genetic code from the mother strand to the template strand to the mRNA strand? What direction are the mRNA’s written?
Mother ACTG Template TGAC mRNA ACUG Use ACU for codon chart Written 5’ to 3’ like mother strand
What are the three steps of transcription?
Initiation- molecular machinery that carries out transcription assembles at the promoter and begins synthesizing RNA copy
Elongation- rna polymerase moves along the gene extending the RNA chain
Termination- transcription ends and RNA molecule and RNA polymerase are released from DNA template
What is precursor mRNA?
A stop for the protein coding gene to make so it can be processed in the nucleus to produce translatable mRNA
What are introns?
What are Exons?
Introns- Non-protein coding sequences that interrupt the protein coding sequence
Exons- the amino acid coding sequences that are retained in finished mRNAs
What is mRNA splicing?
Occurs in the nucleus and removed introns from pre-mRNAs and joins Exons together
Used snRNA to do this
What is alternative splicing?
A mechanism that greatly increases the number and variety of proteins encoded in the cell nucleus without increasing the size of the genome
Why aren’t introns wasteful?
Introns may provide a selective advantage to organisms by increasing the coding capacity of existing genes (alternative splicing) and generating new proteins (exon shuffling)
What is exon shuffling?
A process by which existing protein regions are already selected for due to their useful function, are mixed into novel combinations to create new proteins
What are tRNAs?
Small RNAs of a highly distinctive structure that brings amino acids to the ribosome
Has anticodon
How do the anticodon or tRNA and codon of mRNA pair?
Antiparallel
Anticodon- 3’ to 5’
Codon- 5’ to 3’
What is Francis Crick’s wobble hypothesis?
Proposes that the complete set of 61 sense codons can be read by fewer than 61 distinct tRNA because of the particular pairing properties of the bases of anticodons
What is aminoacylation?
The process of adding an amino acid to a tRNA
What are ribosomes?
Ribonucleoprotein particles that carry out proteins synthesis by translating mRNA into chains of amino acids
What is an aminoacyl-tRNA?
The finished product of aminoacylation or charging that is a tRNA linked to its correct amino acid
What is the A site, P site and E site of a ribosome?
A site- aminoacyl site where incoming aminoacyl-tRNA binds to the mRNA
P site- where the tRNA carrying the growing polypeptide chain is bound
E site- where an editing tRNA bonds as it leaves the ribosome
What are the three major stages of translation?
Initiation- components assemble on the start codon of mRNA
Elongation- assembled complex reads the string of codons while joining the specific amino acid
Termination- completed translation when complex disassembles after the last amino acid of the polypeptide has been added
What are the three final destination points where the final products of translation may be needed?
- The cytosol- simply released to cytoplasm
- The endomembrane system- cotranslational import(rough ER)
- Other membrane bound organelles- post-translational import
What are mutations?
Changes in the sequence of bases in the enticing material
What is base pair substitution mutations?
Change if one particular base to another in the genetic material
(Ends up changing one codon)
What is missense mutation?
Type of base pair Mutation that alters a codon to specify a different amino acid
What is a nonsense mutation?
Another type of base pair mutation that changes a sense (amino acid coding) codon to a nonsense (termination) codon in the m RNA
What are silent mutations?
When a single base pair is deleted or inserted in the coding region of a gene
