Inheritance of Male Pattern Baldness

Inheritance of Male Pattern Baldness

What is Male Pattern Baldness (MPB)?

Male pattern baldness (MPB) is a condition which most men (and some women) will face during their lives. MPB causes in people a receding hair line and their hair will become a lot thinner. In the later stages of MPB complete baldness around the crown and possibly the middle section of the top of the head can occur. But what causes male pattern baldness?

What causes MPB?

Testosterone is a steroid hormone that affects many different areas of the body and their functions, however it is not often realized that testosterone is also the cause of hair loss. When testosterone is in the presence of an enzyme called 5-alpha-reductase, the enzyme will break down testosterone into dihydrotestosterone, which is often referred to as DHT.

Male pattern baldness occurs as a result of hair follicles being sensitive to DHT. If a hair follicle is sensitive to DHT it will miniaturize and eventually no hair will grow where that hair follicle grew. It can be seen that through the process of miniaturizing and loss of hair how the symptoms of MPB are so (Receding hair line, thinning of hair). (WebMD 2010)

How does a person’s genetics affect their chance of having MPB?
In 2005, German researches discovered a gene on the X-chromosome that affects baldness (Dr Barry Starr 2006). This gene (androgen-receptor gene, AR) instructs the making of androgen-receptors (also known as dihydrotestosterone receptors).   If the AR gene allows too many androgen-receptors to be made in the scalp or in hair follicles it can result in more testosterone being on the scalp. This in turn results in the creation of more dihydrotestosterone which then leads to greater loss of hair.

Some people who have MPB have an AR gene that performs normally. This means the AR gene is not the only factor that influences the development of MPB. Two independent studies were conducted to discover a common factor that people with MPB had that people without MPB did not have. Both studies came to the conclusion that people suffering with MPB have changes on their chromosome 20 compared to those without MPB.
Everyone has two chromosome 20s, one from each parent. This allows for one chromosome 20 to be unchanged even though the other is changed. This shows that there are three different combinations of chromosome 20s a person can have (and therefore three different likelihoods of having MPB):

1.       Two unchanged chromosome 20s (0 times more likely to develop MPB)
2.       One unchanged and one changed chromosome 20 (3.7 times more likely to develop MPB)
3.       Two changed chromosome 20s (6.1 times more likely to develop MPB)
(Melinda Beck 2008)

Not just one factor affects the likeliness of developing male pattern baldness.  An AR gene that allows for too many androgen-receptors to be in the scalp or hair follicles will increase the chances of developing MPB dramatically. Certain variations to the chromosome 20 also increase the probability of having MPB. Variations on one chromosome 20 will increase the chance of having MPB by 3.7 times and having variations on both chromosome 20s will increase the chance by 6.1 times.

A Cure For Obesity

A Cure For Obesity

Obesity is a major health concern all over the world. It can activate many other diseases including diabetes. Obesity is defined by the increased body weight caused by excessive accumulation of fat and the latest data recorded estimates that there are at least 300 million obese people in the world . Scientific researchers are constantly searching for efficient and effective ways to help reduce the risk of obesity. It wasn’t until recently that new research from the University of California, San Francisco suggested that ordinary fat cells can be reengineered to burn calories.
Image 1: Image of white fat cells.

Image 2: A scanning electron micrograph of
brown fat tissue .

Basically we have two different kinds of fat cells; white fat cells that store excess energy and, accumulate when weight is gained and brown fat cells which oxidize fuels and dissipate energy in the form of heat. Brown fat cells are the main interest, as experiments have shown they have the potential to counteract obesity. However these brown fat cells exist only in large doses in mice and infants. Adult humans do not have distinct brown fat, but they do appear to have small numbers of brown fat cells in white fat. So therefore to reduce the risk of obesity our bodies need to contain a larger amount of brown fat. Recently while investigating how a common drug given to people with diabetes works in mice, the University of California, San Francisco discovered a protein called PRDM16; found in both men and mice, can throw a switch on fat cells converting them from ordinary calorie-storing white fat cells into calorie-burning brown fat cells . This protein, PRDM16 also is encoded by a gene known as the zinc finger transcription factor that mediates protein-to-protein interactions . This protein can therefore assist the body in converting stubborn white fat cells into active brown fat. However to successfully complete this transition, the protein needs to be stabilized by a safe compound that enables PRDM16 to accumulate and activate receptors that induce brown fat cells before the protein breaks down .



Several experiments have been in place over the past few years to test this theory. As mentioned earlier mice contain large amounts of brown fat and therefore made the perfect test subjects. In the laboratory research, obese, male mice aged 3-4 weeks were injected with many types of drugs that had the potential to raise PRDM16 levels and therefore stabilizing the protein to promote the conversion of white fat cells into brown fat cells . One of the most effective drugs proven was the irisin hormone and within 10 days of treatment, the rodents’ blood sugar and insulin levels stabilized; preventing the onset of diabetes and they lost weight .

These experiments have not yet been tested on humans, however given that the mouse and human forms of the protein PRDM16 are quite similar there is a possibility that these same results will occur in humans; therefore will counteract obesity . The irisin hormone however being effective on mice still may have the possibility to prove ineffective on humans and therefore scientists are continually researching new drugs that target PRDM16 protein to raise and stabilize its levels and therefore offering new hope in the fight against obesity.

Genetic Information Provides Hope for Future in Treating Psychiatric Illnesses

Genetic Information Provides Hope for Future in Treating Psychiatric Illnesses

Genetics play a key role in the causation, development and heritability of many forms of diseases and disorders (Reece, 2011). Unfortunately, advancements in studies relating genomics to psychiatric illnesses have been slow in the past. This is due to the difficulty in identifying genes that contribute to such diseases. However, recent studies on a particular gene have revealed its connection with numerous psychiatric illnesses including ADHD, schizophrenia and autism (Ross RG, 2012).


The genetic component of diseases is associated with mutations of the gene which may induce an effect on the risk of developing illnesses (Reece, 2011). In the case of common non-psychiatric diseases, the risk of developing them can be linked to common variations of a few mutated genes that can be thoroughly analysed (which it has been). However, in the case of psychiatric diseases, it is a different story. A genome-wide association study (International Schizophrenia Consortium et al, 2009) produced novel results suggesting that psychiatric disorders are potentially affected by not a few, but thousands of gene variants, each having only a minute contribution to the disorder.
So how do researchers determine what genes are associated with psychiatric disorders if each gene has only a small effect? The method involves examining large alterations in the DNA nucleotide sequences which are replicated throughout the genome. These large alterations consist of DNA segments that are either missing or duplicated in the sequence. Because the number of altered segments varies as DNA is replicated, the genes are termed copy number variants (Henrichsen CN, 2009).



As genes are involved with many molecular activities such as protein synthesis, studying copy number variants (mutations in genes) is made simpler by recognising abnormal genetic activity.
Research conducted by Williams et al (2012) on 896 children with ADHD showed that the genome of those affected by ADHD exhibited a greater amount of copy number variants. Among the duplications of altered genes was the CHRNA7 gene, which encodes a7 nicotinic receptors. These receptors are crucial in the nervous system and are involved in many mental functions (Mazurov, 2006). Therefore, duplications of the CHRNA7 gene affects a7 nicotinic receptors, which in turn affect cognitive functions and ultimately lead to increased risk of ADHD, schizophrenia and possibly many other psychiatric illnesses.

 This association was further reinforced as four subsequent studies of subjects from the United Kingdom, United States and Canada all demonstrated similiar results – the amount of duplications of CHRNA7 and other copy number variants was greater in the genomes of those affected by ADHD (Williams et al, 2012).
Although the results of current studies (International Schizophrenia Consortium et al and Williams et al) do not have major contributions towards pharmaceutical or therapeutical developments, they are nevertheless fundamental and crucial to successive research. And the hope is that the findings of genetic information will lead to further studies in identifying more genes involved in and developing medicinal solutions for treating psychiatric illnesses.

How Genes Affect the Alcohol Use of Adolescents

How Genes Affect the Alcohol Use of Adolescents

Binge drinking and alcohol abuse is known to be a regular habit for many adolescents. According to the Australian Medical Association (2009), 39.2% of Australian adolescents (aged 14-19) reported acts of binge drinking in 2007. As such, studying the science of why binge drinking occurs is particularly relevant to today’s society. Through many previous scientific studies it has been found that this behaviour is related to genes. In more recent studies however, scientists have been able to determine which specific genotypes relate to these dangerous drinking habits. For example, some previous studies found that the genotypes hypothesised as relevant to alcohol consumption, the SLC6A4 neurotransmitter transporter and the DRD2 dopamine receptor, affected alcohol use whereas other previous studies found evidence contradicting these results. This blog aims to provide information on the recent scientific paper by Van der Zwaluw et al. (2011) which studied these genotypes alongside adolescent drinking motives and in particular, drinking to cope, to further examine the relationship between genetics and alcohol use.

An important factor in adolescent drinking behaviours is their drinking motives. The motives found to be related to adolescent’s drinking were enhancement, social, conformity and coping motives. Those who drank to cope were found to be more responsive to stress and have higher levels of problematic alcohol use than those who drank for any other reason. Van der Zwaluw et al. (2011) studied these drinking motives to compare the effect they have on alcohol use compared to the genotypes, SLC6A4 and DRD2.

 Both of the studied genotypes, SLC6A4 and DRD2, have functions which relate to emotions and feelings. The SLC6A4 genotype has been previously linked to anxiety, depression and other disorders whilst the DRD2 genotype’s function is to control the body’s emotions and positive reinforcement. By studying the functions and different variants of these genotypes, scientists have been able to find a theoretical link between specific variants of the DRD2 and SLC6A4 genotypes and alcohol consumption.

 The recent study by Van der Zwaluw et al. (2011) found that there was no significant relationship between alcohol consumption and the SLC6A4 and DRD2 genotypes. Hence, this recent study contradicts previous studies and the theoretical link between these genotypes and alcohol consumption. However, by also studying the drinking motives of the adolescents, it was found that drinking to cope did significantly affect alcohol use and was linked to alcohol-related problems. This link between drinking to cope and alcohol-related problems in adolescents was increased by the DRD2 genotype. As such, the DRD2 genotype did affect alcohol use but only for specific drinking motives. These findings demonstrate that alcohol use is more affected by drinking motives, such as drinking to cope, than it is by these specific genotypes. Therefore, it can be concluded that, until future research is conducted, there is no significant and direct relationship between genes and alcohol use.

The Disappearing Y Chromosome

The Disappearing Y Chromosome

 The size of the human Y chromosome is only a fraction of what it used to be. Once it was homologous to the X chromosome, but it now contains only 45 out of the 1700 genes it used to have[1]. Based on previous studies and assuming a linear rate of decay, it is expected that the human Y chromosome will disappear in roughly 4.6 million years.

 Does this mean the end of males? Not quite.

 A degenerating sex chromosome seems to be the norm of genetically determined sex[2]. In fact, organisms exist where the male chromosome is completely lacking, supporting the theory of the disappearing Y chromosome[2]. However, a study conducted by Hughes et al. provides new evidence on why the Y chromosome to stay for much, much longer.

 The male specific region of the Y chromosome (MSY) is not capable of genetic recombination with the X chromosome. Without genetic recombination, there are fewer mechanisms for genetic repair, leading to higher rates of mutations, deletions and insertions, all this, pointing to the inevitable degeneration of the Y chromosome.

 Hughes et al. argues that the human Y chromosome has reached stability, where it will not degrade further, by sequencing the genomes of the rhesus macaque and comparing it to that of the chimpanzee and human genome. The study focused on the MSY, identifying five distinct regions or “strata” based on its degree of similarity to the X chromosome.

 Comparison between the macaque MSY and the human MSY revealed that they share the same 18 ancestral genes in strata 1 to 4, indicating that their last common ancestor shared the same genes and that there was no subsequent loss of these genes after the human and macaque lineages diverged 25 million years ago. In strata 5 all species showed significant gene loss, losing 5 ancestral genes (4 for macaque) over the past 30 million years. However, the same genes are found on the human and chimpanzee MSY, indicating that this region has stabilised prior to the human/chimpanzee split.



 The findings of this study contradict the linear model for the degeneration of the Y chromosome as they fail to explain the relative stability of the human MSY genes over the past 25 million years. The results suggest an exponential decay with a baseline constant which extends the lifespan of the human Y chromosome indefinitely into the future.