Topic 3.2: Chromosomes
Essential Idea: Chromosomes carry genes in a linear sequence that is shared by members of a species.
At SHS, Topic 3.2 is taught in the following class unit(s):
Statements & Objectives:
3.2.U1 Prokaryotes have one chromosome consisting of a circular DNA molecule.
3.2.U2 Some prokaryotes also have plasmids but eukaryotes do not.
3.2.U3 Eukaryote chromosomes are linear DNA molecules associated with histone proteins.
3.2.U4 In a eukaryote species there are different chromosomes that carry different genes.
3.2.U5 Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes.
3.2.U6 Diploid nuclei have pairs of homologous chromosomes.
3.2.U7 Haploid nuclei have one chromosomes of each pair.
3.2.U8 The number of chromosomes is a characteristic feature of member of a species.
3.2.U9 A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length.
3.2.U10 Sex is determined by sex chromosomes and autosomes are chromosomes that do not determine sex.
3.2.A1 Cairns’ technique for measuring the length of DNA by autoradiography.
3.2.A2 Comparison of genome size in T2 phage, Escherichia coli, Drosophila melanogaster, Homo sapiens, Paris japonica.
3.2.A3 Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes, Canis familiaris, Oryza sativa, Parascarsis equorum.
3.2.A4 Use karyograms to deduce sex and diagnose Down Syndrome in humans.
3.2.S1 Use of databases to identify the focus of a human gene and its polypeptide product.
3.2.NOS Developments in research follow improvements in techniques- autoradiography was used to establish the length of DNA molecules in chromosomes.
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