Bioknowledgy
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  • IB Biology
    • Syllabus
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    • Practical scheme of work >
      • Practical activities (Labs)
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  • Core
    • 1. Cell biology >
      • 1.1 Introduction to cells
      • 1.2 Ultrastructure of cells
      • 1.3 Membrane structure
      • 1.4 Membrane transport
      • 1.5 The origin of cells
      • 1.6 Cell division
    • 2. Molecular biology >
      • 2.1 Molecules to metabolism
      • 2.2 Water
      • 2.3 Carbohydrates and lipids
      • 2.4 Proteins
      • 2.5 Enzymes
      • 2.6 Structure of DNA and RNA
      • 2.7 DNA replication, transcription and translation
      • 2.8 Cell respiration
      • 2.9 Photosynthesis
    • 3. Genetics >
      • 3.1 Genes
      • 3.2 Chromosomes
      • 3.3 Meiosis
      • 3.4 Inheritance
      • 3.5 Genetic modification and biotechnology
    • 4. Ecology >
      • 4.1 Species, communities and ecosystems
      • 4.2 Energy flow
      • 4.3 Carbon cycling
      • 4.4 Climate change
    • 5. Evolution and biodiversity >
      • 5.1 Evidence for evolution
      • 5.2 Natural selection
      • 5.3 Classification of biodiversity
      • 5.4 Cladistics
    • 6. Human physiology >
      • 6.1 Digestion and absorption
      • 6.2 The blood system
      • 6.3 Defence against infectious disease
      • 6.4 Gas exchange
      • 6.5 Neurons and synapses
      • 6.6 Hormones, homeostasis and reproduction
  • Additional higher level (AHL)
    • 7. Nucleic acids >
      • 7.1 DNA structure and replication
      • 7.2 Transcription and gene expression
      • 7.3 Translation
    • 8. Metabolism, cell respiration and photosynthesis >
      • 8.1 Metabolism
      • 8.2 Cell respiration
      • 8.3 Photosynthesis
    • 9. Plant biology >
      • 9.1 Transport in the xylem of plants
      • 9.2 Transport in the phloem of plants
      • 9.3 Growth in plants
      • 9.4 Reproduction in plants
    • 10. Genetics and evolution >
      • 10.1 Meiosis
      • 10.2 Inheritance
      • 10.3 Gene pools and speciation
    • 11. Animal physiology >
      • 11.1 Antibody production and vaccination
      • 11.2 Movement
      • 11.3 The kidney and osmoregulation
      • 11.4 Sexual reproduction
  • Options
    • A. Neurobiology and behaviour >
      • A.1 Neural development
      • A.2 The human brain
      • A.3 Perception of stimuli
      • A.4 Innate and learned behaviour (AHL)
      • A.5 Neuropharmacology (AHL)
      • A.6 Ethology (AHL)
    • B. Biotechnology and bioinformatics
    • C. Ecology and conservation >
      • C.1 Species and communities
      • C.2 Communities and ecosystems
      • C.3 Impacts of humans on ecosystems
      • C.4 Conservation of biodiversity
      • C.5 Population ecology (AHL)
      • C.6 Nitrogen and phosphorus cycles (AHL)
    • D. Human physiology
  • Giving back - BioKQQAnswers

Essential idea: Every living organism inherits a blueprint for life from its parents.

Genes and hence genetic information is inherited from parents, but the combination of genes inherited from parents by each offspring will be different. In sexual reproduction each parent can only pass on 50% of there genes as the other 50% comes from the second parent.

N.B. One of the most remarkable facts about genes is how alleles show very few changes in bases and cause such large change in phenotypes (characteristics). For instance humans share 50% of their genes with bananas.

Understandings, applications and skills

3.1.U1 A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic.
3.1.U2 A gene occupies a specific position on a chromosome.
3.1.U3 The various specific forms of a gene are alleles.
3.1.U4 Alleles differ from each other by one or only a few bases.
3.1.U5 New alleles are formed by mutation. [Deletions, insertions and frame shift mutations do not need to be included.]
3.1.U6 The genome is the whole of the genetic information of an organism.
3.1.U7 The entire base sequence of human genes was sequenced in the Human Genome Project.
3.1.A1 The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin. [Students should be able to recall one specific base substitution that causes glutamic acid to be substituted by valine as the sixth amino acid in the hemoglobin polypeptide.]
3.1.A2 Comparison of the number of genes in humans with other species. [The number of genes in a species should not be referred to as genome size as this term is used for the total amount of DNA. At least one plant and one bacterium should be included in the comparison and at least one species with more genes and one with fewer genes than a human.]
3.1.S1 Use of a database to determine differences in the base sequence of a gene in two species. [The GenbankĀ® database can be used to search for DNA base sequences. The cytochrome C gene sequence is available for many different organisms and is of particular interest because of its use in reclassifying organisms into three domains.]
[Text in square brackets indicates guidance notes]

Starter

Watch the video where do genes come from by Carl Zimmer

Presentation and notes

The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the development of student notes to aid revision.
Download presentation


Vocabulary

Correct use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.
Download notes


Quick quiz

Use the BioK quick quiz on 3.1 Genes (as directed) to check your understanding of the topic.

Weblinks

Genes and Alleles
3.1 Genes by Stephanie Castle (IB Biology Review)
3.1 Alleles by Stephanie Castle (IB Biology Review)
Sickle Cell Anaemia
3.1 Application: Sickle cell anaemia by Stephanie Castle (IB Biology Review)

Mutations

What is mutation? by Learn.Genetics
Disease & Mutation: DNA Damage by DNA Learning Center

Human Genome Project
Timeline of the human genome by Genome: Unlocking Life's Code
3.1 The genome and human genome project by Stephanie Castle (IB Biology Review)

Nature of science

Developments in scientific research follow improvements in technology—gene sequencers are used for the sequencing of genes. (1.8) [linked to 3.1.U7, 3.1.A1, 3.1.A2, 3.1.S1]

International-mindedness

Sequencing of the human genome shows that all humans share the vast majority of their base sequences but also that there are many single nucleotide polymorphisms that contribute to human diversity.

Theory of knowledge

There is a link between sickle cell anemia and prevalence of malaria. How can we know whether there is a causal link in such cases or simply a correlation?
  • Discovery of a correlation in Science is not used as evidence by itself. More commonly a correlation is used to formulate a hypothesis. The hypothesis is then tested to see if an underlying empirical relationship exists, e.g. is the persistance of sickle cell anemia caused by the presence of the malarial parasite.
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