The Work of Gregor Mendel Section 11 1

The Work of Gregor Mendel Section 11– 1

1. GENETICS n The scientific study of heredity is called. n Genetics

1. Gregor Mendel’s peas. b. When pollen fertilizes an egg cell, a seed for a new plant is formed. c. Pea plants normally reproduce by selfpollination.

What does it mean when pea plants are described as being true-breeding? If the plants are allowed to self-pollinate, they would produce offspring identical to themselves.

1. Mendel the Monk n To perform his experiments, how did Mendel prevent pea flowers from selfpollinating and control their crosspollination? He cut away the pollen-bearing male parts of a flower and dusted that flower with pollen from another plant.

1. Traits n Specific characteristics that vary from one individual to another.

1. Hybrid n The offspring of crosses between parents with different traits.

1. Genes n Chemical factors that determine traits

1. Alleles n The different forms of a gene

1. Principle of Dominance n State n Some the principle of dominance. alleles are dominant and others are recessive.

1. Dominance vs. Recessive n Is the following sentence true or false? n An organism with a recessive allele for a particular form of a trait will always exhibit that form. n False

Dominance vs. Recessive n Circle the letters of the traits controlled by dominant alleles in Mendel’s pea plants. n a. n tall c. yellow

Segregation

Mendel’s Experiment How did Mendel find out whether the recessive alleles were still present in the F 1 plants? n He allowed the F 1 plants to produce an F 2 generation by self-pollination.

Mendel’s Experiment n About one fourth of the F 2 plants from Mendel’s F 1 crosses showed the trait controlled by the allele.

Mendel’s Experiment n Circle the letter of each sentence that is true about Mendel’s explanation of the results from his F 1 cross. a. Mendel assumed that a dominant allele had masked the corresponding recessive allele in the F 1 generation. d. At some point, the allele for shortness was segregated, or separated, from the allele for tallness.

1. Genetics n What are gametes? n They are the sex cells.

Segregation of Alleles In the diagram above, the dominant allele is represented by T and the recessive allele is represented by t.