DNA & RNA

Question 1

DNA and RNA are ____________.

Answer 1

Polynucleotides

Question 2

What are the 3 parts of a nucleotide?

Answer 2

• 5 carbon sugar (Pentose)
• Nitrogenous base (ATCG)
• One or more phosphate groups

Question 3

What are pyrimidines?

Answer 3

C, T, U

• has one 6 membered ring

Question 4

What are Purines?

Answer 4

A, G

• has a 6 membered ring fused to a 5 membered ring

Question 5

What is the sugar for DNA?

What is the sugar for RNA?

What are their differences?

Answer 5

Deoxyribose

Ribose

Deoxyribose lacks an oxygen atom

Question 6

In Animals, some DNA is found in the __________.

In Plants, some DNA is found in the __________.

Answer 6

Mitochondria

Chloroplasts

Question 7

What are the 3 phases of Translation? Describe what happens in each one

Answer 7

Initiation
- initiator tRNA carrying the first amino acid binds to the mRNA start codon. The small and large units of the ribosome come together and translation begins.

Elongation
- Elongation Factor (EF) proteins recruit charged tRNAs to form more amino acids

Termination
- Release Factors (RF) bind to a stop codon in the A site and releases the polypeptides

Question 8

A-T base pair has ___ hydrogen bonds

G-C bade pair has ___ hydrogen bonds

Answer 8

2

3

Question 9

What is polycistronic mRNA?

Answer 9

mRNA that contains 2 or more genes

Question 10

Why is the genetic code in triplets instead of doublets?

Answer 10

If the genetic code was in doublets, it would only produce 16(4^2) combinations of codons, which is not enough to specify 20 amino acids.

Question 11

What are synonymous codons?

Answer 11

Codons that specify the same amino acid

Question 12

Define Third-base Wobble

Answer 12

The flexibility of nucleotide pairing in the 3rd position of the codon and its anticodon

Eg,

UCC, UCU, UCA, UCG all code for Ser
- the 3rd base doesn’t matter

Question 13

For translation, tRNAs need to be charged. What are they charged by? What does this do?

Answer 13

They are charged by Aminoacyl-tRNA Synthetases

• these contact multiple points on tRNA to identify the proper tRNA to charge with an amino acid

Question 14

What are the differences in transcription for prokaryotes and eukaryotes?

Answer 14

• Eukaryotes have 3 RNA Polymerases, prokaryotes have 1
• Eukaryotes form an initiation complex with transcription factors, prokaryotes don’t
• RNA is transcribed first in the nucleus and second in the cytoplasm is eukaryotes, in prokaryotes they are done simultaneously
• Eukaryotes have 5’ capping and polyadenylation, prokaryotes don’t

Question 15

Define monocystronic

Answer 15

One gene in one mRNA

Question 16

Define polycystronic

Answer 16

Many genes on one mRNA

Question 17

What is alternative pre-mRNA splicing?

Answer 17

When different mRNAs can be produced from the same gene, using different promoters or polyadenylation sites or by removal of different exons

Question 18

What are introns?

Answer 18

Segments of DNA that do NOT code for proteins and are spliced out

Question 19

What are exons?

Answer 19

Segments of DNA that DO code for proteins and are joined together after splicing

Question 20

What are alternative promoters?

Answer 20

Promoters that can initiate transcription at distinct start points in different cell types

Question 21

What is alternative polyadenylation?

Answer 21

When a gene has different polyadenylation signals (at the poly-A tail) to encode multiple mRNA transcripts

Question 22

What are the 4 components of PCR (Polymerase Chain Reaction)?

Answer 22

• Double stranded DNA
• 4 DNA Nucleotides
• Heat stable DNA Polymerase
• 2 different DNA primers

Question 23

How many cycles is PCR run through?

Answer 23

30-35

Question 24

Each PCR cycle _________ the number of copies of the target sequence

Answer 24

Doubles

Question 25

What DNA polymerase is used in PCR?

Answer 25

Taq polymerase (it is heat stable)

Question 26

What is autosomal inheritance?

Answer 26

Hereditary transmission of genes carried on autosomes | Autosomes are non sex chromosomes

Question 27

Dideoxynucleotides are used for ___________ because they are _________.

Answer 27

Sequencing, chain terminating

Question 28

What is true reversion?

Answer 28

Reverting the mutation at the same site or within the same codon

Question 29

What is intragenic reversion?

Answer 29

Reverting the mutation at a different part of the gene

Question 30

What is second-site reversion?

Answer 30

Reversion at a different site to generate original function Suppressor mutations because they suppress mutated phenotype

Question 31

What is euchromatin?

Answer 31

Chromosome regions containing chromatid that is not densely compacted. The most expressed genes are located here (These genes are more actively transcribed)

Question 32

What is heterochromatin?

Answer 32

Chromosome regions where chromatin is tightly condensed | Fewer expresses genes here

Question 33

Which DNA is more likely to hold repetitive DNA, euchromatic or heterochromatic?

Answer 33

Heterochromatic

Question 34

What is a nucleosome core particle?

Answer 34

A heterooctameric protein complex that contains two molecules each of the four histones H2A, H2B, H3 and H4.

Question 35

What are “beads on a string”?

Answer 35

Chromatin that consists of nucleosomes and linker DNA

Question 36

What’s the diameter of a nucleosome?

Answer 36

10 nm

Question 37

After chromatin has been condensed from a 10nm-fiber, what state is it next condensed into?

Answer 37

30nm-fiber (solenoid structure)

Question 38

Which RNA polymerase makes mRNAs in Eukaryotes?

Answer 38

RNA polymerase II

Question 39

Scaffold proteins condense chromatin into 300nm-fiber and it forms into _________ in metaphase.

Answer 39

Sister chromatids