Category Archives: genetics

What is CRISPR Cas9?

Have you ever heard about hemophilia? It is a rare genetic disease that disables people from clotting blood. There is not yet therapy for hemophilia. However, a new technology to change the genes related to hemophilia was developed recently. The key point in this new technology is CRISPR-Cas9. It is genetic engineering tool which enables people to cut specific region of DNA and to insert another homologous DNA. Cas9 and guide RNA (gRNA) are important molecules in CRISPR-Cas9.

Cas9, a restriction enzyme, was first discovered in the 1980s. When a virus infects a bacteria, the bacteria cut the intruder’s DNA by using Cas9.

gRNA is made from a small piece of pre-designed RNA sequence. gRNA helps the Cas9 enzyme to cut particular regions of DNA.

CRISPR stands for Clustered Regularly Interspersed Short Palindromic Repeats. Also, Cas means “CRISPR associated.” Even though this method does not destroy surrounding genes, it is possible to change a particular DNA sequence. Treatments for hemophilia using CRISPR-Cas9 are being studied now in the USA. Researchers say, “If a ‘normal blood clotting factor’ gene is inserted into a hemophilia patient, his or her blood will be clotted.”

In addition to hemophilia, CRISPR therapy related to HIV is also being studied. HIV, or Human Immunodeficiency Virus, is a virus that infects the body immune cells and corrupts the immune system.  One typical thing of HIV is that it can go into the immune cell using the specific receptor proteins that are on the surface of the immune cells. Using CRISPR method, scientists found out that getting rid of these proteins makes HIV unable to infect another cell. Then, without the proteins that enables them to infect other cells, HIVs cannot replicate themselves and therefore collapse.

Also, CRISPR is applied to not only curing genetic diseases but also developing plants and animals. By using CRISPR, researchers made MSTN, which limits the growth of pigs, not perform its role. As a result, researchers were able to get a “super pig,” that has more muscles than normal pigs.

The usage of CRISPR can make valuable crops. In 2016, Dr. Yang and his companions made new mushrooms that doesn’t turn into brown by eliminating the enzymes that cause browning in mushrooms. Korean researchers also developed various crops, such as lettuce that has resistance in harmful insects and bean that decreases the level of cholesterol.

Although CRISPR Cas9 is touted through many positive results, it is a controversial topic. For example, CRISPR Cas9 can be used in manipulating embryonic genes, which causes the whole fetus to change. Some countries prohibit this for ethical reasons. In contrast, the Human Fertilisation and Embryology Authority authorized to alter human embryos in the UK in 2016. Even though there are lots of positive effect modifying genes, we must know that there are some ethical issues that we must concern.



Understanding Genetic Variation


Genetic variation is a term that is used to describe the DNA sequence variation in human genomes. It is what makes all people unique, whether in terms of skin color, the shape of our faces, or hair color. Although individuals of same species have similar characteristics, they are rarely identical. That difference in those individuals is referred to as variation.

Amongst people, single nucleotide polymorphisms are the most common type of genetic variation. Each nucleotide polymorphism denotes a difference in a base of single DNA. In a person’s DNA, DNA bases are A, C, G or T.

Genetic variation is a result of different alleles of genes. For instance, looking at eye color, individuals with blue eyes have a unique allele of the gene for eye color, while individuals with brown eyes have a different allele of the gene.

Face shape, height, skin tone and eye color are all determined by our genes. Therefore, any variation that occurs is due to the genes we inherit from our parents. In contrast, while weight is partly influenced by genes, it is highly influenced by environment. For example, how often we exercise and how much we eat.




Understanding Penetrance in Genetics


In genetics, Penetrance is the percentage of people carrying a specific variant of a gene that also shows an associated trait. Penetrance of a disease-causing mutation is the percentage of people with the mutation who display clinical symptoms. For instance, if a mutation in the gene that results in a specific autosomal dominant disorder has 80 percent penetrance, then 80 percent of those with the mutation will have the disease, while 20 percent will not.
If clinical symptoms are shown in all people who have the disease-causing mutation, this condition is said to have complete penetrance. A condition that shows complete penetrance is referred to as neurofibromatosis type 1. In this case, the penetrance is 100 percent.
An allele is said to have incomplete penetrance if some people who have the disease-causing mutation do not express the characteristic even though they are carrying the allele. An autosomal dominant condition that shows incomplete penetrance, for example, is familial breast cancer.
If an allele has low penetrance, the trait that it expresses will not be obvious in an individual that carry the allele. An allele with high penetrance results in a trait that is almost always apparent. In low penetrance cases, it can be difficult to differentiate genetic from environmental factors.

Fatigue is Partly Influenced by Genes

Genes may contribute to why some people suffer from low energy levels or tire easily. According to recent research, being prone to fatigue is partly heritable, with genetic accounting for 8% of differences between individuals who were asked about their tiredness levels.
The study was led by Saskia Hagenaars and Dr. Vincent Deary, from the University of Edinburgh and Northumbria University respectively. They examine genetic make-up of 111,749 people who had reported whether they had low energy or felt tired in the two weeks before collection of data.
Also, the researcher also discovered that genetic predisposition to fatigue was also present in individuals genetically susceptible to various physical and mental health conditions, such as schizophrenia, depression, and smoking. Additionally, an overlap was identified between low levels of energy, and high levels of cholesterol and obesity.
According to the scientists, this raises the likelihood of a genetic linkage between fatigue and a susceptibility to physiological stress. The researchers also found that there was an overlap between a general tendency to poor health and tiredness.
The researchers said that most of the differences in tiredness are mainly environmental. The genetic data accounted for just 8.4% of people’s differences in tiredness. The findings were published in the journal Molecular Psychiatry.

Exercise and Genetics


According to the World Health Organization (WHO), after high blood pressure, high blood sugar and tobacco use, physical inactivity is the 4th leading risk factor for mortality in the world. Therefore, it is important for people to have a physically active lifestyle. But does exercise confer the same benefits on every person to the same extent?
Five universities in the US and Canada recruited 40 African-American families and 90 Caucasian families to the Heritage Family Study. The aim of the study was to investigate genetic role in the cardiovascular, hormonal and metabolic responses to the same twenty-week program of exercise the families undertook.
While race, sex, age had a minimal effect on the training effects, scientists noted in a 2007 report that was published in the American Journal of Epidemiology that there exist clear inter-individual differences in how people respond to regular exercise. These differences are aggregate in families.
The results of the study showed that genes influence how our bodies respond to physical activity. Genes play a big role in determining changes in body composition after exercise programs – such as body mass index, weight, or percentage of body fat.


Researchers Discover New Genetic Roots that Underpin Intelligence

Researchers have made a major development in understanding genes that influence intelligence. Using a large dataset of over 78,000 people with information on intelligence scores and DNA genotypes, the scientists discovered new biological routes and genes for intelligence.
Intelligence is among the most investigated human traits. Despite high heritability estimations of 80 percent in adulthood and 45 percent in childhood, only a few genes had earlier been linked to intelligence. According to a study that was published in the journal Nature Genetics, 52 genes determine human intelligence. Of these genes, 40 are new discoveries.
Also, the study showed that genetic impacts on intelligence are correlated with genetic impacts on educational accomplishment, and also, though less strongly, with intracranial volume, smoking cessation, height, autism spectrum disorder and head circumference in infancy. Inverse genetic associations were reported with depressive symptoms, Alzheimer’s disease, waist-to-hip ratio, waist circumference, schizophrenia, body mass index, and smoking history.
Scientists need to do more research to clarify the exact role of the discovered genes in intelligence. This will enable us to have a complete picture of how different genes result in intelligence differences. Currently, genetic results explain about 5 percent of the total differences in intelligence. While this is a large amount of difference for an intelligence trait, there is still a long road to go.

Genetics Determine our Eye Color

The eye color of a person results from pigmentation of the iris, which surrounds the pupil and helps to control the amount of light that can enter the eye. The color of the eye is mostly categorized as brown, green/hazel, or blue. Globally, brown is the most frequent color of the eye. Lighter eye colors, such as green and blue, are found mainly among people of European ancestry.
Colour of the eye is determined by variations in genes. Most genes that are associated with eye color play a vital role in the production, transport, and storage of a pigment known as melanin. Eye color is directly related to the quality and amount of melanin in the iris. Blue-eyed people have a small amount of melanin in the iris while brown-eyed people have a large amount of this pigment.
A specific area on chromosome 15 plays a key role in eye color. In this area, there are two genes that are located close together: HERC2 and OCA2. HERC2 gene contains a DNA segment that controls the activity of the OCA2 gene. OCA2 gene produces P protein that is involved in melanosomes maturation. Melanosomes are cellular structures that make and store melanin. Therefore, P protein plays an important role in the quality and amount of melanin available in the melanin. Less P protein produces less melanin in the iris, resulting in blue eyes. People with a large amount of melanin in their iris have brown eyes.