Cystic fibrosis is an inherited disorder affecting specific channel proteins in cell-surface 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 →
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 →
Transforming bacteria – Gene Technologies Ep 3
So far in the genetic engineering journey we have learnt how to isolate or produce a DNA fragment, and amplify it in vitro using PCR. Transforming bacteria is a method to amplify a DNA fragment in vivo (in a living organism), and to engineer bacteria to produce a protein. In this article we will look... Continue Reading →
Polymerase Chain Reaction (PCR) – Gene Technologies Ep 2
Once a DNA fragment has been isolated or produced (see the last article), the next step is often to produce many copies of it. One common way to do this is to use the polymerase chain reaction, which is a fairly simple process that can be automated. In this article we will look in detail... Continue Reading →
Producing DNA Fragments – Gene Technologies Ep 1
This article begins a new series about gene technologies. Many gene technologies, especially recombinant DNA technologies, begin with the need to isolate or make DNA fragments. We will look at three different ways that this can be achieved. Restriction endonuclease enzymes This method allows DNA fragments to be "cut out" of existing DNA. Restriction endonucleases,... Continue Reading →
Genetic Diversity – Variation and Biodiversity Ep 2
Genetic diversity is defined as the number of different alleles of each gene in a population. Last week we looked at one method of introducing new alleles into a population - by genetic mutation. Today we will look at other ways that genetic diversity can be increased or decreased, and how it can be measured.... Continue Reading →
