Cell Bio: Chapter 5, 7, 8

Question 1

What is the central dogma?

Answer 1

DNA is made into RNA by transcription; RNA is made into a protein by translation.

Question 2

What is transcription?

Answer 2

The process of synthesizing RNA from the template DNA using RNA polymerase.

Question 3

What are the three key differences in RNA when compared to DNA?

Answer 3

RNA uses ribose as a sugar, the base uracil instead of thymine, and it is generally single-stranded and more reactive than DNA.

Question 4

Which directions are DNA read and synthesized?

Answer 4

DNA is read 3’-5’ by the RNA polymerase to synthesize complementary RNA in the 5’-3’ direction.

Question 5

True/False: The coding strand of DNA has the exact same sequence as the RNA.

Answer 5

False; it does have the same sequence as the coding DNA, but with uracil instead of thymine.

Question 6

Where does eukaryotic transcription occur?

Answer 6

The nucleus. Prokaryotic transcription occurs in the cytosol.

Question 7

How many RNA polymerases do eukaryotes have?

Answer 7

3; RNA polymerase 2 synthesizes mRNA.

Question 8

What do eukaryotes use for signaling transcription?

Answer 8

Transcription factors; prokaryotes use the sigma factor.

Question 9

True/False: Eukaryotes process mRNA before translation.

Answer 9

True; all three steps must be completed before mRNA can leave the nucleus.

Question 10

What is the function of the 5’ cap and 3’ poly-A tail?

Answer 10

Maintaining the structure and stability of mRNA.

Question 11

What is the order that 5’ caps, 3’ poly-A tails, and introns are processed?

Answer 11

3’ caps are added to the mRNA.
Introns are spliced out.
The 3’ poly-A tail is added to the mRNA.

Question 12

How is translation completed in prokaryotes and eukaryotes?

Answer 12

With ribosomes; they start at AUG (methionine).

Question 13

Can one codon code for only one amino acid?

Answer 13

Yes, but there is more than one codon for one amino acid.

Question 14

How many stop codons exist?

Answer 14

3. None of these code for an amino acid.

Question 15

What controls eukaryotic transcription?

Answer 15

Activator and repressor proteins that bind to the DNA.

Question 16

Wht do activator proteins do?

Answer 16

Bind to enhancers in the DNA to turn on transcription by helping to assemble the transcription factors (or changing chromatin packing).

Question 17

What do repressor proteins do?

Answer 17

Bind to silencers in the DNA to turn off transcription by blocking the assembly of transcription factors (or condense chromatin packing).

Question 18

What is combinatorial control?

Answer 18

Whether a gene is on or off, and the degree of activation caused by activators or repressors.

Question 19

How are chromosomes made into chromatin?

Answer 19

When proteins bind to DNA to condense them.

Question 20

What is heterochromatin?

Answer 20

Tightly packed chromatin.

Question 21

What is euchromatin?

Answer 21

Less tightly packed chromatin.

Question 22

How many histone proteins form the disk-shaped complex?

Answer 22

8.

Question 23

How many basepairs of DNA wrap twice around each histone complex?

Answer 23

147 basepairs; this forms the ‘beads on a string’ form of chromatin (core nucleosome).

Question 24

How many basepairs of DNA form the linker between core nucleosomes?

Answer 24

50.

Question 25

What is the H3 histone protein used for?

Answer 25

Regulating chromatin packing; it has a tail extending from the core nucleosome.

Question 26

What do chromatin remodeling complexes use ATP for?

Answer 26

To slide nucleosomes closer together or farther apart depending on the complex.

Question 27

What effect does chromatin remodeling complexes using ATP have on transcription?

Answer 27

It increases or decreases transcription, and the access of transcription factors and RNA polymerases to the DNA

Question 28

How can the N terminal tails of histones be modified?

Answer 28

With covalent attachment of different chemical groups like acetyl, methyl and phosphate groups.

Question 29

What can adding chemical groups to N terminal tails do?

Answer 29

Alter how tightly or loosely they condense the chromosomes (increases or decreases gene expression).

Question 30

What happens if other proteins bind to the modified N terminal tails?

Answer 30

It also can increase or decrease condensation of the chromosomes.

Question 31

What are the two ways transcription is increased by altering chromosome structure?

Answer 31

Histone acetyltransferases add acetyl groups to the N terminal tail of histone H3. Chromatin remodeling complexes use ATP to move nucleosomes farther apart.

Question 32

What are the four different ways transcription can be blocked by a repressor?

Answer 32

They can interfere with activator binding. The can mask the activator. They can recruit chromatin remodeling complexes to tighten the nucleosomes. They can recruit histone deacetylases and other enzymes to remove modifications from chromatin.

Question 33

How is cell differentiation controlled?

Answer 33

By the combinations of transcription factors that are or not expressed in any given cell type.

Question 34

What are post-translational modifications used for?

Answer 34

Changing protein activity after protein synthesis is complete.