16.2.4

Multiple Alleles

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Multiple Alleles

Although only two alleles per gene are found in an individual diploid organism, there may be multiple alleles at the population level. This means many possible combinations of alleles can exist.

Homologous chromosomes

Homologous chromosomes

  • Chromosomes in diploid organisms exist in homologous pairs.
  • Homologous chromosomes consist of the same genes in the same order.
  • The only variation between homologous chromosomes is in the alleles.
  • Two alleles can be present for one gene.
Multiple alleles

Multiple alleles

  • Although only two alleles can be present in an organism, there could be multiple different alleles for a single gene.
  • Multiple alleles provide many different genotype combinations.
  • This creates large variation at the population level.
Rabbit coat colour

Rabbit coat colour

  • Four phenotypes exist for the c gene (coat colour):
    • CC - brown fur.
    • cchcch - blacktipped white fur.
    • chch - black fur on the extremities and white fur elsewhere.
    • cc - white fur.
Dominance hierarchy

Dominance hierarchy

  • Multiple alleles have a dominance hierarchy.
  • E.g. rabbit coat colour.
    • CC is dominant over all other allele combinations.
    • cchcch is incompletely dominant over chch and cc.
    • chch is dominant over cc.
Jump to other topics
1

Cell Structure

1.1

Cell Structure

1.1.1Studying Cells - Microscopes1.1.2Introduction to Eukaryotic & Prokaryotic Cells1.1.3Ultrastructure of Eukaryotic Cells1.1.4Ultrastructure of Eukaryotic Cells 21.1.5Ultrastructure of Eukaryotic Cells 31.1.6Prokaryotic Cells1.1.7Viruses1.1.8End of Topic Test - Cell Structure1.1.9Exam-Style Question - Microscopes1.1.10A-A* (AO2/3) - Cell Structure
2

Biological Molecules

2.1

Testing for Biological Modules

2.1.1Tests for Sugars & Starch2.1.2Tests for Lipids & Proteins
2.2

Carbohydrates & Lipids

2.2.1Monomers & Polymers2.2.2Carbohydrates2.2.3Examples of Carbohydrates2.2.4Triglycerides & Phospholipids2.2.5Types of Fatty Acids2.2.6Exam-Style Question - Carbohydrates2.2.7End of Topic Test - Carbohydrates & Lipids
2.3

Proteins

2.3.1Amino Acids & Overview of Protein Structure2.3.2Primary & Secondary Structure2.3.3Tertiary & Quaternary Structure2.3.4Globular & Fibrous Proteins2.3.5Haemoglobin2.3.6Collagen2.3.7End of Topic Test - Proteins
2.4

Water

2.4.1Water Structure & Function2.4.2End of Topic Test - Water
3

Enzymes

3.1

Enzymes

3.1.1Enzyme Action3.1.2Factors Affecting Enzyme Activity3.1.3Factors Affecting Enzyme Activity 23.1.4A-A* (AO2/3) - Enzymes
4

Cell Membranes & Transport

4.1

Biological Membranes

4.1.1Fluid Mosaic Model4.1.2Cell Signalling4.1.3End of Topic Test - Biological Membranes4.1.4Exam-Style Question - Membranes
4.2

Movement Into & Out of Cells

4.2.1Passive Movement Across the Membrane4.2.2Active Movement Across the Membrane4.2.3Osmosis4.2.4Osmosis & Plant Cells4.2.5Surface Area to Volume Ratio4.2.6Adaptions to Surface Area to Volume Ratio4.2.7Calculations - Volume4.2.8Calculations - Surface Area
5

The Mitotic Cell Cycle

5.1

Replication & Division of Nuclei

5.1.1Chromosomes5.1.2The Cell Cycle5.1.3Mitosis5.1.4Role of Mitosis5.1.5Stem Cells5.1.6Mitosis & Cancer5.1.7End of Topic Test - Replication & Division5.1.8A-A* (AO2/3) - Cell Cycle & Transport
6

Nucleic Acids & Protein Synthesis

6.1

Nucleic Acids

6.1.1Introduction to DNA & RNA6.1.2Nucleotides6.1.3Polynucleotides6.1.4ADP & ATP6.1.5DNA6.1.6DNA Replication6.1.7RNA6.1.8End of Topic Test - Nucleic Acids & ATP
6.2

Protein Synthesis

6.2.1The Genetic Code6.2.2Polypeptide Synthesis6.2.3RNA Processing in Eukaryotes6.2.4Mutations6.2.5Exam-Style Question - Protein Synthesis6.2.6A-A* (AO2/3) - Coronavirus Translation
7

Transport in Plants

7.1

Transport in Plants

7.1.1Plant Vessels7.1.2Xylem7.1.3Investigating Transpiration7.1.4Adaptations to Water Availability7.1.5Phloem7.1.6End of Topic Test - Transport in Animals & Plants7.1.7A-A* (AO2/3) - Transport in Animals & Plants
8

Transport in Mammals

8.1

Circulatory System

8.1.1Double Circulation8.1.2Blood Vessels8.1.3Important Blood Vessels8.1.4Blood Cells8.1.5Tissue Fluid
8.2

Transport of Oxygen & Carbon Dioxide

8.2.1Haemoglobin8.2.2Oxygen Dissociation
8.3

The Heart

8.3.1Structure of the Heart8.3.2The Cardiac Cycle8.3.3Coordination of Heart Action
9

Gas Exchange

9.1

Gas Exchange System

9.1.1Mammalian Gas Exchange9.1.2Smoking
10

Infectious Diseases

10.1

Infectious Diseases

10.1.1Transmission of Disease10.1.2Tuberculosis10.1.3HIV10.1.4Malaria10.1.5Cholera10.1.6Measles
10.2

Antibiotics

10.2.1Antibiotics
11

Immunity

11.1

The Immune System

11.1.1Phagocytes11.1.2Antigens11.1.3Lymphocytes11.1.4Primary & Secondary Response
11.2

Antibodies & Vaccination

11.2.1Antibodies11.2.2Monoclonal Antibodies11.2.3Immunity11.2.4Vaccines11.2.5Exam-Style Question - Immune System11.2.6A-A* (AO2/3) - Disease & Immune System
12

Energy & Respiration (A2 Only)

12.1

Energy

12.1.1Energy & ATP12.1.2Respiratory Substrates & Quotient12.1.3Respirometers
12.2

Respiration

12.2.1Introduction to Respiration12.2.2Anaerobic Respiration12.2.3Aerobic Respiration12.2.4Chemiosmosis & Coenzymes12.2.5Mitochondria12.2.6Respiration Experiments12.2.7End of Topic Test - Respiration12.2.8A-A* (AO3/4) - Respiration
13

Photosynthesis (A2 Only)

13.1

Photosynthesis

13.1.1Introduction to Photosynthesis13.1.2Light-Dependent Reactions13.1.3Light-Independent Reactions13.1.4Limiting Factors13.1.5Investigating Photosynthesis13.1.6End of Topic Test - Photosynthesis13.1.7A-A* (AO3/4) - Photosynthesis
14

Homeostasis (A2 Only)

14.1

Homeostasis

14.1.1Homeostasis14.1.2Negative Feedback
14.2

The Kidney

14.2.1Kidneys & Osmoregulation
14.3

Cell Signalling

14.3.1Messengers & cAMP
14.4

Blood Glucose Concentration

14.4.1Blood Glucose Concentration14.4.2Controlling Blood Glucose14.4.3Urinalysis
14.5

Homeostasis in Plants

14.5.1Stomata & Guard Cells
15

Control & Coordination (A2 Only)

15.1

Control & Coordination in Mammals

15.1.1Neurones15.1.2Receptors15.1.3Taste15.1.4Reflexes15.1.5Action Potentials15.1.6Saltatory Conduction15.1.7Synapses15.1.8Cholinergic Synnapses15.1.9Neuromuscular Junction15.1.10Skeletal Muscle15.1.11Sliding Filament Theory Contraction15.1.12Sliding Filament Theory Contraction 215.1.13Menstruation15.1.14Contraceptive Pill
15.2

Control & Co-Ordination in Plants

15.2.1Venus Flytrap15.2.2Auixns15.2.3Gibberellins
16

Inherited Change (A2 Only)

16.1

Passage of Information to Offspring

16.1.1Meiosis16.1.2Gametogenesis16.1.3Meiosis & Genetic Diversity
16.2

Genes & Phenotype

16.2.1Key Terms in Genetics16.2.2Inheritance16.2.3Linkage16.2.4Multiple Alleles16.2.5Chi-Squared Test16.2.6Mutations16.2.7Specific Mutations16.2.8End of Topic Test - Genetics16.2.9A-A* (AO2/3) - Genetics
16.3

Gene Control

16.3.1lac Operon16.3.2Transcription Factors16.3.3Gibberellins & DELLA Proteins
17

Selection & Evolution (A2 Only)

17.1

Variation

17.1.1Phenotypic Variation17.1.2Continuous & Discontinuous Variation17.1.3t-Tests
17.2

Natural & Artificial Selection

17.2.1Natural Selection & Evolution17.2.2Types of Selection17.2.3Types of Selection Summary17.2.4Genetic Drift & Founder Effect17.2.5Populations17.2.6Hardy-Weinberg Principle17.2.7Artificial Selection
17.3

Evolution

17.3.1Evolution by Natural Selection17.3.2Evidence for Evolution17.3.3Speciation17.3.4Extinction
18

Classification & Conservation (A2 Only)

18.1

Biodiversity

18.1.1Key Terms18.1.2Biodiversity18.1.3Sampling Methods18.1.4Correlation18.1.5Spearman’s Rank18.1.6Measuring Biodiversity
18.2

Classification

18.2.13-Domain Classification System18.2.2Linnaean Classification System
18.3

Conservation

18.3.1Importance of Biodiversity18.3.2Conservation18.3.3Zoos, Seedbanks, & Other Conservation Methods18.3.4Assisted Reproduction & Contraception18.3.5Non-Governmental Organisations
19

Genetic Technology (A2 Only)

19.1

Manipulating Genomes

19.1.1Recombinant DNA & Genetic Engineering19.1.2Restriction Endonucleases19.1.3Gel Electrophoresis19.1.4DNA Probes & Microarrays19.1.5End of Topic Test - Manipulating Genomes19.1.6A-A* (AO2/3) - Manipulating Genomes
19.2

Genetic Technology Applied to Medicine

19.2.1Bioinformatics19.2.2Applications of Recombinant DNA19.2.3Genetic Screening19.2.4Gene Therapy19.2.5Ethics19.2.6DNA Profiling & Forensics
19.3

Genetically Modified Organisms in Agriculture

19.3.1GM Crops & Livestock19.3.2Ethics

Practice questions on Multiple Alleles

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Which of the following statements are true for multiple alleles?True / false
  2. 2
    How many alleles can be present in an organism for one gene?Multiple choice
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Linkage

Chi-Squared Test