A-Level Biology & Chemistry and GCSE Science Tuition. A-Level Biology Revision.
Producing a serial dilution is a really useful skill for all sort of biology experiments. In this article we will look at how to prepare a serial dilution, and how it could be used to produce a calibration curve for a colorimeter experiment. How to prepare a serial dilution In A-Level biology, you will probably... Continue Reading →
Cystic fibrosis is an inherited disorder affecting specific channel proteins in cell membranes. In this article we will look at how it is inherited, how chloride ion transport is affected, and the symptoms which develop as a consequence. Inheritance of cystic fibrosis Cystic fibrosis is an inherited recessive disorder, meaning it is caused by a... Continue Reading →
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 (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 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 →
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, substrate, and product 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 is when the expression of an allele of one gene masks the expression of the alleles of another. The genes must code for the same characteristic in order for this to work. Let's use flower colour as an example. Epistasis example: flower colour In the diagram below, the flower pigment molecule begins as white.... Continue Reading →
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 looks at the possibilities of two characteristics being inherited together. Each characteristic is coded for by a separate gene. In this case it is much easier to use a Punnett square to work out the possible genotypes of the offspring as a genetic diagram would get very messy and difficult to read. In... Continue Reading →
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 →
