Gregor Mendel Flashcards
Who is Gregor Mendel
An Austrian monk who was the first person to attempt to discover scientifically the laws at work in heredity.
He conducted careful experiments on pea plants, concentrating on a few hereditary characteristics. He also applied mathematical techniques to analyse his results.
What were Mendel’s three laws?
By applying mathematical principles to his observations Mendel figured out three principles which have become the basic laws of genetics:
The Law of Dominance
The Law of Segregation
The Law of Independent Assortment
Basis of forming Law of Dominance
Basis: Mendel crossed homozygous round-seed pea plants with homozygous wrinkled seed pea plants. All offspring produced were heterozygous yet they were all round seeds.
Law of Dominance
A dominant expression of a trait is seen in the offspring when contrasting genes for the trait are present. The wrinkled-seed expression is recessive since it was hidden in the heterozygous offspring.
Basis of forming Law of Segregation
Mendel found that when he crossed hybrid tall pea plants, he obtained nearly three tall plants for every short plant.
Law of Segregation
During meiosis pairs of genes separate. One gene from each pair goes into a haploid sperm or egg. This means a sperm produced by a pea plant that is heterozygous for stem length (Tt) could carry a gene for tall (T) or a gene for short (t).
Basis of forming Law of Independent Assortment
During meiosis, homologous pairs of chromosomes separate. The genes located on one homologous pair (Rr) go into gametes independently of the genes located on another homologous pair (Yy). As a result gametes containing different combinations of genes are produced.
Law of Independent Assortment
A gene goes into a sperm or egg independently of other genes. Each gene is an independent unit that is inherited on its own. For example, a gene for wrinkled peas assorts independently of the gene for yellow peas.
Why did Mendel decide to use pea plants
They’re easy to grow, have a short life cycle, they’re reproduction could be controlled.
Artificial pollination
Involves removing stamens before natural pollination occurs. Later the mature pistil is hand-pollinated by applying the desired pollen to the pistil. The flower is covered to prevent further contamination
Factors contributing to Mendel’s success
- He selected only a few characteristics/traits for study.
- Cross-pollinated by hand
- Started breeding experiments with pure strains for each characteristic studied
- Characteristics in pea plants are determined by a single pair of genes (plant height T and t gene)
- He repeated his experiments several times and kept records
