Tag Archives: dna

The Improbability of You: Meiosis Part One

31 Jul

In this video, we talk about how improbable it is that you exist, the durability of genetic information across time, your relatedness to all living this on earth, and your uniqueness. These concepts will lay the foundation for explaining meiosis — the cellular dance that makes you a mosaic of your ancestors who is different from everyone else, even your siblings.


The genetic alphabet

20 Oct

Illustration by D. Leja, courtesy of the National Human Genome Research Institute, http://www.genome.gov.

The genes in our chromosomes are often compared to recipes inside of a cookbook.

But if we were to open one of these cookbooks, we would find that the recipes are all written in a unique language.

Whereas we have 26 letters in our alphabet, the DNA alphabet is only four letters long: A, T, G, C.

Each letter represents a chemical base: adenine (A), thymine (T), guanine (G), and cytosine (C).

Looking at DNA directly, we see the As, Ts, Gs, and Cs arranged on that most famous genetic shape, the double helix.

To picture this shape, imagine you are holding a toy rubber ladder that you twist on both ends.  The sides of the ladder are sugar and phosphate molecules; the rungs of the ladder are As paired with Ts, or Cs paired with Gs, fitted together in units called base pairs.

If you unravel the DNA, you reveal the recipes of As, Ts, Cs, and Gs that are written into genes in the form of three-letter words called codons (so named because they are little codes). Continue reading

Cheat Sheet: Genes, Chromosomes and DNA

25 Sep

Nature is the type of cook who is lost without her recipes. Chromosomes are cookbooks, and we have two editions of each.  The recipes are genes.

When we talk about our genes, we are talking about the packages of biological information that we inherit from our parents, and less directly, from our millions of ancestors.

According to the researchers who mapped the human genome, a person has about 20 to 25,000 genes.

Our genes are made up of DNA (deoxyribonucleic acid) strung together by the millions to make thread-like strands called chromosomes at the center (nucleus) of almost all of the trillions of cells in our bodies.

We have 46 chromosomes–23 from mom, 23 from dad.  Each set (mom’s and dad’s) contains only slightly different versions of the same genes.  Technically, each version is called an allele (pronounced uh-LEEL).

Our bodies read our genetic “recipes” in order to cook up amino acids that are the building blocks of proteins.  Proteins, in turn, help our bodies to form, grow, heal, move and function.

Explore the “Cheat Sheets” category to read index cards covering the basics of genetics.