Deviations from the expected chromosomal number, or mutations in the structure of the chromosome, are inherited in predictable Mendelian fashion; they often result in dead organisms or substantial changes in phenotype. Aneuploidy is the gain or loss of one or more chromosomes from the diploid amount, resulting in conditions of monosomy, trisomy, tetrasomy. Studies of monosomy (Turner Syndrome XO) and trisomic disorders (Down's Syndrome) have increased our understanding of the delicate balance that must exist in order for normal development to occur. When complete sets of chromosomes are added to the diploid number, polyploidy is created. These sets may have identical or diverse genetic origin. Large segments of the chromosome may be modified by deletions or duplications. Deletions may produce serious conditions such as Cri-du-chat Syndrome in humans. Duplications may be important as a source of redundant or unique genes, but this usually has no effect on health. Inversions and translocations, while altering the gene order along chromosomes, cause no net loss of genetic information. In an inversion, a sequence of genes is turned around. This does not affect health unless a critical gene sequence is physically disrupted. Most children with Chronic Myeloid Leukemia have a translocation or mixed up chromosome, in which the tip of chromosome 22 is attached to chromosome 9. However, this type of heterozygous combination may cause genetically abnormal gametes during meiosis, often being lethal.
A change in chromosome number or in the arrangement of a chromosome region often results in phenotypic variation or disruption of development of an organism. Such phenotypic variations are passed to offspring in a predictable manner, resulting in many interesting genetic situations.
Target Age Ability Group: Regular or Honors Biology
Student/Class Time Required:
One or two days for teacher to review concepts/terms listed below. One or two days for students to complete worksheet and review concepts.
Note: based on 80 minute classes
Teachers should review the following concepts and key terms before assigning the student worksheets:
After the regular classroom presentations of the above concepts/key terms are completed, use these worksheets as a culminating activity.
This activity may be done in pairs or as a cooperative group exercise. It is not a test! It is not a "quiet" exercise for review! It is a learning module. The teacher should encourage open discussions of the questions and answers.
Students should bring as many references as necessary to facilitate the completion of the worksheets and to teach each other the concepts being discussed.
Worksheets are "completed" individually (overnight) and handed in for grading. Grading can be based on the degree of completion, added illustrations and examples along with full explanations.
Your grade on this activity will be based on the degree of completion of your answers, and added illustrations and examples along with full explanations. If you need more room, please attach sheets to the booklet.
Part 1: Answer the following questions. [use extra attached sheets]
Recall and Review:
Part 2: Gene Mutations
Questions #7 - #13 refer to the DNA master strand listed below:
Note: Questions: #14 - #21 refer to the DNA master strand listed below:
Note: Questions #22 - #33 refer to the DNA master strand listed below: