Area of Study 1: Heredity
This area of study focuses on molecular genetics and the investigation not only of individual units of inheritance, but also of the genomes of individuals and species. Students investigate inheritance in asexually reproducing organisms and the mechanism and patterns of transmission of heritable traits in sexually reproducing organisms.
Students examine the process of meiosis in terms of inputs and outputs and, in accounting for variations in offspring, consider the interplay between genotype and environmental factors, the significance of mutations in DNA, and the relationship between alleles.
All prokaryotes reproduce asexually, without the formation and fusion of gametes. Many plants and fungi also reproduce asexually, meaning that they are genetically identical to their parent. Types of asexual reproduction include:
- Binary fission (bacteria)
- Budding (yeast)
- Vegetative reproduction (strawberry runners, aloe)
- Sporulation (fungi, algae, ferns)
- Fragmentation (annelids, sea-stars)
- Parthenogenesis (some lizards, sharks and stick-insects)
This week we will begin to study molecular genetics – the foundations of ‘who we are’, before environmental factors play a role. Half your DNA comes from your mother (eggs produced in the ovaries) and half from your father (sperm produced in the testes). This DNA contains genes and genes code for proteins, so the gametes (eggs and sperm) contain the genetic instructions that cross the generation gap, giving you the characteristics that you share with your biological parents. The genetic instructions in an organism make up it’s genotype, which is expressed visually as the phenotype (physical, biochemical and physiological traits).
Humans have 23 pairs of chromosomes, often referred to as the diploid number or 2n=46. The image above is called a karyotype, used to assist with chromosomal analysis – is this one from a male or female? Chromosomes can be distinguished by their relative size, position of the centromere and the patterns of light an dark bands. Matching pairs are said to be homologous. A human male has non-homologous sex chromosomes (XY).
More Resources for this Unit:
- Douchy’s videos
- Douchy’s podcasts
- The Biology Place – some good animations.
- Biology animations – more animations.
- Click4Biology – Comprehensive information.
- Biology Interactive tutorials
- Educator AP Biology – animated videos
- Biology4kids – simplified definitions of conccepts
- i-Biology – a list of great resources, particularly for IB Biology