Lesson 1: Mendelian Genetics Flashcards
Gene
Segment of DNA
Allele
Version of a gene
Genotype
The combo of alleles that code for a trait
Phenotype
The physical representation of a trait
Homozygous
A genotype that contains 2 of the SAME alleles
Heterozygous
A genotype that contains 2 different alleles
Dominant
The version of a trait (phenotype) that is more commonly seen
Recessive
The version of a trait (phenotype) that is less commonly seen
The “blending” theory of inheritance
Before Mendel’s work, the most popular theory of inheritance that the qualities of the parents blended to form the qualities of the child (offspring)
The “blending” theory of inheritance example
A tall parent and a short parent would produce a child of medium height
Gregor Mendel
Was an Austrian monk who worked with pea plants, he was the first to identify units of heredity (genes)
—discredited the blending theory
What did Gregor Mendel predict/conclude
—He was the first person to predict how traits were transferred from one generation to the next
—Concluded that inherited characteristics were carried in discrete, independent units (later called genes)
Why did Mendel use peas: Reason 1
The common pea plant was available throughout Europe
Why did Mendel use peas: Reason 2
It’s easy to grow and matures quickly
Why did Mendel use peas: Reason 3
Pea plants self- pollinate, allowing Mendel to control which plants reproduced
Why did Mendel use peas: Reason 4
Different varieties of pea plants have different traits that can be easily observed from one generation to the next
Mendel’s Experiment p1
-Mendel selectively fertilized pea plants with the pollen from other plants and analyzed the hereditary patterns of certain traits via:
-obtaining purebred plants for the traits he wanted to study.
–A purebred organism results from many generations of
selective breeding.
Mendel’s Experiment p2
-Plant height was one of the traits Mendel used in his studies of the pea plant.
-Once he had a purebred short and a purebred tall plant he would cross-pollinate them and observe the results
-Mendel called this purebred cross the P/Parent Generation
Mendel’s Experiment p3– the results
-The offspring of the P generation is were called the F1 generation. These peas were all tall
-Mendel then cross-pollinated these plants with e/o and created the F2 generation. These plants were 75% tall and 25% short
Mendel’s Conclusion— The principle of Dominance
These results led Mendel to conclude that the tall trait was dominant and the short trait was recessive
Mendel’s Conclusion— The principle of segregation
Genes are normally paired but are separated during gamete formation
Mendel’s Conclusion— The principle of of independent assortment
Each factor’s distribution in the gametes is not related to the distribution of any other factor
