Inheritance: Chromosomes and Genes

Inheritance involves the transfer of genetic characteristics from parents to their offspring, which are either directly visible or unseen traits.
Chromosomes are bundles of tightly coiled DNA located in the nucleus of almost every cell in our body. Humans normally have 23 pairs of chromosomes, totalling 46.
Genes are the segments of DNA found on chromosomes that determine the characteristics of an individual. They are the basic genetic units responsible for the physical and inheritable characteristics or phenotype of an organism.
A single chromosome contains many genes, not all of which are expressed at the same time. When a gene is expressed, it is transcribed into mRNA and then translated into a protein that carries out a particular function in the body.
Genes are passed from parents to offspring in their gametes. This transmission of genetic information is known as inheritance.
Each individual has two copies of each gene – one from the mother and one from the father.
Different versions of the same gene are called alleles. These differences in alleles contribute to the variation in physical appearance among individuals.
Gregor Mendel’s laws, including the law of segregation and the law of independent assortment, form the basis of our understanding of genetic inheritance. These laws describe how genes behave during the formation of gametes and in subsequent generations.
Sex determination in humans is controlled by the presence of two X chromosomes (XX) in females and one X and one Y (XY) in males.
Punnett squares are commonly used to predict the outcomes of genetic crosses, including inheritance patterns of specific traits and probability of offspring having particular genotypes or phenotypes.
Genetic mutations can cause changes in the DNA sequence of a gene, leading to different characteristics or diseases. Mutations can be spontaneous or can be caused by environmental factors like radiation or chemicals.
Variation within a species can be due to genetic factors (genetic variation), the environment (environmental variation), or a combination of both (interaction of genes and the environment).
An understanding of genomics allows scientists to study and combat genetic diseases, and it is instrumental in the development of personalised medicine.
The Human Genome Project was a huge scientific endeavour that mapped all of the genes in the human genome. This information has greatly increased our understanding of human biology and disease.