Unit 8 Objectives: Genetics
By the end of this unit, you should be able to
1. Discuss Mendel’s work.
2. Distinguish between genotype and phenotype, heterozygous and homozygous, dominant and
recessive traits.
3. Use a Punnett square to predict the results of monohybrid and/or dihybrid crosses and state the
phenotypic and genotypic ratios of each.
4. Use the laws of probability to calculate the chances of an individual having a specific genotype
or phenotype.
5. Define and give an example of pleiotropy, epistasis, polygenic inheritance, co-dominance and
incomplete dominance.
6. Describe the inheritance and expression of sickle cell anemia, Tay-Sachs, and Huntington’s.
7. Given a simple family pedigree, deduce the genotypes for the family members.
8. Describe what the term multifactorial means and give two examples.
9. List and describe two tests that can be completed to screen for genetic disorders. What ethical
and social issues are associated with this?
10. State Mendel’s Laws.
11. Describe the inheritance and expression of Down’s and Klinefelter’s Syndrome.
12. Explain how linked and sex-linked genes are inherited.
13. Explain situations where the genome has evolved to respond to the environment.
14. Understand the use of the Chi Square test in studying data from genetic crosses.
15. Understand how restriction enzymes and gel electrophoresis are used to isolate DNA fragments.
16. Describe DNA cloning and how it can be used to induce bacteria to produce eukaryotic gene
products.
17. Know the practical uses of Southern Blotting and PCR.
Free Response
1. State the conclusions reached by Mendel in his work on the inheritance of
characteristics. Explain how each of the following deviates from these
conclusions:
a. Autosomal linkage
b. Sex-linked (X-linked) inheritance
c. Polygenic (multiple-gene) inheritance
2. Discuss Mendel's laws of segregation and independent assortment. Explain how the
events of meiosis I account for the observations that led Mendel to formulate
these laws.
3.A.3. The chromosomal basis of inheritance provides an understanding of the pattern of passage
(transmission) of genes from parent to offspring.
a. Rules of probability can be applied to analyze passage of single gene traits from parent to
offspring.
b. Segregation and independent assortment of chromosomes result in genetic variation.
1. Segregation and independent assortment can be applied to genes that are on
different chromosomes.
2. Genes that are adjacent and close to each other on the same chromosome tend to
move as a unit; the probability that they will segregate as a unit is a function of the
distance between them.
3. The pattern of inheritance (monohybrid, dihybrid, sex-linked, and genes linked on the
same homologous chromosome) can often be predicted from data that gives the parent
genotype/ phenotype and/or the offspring phenotypes/genotypes.
c. Certain human genetic disorders can be attributed to the inheritance of single gene traits or
specific chromosomal changes, such as nondisjunction.
To foster student understanding of this concept, instructors can choose an illustrative example
such as:
•Sickle cell anemia
•Tay-Sachs disease
•Huntington’s disease
•X-linked color blindness
•Trisomy 21/Down syndrome
•Klinefelter’s syndrome
d. Many ethical, social and medical issues surround human genetic disorders.
To foster student understanding of this concept, instructors can choose an illustrative example
such as:
•Reproduction issues
•Civic issues such as ownership of genetic information, privacy, historical contexts
3.A.4. The inheritance pattern of many traits cannot be explained by simple Mendelian genetics.
a. Many traits are the product of multiple genes and/or physiological processes.
1. Patterns of inheritance of many traits do not follow ratios predicted by Mendel’s
laws and can be identified by quantitative analysis, where observed phenotypic ratios
statistically differ from the predicted ratios.
b. Some traits are determined by genes on sex chromosomes.
To foster student understanding of this concept, instructors can choose an illustrative example
such as:
•In mammals and flies, females are XX and males are XY; as such, X-linked
recessive traits are always expressed in males.
3.C.1. Changes in genotype can result in changes in phenotype.
c. Errors in mitosis or meiosis can result in changes in phenotype.
1. Changes in chromosome number often result in new phenotypes, including sterility
caused by triploidy and increased vigor of other polyploids. [See also 3.A.2]
2. Changes in chromosome number often result in human disorders with developmental
limitations, including Trisomy 21 (Down syndrome) and XO (Turner syndrome).
4.C.2. Environmental factors influence the expression of the genotype in an organism.
a. Environmental factors influence many traits both directly and indirectly.
To foster student understanding of this concept, instructors can choose an illustrative example
such as:
• Height and weight in humans
b. An organism’s adaptation to the local environment reflects a flexible response of its
genome.
To foster student understanding of this concept, instructors can choose an illustrative example
such as:
• Alterations in timing of flowering due to climate changes