IB生物 复习课件 03 遗传学 IB Biology Reviewed PPT 03 Genetics.pptx

Genetics The official IB guide for Genes 3.1 Genes /server2/rest/app/tsm.xql?doc=d_4_biolo_gui_1402_4_epart=3chapter=3 Distinguish between alleles, genes and genomes Gene: a heritable factor that controls a specific characteristic. Allele: one specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene. Genome: the whole of the genetic information of an organism Distinguish between the number of genes that an organism has and its genome size Describe the Human Genome Project and its consequences Define gene mutation and identify its role in the creation of new alleles Gene mutation is a change in the nucleotide sequence . The most significant type of mutation is a base substitution. New alleles are formed from other alleles by mutation Mutations can be passed onto offspring and cause genetic disease that becomes heritable. Sickle cell anaemia Sickle cell anaemia is caused by a single nucleotide polymorphism. The structure of the resultant polypeptide changes the shape of red blood cells from round disks to half-moons. Half-moons shape causes congestion in the bloodstream. The official IB guide for Chromosomes 3.2 Chromosomes Compare eukaryotic and prokaryotic chromosomes Define the terms diploid and haploid and homologous chromosomes Homologous chromosomes are found in the nuclei in the cells of diploid organisms. But if each chromosome exists alone with no partner, the cell is said to be haploid. Human somatic cells are diploid and contain 44 chromosomes in 23 homologous pairs; human gametes are haploid and contain only 23 chromosomes, one of each pair found in the body cells. Describe how the length of DNA molecules can be measured by autoradiography Karyograms A karyogram is a photograph or diagram of stained chromosomes. The karyogram image is organised so that each chromosome is separated from the others. A karyogram shows the karyotype of the cell which is the numbe