I got my love handles, those pesky rounds bits around my stomach, from my mother and she got them from my grandmother. My Irish friend got his red hair from generations he has never known.
Have you ever wondered how you came to be the way you are? Why you inherited your grandmother’s big hips or didn’t inherit your grandfather’s blue eyes?
With September being Heritage Month, it seems appropriate that we know what our heritage is, where we come from but also how we received this heritage.
An amazing 99.9% of your DNA is identical to that of every other person in the world, yet not even identical twins are the same. That 0.1% makes you who you are, unique in every way.
All these questions about who you are can be answered through genetics. Every cell in our bodies, 50 to 75-trillion cells, contains about 20 000 different genes. Even though all the cells contain the same components they serve different functions.
Genes, the small components that make up DNA molecules, hold information to build cells and pass on genetic traits such as skin colour and health conditions. In a way, genes are like your body’s instruction manual.
A chromosome is made up of chromatin, a complex of DNA, RNA and proteins. The structure and organisation of chromosomes, which look like a fattened X, is achieved through coiling and an extensive packing ratio.
“If you had to take only one cell from your body and stretch the chromosomes out, it would be about two metres long,” says Jean Mollett from the school of molecular and cell biology at Wits.
Your genes are on the 46 chromosomes that are in an average human cell. We receive 23 chromosomes from our mother and 23 from our father.
There are about 8-million possible genetic combinations when chromosomes recombine during the process of meiosis, in which we get our genetic makeup from our parents’ DNA.
This means the resulting zygote, or combined chromosomes, is composed of 1 in 70-trillion possible combinations of chromosomes. That is how unique you are: a 1 in 70-trillion chance that you are who you are.
Genetic inheritance is determined by meiosis, which is when new cells are created with half of the chromosomes.
Mitosis is the process of basic cell division in which cells are multiplied.
“Through the process of mitosis, chromosomes duplicate and then divide one cell into two genetically identical cells,” Mollett says. (See figure 1.)
“Meiosis is necessary to halve the chromosome number, so that the numbers remain constant from one generation to the next.” (See figure 2.)
Meiosis occurs in females when they are in their mother’s womb while it occurs in males when they reach puberty. Meiosis takes place in the ovaries and testes. Mitosis, on the other hand, occurs every day as we make new cells.