Biology 11-1: The Work of Gregor Mendel

hybrid

Offspring of crosses between parents with different traits. (They inherit different alleles.)

genetics

Scientific study of heredity.

segregation

Separation of alleles during gamete formation. After this, sperm and egg each contribute an allele from each trait to offspring.

gene

Sequence of DNA that codes for a protein and thus determines a trait; *factor* that is passed from parent to offspring.

cross pollination

Type of flower reproduction: Offspring mixed, sexual. Taking sperm from another plant and placing on stigma of another.

self pollination

Type of flower reproduction: Asexual, sperm fertilizes egg from the same flower. Called true breeding when identical offspring are produced.

zygote

When sperm and egg cells come together.

alleles

For each trait, an organism inherits two ___________, one from each parent. They may be the same or different.

Mendel's experiments

Mendel studied pea plants. - Would transfer pollen from one plant to another, called a cross, and study the traits of the offspring. - From his experiments he concluded that the inheritance of many genetic characteristics followed a few simple rules. - These rules, or "Laws of Heredity", are the foundation of modern genetics.

principle of dominance

Mendel's second conclusion, which states that some alleles are dominant and others are recessive.

genotype

The genetic makeup of an organism, represented by letters. TT, Tt, tt. Inherited.

phenotype

The physical trait that each combination creates. Tall, short. Influenced by genotypes and the organism's environment.

principles

Law of Segregation: Two alleles must separate during gamete formation, each gamete has 1 allele. Sperm and egg will unite and contribute each allele to offspring. Rule of Dominance: If a dominant allele is present, that will be the trait expressed in the offspring.

Gregor Mendel

"Father of Genetics" - Austrian monk who did the 1st known studies on how physical traits are inherited- 1800s. - 1st person to succeed in predicting how traits are passed from one generation to the next (1866).

heterozygous

An organism with two different alleles for a gene (ex: Tt).

homozygous

An organism with two identical alleles for a gene (ex: TT or tt).

heredity

The *delivery* of characteristics from parent to offspring.

allele

One of a number of different *forms* of a gene.

experiment

P generation: Short x tall, true-breeding. TT x tt F1 Generation: All tall. Tt x Tt F2 Generation: 3 tall, 1 short. 3:1, TT Tt Tt tt Mendel did this for 7 traits.

fertilization

Process in sexual reproduction in which male and female reproductive cells join to form a new cell.

gamete

Sex cell.

trait

Specific *characteristic* of an individual.