- The work of Gregor Mendel (an Austrian priest in the 1800's) laid the foundation for much of our understanding of inheritance patterns and as a result, is credited as the "father of genetics".
- During his time, scientists did not fully understand how traits could be expressed without being "diluted"
- Mendel selected seven traits in pea plants to study: seed shape, seed color, pod shape, pod color, plant height, flower color, and flower position. (pea plants are pure breeding:meaning that they produce offspring identical to themselves because they self pollinate)
- Mendel cross-pollinated plants with contrasting traits and observed the resulting offspring. This type of cross is called a mono-hybrid cross.
- Mendel crossed a tall pea plant with a pure bred short plant. He cut away the male parts from the flowers of both pars and dusted the female parts with the pollen from the different plants. He called each generation the parental generation of the P generation.
- He called the offspring of the parents the first filial, or F1 generation. Filial is a Latin word meaning "child of offspring to parent."
- He then allowed the F1 generation to self pollinate and the offspring were called the F2 generation. After repeated trials, he found that the F1 produced a ratio of about three-fourths tall plants and about one-fourth short plants in the F2 generation.
- Mendel concluded that organisms inherit two copies of each unit, one from each parent. He also concluded that organisms donate a single unit of inheritance in the sex cells, and the two copies separate, or segregate, during gamete (sex cell) formation. This became known as the law of segregation
- He also noticed that when the unit for tall plants is combined with the unit for short plants, tall plants are always produced.
- Recessive traits can only be expressed when there are two units combined together for that trait
- distinct hereditary units are called genes and are located in the chromosomes.
- the location of a gene on a chromosome is called the locus
- organisms that are the result of sexual reproduction have an even number of chromosomes because half of the chromosomes are inherited from the father, and the other half are inherited from the mother. Humans have 46 chromosomes
- Mendel's law of segregation explains that chromosomes are paired AND genes are paired.
- Each form of the gene will code for a different outcome
- Reginald C. Punnett helped introduce the mathematics of probability into the study of genetics. He is credited with with the creation of the Punnett Square
- Eggs and sperm contain one of each pair of chromosomes and hence, one copy of each gene
- Based on the law of segregation, each allele will separate when the gametes are formed
- The Punnett square helped to verify Mendel's data
- How was Mendel able to control his experiments with pea plants - Mendel cut off the male parts of the plants and pollinated the female parts
- What were Mendel's conclusions that led to the law of segregation - Mendel concluded that organisms inherit two copies of each unit, one from each parent. He also concluded that organisms donate a single unit of inheritance in the sex cells, and the two copies separate, or segregate, during gamete (sex cell) formation. This became known as the law of segregation
- How did the Punnett square help to verify Mendel's conclusions - Mendel used the theory of probability to conclude the offspring of two parents mathematically
- How are the terms genes, homologous chromosomes, alleles, locus, dominant, and recessive related - They all have to do with genes. The locus is the location of the gene on the chromosome. Alleles are the form of a gene. These alleles can be dominant or recessive
- In guinea pigs, black coat color is dominant to white coat color. Show the cross between a homozygous black-coat guinea pig and a heterozygous guinea pig. What percent of the offspring will have white coat color - none of the guinea pigs have a white coat