2.1.3 Nucleotides

Question 1

DNA and RNA are both examples of…

Answer 1

Nucleic acids

Question 2

Name the monomer that makes up nucleic acids.

Answer 2

Nucleotides

Question 3

Name the three parts of a nucleotide.

Answer 3

• Phosphate group
• Pentose sugar
• Nitrogenous base

Question 4

Which type of pentose sugar is found in RNA?

Answer 4

Ribose

Question 5

What is the difference between ribose and deoxyribose?

Answer 5

Ribose has an extra oxygen atom

Question 6

Which type of pentose sugar is found in DNA?

Answer 6

Deoxyribose

Question 7

Name the four nitrogenous bases in DNA.

Answer 7

Adenine, cytosine, guanine, thymine

Question 8

Name the four nitrogenous bases in RNA.

Answer 8

Adenine, cytosine, guanine, uracil

Question 9

Does this structure show a purine or a pyrimidine?

Answer 9

Purine

Question 10

Does this structure show a purine or a pyrimidine?

Answer 10

Pyrimidine

Question 11

Which bases are purines?

Answer 11

Adenine and guanine

Question 12

Which bases are pyrimidines?

Answer 12

Cytosine, thymine and uracil

Question 13

Which type of bond links together two or more nucleotides in a chain?

Answer 13

Phosphodiester bond

Question 14

Which type of reaction occurs when a phosphodiester bond is formed?

Answer 14

Condensation reaction

Question 15

How many phosphate groups are in ATP?

Answer 15

Three

Question 16

Which type of pentose sugar is found in ATP and ADP?

Answer 16

Ribose

Question 17

Which type of nitrogenous base is found in ATP and ADP?

Answer 17

Adenine (a purine)

Question 18

How many phosphate groups are in ADP?

Answer 18

Two

Question 19

What is the main difference between the structure of ATP and ADP?

Answer 19

• ATP contains three phosphate groups
• ADP contains two phosphate groups

Question 20

Describe how ADP is formed.

Answer 20

• A high energy phosphate bond breaks in ATP
• 7.6 kCal is released
• ATP is converted into ADP

Question 21

In a DNA strand, is the 5’ (prime) end the phosphate end or the deoxyribose end?

Answer 21

Phosphate end

Question 22

Which type of bond occurs between base pairs in DNA?

Answer 22

Hydrogen bonds

Question 23

Describe the shape of a DNA molecule.

Answer 23

Double helix

Question 24

Which base forms a complementary base pair with adenine?

Answer 24

Thymine in DNA

Uracil in RNA

Question 25

Which base forms a complementary base pair with cytosine?

Answer 25

Guanine

Question 26

Name the enzyme that 'unzips' the DNA double helix during DNA replication.

Answer 26

DNA helicase

Question 27

How does DNA helicase 'unzip' the DNA double helix during DNA replication?

Answer 27

Breaking hydrogen bonds between the base pairs

Question 28

Name the enzyme that catalyses condensation reactions between adjacent nucleotides during DNA replication.

Answer 28

DNA polymerase

Question 29

In which direction can nucleotides be synthesised?

Answer 29

5' to 3' (5 prime to 3 prime) (From the phosphate end to the deoxyribose end)

Question 30

Why is DNA replication described as semi-conservative?

Answer 30

The new DNA molecule is made up of: - One strand that is conserved from the original DNA molecule - One strand that is formed from free nucleotides

Question 31

Why is the genetic code described as being universal?

Answer 31

In almost all living organisms, the same triplet code codes for the same amino acid

Question 32

The base sequence is read in groups of...

Answer 32

3

Question 33

How many different DNA triplets (or RNA codons) are there in the genetic code?

Answer 33

64

Question 34

The genetic code is described as 'degenerate'. Why is this?

Answer 34

Most amino acids are coded for by more than one codon (triplet code)

Question 35

A base deletion is an example of which type of mutation?

Answer 35

A frameshift mutation

Question 36

Name the molecule that is made during transcription.

Answer 36

mRNA

Question 37

Why doesn't DNA travel from the nucleus to the ribosome for protein synthesis?

Answer 37

DNA is too large to leave the nucleus

Question 38

What happens during transcription?

Answer 38

DNA is transcribed (copied) and a molecule of mRNA is produced

Question 39

Where does transcription occur?

Answer 39

In the nucleus

Question 40

Describe the process of transcription in protein synthesis.

Answer 40

- Free activated RNA nucleotides pair up via hydrogen bonds with their complementary base pairs on the exposed DNA strand - Sugar phosphate groups are bonded together with phosphodiester bonds by the enzyme RNA polymerase - When the gene has been transcribed, hydrogen bonds between DNA and RNA break - mRNA leaves the nucleus through pores in the nuclear envelope

Question 41

What happens during translation?

Answer 41

mRNA is translated and an amino acid sequence is produced.

Question 42

What is tRNA?

Answer 42

Free nucleotides in the cytoplasm that contain a region where an amino acid can attach

Question 43

What is an anticodon on tRNA?

Answer 43

A triplet of unpaired bases

Question 44

Describe the process of translation in protein synthesis.

Answer 44

1. mRNA attaches to the ribosomes 2. Free tRNA molecules bind with specific amino acids 3. Anticodons (on the tRNA) bind with complementary codons (on the mRNA) 4. A peptide bond is formed between the amino acids 5. This continues until a stop codon is reached

Question 45

Which type of bond occurs between amino acids in a polypeptide chain?

Answer 45

Peptide bond

Question 46

Which amino acid is always carried by the first tRNA?

Answer 46

Methionine

Question 47

What is the triplet code of the 'start codon'?

Answer 47

AUG