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Date May 2017 Marks available 1 Reference code 17M.1.SL.TZ1.21
Level Standard level Paper Paper 1 Time zone Time zone 1
Command term Question number 21 Adapted from N/A

Question

Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is based on DNA sequences and the cladogram on the right is based on comparing protein sequences.

What is the reason that cladograms based on DNA sequences are more reliable predictors of the phylogenetic relationship of species than cladograms based on protein sequences?

A. Amino acids are not as chemically stable as DNA nucleotides.

B. DNA mutates but amino acids do not.

C. Several different triplets of bases can code for the same amino acid.

D. There are 20 different amino acids but only 4 nucleotides.

 

Markscheme

C

Examiners report

[N/A]

Syllabus sections

Core » Topic 4: Ecology » 4.1 Species, communities and ecosystems
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Core » Topic 5: Evolution and biodiversity » 5.1 Evidence for evolution
Core » Topic 2: Molecular biology » 2.1 Molecules to metabolism
Core » Topic 3: Genetics » 3.1 Genes
Core » Topic 1: Cell biology » 1.1 Introduction to cells
Core » Topic 6: Human physiology » 6.1 Digestion and absorption
Core » Topic 3: Genetics » 3.2 Chromosomes
Core » Topic 6: Human physiology » 6.2 The blood system
Core » Topic 5: Evolution and biodiversity » 5.2 Natural selection
Core » Topic 4: Ecology » 4.2 Energy flow
Core » Topic 2: Molecular biology » 2.2 Water
Core » Topic 1: Cell biology » 1.2 Ultrastructure of cells
Core » Topic 1: Cell biology » 1.3 Membrane structure
Core » Topic 3: Genetics » 3.3 Meiosis
Core » Topic 4: Ecology » 4.3 Carbon cycling
Core » Topic 2: Molecular biology » 2.3 Carbohydrates and lipids
Core » Topic 5: Evolution and biodiversity » 5.3 Classification of biodiversity
Core » Topic 6: Human physiology » 6.3 Defence against infectious disease
Core » Topic 2: Molecular biology » 2.4 Proteins
Core » Topic 5: Evolution and biodiversity » 5.4 Cladistics
Core » Topic 3: Genetics » 3.4 Inheritance
Core » Topic 1: Cell biology » 1.4 Membrane transport
Core » Topic 6: Human physiology » 6.4 Gas exchange
Core » Topic 4: Ecology » 4.4 Climate change
Core » Topic 1: Cell biology » 1.5 The origin of cells
Core » Topic 3: Genetics » 3.5 Genetic modification and biotechnology
Core » Topic 6: Human physiology » 6.5 Neurons and synapses
Core » Topic 2: Molecular biology » 2.5 Enzymes
Core » Topic 2: Molecular biology » 2.6 Structure of DNA and RNA
Core » Topic 6: Human physiology » 6.6 Hormones, homeostasis and reproduction
Core » Topic 1: Cell biology » 1.6 Cell division
Core » Topic 2: Molecular biology » 2.7 DNA replication, transcription and translation
Core » Topic 2: Molecular biology » 2.8 Cell respiration
Core » Topic 2: Molecular biology » 2.9 Photosynthesis
Core » Topic 1: Cell biology
Core » Topic 2: Molecular biology
Core » Topic 3: Genetics
Core » Topic 4: Ecology
Core » Topic 5: Evolution and biodiversity
Core » Topic 6: Human physiology
Core

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