Transcript Genetics
Meiosis/Genetics Topic 4 Stages of Meiosis Meiosis Stage 2 Genes and Chromosomes • Terminology: • Genotype – genetic constitution of a gene/org • Phenotype – physical expression of a gene • Dominant allele – form of the gene that is expressed even when only 1 is present • Recessive allele – form of the gene that is only expressed when both alleles are recessive Terminology cont’d • Codominant allele – when two two forms of a gene are both expressed when paired together • Locus – the location of a gene/allele on a chromosome • Homozygous – when both alleles of a gene are the same (ex. aa, AA) • Heterozygous – when both alleles of a gene Terminology cont’d • Carrier – an individual of heterozygous makeup that carriers, and therefore can pass on, a disease causing allele but doesn’t express that trait • Test cross – when an individual of known phenotype but unknown genotype (AA or Aa) is crossed with a homozygous recessive individual in order to determine its genetic make-up. Mendelian Genetics – Monohybrid Cross Classical Punett's Square is a way to determine ways traits can segregate parental P cross a a A Aa Aa F1 cross A Aa Aa A a A AA Aa testcross: mating F1 generation to the parental (usually recessive) strain a a A Aa Aa ? aa aa a Aa aa Some genes have more than two alleles- Blood surface antigens Blood type also and ex. Of Codominance Sex-linkage basics Sex-linkage notes page Pedigree basics Pedigrees and pedigree analysis Sex-linked Pedigree