A Level Biology (Year 13) "Autosomal Linkage"

In this A level Biology video, we look at autosomal linkage. First we look again at the phenotype ratio produced when we carry out a dihybrid cross involving heterozygous individuals with two unlinked genes and why this supports Mendel's law of independent assortment. We then look at what is meant by autosomal linkage and see how crossing linked genes produces a different phenotype ratio from unlinked genes. Next we explore recombinants and see how these arise from crossing over. Finally, we look at how to calculate recombination frequency and what this tells us about the degree of crossing over. Image credits: Human male karyotype https://commons.wikimedia.org/wiki/File:Human_male_karyotype.gif Courtesy: National Human Genome Research Institute, Public domain, via Wikimedia Commons