![]() This outcome shows that the genes for smooth, yellow peas are dominant while the genes for wrinkly, green peas are recessive.However, when two smooth, yellow peas from this first generation were crossed to produce a second generation (F2), the result was 75 percent smooth, yellow peas and 25 percent wrinkly, green peas (3:1).Every single pea resulting from this first cross, the first generation (F1), was smooth and yellow.In one experiment he cross fertilised smooth, yellow pea plants with wrinkly, green peas:.Sometimes he transferred pollen to and from flowers on the same plant (self-fertilisation) or from another plant’s flowers (cross fertilisation).Gregor used peas in his experiments primarily because he could easily control their fertilisation, by transferring pollen from plant to plant with a tiny paintbrush.From years of experiments using the common pea plant, Gregor Mendel was able to describe the way in which genetic characteristics are passed down from generation to generation.The simplest form of inheritance was uncovered from the work of an Austrian monk called Gregor Mendel in 1865.Most phenotypes are influenced by an individual’s genotype, although environment can also play a role (nature versus nurture).For example, if we are talking about eye colour the phenotype of an individual may mean blue, brown or green eyes. The phenotype is a description of the physical characteristics of an organism.Illustration to show the inheritance of dominant and recessive alleles for eye colour. This is because the allele for brown eyes is dominant, while the allele for blue eyes is recessive (see image below).As a result, the individuals phenotype will be brown eyes.For example, if we are talking about the genotype for eye colour we may say an individual has one brown eye allele (B) and one blue eye allele (b). ![]() The genotype of an individual influences their phenotype.It can be used to describe an entire genome or just an individual gene and its alleles. The genotype is a description of the unique genetic makeup of an individual.When an egg joins with a sperm containing a Y chromosome, the result is a boy.When an egg joins with a sperm containing an X chromosome, the result is a girl.Male gametes (sperm) can carry either an X or a Y.Female gametes (eggs) therefore always carry an X chromosome.Males have an X chromosome and a Y chromosome (XY).The sex of an individual is determined by the sex chromosomes called the X chromosome and the Y chromosome.This is why diseases can run in families.If there is a mutation in the genetic material, this can also be passed on from parent to child.This passing down of genetic material is evident if you examine the characteristics of members of the same family, from average height to hair and eye colour to nose and ear shape, as they are usually similar.Each of the cells in the new person contains genetic material from the two parents.This cell (the fertilised egg) has two sets of 23 chromosomes (diploid) and the complete set of instructions needed to make more cells, and eventually a whole person.However, in sexual reproduction the sperm cell combines with the egg cell to form the first cell of the new organism in a process called fertilisation.An exception to this rule are the sex cells (egg and sperm), also known as gametes, which only have one set of chromosomes each (they are haploid).Most of our cells contain two sets of 23 chromosomes (they are diploid).Inheritance describes how genetic material is passed on from parent to child.We get one copy of our genome from each of our parents. ![]()
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