Gregor Mendel's studies laid the foundation for modern genetics. In a series of elegant experiments, Mendel was able to deduce the most fundamental laws of single-gene and multiple-gene inheritance without having the scientific data on chromosomes, their structure, or meiotic segregation. In this lab, you will learn about and apply examples for 3 different patterns of human inheritance of traits.
Punnett Square is a tool used to theoretically predict genotypes of the progeny from the genotypes of parents as a result of sexual reproduction. Genes from parental gametes are written as rows and columns of the Punnett Square. All possible genotypes of progeny are obtained by crossing over all of the possible combinations of parental genes.
What is dominant/recessive inheritance?
Dominant/recessive inheritance is the type of inheritance when dominant phenotype is expressed in individuals having homozygous dominant and heterozygous genotypes, while recessive phenotype is expressed only in individuals with homozygous recessive genotype (Learn Genetics).
What is X-linked inheritance?
X-linked inheritance is the type of inheritance when any trait caused by mutated X-chromosome is expressed in males (they have only 1 X-chromosome) and females who are homozygous for this mutation (Genetics Home Reference).
What is codominant inheritance of genes?
Codominance is the type of inheritance when both alleles are expressed in the phenotype.
Exercise 1: Color Blindness
Choose the parental gametes, and align these in the correct positions around the Punnett square. (Type in the correct gametes. Pink are the female gametes, and blue are the male gametes. XC is the gene for normal vision, and Xc is the gene for color blindness.)
C
Choose the correct genotype of the progeny to fill in the Punnett square.
(Type the correct genotypes in the boxes.)
__XC____ __Xc____
__Xc____
___Y___
Exercise 2: Freckles
Choose the parental gametes and align these in the correct positions around the Punnett square. (Type in the correct gametes. The pink are female gametes, and the blue are male gametes.)
Choose the correct genotype of the progeny to fill in the Punnett square.
(Type in the genotypes.)
__F____ __f____
___f___
__f____
Exercise 3: Blood Type
A male has Type A blood, and a female has Type B blood. Could they have a child with Type O blood? Demonstrate how this is genetically possible by filling out the Punnett square.
Choose the correct parental gametes from all of the potential blood type gametes below, and align these in the correct positions around the Punnett square. (Type in the correct gametes. The pink are female gametes, and the blue are male gametes.)
Choose the correct genotypes of the progeny, and fill in the Punnett square.
(Type the correct genotypes into the boxes from the possible genotypes shown below).
___IB___ ___i___
___IA___
___i___
References
What are Dominant and Recessive? (2017). Learn.genetics.utah.edu. Retrieved 25 January 2017, from http://learn.genetics.utah.edu/content/basics/patterns/
What are the different ways in which a genetic condition can be inherited? (2017). Genetics Home Reference. Retrieved 25 January 2017, from https://ghr.nlm.nih.gov/primer/inheritance/inheritancepatterns
