blueprint of life 2.2 Flashcards
outline the experiments carried out by Gregor Mendel
1822-1884Mendel examined the following seven characteristics found in peas:
Flower colour, purple or white Flower position, axial or terminal Seed colour, yellow or green Seed shape, round or wrinkled Pod shape, inflated or constricted Pod colour, green or yellow Stem height, tall or short. Mendels explanation of his results were as such: -inheritance is not the blending of characteristics -inheritance is controlled by a pair of particles in the cells which he called factors -these two factors segregate from one another when sex cells are formed -characteristics are either dominant or recessive.
describe the aspects of the experimental techniques used by Mendel that led to his success
Mendel was successful because he:
- used peas, which were easily grown and produced successive generations rapidly
- selected easily observable characteristics
- strictly controlled the fertilisation process
- used mathematics rigorously to analyse his results
- used large numbers of plants
- studied traits that had two easily identified factors.
describe outcomes of monohybrid crosses involving simple dominance, using Mendel’s explanations
- mono-hybrid crosses involves looking at one characteristic only.
- an example of this could be, true breeding (homozygous) tall plant crossed with a true breeding (homozygous) short plant. This produces a first generation where all of the plants are tall. Mendel explained the first generation trait as the dominant factor.
distinguish between homozygous and heterozygous genotypes in monohybrid crosses
- Alternative factors for the same characteristics are termed alleles, e.g. tall and short are alleles for height; purple and white are the alleles for flower colour.For each characteristic there are at least two factors controlling the phenotype. Gametes (sperm and egg) from each parent contain only one factor. When gametes are formed the pair of factors segregate (separate).
- Factors that are the same are termed homozygous, e.g. TT and tt.
- Factors that are different are termed heterozygous, e.g. Tt.
distinguish between the terms allele and gene, using examples
genotype: the type and arrangement of genes( or gene pair)
genes: are pasted from parent to offspring, characteristics are controlled by at less two genes, half the genes come from each parent.
alleles: is an alternative for a particular inheritable characteristic, e.g. tall (T) and short (t) are two alleles for the characteristic of height in some plants. they form heterozygous. non-pure breeding or hybrid organism is heterozygous
process information from secondary sources to identify and describe an example of hybridisation within a species and explain the purpose of this hybridisation
Hybridisation means the breeding of two different types of plants or animals. For example, a mule is the result of the union between a horse and a donkey, two different species.
Many, probably most agricultural animals and plants are the result of hybridisation. This results in offspring with desirable characteristics e.g. cross breeding cattle to produce better meat or to be tick resistant and Triticale a grain that is a cross between wheat and rye, two different species. Hybridisation is a good way of producing new commercial plants and animals.
outline the reasons why the importance of Mendel’s work was not recognized until some time after it was published
Mendel began his work in 1858 and published the results of his experiments in 1866, but his work lay undiscovered until 1900 when others performed similar experiments. It was only then that the importance of his work was realized. It is unclear why such original work went unnoticed, perhaps:
- Mendel was not a recognized, high profile member of the scientific community - he presented his paper to only a few people at an insignificant, local, scientific meeting - other scientists did not understand the work or its significance.
