Genes are the things that determine physical traits ─ how we look ─ and lots of other stuff about us. They carry information that helps make you who you are: curly or straight hair, long or short legs, are all passed through generations of your family in genes. Each cell in the human body contains about 25,000 to 35,000 genes, which carry information that determines our traits. Traits are characteristics we inherit from our parents; this means our parents pass some of their characteristics onto us through genes.
Genes hang out all lined up on threadlike things called chromosomes. Chromosomes come in pairs, and there are hundreds, sometimes thousands, of genes in one chromosome. The chromosomes and genes are made of DNA, which is short for deoxyribonucleic acid.
What is DNA?
DNA exists as two long, paired strands spiralled into the famous double helix. Each strand is made up of millions of chemical building blocks called bases. While there are only four different chemical bases in DNA (adenine, thymine, cytosine, and guanine) the order in which the bases are covered determines the information available, much as specific letters of the alphabet combined to form words and sentences.
DNA resides in the core, or the nucleus, of each of the body’s trillions of cells. Every human cell contains the same DNA. Each cell has 46 molecules of double-stranded DNA. Each molecule is made up of 50 to 250 million bases housed in a chromosome.
How do Genes work?
Each gene has a special job to do. It carries blueprints ─ the instructions ─ for making proteins in the cell. Proteins are the building blocks for everything in our body. Bones and teeth, hair and earlobes, muscles and blood, all are made up of proteins. Those proteins help our bodies grow, work properly and stay healthy. Scientists today estimate that each gene in the body may make as many as 10 different proteins. That was over 300,000 proteins!
Like chromosomes, genes come in pairs. Each of our biological parents has two copies of each of their genes, and each parent passes along just one copy to make up the genes we have. Genes that are passed onto us determine many of our traits, such as your hair colour and skin colour.
When there is problem with Genes:
Sometimes parents pass altered or defective genes onto their offspring. If gene does not work properly it can cause diseases or illness. Let us take the example of Haemoglobin. Haemoglobin is an important protein that is needed for Red Blood Cells to carry oxygen throughout the body. If parents pass on altered haemoglobin genes to their child, the child may only be able to make a type of haemoglobin that doesn’t work properly. This can cause a condition known as anaemia, a condition in which a person has fewer healthy Red Blood Cells.
Anaemia that is inherited can sometimes be serious enough to require long-term medical care. Sickle cell anaemia is one kind of anaemia that is passed on through genes from parents to children.
Cystic fibrosis is another illness that some children inherit. Parents with CF gene can pass it onto their child. People who have CF often have trouble breathing because their bodies make a lot of mucus that gets stuck in the lungs. They will need treatment throughout their lives to keep their lungs as healthy as possible.
Difference between Genotype and Phenotype:
Genotype: a genotype is an individual’s collection of genes. The term can also refer to the two alleles inherited for a particular gene.
Phenotype: a phenotype is an individual’s observable traits, such as height, eye colour and blood type. The genetic contribution to the phenotype is called the genotype. Some traits are largely determined by the genotype, while other traits are largely determined by environmental factors.
Variant forms of the same gene. Different alleles produce variations in inherited characteristics such as eye colour i.e., alleles for black, brown, green eyes or blood types such as alleles for A,B,O blood group.