Case 12 Listen to what Mendel had to say!
1. What is population genetics and what affects this population genetics?
Population genetics is the study of the genetic composition of populations, including
distributions and changes in genotype and phenotype frequency in response to the
processes of natural selection, genetic drift, mutation and gene flow.
2. What is the mendels law?
Mendel discovered that by crossing true-breeding white flower and true-breeding purple
flower plants, the result was a hybrid offspring. Rather than being a mix of the two colors, the
offspring was purple flowered. He then conceived the idea of heredity units, which he called
“factors”, one of which is a recessive characteristic and the other dominant. Mendel said that
factors, later called genes, normally occur in pairs in ordinary body cells, yet segregate
during the formation of sex cells. Each member of the pair becomes part of the separate sex
cell. The dominant gene, such as the purple flower in Mendel’s plants, will hide the recessive
gene, the white flower.
Mendel stated that each individual has two alleles for each trait, one from each parent. Thus,
he formed the “first rule”, the Law of Segregation, which states individuals possess two
alleles and a parent passes only one allele to his/her offspring. One allele is given by the
female parent and the other is given by the male parent. The two factors may or may not
contain the same information. If the two alleles are identical, the individual is called
homozygous for the trait. If the two alleles are different, the individual is called heterozygous.
The presence of an allele does not promise that the trait will be expressed in the individual
that possesses it. In heterozygous individuals, the only allele that is expressed is the
dominant. The recessive allele is present, but its expression is hidden. The genotype of an
individual is made up of the many alleles it possesses. An individual’s physical appearance,
or phenotype, is determined by its alleles as well as by its environment.
homozygous: of an organism in which both copies of a given gene have the same allele
heterozygous: of an organism which has two different alleles of a given gene
allele: one of a number of alternative forms of the same gene occupying a given position on
a chromosome
1. What is population genetics and what affects this population genetics?
Population genetics is the study of the genetic composition of populations, including
distributions and changes in genotype and phenotype frequency in response to the
processes of natural selection, genetic drift, mutation and gene flow.
2. What is the mendels law?
Mendel discovered that by crossing true-breeding white flower and true-breeding purple
flower plants, the result was a hybrid offspring. Rather than being a mix of the two colors, the
offspring was purple flowered. He then conceived the idea of heredity units, which he called
“factors”, one of which is a recessive characteristic and the other dominant. Mendel said that
factors, later called genes, normally occur in pairs in ordinary body cells, yet segregate
during the formation of sex cells. Each member of the pair becomes part of the separate sex
cell. The dominant gene, such as the purple flower in Mendel’s plants, will hide the recessive
gene, the white flower.
Mendel stated that each individual has two alleles for each trait, one from each parent. Thus,
he formed the “first rule”, the Law of Segregation, which states individuals possess two
alleles and a parent passes only one allele to his/her offspring. One allele is given by the
female parent and the other is given by the male parent. The two factors may or may not
contain the same information. If the two alleles are identical, the individual is called
homozygous for the trait. If the two alleles are different, the individual is called heterozygous.
The presence of an allele does not promise that the trait will be expressed in the individual
that possesses it. In heterozygous individuals, the only allele that is expressed is the
dominant. The recessive allele is present, but its expression is hidden. The genotype of an
individual is made up of the many alleles it possesses. An individual’s physical appearance,
or phenotype, is determined by its alleles as well as by its environment.
homozygous: of an organism in which both copies of a given gene have the same allele
heterozygous: of an organism which has two different alleles of a given gene
allele: one of a number of alternative forms of the same gene occupying a given position on
a chromosome
