The image shows a single litter of kittens. How are they similar to one another? [ ]
How do they differ from one another? [ ]
What do you think their parents looked like? [ ]
Heredity is the passage of genetic information from parents to offspring. The rules of inheritance were discovered in the 19th century by Gregor Mendel. With the Mouse Genetics (One Trait) Gizmo™, you will study how one trait, or feature, is inherited.
Drag two black mice into the Parent 1 and Parent 2 boxes. Click Breed several times. What do the offspring look like?
The appearance of each mouse is also called its phenotype.
Click Clear, and drag two white mice into the parent boxes. Click Breed several times. What is the phenotype of the offspring now? [ ]
Do you think mouse offspring will always look like their parents? [ ]
Drag a black mouse and a white mouse into the parent boxes, but don’t click Breed yet.
Question: What patterns are shown by offspring traits?
Predict: What do you think the offspring of a black mouse and a white mouse will look like?
Observe: Click Breed several times. What do you see? [ ]
Observe: Drag two offspring into the Holding Cages. These mice are called hybrids because their parents had different traits. Click Clear, and then breed the two hybrids.
What do you see now? [ ]
Experiment: Turn on Show statistics. Click Breed until there are 100 offspring.
How many offspring were black? [ ] How many were white? [ ]
Explore: Try other combinations of mouse parents. Write the results of each experiment in your notes. When you have finished, answer the following questions. (Note: You can refer to the parents as “pure black,” “pure white,” or “hybrid.”)
Which parent combination(s) yield only white offspring? [ ]
Which parent combination(s) yield only black offspring? [ ]
Which parent combination(s) yield a mixture of black and white offspring? [ ]
Activity B: Genetics basics
Get the Gizmo ready:
Drag a black mouse and a white mouse into the parent boxes.
Introduction:Inherited traits are encoded on a molecule called DNA (deoxyribonucleic acid). Genes are segments of DNA that control a particular trait. Most genes have several different versions, or alleles. The genotype is the allele combination an organism has.
Question: How do alleles determine fur color?
Observe: Turn on Show genotype. Move your cursor over a mouse to see its genotype.
What is the genotype of the black parent? [ ] White parent? [ ]
These mice are homozygous for fur color, meaning both alleles are the same.
Click Breed. What is the genotype of the offspring mice? [ ]
These mice are heterozygous for fur color, meaning the alleles are different.
Analyze: Dominant alleles are always expressed when present. Recessive alleles are not expressed when the dominant allele is also present. Look at the two alleles for fur color.