PILT Study Guide - Final Guide: Gregor Mendel, Punnett Square, Plant Genetics
Final Exam Review
BIOL 1610
Chapter 14
- Know who Gregor Mendel was and what he did.
• Grew up in Austria.
• Excelled in school.
• 1843 at age 21 entered a monastery.
• Wanted to be a teacher but failed exams.
• 1851 left the monastery to study physics and chemistry (learned how to experiment).
• Returned to the monastery in 1857 started breeding garden peas to study inheritance. He taught us about plant
genetics.
• He controlled experiments by cross pollinating with a paintbrush. He showed a 3 : 1 ratio as a result.
• Conducted a model with 4 main laws:
• 1st – alternate versions of genes account for variations in inherited characters. These alternate versions are called
alleles.
• 2nd – for each character, an organism inherits two copies of a gene, one from each parent.
• 3rd – If the two alleles at a locus differ, then one, the dominant allele, determines the organism’s appearance; the
other, the recessive allele, has no noticeable effect on the organism's appearance.
• 4th – The law of segregation, states two alleles for a heritable character segregate during gamete formation and end
up in different gametes.
- Be able to answer questions about basic mendelian genetics and be able to predict the F1 and F2 generations
using a Punnett square.
• P Generation – Parental generation
• F1 generation – 1st filial generation (filial comes from Latin for son)
• F2 generation – 2nd filial generation
- Be able to give a probability for a genotype or phenotype in the offspring of a cross.
• Phenotype – appearance or observable traits
• Genotype – genetic makeup
- Understand the more complex patterns of inheritance (i.e. Incomplete dominance or epistasis).
Incomplete Dominance: Neither allele is completely dominant heterozygous offspring will be somewhere in between
the parent alleles.
• Snap dragons can breed one red flower with one white flower. The F1 generation will result with pink flowers. The F2
generation will result in a one red x two pink x one white ratio.
Codominance: Two alleles each affect the phenotype in separate, distinguishable ways.
• When breeding cattle, if a white and red are bred a roan color will result. This is shown with a mix of the two colors.
The two are both dominant and both show up in the cow with a spotted color.
Multiple Alleles: Even though pea plants have two alleles, most genes have more than two alleles.
• There are 4 types of blood. There is A, AB, B, and O blood types. These are the phenotypes for blood, the blood
group. There are three alleles with blood type. Blood has an IA, IB, and i. The first two are co-dominant while the third is
recessive. IAhas an A carbohydrate and IBhas a B carbohydrate. There is no carbohydrate on i. The genotypes for type
A blood is IAIAor IAi. Type B blood has IBIBor IBi. Type AB blood has IAIBand type O blood has ii as the genotype.
Type A blood has carbohydrate A antigens, triangular shaped. Type B blood has carbohydrate B antigens, circular
shaped. Type AB blood has both carbohydrates while type O blood has none.
Pleiotropy: A gene affects more than one trait.
Document Summary
He taught us about plant genetics: he controlled experiments by cross pollinating with a paintbrush. He showed a 3 : 1 ratio as a result: conducted a model with 4 main laws, 1st alternate versions of genes account for variations in inherited characters. Be able to give a probability for a genotype or phenotype in the offspring of a cross: phenotype appearance or observable traits, genotype genetic makeup. Understand the more complex patterns of inheritance (i. e. incomplete dominance or epistasis). Incomplete dominance: neither allele is completely dominant heterozygous offspring will be somewhere in between the parent alleles: snap dragons can breed one red flower with one white flower. The f1 generation will result with pink flowers. The f2 generation will result in a one red x two pink x one white ratio. Codominance: two alleles each affect the phenotype in separate, distinguishable ways: when breeding cattle, if a white and red are bred a roan color will result.
