Chapter 13

Question 1

What are auxotrophs?

Answer 1

Mutant strains that are unable to grow on Minimal mediums (MM)

Question 2

What did Tatum and Beadle discover with their experiments?

Answer 2

They showed the direct relationship between genes and enzymes which they put forest as the one gene-one (enzyme) hypothesis

Question 3

What are the two steps on he pathway from gene to polypeptide?

Answer 3

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

Question 4

What is the enzyme used in transcription?

Answer 4

RNA polymerase creates an RNA sequence complementary to the DNA sequence

Question 5

Where does transcription and translation take place in prokaryotes? Eukaryotes?

Answer 5

Eukaryotes- transcription- nucleus
Translation- cytoplasm before ribosome
Prokaryotes- transcription- cytoplasm
Translation- throughout the cell

Question 6

What is a codon?

Answer 6

The three letter word of the genetic code

Question 7

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?

Answer 7

Mother         ACTG
Template     TGAC
mRNA          ACUG
Use ACU for codon chart
Written 5’ to 3’ like mother strand

Question 8

What are the three steps of transcription?

Answer 8

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

Question 9

What is precursor mRNA?

Answer 9

A stop for the protein coding gene to make so it can be processed in the nucleus to produce translatable mRNA

Question 10

What are introns?

What are Exons?

Answer 10

Introns- Non-protein coding sequences that interrupt the protein coding sequence
Exons- the amino acid coding sequences that are retained in finished mRNAs

Question 11

What is mRNA splicing?

Answer 11

Occurs in the nucleus and removed introns from pre-mRNAs and joins Exons together
Used snRNA to do this

Question 12

What is alternative splicing?

Answer 12

A mechanism that greatly increases the number and variety of proteins encoded in the cell nucleus without increasing the size of the genome

Question 13

Why aren’t introns wasteful?

Answer 13

Introns may provide a selective advantage to organisms by increasing the coding capacity of existing genes (alternative splicing) and generating new proteins (exon shuffling)

Question 14

What is exon shuffling?

Answer 14

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

Question 15

What are tRNAs?

Answer 15

Small RNAs of a highly distinctive structure that brings amino acids to the ribosome
Has anticodon

Question 16

How do the anticodon or tRNA and codon of mRNA pair?

Answer 16

Antiparallel
Anticodon- 3’ to 5’
Codon- 5’ to 3’

Question 17

What is Francis Crick’s wobble hypothesis?

Answer 17

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

Question 18

What is aminoacylation?

Answer 18

The process of adding an amino acid to a tRNA

Question 19

What are ribosomes?

Answer 19

Ribonucleoprotein particles that carry out proteins synthesis by translating mRNA into chains of amino acids

Question 20

What is an aminoacyl-tRNA?

Answer 20

The finished product of aminoacylation or charging that is a tRNA linked to its correct amino acid

Question 21

What is the A site, P site and E site of a ribosome?

Answer 21

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

Question 22

What are the three major stages of translation?

Answer 22

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

Question 23

What are the three final destination points where the final products of translation may be needed?

Answer 23

1. The cytosol- simply released to cytoplasm
2. The endomembrane system- cotranslational import(rough ER)
3. Other membrane bound organelles- post-translational import

Question 24

What are mutations?

Answer 24

Changes in the sequence of bases in the enticing material

Question 25

What is base pair substitution mutations?

Answer 25

Change if one particular base to another in the genetic material
(Ends up changing one codon)

Question 26

What is missense mutation?

Answer 26

Type of base pair Mutation that alters a codon to specify a different amino acid

Question 27

What is a nonsense mutation?

Answer 27

Another type of base pair mutation that changes a sense (amino acid coding) codon to a nonsense (termination) codon in the m RNA

Question 28

What are silent mutations?

Answer 28

When a single base pair is deleted or inserted in the coding region of a gene