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Syllabus

3.4 Inheritance

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Core » Topic 3: Genetics » 3.4 Inheritance

Description

Nature of science:
Making quantitative measurements with replicates to ensure reliability. Mendel’s genetic crosses with pea plants generated numerical data. (3.2)

Understandings:

Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed.
Gametes are haploid so contain only one allele of each gene.
The two alleles of each gene separate into different haploid daughter nuclei during meiosis.
Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles.
Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects.
Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles.
Some genetic diseases are sex-linked. The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes.
Many genetic diseases have been identified in humans but most are very rare.
Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer.

Applications and skills:

Application: Inheritance of ABO blood groups.
Application: Red-green colour blindness and hemophilia as examples of sex-linked inheritance.
Application: Inheritance of cystic fibrosis and Huntington’s disease.
Application: Consequences of radiation after nuclear bombing of Hiroshima and accident at Chernobyl.
Skill: Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.
Skill: Comparison of predicted and actual outcomes of genetic crosses using real data.
Skill: Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases.

Guidance:

Alleles carried on X chromosomes should be shown as superscript letters on an upper case X, such as X^h.
The expected notation for ABO blood group alleles is:

  Phenotype
    O
    A
    B
    AB

  Genotype
    ii
    |^A| ^A or | ^Ai
    |^B| ^B or | ^Bi
    |^A| ^B

Theory of knowledge:

Mendel’s theories were not accepted by the scientific community for a long time. What factors would encourage the acceptance of new ideas by the scientific community?

Utilization:
Syllabus and cross-curricular links:
Biology
Topic 1.6 Cell division

Aims:

Aim 8: Social implications of diagnosis of mutations, including the effects on the family and stigmatization.

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DP Biology Questionbank

3.4 Inheritance

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