Nucleotides & Nucleic Acids

Question 1

What 3 things compose Nucleotides?

Answer 1

• Phosphate group
• Nitrogenous base
• Pentose sugar

Question 2

How many polynucleotide chains are in DNA?

Answer 2

Two

Question 3

Both strands in DNA consist of what structure?

Answer 3

A Sugar-Phosphate backbone

Question 4

What type of bonds join nucleotides?

Answer 4

Phosphodiester bonds

Question 5

What bond forms to join two complementary bases?

Answer 5

Hydrogen bonds

Question 6

What must happen to the DNA in the nucleus?

Answer 6

It must be packaged

Question 7

DNA winds around what, allowing it to become condensed?

Answer 7

Histone Proteins

Question 8

How is DNA found in Mitochondria?

Answer 8

In naked loops.

Question 9

Give two functions of DNA

Answer 9

• Acts as information store

- Needs to be replicable

Question 10

Why are Hydrogen bonds used to hold the two strands together in DNA?

Answer 10

• Strong enough to maintain DNA structure

- Weak enough to overcome during DNA replication

Question 11

In what phase of the cell cycle does DNA replication occur?

Answer 11

The ‘S’ phase

Question 12

Which enzyme unwinds/unzips the DNA strands?

Answer 12

DNA Helicase

Question 13

Which enzyme bind nucleotides together with covalent bonds?

Answer 13

DNA Polymerase

Question 14

Outline the process of DNA replication

Answer 14

• DNA helicase breaks hydrogen bond between base pairs, and unzips the helix
• Exposed bases act as a template for new strand
• Free nucleotides move towards exposed bases
• DNA polymerase binds nucleotides together with covalent bonds.
• Forming sug/phos backbone
• This process happens to both strands

Question 15

What is the name given to a sequence of 3 bases codes for one amino acids?

Answer 15

A triplet code

Question 16

What is Transcription?

Answer 16

The process of copying RNA from DNA

Question 17

Outline the process of Transcription

Answer 17

1. DNA strand unzips from DNA Helicase
2. RNA nucleotide bases pair up with exposed DNA bases
3. RNA Synthase forms covalent bonds between the nucleotide bases
4. RNA is SINGLE stranded
5. mRNA strand formed and breaks away from DNA
6. DNA zips itself up due to natural formation of ‘H’ bonds
7. mRNA now free to leave nucleus through pores.

Question 18

Outline the process of Translation

Answer 18

1. RNA leaves nucleus and
   attaches to ribosome
2. tRNA carries
   corresponding amino acid to each on the mRNA
3. Anti-codon is a triplet of bases that from part of a tRNA molecule + ensure correct amino acid is joined onto polypeptide chain
4. Its active, so needs ATP
5. Amino acid transported by tRNA attaches to ribo.
6. Adjacent amino acids join by peptide bonds creating polypeptide chain
7. Process continues until ribosome reaches stop codon on the mRNA

(Polypeptide chain breaks loose from the ribosome)

Question 19

What is Translation?

Answer 19

The second step of protein synthesis — the process of creating polypeptides based off mRNA