Lecture 3

Question 1

Define amino acid.

Answer 1

the building blocks of polypeptides

Question 2

How many animo acids are there?

Answer 2

20

Question 3

Define peptide bond.

Answer 3

between the carboxyl group of one animo acid and amino group the next

Question 4

What are the three parts of an animo acid?

Answer 4

-carboxyl group
-R-group
-amino group
(usually an additional hydrogen)

Question 5

Define polypeptide.

Answer 5

a string of amino acids joined by peptide bonds

Question 6

What is the START codon?

Answer 6

AUG–> Met–> M (read on mRNA 5’–>3’)

Question 7

What are the STOP codons?

Answer 7

1) UUA
2) UUG
3) UGA

Question 8

In which direction is an mRNA translated?

Answer 8

from the 5’–> 3’

Question 9

In which direction is a polypeptide synthesized?

Answer 9

from the amino (N-terminus) to the carboxyl (C-terminus)

Question 10

Define UTR.

Answer 10

UnTranslated Region; often two on each end that help initiate and terminate translation

Question 11

What are the 3 phases of translation?

Answer 11

1) Initiation (finds start codon, assembles ribosome complex)
2) Elongation (A–> P–> E)
3) Termination (@ stop codon- blank tRNA, release factors–> disassemble)

Question 12

Where does translation happen in a bacteria vs a eukaryote?

Answer 12

cytoplasm vs inside nucleus–> coupling of transcription and translation in prokaryotes

Question 13

Define polycistronic mRNA.

Answer 13

in bacteria, an mRNA that codes for multiple genes

Question 14

Define synonymous codons.

Answer 14

codons that specify for the same animo acid–> redundancy

Question 15

Define third-base wobble.

Answer 15

How the third codon is often “flexible” and if changed will still result in the same amino acid

Question 16

How do aminoacyl-tRNA synthesases “translate” the genetic code?

Answer 16

they provide tRNA with a charge in order to pair the correct amino acids (so the tRNA can read the mRNA aka “google translate”)

Question 17

What side of the tRNA attaches to an amino acid?

Answer 17

the CCA terminus at the 3’ end

Question 18

Define point mutation.

Answer 18

a change in one or more DNA base pairs

Question 19

Define silent mutation.

Answer 19

does not alter the phenotype (protein produced)

Question 20

Define missense mutation.

Answer 20

a change in a base that may or may not affect the protein (redundancy)

Question 21

Define nonsense mutation.

Answer 21

usually and early stop–> probably nonfunctional

Question 22

Define frameshift mutation.

Answer 22

insertion or deletion of a single base pair that changes the reading frame

*a +/- 3x codon can change the protein but it will not change the frame

Question 23

Define regulatory mutation.

Answer 23

a mutation that occurs in a noncoding region of the mRNA
–>can change #/production of mRNAs

Question 24

Define forward mutation.

Answer 24

coverts w+ to a mutant

Question 25

Define reverse mutation.

Answer 25

converts mutant to w+ or near w+

Question 26

What is the effect of redundancy in the genetic code?

Answer 26

emphasizes variability w/o selective pressure from evolution