Genomics Video 1
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Genomics Video 1


Genomics: Observing Evolution Introduction to Terms Genomics is the study of genomes. A genome is the complete set of genetic information
that an organism needs to function. It is a set of instructions that influences
—along with an organism’s environment— how every cell in that organism’s body
will grow and develop. And that is true for all living things on the planet. Genomes are comprised of DNA. DNA is short for deoxyribonucleic acid, is a long molecule made up of four repeating units
called cytosine, guanine, adenine, and thymine. Incredibly these same four molecules called nucleotides
encode the genetic information needed for every living thing on earth. In a DNA molecule, the four repeating units create two chains
with adenine always pairing to thymine and cytosine to guanine. These sets of bonded molecules are what we call a base pair. The chains coil around each other in the form of a double helix
which is wound up tightly and packaged into chromosomes. Nearly every cell in the body carries a full set of chromosomes
in its nucleus, and therefore, a full set of the organism’s DNA. This complete set of DNA is the organism’s genome. Each chromosome has specific sets of DNA arranged as genes. Genes are the basic units of heredity. They are, biologically, what makes you
a unique member of the human species. The human genome consists of approximately 3 billion base pairs. If you were to stretch out the base pairs from a
single cell in your body, they would span over 6 feet. If you were to stretch out all of the base pairs from every cell in your body,
they would span the entire diameter of the solar system—twice! In a human cell, the 3 billion base pairs
are distributed across 23 pairs of chromosomes. But the number of base pairs
that make up a genome varies across organisms. For example, a banana has about
500 million base pairs across 11 pairs of chromosomes, while a fruit fly has over 139 million base pairs
distributed across 4 pairs of chromosomes. But while every organism within a species shares the same amount of DNA,
the sequence of their DNA is never exactly identical. Individual organisms of the same species
will share most of the same DNA sequences —any two humans share about 99.9%—however they will have
sequences that are different from one another. These distinct genetic sequences are what make every organism unique,
even within their own species. The difference in genetic characteristics within a species
is what we call genetic diversity. Think of a genome as a cookbook. A cookbook contains recipes needed to make a meal. Each recipe lists the necessary ingredients,
as well as directions for preparing and cooking the dish. In the same way, a human genome contains genes that include
the ingredients and instructions needed to make a person — muscles, bones, organs, nerves,
and the rest of the tissues that make up a human being. In cooking, some changes to recipes have no effect on the end product,
some are disastrous, and others may actually improve the dish. The same is true of genes. Genetic sequences change, or mutate, for a variety of reasons
like exposure to environmental factors and fluke accidents during the replication process. Mutations can have neutral, negative, or positive effects
on the individual organism and, ultimately, the species. Evolution is the process by which genetic information changes
within a population as it gets passed from one generation to the next. But evolution isn’t always something we can see with the naked eye. Genomics allows us to see changes in DNA sequences at a molecular level,
giving us a new and powerful tool for observing evolution.

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