Nucleotides and nucleic acids

Question 1

Name the monomer that makes up nucleic acids

Answer 1

Nucleotides

Question 2

What is a nucleotide?

Answer 2

Phosphate group attached to pentose sugar attached to nitrogenous base

Question 3

State the difference between a purine and pyrimidine. Give examples for each.

Answer 3

-Pyrimidine: Single C ring (T & C)
-Purine: Double C ring (A & G)

Question 4

Why is having complementary DNA base pairs in semi-conservative replication important?

Answer 4

-Create identical copies of DNA
-Reduces copying errors which would result in mutations

Question 5

Name the 2 enzymes involved in semi-conservative replication

Answer 5

-DNA helicase
-DNA polymerase

Question 6

Describe the process of semi-conservative replication of DNA

Answer 6

-2 types: continuous & discontinous
CONTINUOUS
-Leading strand replicated in 5’->3’ direc TOWARDS replication fork
-DNA helicase breaks H bonds between complementary base pairs
-Unwinds double helix structure -> 2 strands separate
-DNA polymerase joins free, activated nucleotides w/ phophodiester bonds (via condensation REACTION)
DISCONTINUOUS
-Lagging strand replicated 5’->3’ AWAY from replication fork
-Creates DNA Okazaki fragments
-Fragments joined by DNA ligase

Question 7

State the function of DNA polymerase

Answer 7

Join together adjacent nucleotides
(To remember: polymerase creates polymer)

Question 8

What is semi-conservative replication?

Answer 8

Daughter DNA has 1 original DNA strand & 1 newly synthesised DNA strand

Question 9

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

Answer 9

S phase in interphase

Question 10

State 4 properties of the genetic code

Answer 10

Triplet
-3 bases (codon) code for 1 AA
Degenerate
-Some AA coded for by >1 codon
Universal
-Same triplet codes for same AA in almost all living organisms
Non-overlapping
-Each base = only part of 1 triplet

Question 11

Name the start codon and its code

Answer 11

Methionine (AUG)

Question 12

Describe the process of translation

Answer 12

-mRNA binds to ribosome at start codon
-tRNA w/ complementary anticodon forms H bonds w/ mRNA (arries AA methionine)
-Ribosome moves along mRNA bringing tRNA w/ complementary anticodons, putting AA in correct sequence
-Peptide bonds form between AA (catalysed by ribosomal enzyme) (ATP used)
-Empty tRNA molecules leave ribosome to collect another AA
-Process repeated until stop codon reached
-Completed peptide chain (primary structure) detaches