Question

RNA differs from DNA in that it:

all of the above

contains ribose sugar

contains uracil

is usually found as a single-stranded molecule in cells

Question 21 pts

The correct order of steps in a PCR cycle is:

Extension, denaturation, annealing

Annealing, extension, denaturation

Annealing, denaturation, extension

Denaturation, annealing, extension

The goal of the polymerase chain reaction (PCR) is to:

Amplify a small amount of DNA sequence

Cleave DNA molecules

Digest bacterial plasmids

Sequence DNA

Which of the following is incorrect?

Adenine pairs with Thymine

Two strands of DNA double helix are held together by covalent bonds

Cytosine pairs with Guanine

Nucleotides in DNA consist of deoxyribose sugar, phosphate group and a nitrogenous base

What are the 3 main components of a DNA nucleotide?

A phosphate group, a nitrogenous base, a ribose

A phosphate group, a nitrogenous base, a deoxyribose

An alcohol functional group, a nitrogenous base, a ribose

An alcohol functional group, a nitrogenous base, a deoxyribose

At which temperature does a DNA double helix denature?

15

95

85

75

Cytosines and guanines are paired by 2 hydrogen bonds, while adenines and thymines are paired by 3 hydrogen bonds.

True

False

Hydrogen bonds are weaker than covalent bonds. During PCR, hydrogen bonds are broken during the denaturation step.

True

False

Answer 1

1. All of above

Feature	RNA	DNA
Sugar	5 carbon ribose sugar	5 carbon deoxyribose sugar
Purines	adenine, guanine	adenine, guanine
Pyrimidines	cytosine, uracil	cytosine, thymine
Strand	mainly single stranded	mainly double stranded

2. Denaturation, annealing, extension

PCR, polymerase chain reaction, is a chain of reactions catalysed by DNA polymerase enzyme. It includes 3 steps -

Denaturation - in this step double stranded DNA gets separated into two strands so, that a primer can join two those strands. It occurs at 94-95℃.

Annealing - in this step 18-20 nucleotides long primer binds to end of 3' DNA of both the strands. It occurs at 50-55℃.

Extension - in this step DNA polymerase 3 enzyme adds nucleotides to the primers, to elongate the DNA. The occurs at 72℃.

3. Amplify........

The third step of polymerase Chain Reaction extension is also known as amplification and elongation because in this step the gene of interest is being elongated. Apart from its elongation, its copy number also increases as well.

PCR is a very important technique used in Recombinant DNA technology because it amplifies the gene of our interest.

3' DSDNA 5 ' 3' |denaturation 3' SSDNA 5* 3' in

annealing of primers 3' 5* 3' 5' 5' 3' 33 elongation 3' 5' 5' 3' 5'* 3' 3' 5' in

4. Two strands of ..........

Adenine pairs with thymine with 2 hydrogen bonds, whereas cytosine pairs with guanine with 3 hydrogen bonds. So, the two strands of DNA are attached to each other by hydrogen bond. Phosphodiester bond, a covalent bond, is present between adjacent nucleotides of the same strand.

Nitrogenous base and sugar attach to form a nucleoside and when phosphate is added it becomes a nucleotide.

5. Phosphate, nitrogenous base, deoxyribose

Explained in question 1

6. 95℃

It is fact to remember. Denaturation of DNA occurs because weak hydrogen bonds present between two complementary strands of DNA, break and therefore the strands uncoil and denature. However, when the temperature is decreased, strands coil again, called renaturation.

7. False

Explained in question 4

8. True

Explained in question 1 and 2

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