Chapter 13

Question 1

What are protein encoding or structural genes

Answer 1

Genes that encode polypeptides
These are transcribed into mRNA

Question 2

What is the main function of genetic material

Answer 2

Encode the production of cellular proteins

Question 3

What is the one gene one enzyme hypothesis

Answer 3

A single gene is controlled by the synthesis of a single enzyme

Question 4

How can one gene encode multiple polypeptides

Answer 4

Alternative splicing

Question 5

What does translation rely on?

Answer 5

The genetic code which is a translator of info on mRNA to determine which amino acid is next

Question 6

How is genetic information coded

Answer 6

Within mRNA in groups of three nucleotides (codons)

Question 7

What is the start codon

Answer 7

AUG or methionine

Question 8

What are the stop codons

Answer 8

UAA, UAG, and UGA

Question 9

What does it mean that the genetic code is degenerative

Answer 9

Some amino acids are coded by more than one codon
Always occurs at the codons third position

Question 10

What does it mean that the genetic code is universal

Answer 10

All organisms for the most part have the same amino acids and share the same code

Question 11

Which direction does polypeptide synthesis work

Answer 11

5 to 3 prime

Question 12

What happens during each cycle of elongation

Answer 12

A peptide bond is formed between the carboxyl group of the last amino acid in the polypeptide chain and the amino group in the amino acid group

Question 13

What are the two ends of a polypeptide chain

Answer 13

N terminus and C terminus
Amino group and carboxyl group

Question 14

What holds polypeptides together

Answer 14

Peptide bonds

Question 15

What is the primary structure of a protein

Answer 15

Amino acid sequence
Can be folded further with the assistance of chaperones

Question 16

What are protein secondary structures

Answer 16

The primary structures form regular repeating shapes
Helix and sheets
Stabilized by hydrogen bonds located in the backbone

Question 17

What is the tertiary structure of a protein

Answer 17

Final confirmation of proteins that are composed of a single polypeptide
Structure is determined by hydrophobic and ionic interactions but also hydrogen bonds

Question 18

What is the quaternary structure of a protein

Answer 18

Various polypeptides associated with one another to make a functional protein

Question 19

What happens during mRNA - tRNA recognition

Answer 19

The anticodon in tRNA binds to a complementary codon in mRNA

Question 20

How are tRNAs named

Answer 20

According to the amino acid they have

Question 21

What orientation is the anticodon

Answer 21

Anti parallel to the codon

Question 22

What is the secondary structure of tRNA

Answer 22

A cloverleaf pattern
Three stem loop structures
A few variable sites and an acceptor stem with a three prime single strand region (CCA)

Question 23

In regard to nucleotides which ones do tRNA have

Answer 23

U,G,A,C and modified ones too (a lot of modified)

Question 24

What are aminoacyl -tRNA synthetases

Answer 24

Enzymes that attach amino acids to tRNAs
Catalyze two step reactions that involve an amino acid, tRNA, and ATP

Question 25

What are the sequences throughout the tRNA used as

Answer 25

Recognition sites

Question 26

What are the aminoacyl tRNa synthetases responsible for

Answer 26

The second genetic code which means the selection of amino acids must be highly accurate or the polypeptide will be nonfunctional

Question 27

What can modified bases affect

Answer 27

Translation rates Recognition by aminoacyl tRNA synthetases Codon anticodon recognition

Question 28

What is the wobble hypothesis

Answer 28

In the Codon anticodon recognition process the first two positions pair strictly using the AU/GC rule

Question 29

What are isoacceptor tRNAs

Answer 29

tRNAs that are able to recognize the same codon

Question 30

Where does translation occur

Answer 30

On the surface of a ribosome

Question 31

How many types of ribosomes do bacterial and eukaryotic cells have

Answer 31

Bacteria has one in the cytoplasm Eukaryotic cells have two, one in the mitochondria and one in the chloroplast

Question 32

What are ribosomes composed of

Answer 32

Large and small subunits Each subunit is formed from the assembly of proteins and rRNA

Question 33

Which subunit attaches the mRNA

Answer 33

Small

Question 34

What are the small units sedimentation coefficient

Answer 34

30s, 50s, 70s

Question 35

What are the eukaryotic sedimentation coefficients

Answer 35

40s, 60s, 80s

Question 36

During bacterial translation where does the mRNA lie

Answer 36

On the surface of the 30s subunit

Question 37

Where does a a polypeptide exit

Answer 37

Through a channel within the 50s subunit

Question 38

What are the three sites within the ribosome

Answer 38

Peptidyl site where the growing polypeptide chain is Aminoacyl site where the codon is opened and a new tRNA is added Exit site where the tRNA leaves

Question 39

What is the binding of the mRNA to the 30s subunit facilitated by

Answer 39

The ribosomal binding site

Question 40

What makes the initiation complex

Answer 40

The mRNA, initiator tRNA and ribosomal subunits This process takes three initiation factors

Question 41

The initiator tRNA recognizes the start codon in mRNA why is this significant

Answer 41

It carries a methionine that has been covalently modified to N-formylmethionine

Question 42

How is eukaryotic initiation different than bacterial

Answer 42

The initiator tRNA carries a methionine instead

Question 43

How does initiation start

Answer 43

The ribosome scans until it reads the first AUG after the 5’ cap The entire assembly moves along the mRNA

Question 44

What is elongation

Answer 44

Amino acids are added to the polypeptide chain Faster in bacteria than eukaryotes

Question 45

What happens after peptide bond formation

Answer 45

tRNAs at the P and A sites move down one into the E and P site

Question 46

How does termination occur

Answer 46

The stop codon is reached in the mRNA Stop codons are also considered to be nonsense codons

Question 47

How are nonsense codons recognized

Answer 47

By release factors which hydrolyze the last covalent bond of the last amino acid to tRNA

Question 48

How many release factors do bacteria and eukaryotes have

Answer 48

Bacteria have 3 Eukaryotes have 2

Question 49

Why is bacteria lacking a nucleus important

Answer 49

Both transcription and translation occur in the cytoplasm

Question 50

True or false: transcription ends then translation begins

Answer 50

False, translation starts before the end of transcription (known as coupling)

Question 51

As soon as an mRNA strand is long enough what can happen

Answer 51

A ribosomes will attach to the five prime end and translation can start