In A-Level biology, there are four biochemical tests to learn for four different biological molecules. This article gives full details of the tests, and a helpful colour summary at the bottom. Test for reducing and non-reducing sugars A sugar is a monosaccharide or disaccharide. The vast majority of sugars learnt about in A-Level biology (glucose,... Continue Reading →
HIV and AIDS – Diseases Ep 2
HIV (human immunodeficiency virus) is a virus which can eventually lead to development of AIDS (acquired immunodeficiency syndrome). However, it is not the virus itself which causes AIDS symptoms; HIV weakens the immune system, meaning other infections can take hold more easily. In this article we will look at HIV structure, replication, and development of... Continue Reading →
Cardiovascular Disease – Diseases Ep 1
Cardiovascular disease is a non-communicable disease; it is not caused by a pathogen and cannot be passed from person to person. Most cardiovascular disease begins with atherosclerosis developing in an artery due to factors such as high blood pressure. In this article we will look at how atheromas develop, cardiovascular disease risk factors, and treatments.... Continue Reading →
Enzyme-Controlled Reactions – Practical Skills Ep 1
The aim of this practical is to investigate the rate of enzyme-controlled reactions. The details of the practical itself vary depending on what the enzyme, substrates, and products are. Let's use catalase as an example. Catalase is an intracellular enzyme which catalyses the conversion of toxic hydrogen peroxide (the substrate) into oxygen and water (the... Continue Reading →
Epistasis – Inheritance Ep 5
Epistasis is when the expression of an allele of one gene masks the expression of the alleles of another. Let's use flower colour as an example. Epistasis example: flower colour In the diagram below, the flower pigment molecule begins as white. In order for the white pigment to be converted into a blue pigment, the... Continue Reading →
Autosomal Linkage and Sex Linkage – Inheritance Ep 4
Autosomal linkage and sex linkage are two cases where inheritance is very dependent on which chromosome the genes are found on. This is definitely the most difficult concept to get your head around for this topic for A-Level biology - make sure to have a good understanding of meiosis before you start. Autosomal Linkage Autosomes... Continue Reading →
Dihybrid Inheritance – Inheritance Ep 3
Dihybrid inheritance looks at the possibilities of two characteristics being inherited together. Each characteristic is coded for by a separate gene. Punnett squares can be used to work out the possible genotypes and phenotypes of the offspring. In the example below, we are looking at the inheritance of wing colour in beetles as we did... Continue Reading →
Codominance and Multiple Alleles – Inheritance Ep 2
In the last article we looked at inheritance of a characteristic coded for by a single gene which has one dominant allele and one recessive allele. However, sometimes alleles can be codominant or there can be more than two alleles for a gene. This increases the number of possible phenotypes. Let's look at each case... Continue Reading →
Monohybrid Inheritance – Inheritance Ep 1
A diploid organism (e.g. a human) has two alleles of each gene in their chromosomes. Alleles are alternative forms of a gene, so an organism could have two of the same allele (homozygous) or two different alleles (heterozygous) at a particular locus. The alleles an organism has (the genotype) will determine what characteristics it has... Continue Reading →
Electrophoresis – Gene Technologies Ep 4
Electrophoresis is a method used to separate fragments of DNA or RNA based on their size (length*) using an electric current. It has applications in processes such as genetic fingerprinting and disease diagnosis. DNA and RNA are negatively charged which means they will move towards a positive electrode. This technique can be used for proteins,... Continue Reading →
