IB Exam (Unit 3)

U1: What are DNA and RNA’s monomers?

nucleotides

U2: Compare the structure of RNA and DNA.

	number of strands present	Base Composition	Type of Pentose
DNA	2	A, C, G, T	deoxyribose
RNA	1	A, C, G, U	ribose

U3: Explain the structure of DNA

• double-helix

• two antiparallel strands of nucleotides

• linked by hydrogen bonding between complimentary base pairs

U4: Explain the structure of DNA

A1: Who clarified the structure of DNA with models?

Watson and Crick

S1: Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons, and rectangles to represent phosphates, pentoses and bases

U: State qualities of the replication of DNA

• semi-conservative

• depends on complimentary base pairing

U: Explain DNA Helicase’s Job

• unwinds the double helix

• separates the two strands by breaking hydrogen bonds

U: Explain DNA Polymerase’s Job

• links nucleotides together to form a new strand

• uses a pre-existing strand as a template

U: Define Transcription

the synthesis of mRNA copied from the DNA base sequences by RNA polymerase

U: Define Translation

the synthesis of polypeptides on ribosomes

U: Explain that the amino acid sequence of polypeptides is determined by…

mRNA according to the genetic code

U: Describe how Codons of three bases on mRNA correspond to…

one amino acid in a polypeptide

U: What does Translation depend on?

complimentary base-pairing between codons on mRNA and anticodons on tRNA

balls

A: Use of Taq DNA polymerase to produce multiple copies of DNA rapidly by the Polymerase Chain Reaction (PCR)

• PCR allows for strands of DNA to be replicated into the millions

• To speed up PCR, it is carried out at high temperatures

• special type of heat-stable DNA polymerase: Taq DNA polymerase

  • obtained from Thermus aquaticus, a bacterium that is adapted to living in hotsprings,

• Millions of copies of the DNA can be produced by PCR in a few hours because of the high temperatures used

A: Taq DNA Steps

1. DNA heated to 95°C to separate strands

2. DNA cooled to 53°C to allow primer to bind

3. DNA reheated to 73°C to separate strands

A:

• The gene that codes for insulin has been transferred from humans to the bacterium E. coli and to other organisms, to produce insulin

• aa sequence for insulin in bacteria = aa sequence in humans

  • because of universality of genetic code

  • codons in bacteria = codons in human mRNA

• there are some exceptions

S: Use a table of the genetic code to deduce which codons corresponds to which amino acids

1. Identify if the given nitrogenous base is the

   1. 5’ strand - match complementary letters, turn into codons, and chart

   2. 3’ strand - match same letter for codon, chart

   3. mRNA strand -order codon, chart

   4. Anti-codon - find opposite letter, chart

2. ALWAYS DOUBLE CHECK

S: Analyze of Messelson and Stahl’s results to obtain support for the theory of semi-conservative replication of DNA

• E. coli cultures in N¹⁵ environments

• they were transferred to N¹⁴ environments

• After 1 generation, DNA was intermediate in density between N¹⁴ and N¹⁵

• After 2 generations, N¹⁴+N¹⁵ DNA was present along side solid N¹⁴ DNA

• simply: it kept a strand of the old DNA and created a new strand with the light nitrogen

S: Deduce the DNA base sequence for an mRNA strand

1. Template strand of DNA is usually 3’-XXX-5’

2. mRNA is always 5’-XXX-3’

U: Define Cellular Respiration

the controlled release of energy from organic compounds to produce ATP

U: True of False: ATP from cell respiration is not immediately available as a source of energy in the cell

false, it can be used right away

U: True of False: ATP from cell respiration is not immediately available as a source of energy in the cell

U: State that Anaerobic Cell Respiration gives a ______ yield of ATP from glucose

small!

U: Explain that Aerobic Cell Respiration requires ______ and gives a _____ yield of ATP from glucose.

1. Oxygen (O₂)

2. large