Chapter 8 Part 1

Question 1

Describe Central Dogma

Answer 1

• refers to the flow of genetic information
• information is stored within DNA then converted to RNA and then used to produce proteins
• only one direction! Left to Right

Question 2

What is the one thing that does not follow Central Dogma?

Answer 2

Retro viruses like HIV
reverse transcription (goes from RNA to DNA)

Question 3

DNA to RNA is what?

Answer 3

transcription

Question 4

RNA to proteins is?

Answer 4

Translation

Question 5

Define Genetics

Answer 5

• the study of heredity - how traits are passed on
• genetics field was a field before DNA was discovered
• now it refers to the study of Genes and DNA
• how DNA stores info
• how the information stored within DNA is accessed
• how DNA is replicated

Question 6

Define Genes

Answer 6

segments of DNA that encode functional products, usually proteins

Question 7

Define Genome

Answer 7

all the genetic information in a cell and includes all chromosomes and any other forms of DNA (e.g. plasmids)

Question 8

Define Chromosomes

Answer 8

Large pieces of DNA that store essential genetic information
Humans: 23 pairs of linear chromosomes
bacteria: typically 1 circular chromosomes but there are exceptions

Question 9

Describe the structure of DNA

Answer 9

• a double helix
• backbone consisting of deoxyribose-phosphate
• 2 strands are held together by H-H bonds between complementary bases (AT & CG)
• Strands are anti-parallel
• order of the bases forms the genetic instructions of the organism

Question 10

In the diagram, what do the black dots represent?

Answer 10

Hydrogen bonds

Question 11

DNA strands are what?

Answer 11

Complementary meaning
one strand can act as a template for the production of a new strand

Question 12

What are the 2 strands called?

Answer 12

Original - conserved
New strand - semi-conservative replication

Question 13

What enzymes are in the DNA replication process?

Answer 13

1. Helicase
2. RNA primase
3. RNA polymerase

Question 14

Define Helicase

Answer 14

1. separates the DNA strands - unzips the DNA
2. Breaks the H-H bonds between base pairs (denatures the DNA)
3. reveals the bases so the strand can be used a template for the synthesize of a new strand
4. Forms a replication fork
5. as the helicase “unzips” the DNA, stabilizing proteins bind the single-stranded DNA

Question 15

How does the replication fork work?

Answer 15

one fork moves in a clockwise direction and the other fork moves counterclock wise

Question 16

Why are stabilizing proteins important?

Answer 16

it prevents the degradation of the unzipped DNA (the single strands once helicase unzips the DNA)

Question 17

Why is an RNA primer needed?

Answer 17

DNA polymerase can’t initiate DNA synthesis on its own

Question 18

What is the next step after helicase unzips the DNA?

Answer 18

RNA primase synthesizes a short RNA primer that is complementary to the sequence of the template strand

Question 19

Is RNA primer single stranded or double stranded?

Answer 19

Single stranded and it will eventually get replaced

Question 20

What happens after the RNA primer has been synthesized?

Answer 20

DNA polymerase adds nucleotides to the growing DNA strand

Question 21

How does DNA polymerase read?

Answer 21

Reads the template in 3’ to 5’ direction
Synthesizes DNA ONLY in the 5’ to 3’ direction

Question 22

What happens after DNA polymerase begins synthesizing DNA?

Answer 22

The RNA primer is removed by RNase

Question 23

Describe the leading strand

Answer 23

• DNA is synthesized continuously
• DNA polymerase is moving toward the helicase

Question 24

Describe the lagging strand

Answer 24

DNA is synthesized in short patches
DNA polymerase is moving away from the helicase

Question 25

What are the short patches called in the lagging strand?

Answer 25

Okazaki fragments

Question 26

How are the okazaki fragments sealed?

Answer 26

by ligase

Question 27

Translation is ___ while Transcription is on a ____

Answer 27

whole chromosome gene by gene basis

Question 28

Define transcription

Answer 28

RNA synthesis - now accessing the info stored within DNA and converting it to an intermediate form (mRNA) that will be used for protein production - Ribosomal RNA (rRNA) and transfer RNA (tRNA) are NOT used for protein production but instead are functional as RNAs

Question 29

What is the difference in structures between DNA and RNA?

Answer 29

DNA has no OH on the 2nd carbon ( 3 total OH) while RNA has 4 OH total

Question 30

rRna does what?

Answer 30

forms ribosomes

Question 31

tRNA does what?

Answer 31

delivers amino acids

Question 32

List the 3 stages of Transcription

Answer 32

1. Initiation 2. Elongation 3. Termination

Question 33

What does initiation do?

Answer 33

RNA polymerase binds to DNA at the promoter in transcription

Question 34

What is a promoter?

Answer 34

A DNA sequence that directs RNA polymerase to the start of the gene

Question 35

What does Elongation do?

Answer 35

RNA polymerase adds RNA nucleotides to the 3' end of the growing RNA strand

Question 36

What does Termination do?

Answer 36

Release of RNA polymerase and RNA from the DNA

Question 37

Many RNAS are produced from a single gene including simultaneously. this is called what?

Answer 37

Expression level - highly expressed means many RNA molecules are produced and many protein molecules as well - can change is expression level from high, low, intermediate, or no expression at all

Question 38

What is translation?

Answer 38

Protein synthesis - converting the message contained with mRNA into a chain of AA (polypeptides) - based on genetic code

Question 39

What is genetic code?

Answer 39

Includes Codons - 3 mRNA nucleotides that code for an amino acid 61 sense codons code for 20 AA 3 nonsense (stop) codons that terminate translation (UGA, UAG, UAA) 1 start codon (AUG)

Question 40

How are amino acids encoded?

Answer 40

by multiple codons that are degenerate/redundant

Question 41

What does AUG do?

Answer 41

a start codon that adds methyine

Question 42

What is translation performed by?

Answer 42

Ribosomes

Question 43

What are ribosomes?

Answer 43

complexes composed of both protein and rRNA

Question 44

How does translation work ? (in the ribosomes)

Answer 44

For each codon, there is a tRNA with a matching anitcodon that transports the appropriate AA for incorporation into the growing polypeptide chain

Question 45

How are amino acids joined?

Answer 45

peptide bonds

Question 46

Where does transcription and translation occur in bacteria?

Answer 46

in the cytoplasm (no nucleus)

Question 47

Why does transcription and translation happen at the same time in bacteria?

Answer 47

enables rapid production of proteins and responding quickly to the environmental stimuli

Question 48

Describe out the steps of translation in a ribosomal unit