The Foundations of Genetics At the core of inheritance and variation lies the molecule of DNA , which contains the instructions for an organism's characteristic...
At the core of inheritance and variation lies the molecule of DNA, which contains the instructions for an organism's characteristics. These instructions are organized into functional units called genes, which are found on chromosomes. Different versions of the same gene are called alleles, which can be either dominant or recessive.
We can use Punnett squares to predict the possible genotypes and phenotypes of offspring based on the parents' alleles. This helps understand patterns of inheritance for different traits.
Problem: In pea plants, the allele for tall plants (T) is dominant over the allele for short plants (t). If a heterozygous tall plant (Tt) is crossed with a short plant (tt), predict the offspring's genotypes and phenotypes.
Solution:
Variation arises from genetic factors (differences in genes and alleles inherited from parents) and environmental factors (such as climate, nutrition, and lifestyle).
According to Darwin's theory of evolution by natural selection, individuals with favorable variations are more likely to survive and reproduce, passing on their advantageous traits to subsequent generations. Over time, this process can lead to the formation of new species (speciation).
Evidence for evolution includes fossils (remains of ancient organisms) and the development of antibiotic resistance in bacteria.
Knowledge of genetics and variation is applied in selective breeding (selectively breeding organisms with desired traits) and genetic engineering (directly modifying an organism's genetic material). These techniques have applications in agriculture and medicine but also raise ethical concerns.