Telomere
Do you know what telomere is? Telomeres are nucleotide sequences that sit like a cap on the ends of the linear chromosomes and protect the DNA from mutation and progressive degradation. Now scientists know that telomeres are very important for survival. unfortunately telomere lengths shorten with age and this predisposes old people to malignant changes. Lifestyle factors such as smoking, lack of physical activity, obesity, stress, and exposure to pollution can increase the speed of telomere shortening. Today everybody wants to know how to keep their telomeres lengthy and healthy, or even increase the length of their telomeres, if possible. There is an enzyme called telomerase that can slow, stop, or even reverse telomere shortening but sadly the telomerase level in our bodies declines as we age. Do you think it will be possible someday to lengthen life expectancy or even reach immortality with maintaining the length of telomeres?
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Deoxyribonucleic Acid (DNA)
James Watson is the scientist who first proposed the double helix structure of the DNA molecule in 1953, around 70 years ago. Double helix is the appearance of two intertwined strands of nucleotide molecule sequences containing the genetic instruction of organisms. This genetic information is squeezed into what we know as chromosomes and settle in the nucleus, in animals and plants (eukaryotes). This double helix structure is the base of the great branch of genetics. Gregor Mendel, a Christian friar, was the first to study genetics scientifically in the 19th century on pea plants. Charles Darwin's theory of evolution is also based on inheritance and genetics. However, at their time, they didn't know any of the things we now know about DNA and its fantastic structure.
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James Watson
As mentioned in the last section, the double structure of DNA, its discovery, and its study is linked with the name of James Watson. He received the Nobel Prize in Physiology or Medicine on 1962 for his endeavor's in this field. There are always other people that help such great advancements in science, people we have not even hear of. Rosalind Elsie Franklin was an English scientist who contributed a lot in understanding the structure of DNA. Her contribution was not acknowledged enough in this field during her short lifetime. She passed away because of cancer at the age of 38 and was never nominated for a Nobel Prize. Talking about James Watson, I should mention his controversial ideas about intelligence and race. During his interviews he has repeatedly asserted that some races are genetically more intelligent. His comments has caused much controversy and opposition. He has lost some of his honorary titles due to these statements.
Down Syndrome
You may know someone with Down Syndrome in your family or neighborhood. They are lovely, warm-hearted, and kind. Patients with Down Syndrome usually suffer from a spectrum of health problems and their IQ scores are usually lower than normal. Did you know that there are some patients with Down Syndrome with relative normal intelligence and life style? These guys can function normally, have a job, and even marry and create a family. How can this be possible? In Down Syndrome, there is an extra chromosome 21, that is why it is sometimes called trisomy 21. people with Down Syndromes have 47 chromosomes rather than 46. but there is a rare kind of Down Syndrome that is the result of mosaicism. In this unusual variant, some cells in the body are normal and some other have an extra chromosome 21. In this rare condition, symptoms are mild and the IQ can be rather normal.
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Genotype Vs. Phenotype
There are two terms in genetics: genotype and phenotype. Do you know the distinction between these two? Genotype, as you might know, is the organism's heredity information that is stored in its genome (the DNA). Genotype gives the command or in other words is the road map. On the other hand, phenotype is the organism's actual observed properties. With this definition you may expect that with a given genotype, you will always have a specific phenotype. But there is something called phenotype plasticity. It means that environment also has a strong influence on the phenotype. You may have a specific genotype but due to environmental situations your phenotype may differ.
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Epigenetics
When you study genetics today, you inevitably have to deal with epigenetics. Epigenetics is relatively a new concept in genetics. You have so many genes in your genetic map but among all, only some are translated and some are not. In other words, some genes are expressed and you see its effect in the phenotype while others genes are silent or asleep. This explains phenotype plasticity in the previous section. Environmental and external factors can cause a gene to become active or silent. These changes then get passed on to next generations. Epigenetic is a very important concept in genetic because there is no need for the DNA sequence to change. DNA sequence changes, due to mutation, takes a very long time and need many generation for a notable change to appear while with epigenetics, these changes appear easy and soon.
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Mutation
One of the most important topic in genetics is mutation. It is the mutation that changes the DNA sequence and genotype. Mutations happen a lot and on a daily basis in every organism. In the Covid-19 pandemic, you can see this obviously. Every day you hear new variants of the virus appearing in different parts of the world: Great Britain, South Africa, Brazil, India. It is important to know that mutation happens much more than what is seen. However, most mutated cells are killed by organism's various defense mechanisms. Many other mutations are silent and cause no observable effect.
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Mitochondria
You can find DNA molecules not only in the cell nucleus but also in the mitochondria. Mitochondria is another part of the eukaryotic cells and is responsible for chemical energy production (ATP). Unlike DNA in the nucleus which is double helix, the DNA in mitochondria is organized as several copies of a single, usually circular chromosomes; this likens them to prokaryotic cells such as bacteria. One theory about the origin of mitochondria suggests that mitochondria was once a free living prokaryotic organism and has emerged into a symbiotic relationship by entering the eukaryotic cells many million years ago. You know that while the "Y" chromosome is descended from the father side, mitochondria has its origin in the mother side and by studying the mitochondria in a person you can gather useful information about his/her matrilineal lineage.
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How Are Chimpanzees Similar To Humans?
Human genome is much similar to primate genomes. Among orangutans, guerillas, and chimpanzee DNAs, chimpanzees have the most similarity with human DNA. When DNA insertions and deletions are taken into account, humans and chimps share 96 percent of their sequence. How can this be possible - This much difference in phenotype with this much similarity in genetic sequence? This can be understandable if you consider that this 4 percent difference in insertion and deletions and reverse mutations can cause so many genes to be active or inactive.
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Haplogroup
Haplogroup is another term in genetics. Study of haplogroups are based on mutations that happen once in a while in different parts of the DNA sequence and pass on to the next generations. By studying haplogroups you can search for the ancestral origins dating back thousands of years. Since Y chromosome passes from father to child, by studying haplogroups on the "Y" Chromosome, you can gather information about the patrilineal lineage. On the other hand, Mitochondria pass from the mother to the offspring, so by studying haplogroups on mitochondria, you are actually looking for your mother ancestry. Do you know anyone who has taken an ancestry test. In ancestry tests, they give you some information about your ancestral origin in the past. It should be interesting. Haplogroups are identified by a letter of the alphabet. A and B haplogroups are the oldest ones and closest to our common ancestor (scientific Adam and Eve). You can find A and B haplogroups in indigenous tribes of Pygmies in Africa.