Genetics Problems: Predicting Genotype and Phenotype Using Punnett Square

Name: ______________________________
Date: _______________________________
BIOL 1014 Lab 9 Genetics Problems
Skills: Punnett Square Use and Genetics Terminology
Objective: Use Punnett Squares to accurately predict genotype and phenotype percentages for offspring involving various types of inherited traits. There is additional information about this procedure in section 12.2 in your textbook. The problems below will have multiple parts/questions, please make sure that you answer all parts/questions in each problem.
4597400508000
Vocabulary
Allele – Alternate forms of a gene.
Cross – Mating of two parent organisms
Dominant Trait – A genetic trait is considered dominant if it is expressed in an organism who has only one copy of that gene. In genetic terms, a dominant trait is one that is phenotypically expressed in heterozygotes. (Example: Both RR and Rr have round seeds.)
F1 Generation – The first set of offspring from the original parents.
F2 Generation – The second generation of offspring.
Gene – Section of a chromosome that carries the information for a specific trait.
Genotype – The fundamental genetic makeup of an organism for a specific trait; the combination of the two alleles located on the homologous chromosomes that determines the expression (phenotype) of the trait. The genotype is represented by two letters, which are in upper and lower case to represent different alleles. (Example: R is genotype for the dominant trait of a round pea seed and r is the genotype for the recessive trait of a wrinkled pea seed.)
Heterozygous – The genotype has a dominant gene and a recessive gene for the same trait. (Rr)
Homozygous – The genotype has both letters being exactly the same, meaning the organism either has 2 genes for a dominant or a recessive trait rather than one of each. (RR or rr)
Offspring – New organisms resulting from a cross.
Phenotype – The way a trait physically expresses itself in an organism. (Example: wrinkled seeds vs. smooth
seeds, red flowers vs. white flowers.)
Probability – The chance/possibility that a specific event will occur. Expressed mathematically using percentages or ratios.
Punnett Square – A mathematical tool that helps predict the offspring outcome (both genotypes and phenotypes) of a cross between two parents with known genotypes.
Recessive Trait – Refers to an allele that causes a phenotype that is only seen in homozygous genotype and never in a heterozygous genotype. If a genetic trait is recessive, the organism needs to inherit two copies of the gene for the trait to be expressed. Thus, both parents must be carriers of the trait in order for the offspring to express that trait. (Example: rr is expressed as wrinkled seeds.)
BIOL 1014 Lab 9 Genetics Problems
10001256223000
Practice Problem
Gregor Mendel was an Austrian Monk who is considered the father of genetics. By completing many observations and keeping meticulous records, Mendel was able to categorize several inherited traits in the common garden pea plant. This was a hearty plant that reproduced quickly which made it a good candidate for studies of this type. The table on the ri...