DNA, Genes and Chromosomes

 

The sum of a dog’s genetic material can be thought of as a cook book which is split into chapters containing recipes.  These recipes are the dog's genes and the letters that make up each recipe is its DNA.  Just as a recipe can be used to make a dish of food, a gene can be used to make a protein, a building block of a dog's body.

What is DNA?

DNA, or deoxyribonucleic acid, is found in all known living things and acts like a set of biological instructions. These instructions make every breed, species and dog (apart from identical siblings) unique. DNA is found in nearly every single cell in the body, apart from red blood cells, and tells a dogs body how to grow, develop, work and reproduce.  

How are a dog’s genetic instructions stored?

A dog’s genetic instructions are stored as a type of code that is made up of units called bases.  There are four different bases found in DNA and these are named adenine (A), guanine (G), cytosine (C) and thymine (T).  Each base unit is linked to a sugar molecule and a phosphate molecule, which allows a string of bases to form.  Just as a sequence of letters can be used to form words, and words be used to form sentences, so too can the sequences of bases on the string be used to produce the proteins that make up each organism. Proteins are the building blocks for ever organism and make up bones, teeth, hair, muscle etc.

The importance of DNAs structure

Two complementary strings of bases lie parallel to one another and lock together to form a structure similar to a spiral staircase, called a double helix.  Bases from each of the two strings zip together to form the “steps” of the structure.  Each base will only bond to a specific partner base, for example adenine always bonds with thymine, and cytosine always bonds with guanine.  This feature of DNA is particularly important when it comes to producing new cells with the same DNA, which is vital for growth, maintenance and repair.  When cells divide the double helix structure unzips, freeing up each of the two string of bases to bond to another set of bases, therefore producing two copies of the original DNA.

How many base pairs does a dogs DNA have?

The dog genome (the sum of its genetic material) contains 2.8 billion base pairs of DNA.

What is a gene?

A gene is a section of DNA that has specific instructions for making a particular molecule, usually a protein.  Each dog has two copies of every gene, one of which is inherited from its mother and one from its father.  These two genes may be the same or they may be slightly different.  These different versions of the same gene are called alleles.  These differing genes contribute to each dog’s unique physical features and account for the differences between each dog and each breed.

How many genes does a dog have?

There are around 19,000 protein coding genes in the dog genome.

What is a chromosome?

Chromosomes are structures found inside a cell’s nucleus (the core of a cell) and are composed of DNA wound around proteins. The structure of a chromosomes keeps DNA tightly packed and wound around spool-like proteins called histones.  Without these structures, DNA would be far too long to fit inside each cell.  If unwound and placed end to end, the DNA from one dog’s cell would reach up to several feet long.  In order for a dog to function, each cell must frequently divide and replace old cells with new ones. Chromosomes ensure that DNA is evenly distributed and are accurately copied during cell division.

How many chromosomes does a dog have?  

Each cell in a dog’s body contains 39 pairs of chromosomes.

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