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17. Inheritance

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  1. 17.1 Chromosomes, genes and proteins

    1. 17.1.1Chromosomes are made of DNA, which

      • State that chromosomes are made of DNA, which contains genetic information in the form of genes

    2. 17.1.2Gene as a length of DNA that codes

      • Define a gene as a length of DNA that codes for a protein

    3. 17.1.3Allele as an alternative form

      • Define an allele as an alternative form of a gene

    4. 17.1.4Inheritance of sex in humans

      • Describe the inheritance of sex in humans with reference to X and Y chromosomes

    5. 17.1.5Sequence of bases in a gene determines

      • State that the sequence of bases in a gene determines the sequence of amino acids used to make a specific protein (knowledge of the details of nucleotide structure is not required)

    6. 17.1.6Different sequences of amino acids

      • Explain that different sequences of amino acids give different shapes to protein molecules

    7. 17.1.7DNA controls cell function

      • Explain that DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters

    8. 17.1.8Protein is made

      • Explain how a protein is made, limited to: • the gene coding for the protein remains in the nucleus • messenger RNA (mRNA) is a copy of a gene • mRNA molecules are made in the nucleus and move to the cytoplasm • the mRNA passes through ribosomes • the ribosome assembles amino acids into protein molecules • the specific sequence of amino acids is determined by the sequence of bases in the mRNA (knowledge of the details of transcription or translation is not required)

    9. 17.1.9Most body cells in an organism contain

      • Explain that most body cells in an organism contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs

    10. 17.1.10Haploid nucleus as a nucleus

      • Describe a haploid nucleus as a nucleus containing a single set of chromosomes

    11. 17.1.11Diploid nucleus as a nucleus

      • Describe a diploid nucleus as a nucleus containing two sets of chromosomes

    12. 17.1.12Diploid chromosome pairs

      • State that in a diploid cell, there is a pair of each type of chromosome and in a human diploid cell there are 23 pairs

  2. 17.2 Mitosis

    1. • Describe mitosis as nuclear division giving rise to genetically identical cells (details of the stages of mitosis are not required)

    2. • State the role of mitosis in growth, repair of damaged tissues, replacement of cells and asexual reproduction

    3. • State that the exact replication of chromosomes occurs before mitosis

    4. • State that during mitosis, the copies of chromosomes separate, maintaining the chromosome number in each daughter cell

    5. • Describe stem cells as unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions

  3. 17.3 Meiosis

    1. • State that meiosis is involved in the production of gametes

    2. • Describe meiosis as a reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells (details of the stages of meiosis are not required)

  4. 17.4 Monohybrid inheritance

    1. • Describe inheritance as the transmission of genetic information from generation to generation

    2. • Describe genotype as the genetic make-up of an organism and in terms of the alleles present

    3. • Describe phenotype as the observable features of an organism

    4. • Describe homozygous as having two identical alleles of a particular gene

    5. • State that two identical homozygous individuals that breed together will be pure-breeding

    6. • Describe heterozygous as having two different alleles of a particular gene

    7. • State that a heterozygous individual will not be pure-breeding

    8. • Describe a dominant allele as an allele that is expressed if it is present in the genotype

    9. • Describe a recessive allele as an allele that is only expressed when there is no dominant allele of the gene present in the genotype

    10. • Interpret pedigree diagrams for the inheritance of a given characteristic

    11. • Use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1: 1 and 3: 1 ratios

    12. • Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypes

    13. • Explain how to use a test cross to identify an unknown genotype

    14. • Describe codominance as a situation in which both alleles in heterozygous organisms contribute to the phenotype

    15. • Explain the inheritance of ABO blood groups: phenotypes are A, B, AB and O blood groups and alleles are IA, IB and Io

    16. • Describe a sex-linked characteristic as a feature in which the gene responsible is located on a sex chromosome and that this makes the characteristic more common in one sex than in the other

    17. • Describe red-green colour blindness as an example of sex linkage

    18. • Use genetic diagrams to predict the results of monohybrid crosses involving codominance or sex linkage and calculate phenotypic ratios