Content from Exam 2

Question 1

What are the 3 parts of a nucleotide?

Answer 1

1.) sugar
2.) base
3.) 1-3 phosphate groups

Question 2

How do the three parts of a nucleotide change between DNA/RNA?

Answer 2

DNA has the sugar deoxyribose while RNA has the sugar ribose; DNA has Thymine and RNA has Uracil base

Question 3

What are the five universal bases?

Answer 3

1.) Cytosine
2.) Uracil
3.) Thymine
4.) Adenine
5.) Guanine

Question 4

What are purines and pyrimidines?

Answer 4

Purines have a double ring (A and G)

Pyrimidines have a single ring like a pie (C, U, T)

Question 5

Which bases only belong to DNA and RNA?

Answer 5

DNA has Thymine and RNA has Uracil only

Question 6

Similarities and Differences between DNA and RNA

Answer 6

Similarities: Both DNA and RNA are formed of monomers known as nucleotides; both of these molecules possess four nitrogenous bases, a phosphate group, and a sugar.

Differences: DNA contains Thymine while RNA contains Uracil; DNA is double stranded while RNA is usually single stranded (unless looped); DNA contains deoxyribose while RNA contains ribose as a sugar

Question 7

Know the different binding sites of RNA and how tRNA goes through them during translation and what is done at each site . . .

Answer 7

Large subunit tRNA binding sites (APE)
A-site: new aa-tRNA enters, tests codon/anticodon match
P-site: holds growing polypeptide, site of peptide bond synthesis
E-site: exit site for spent tRNA

Question 8

Transcription and Translation practice problems

Answer 8

AUG . . . is the start codon

Question 9

What is the central dogma of molecular biology?

Answer 9

DNA –> RNA –> Protein

Question 10

Know the different processes of the central dogma and where they occur . . .

Answer 10

DNA –> RNA (transcription is in the nucleus)
RNA –> protein (translation is in the cytoplasm)

Question 11

What are the three stages of transcription and what happens during each?

Answer 11

1.) Initiation: melting of the two strands of DNA and initiation of RNA synthesis
2.) Elongation: incorporation of complementary RNA nucleotides
3.) Termination: RNA synthesis ends and RNA transcript is released . . .

Question 12

What is/are the differences between the coding and template strand of DNA strands?

Answer 12

The coding strand is the strand of DNA that contains the sequence of the RNA that is produced (aka the non template strand; always written out as 5’ –> 3’)

The template strand is the strand that is actually copied during transcription

Question 13

What are the 3 RNA processing steps that are performed on a primary transcript before mRNA is exported from the nucleus in eukaryotes?

Answer 13

1.) 5’ cap added
- 7 methylguanosine, 5’ to 5’ triphosphate bride
2.) 3’ ploy A tail added
- Poly-A polymerase recognizes the polyadenylation signal sequence (AAUAAA) ; adds a long stretch of adenines to the 3’ end of the transcript
3.) RNA splicing
- process that removes introns from eukaryotic mRNAs and splices exons back together

Question 14

What are the 5 components of an amino acid?

Answer 14

1.) central carbon atom
2.) amino group
3.) carboxyl group
4.) hydrogen atom
5.) R group/side chain/functional group

Question 15

What are the 3 stages of translation and what happens during each?

Answer 15

1.) Initiation: mRNA binds to small subunit and large subunit binds
2.) Elongation: amino acids added in order encoded on mRNA (APE)
3.) Termination: protein synthesis ends and protein is released . . .

Question 16

What are the 4 levels of the structural organization of proteins and explain each?

Answer 16

1.) Primary- one fold
- active conformation: functional 3D structure of a protein
2.) Secondary- two fold
- local interactions: hydrogen bonds may form along the chain, creating alpha helix or beta sheet
3.) Tertiary- three fold
- final 3D shape of SINGLE protein chain
4.) Quaternary- four fold
- MULTIPLE polypeptide chains interacting to create protein complexes (ex. hemoglobin)

Question 17

What are the 2 different pathways for proteins and where does translation occur for each pathway?

Answer 17

1.) Cytoplasmic translation- aka non-secretory pathway
- cytosol
- mitochondria
- chloroplast
- peroxisome
- nucleus

2.) ER translation- secretory pathway
- plasma membrane
- lysosome

Question 18

What are the final destinations for the proteins for each pathway?

Answer 18

Cytoplasmic translation pathway keeps proteins in the cell while ER translation takes proteins out of the cell (secreted)

Question 19

What are the 2 basic parts of a virus and explain?

Answer 19

1.) Capsid- protein coating
2.) Genome- DNA or RNA encoding instructions to infect a host cell and make more viruses

Question 20

What is the lytic life cycle of a virus vs. the lysogenic life cycle?