Chapter 17

Question 1

Gene expression

Answer 1

Process by which DNA directs protein synthesis

Question 2

How does RNA’s structure differ from DNA’s?

Answer 2

1. Sugar is ribose instead of deoxyribose
2. Single stranded
3. Uracil instead of Thymine
4. Nonhelical

Question 3

Why must only eukaryotic pre-mRNA go through RNA process?

Answer 3

It must pass through the nuclear envelope

Question 4

Primary trasnscript

Answer 4

Initial RNA transcript from a gene (pre-mRNA)

Question 5

What does RNA polymerase do?

Answer 5

• Pries DNA strands apart

- Hooks RNA nucleotides together

Question 6

What is the stretch of DNA that is transcribed?

Answer 6

Transcription unit

Question 7

Where does the RNA polymerase attach to to start initiation?

Answer 7

Promoter

Question 8

What is the TATA box?

Answer 8

Stretch of nucleotides in the promoter region

Question 9

What do transcription factors do?

Answer 9

Bind to promoter to signal RNA polymerase to come over to the promoter

Question 10

What signals RNA polymerase to bind to the promoter?

Answer 10

Transcription factors

Question 11

What does the transcription initiation complex consist of?

Answer 11

RNA polymerase II and transcription factors

Question 12

How does DNA reallign so quickly after RNA polymerase transcribes the template strand?

Answer 12

Previous RNA stretches peel away

Question 13

What happens in termination for eukaryotes?

Answer 13

RNA strand is cut from the polymerase that continues to transcribe past the DNA strand

Question 14

What three things occur in RNA processing?

Answer 14

• Introns are cut away
• 5’ cap is added
• Poly-A tail is added

Question 15

What are the functions of the 5’ cap and poly-A tail?

Answer 15

• Facilitate export of mRNA
• Protect mRNA from hydrolytic enzymes
• Help ribosomes attach to 5’ end

Question 16

Introns

Answer 16

Noncoding sequences between coding sequences

Question 17

What does RNA splicing do?

Answer 17

Removes introns and joins exons

Question 18

What do spliceosomes consist of?

Answer 18

small sibonucleicproteins (snRNP) and proteins

Question 19

Spliceosomes are a type of what?

Answer 19

Ribozyme

Question 20

Ribozyme

Answer 20

RNA molecule that functions as an enzyme

Question 21

What performs RNA splicing?

Answer 21

Spliceosomes

Question 22

What properties of RNA allow it to function as an enzyme?

Answer 22

1. Can form 3D shape from ability to pair with itself (specific structure)
2. Some bases in RNA contain functional groups
3. May hydrogen bond with other nucleic acid molecules (adding specificity)

Question 23

What is alternative RNA splicing?

Answer 23

Fact that some genes can form different polypeptide types depending on which parts are treated as exons during splicing

Question 24

Why can the number of different proteins an organism can produce be larger than its number of genes?

Answer 24

Alternative RNA splicing

Question 25

Domains

Answer 25

Discrete regions of proteins

Question 26

How can exon shuffling result in new proteins?

Answer 26

Introns provide more area for crossover of exons

Question 27

What are ribosomes made up of?

Answer 27

Proteins and ribosomal RNA (rRNA)

Question 28

What are the three binding sites of ribosomes?

Answer 28

E site, P site, A site

Question 29

What is the start codon that the small ribosomal subunit stops at?

Answer 29

AUG

Question 30

What is the initiator tRNA carrying to pair with codon AUG?

Answer 30

Methionine

Question 31

What brings the large subunit the complete the translation initiation complex?

Answer 31

Initiation factors

Question 32

What does the translation initiation complex consist of?

Answer 32

Both ribosomal subunits, mRNA, initial tRNA

Question 33

In translation, protein factors aid in each of the three processes. Which factors are used in each and how?

Answer 33

1. Initiation: initiation factors bring in large subunit 2. Elongation: elongation factors help to add amino acids in polypeptide chain 3. Termination: release factors hydrolyze polypeptide chain

Question 34

When does termination in translation occur?

Answer 34

When a stop codon in mRNA reaches the A site

Question 35

When stop codon in the mRNA reaches the A site what happens?

Answer 35

Release factor accepted at A site to hydrolyze bonds and split polypeptide

Question 36

Polyribosome

Answer 36

String of ribosomes translating 1 strand of mRNA at the same time

Question 37

How are polypeptides usually made functional after translation?

Answer 37

1. Polypeptide chains modified | 2. Completed proteins sent to specific sites

Question 38

WHat are some types of post-translational modifications?

Answer 38

- Enzymes cleave polypeptides | - Polypeptides come together

Question 39

What are the 2 types of ribosomes?

Answer 39

Free and bound

Question 40

Free ribosomes make proteins for/that ___, bound ribosomes make proteins for ____

Answer 40

- that function in cytosol | - for endomembrane system/for secretion

Question 41

What are polypeptides destined for ER/secretion marked by?

Answer 41

Signal peptide

Question 42

A signal peptide calls for what to bring the ribosome to the ER?

Answer 42

Signal-reception particle (SRP)

Question 43

Mutation

Answer 43

Change in genetic material of a cell or virus

Question 44

What are the 2 categories of point mutations

Answer 44

1. Substitutions | 2. Insertions/deletions

Question 45

What are the 3 types of point mutation substitituions?

Answer 45

1. Silent mutation creates the same amino acid 2. Missense mutation still codes for amino acid 3. Nonsense mutation changes amino acid codon to stop codon

Question 46

What are frameshift mutations?

Answer 46

Alteration of reading frame from insertion/deletion

Question 47

How can mutations arise?

Answer 47

- Spontaneously during DNA replication, recombination, or repair - From mutagens