Unit 6

Question 1

What does “antiparallel” mean?

Answer 1

The subunits/backbones run in opposite directions.

Question 2

What are the structural differences between DNA in prokaryotes and eukaryotes?

Answer 2

Prokaryotes → double-stranded circular DNA molecules with a small amount of proteins
Eukaryotes → linear DNA molecules with a large amount of proteins

Question 3

What are the base pairing rules and how does it differ between DNA and RNA?

Answer 3

Adenine and thymine
Guanine and cytosine
In RNA, thymine is replaced with uracil

Question 4

What is a helicase?

Answer 4

Enzymes that untwist the double helix at the replication forks

Question 5

What does DNA polymerase do?

Answer 5

Catalyze the synthesis of new DNA at the replication fork

Question 6

What does topoisomerase do?

Answer 6

Relieves the strain of twisting the double helix by breaking/swiveling/rejoining DNA strands

Question 7

What does ligase do?

Answer 7

The segments created in the lagging strand are joined together by DNA ligase

Question 8

What direction is DNA synthesized?

Answer 8

5’ to 3’ end. Nucleotides can only be added to the 3’ end of a strand.

Question 9

What is meant by DNA replication being semi-conservative?

Answer 9

Each daughter molecule will have one old strand and one new strand

Question 10

What is the leading strand?

Answer 10

DNA polymerase creates a leading strand when it continuously synthesizes toward the replication fork

Question 11

What is the lagging strand?

Answer 11

To create the lagging strand the DNA polymerase must work away from the replication fork. It is synthesized as a series of segments which are joined by ligase

Question 12

How is transcription different in prokaryotes and eukaryotes?

Answer 12

Prokaryotic transcription takes place in the cytoplasm while eukaryotic transcription takes place in the nucleus

Question 13

What does the RNA polymerase do?

Answer 13

Pries apart the DNA strands and joins together the RNA nucleotides

Question 14

How do new nucleotides match up to form the new mRNA strand?

Answer 14

Complementary base pairing

Question 15

What direction is the mRNA synthesized?

Answer 15

5’ to 3’ direction

Question 16

What is the difference between the template and coding strand of DNA?

Answer 16

Template strand is one of the strands of DNA that provides a template for the creation of the coding strand

Question 17

What kind of cell does RNA processing occur in?

Answer 17

Eukaryotic

Question 18

When does RNA processing take place?

Answer 18

After transcription and before translation

Question 19

Where does RNA processing take place?

Answer 19

The nucleus

Question 20

What is added to the ends of the mRNA molecule?

Answer 20

5’ end → modified nucleotide 5’ cap
3’ end → poly-A tail

Question 21

What is an intron?

Answer 21

Noncoding segments in a gene (introns are in the way)

Question 22

What is an exon?

Answer 22

Regions that are expressed, translated into amino acid sequences (exons are expressed)

Question 23

What do spliceosomes do?

Answer 23

Catalyze the splicing reactions

Question 24

What is alternative splicing?

Answer 24

Some genes can encode more than one kind of polypeptide depending on which segments are treated as exons during splicing

Question 25

How is translation different in prokaryotes and eukaryotes?

Answer 25

Prokaryotes → translation can begin before transcription is finished Eukaryotes → the nuclear envelope separates the two processes

Question 26

What is the difference between codons and anticodons?

Answer 26

Codons are on mRNA, anticodons are on tRNA They are complementary and bind to each other to create the amino acid chain

Question 27

What is the structure of tRNA?

Answer 27

- Consists of a single RNA strand that twists into a 3D shape due to hydrogen bonding - Roughly L shaped with 5’ and 3’ ends located near one end of the structure - 3’ end is an attachment site for an amino acid

Question 28

What does tRNA do?

Answer 28

Enables translation of a given mRNA codon into an amino acid

Question 29

Where is rRNA found?

Answer 29

Within the ribosomes

Question 30

What does rRNA do?

Answer 30

Helps form ribosomes

Question 31

What are the three phases of translation?

Answer 31

Initiation, elongation, termination

Question 32

What triggers initiation?

Answer 32

A start codon

Question 33

What is elongation?

Answer 33

The matching of mRNA codons and tRNA anticodons to bring in amino acids

Question 34

What triggers termination?

Answer 34

A stop codon

Question 35

What are regulatory sequences?

Answer 35

Sections of DNA that can help control transcription by interacting with regulatory proteins

Question 36

What are epigenetic changes?

Answer 36

Reversible modifications of DNA or histones

Question 37

What is methylation?

Answer 37

The addition of methyl groups so that DNA is more tightly packed around the histones and can't be transcribed

Question 38

What is acetylation?

Answer 38

The addition of acetyl groups to open up the chromatin structure, promoting the initiation of transcription

Question 39

Are epigenetic changes heritable?

Answer 39

For epigenetic changes to be heritable they must occur in the organism's gamete

Question 40

What are promoters?

Answer 40

Sections of DNA found before the gene where RNA polymerase and transcription factors bind to start transcription

Question 41

What are negative regulatory molecules?

Answer 41

They bind to DNA to block transcription and inhibit gene expression

Question 42

What do small RNA molecules do

Answer 42

Regulate gene expression by binding to mRNA so that it cannot be translated by ribosomes or is marked to be broken down

Question 43

What are operons?

Answer 43

Groups of related genes transcribed together into a single mRNA, typically in prokaryotes

Question 44

What do eukaryotes use for gene regulation?

Answer 44

Specific transcription factors, activators, enhancers, mediator proteins

Question 45

What does electrophoresis do

Answer 45

Separates molecules (alleles) according to size

Question 46

What does PCR do?

Answer 46

Replicates DNA fragments

Question 47

What does bacterial transformation do?

Answer 47

Inserts new DNA into bacterial cells

Question 48

What does DNA sequencing do

Answer 48

Determines the order of nucleotides in a strand of DNA

Question 49

What are the types of mutations?

Answer 49

Substitutions, insertions or deletions (frame shift mutations) Silent (no effect, codes for the same amino acid), missense (codes for different amino acid), nonsense (changes an amino acid into a stop codon)

Question 50

How are genes regulated in prokaryotes?

Answer 50

The operon can be switched on or off by a repressor A corepressor binds to the repressor to switch off an operon An inducer binds to the repressor to switch on an operon