GENETICS
Though all humans share the same basic body plan, each of us (apart from identical twins) has a unique mixture of features. That is because the set of instructions – called genes – required to construct a human varies slightly from person to person. Genetics is the study of how the genes we inherit from our parents shape the way we are.
- DNA Long molecules of DNA (deoxyribonucleic acid) are found in everybody cell. When magnified, DNA resembles a twisted ladder with “rungs” made from four types of chemicals called bases. The sequence of bases along a section of DNA forms an instruction – a gene – for making one of the proteins that build and run a cell.
- CHROMOSOMES A cell’s DNA molecules are packaged into 23 pairs of chromosomes, which are found in the nucleus, the cell’s control centre. Normally they are long and thin, but when a cell prepares to divide into two new cells, each chromosome shortens – as its DNA coils up – and duplicates, taking on the X-shape shown here.
- INHERITANCE We inherit half of our chromosomes from each of our parents. A set of 23 chromosomes contains about 25,000 genes. Maternal and paternal chromosomes carry matching pairs of each gene – such as the gene that controls eye colour – but not necessarily the same version. If two versions are present, only one – the dominant gene – has an effect.
- GENETIC SIMILARITY As brothers and sisters inherit a selection of genes from the same two people, their parents, they are more likely to resemble each other than they would a non-relative. Identical twins share almost identical genes, so they look the same and are of the same sex.
Picture Credit : Google
