• Gregor Mendel?was an Austrian monk
• He was trained in mathematics and natural history at the University of Vienna
• In the mid-19th century, Mendel carried out breeding experiments on large numbers of pea plants whilst looking after the monastery gardens
• He studied how?characteristics were passed on between generations of plants
• Due to his extensive work on the understanding of inheritance, he is sometimes called the?father of genetics

Mendel's groundbreaking work

• Mendel carefully?transferred pollen?from one pea plant to the reproductive parts of another
• This technique?eliminated any uncertainty?from his data since he knew which plants were fertilized by which pollen
• He?collected the pea seeds from these plants?and grew them in favourable conditions to find out their characteristics
• He also?cross-bred offspring peas?in order to find out which, if any characteristics would appear in future generations
• Mendel investigated the?height?of pea plants, the?colours of their flowers?and the?smoothness of their seed coat

Mendel's pea plant crosses

Mendel's Pea Plant Results Table

• Mendel found that characteristics were?inherited?in a?predictable pattern
• All?pea plants in the first generation had the same characteristic as?one?of the parental plants
• The offspring plants in the second generation had characteristics of?both?parent plants in a?3:1 ratio
• Without knowing it, Mendel had discovered genes, he referred to them as?'units of inheritance'
• He also discovered that some genes are?dominant?and some genes are?recessive
• Different forms of the same gene are called?alleles

NOS: Making quantitative measurements with replicates to ensure reliability; Mendel's genetic crosses with pea plants generated numerical data

• Mendel was not the first to investigate inheritance using plants
• However, he was the first to generate strong numerical (quantitative) data, as opposed to observations only (qualitative)
• Mendel also used a?large number?of pea plants in his studies, for example in one investigation he recorded the characteristics for over 7,000 pea seeds
• By recording data for such a large number of seeds he ensured?reliability?in his conclusions
• Many replicates?are important in a scientific investigation because they allow for:
  • Ensuring reliability of results
  • Identification of anomalous points
  • Further statistical analysis to establish a significant difference

• Gametes are the?sex cells?of an organism
• For example, the?sperm?and?egg?(ovum) cells in humans
• The?egg is larger than the sperm?as most of its space contains food to nourish a growing embryo
• The sperm cell contains?many mitochondria?to release energy for its motion
• Gametes?fuse?during fertilization to form a?zygote
• These sex cells are formed during?meiosis?and only have?one?copy of each chromosome and so are?haploid?cells
  • For humans, that means the sperm and egg cells contain?23 single chromosomes?in their nucleus
  • As there is only?one chromosome from each homologous pair?there is only?one allele?of each gene present
    • This allele may be dominant, recessive or?co-dominant

The structure of human gametes - the sperm and egg