3.2 Chromosomes
Essential Idea:
Essential Idea:
Chromosomes carry genes in a linear sequence that is shared by members of a species
Chromosomes carry genes in a linear sequence that is shared by members of a species
Understandings:
- Prokaryotes have one chromosome consisting of a circular DNA molecule
- Some prokaryotes also have plasmids but eukaryotes do not
- Eukaryote chromosomes are linear DNA molecules associated with histone proteins
- In a eukaryote species there are different chromosomes that carry different genes
- Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes
- Diploid nuclei have pairs of homologous chromosomes
- Haploid nuclei have one chromosome of each pair
- The number of chromosomes is a characteristic feature of members of a species
- A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length
- Sex is determined by sex chromosomes and autosomes are chromosomes that do not determine sex
Applications:
- Cairns' technique for measuring the length of DNA molecules by autoradiography
- Comparison of genome size in T2 phage, Escherichia coli, Drosophila melanogaster, Homo sapiens and Paris japonica
- Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes, Canis familiaris, Oryza sativa and Parascaris equorum
- Use of karyograms to deduce sex and diagnose Down syndrome in humans
Skills:
Use of databases to identify the locus of a human gene and its polypeptide product
Nature of science:
Developments in research follow improvements in techniques—autoradiography was used to establish the length of DNA molecules in chromosomes. [Linked to 3.2.A1]
International-mindedness:
- Sequencing of the rice genome involved cooperation between biologists in 10 countries.
Introductory Video
Introductory Video
Powerpoint
Powerpoint
Useful Videos
Useful Videos
Unit Summary Questions
Unit Summary Questions
3.2 Chromosomes Unit Summary Questions.pdfAdditional Activities
Additional Activities
