General Biology 111
Exam #4 Homework
Chapter 12 and 13- Homework
1. Koelreuter’s experiments signaled the beginning of modern genetics. The experiment was hybridizied tobacco plants.
2. Knight was a senior research scientist at the MIT Computer Science and Artificial Intelligence Laboratory, part of the MIT School of Engineering. He crossed true-breeding peas: purple and white flowers; all offspring had purple flowers and the next generation of offspring had both flower colors; more purple than white. What he failed to do was quantify his results.
3. A gene is the basic unit of heredity, an allele is one of two or more alternative states of a gene, homozygous means when being a homozygote, having two identical alleles of the same gene, heterozygous means having two different alleles of the same gene, a genotype is the genetic constitution underlying a single trait or set of traits, a phenotype is the realized expression of the genotype; the physical appearance or functional expression of a trait.
4. A monohybrid cross is a mating between individuals who have different alleles at one genetic locus of interest.

5. Mendel determined that plants did not produce blended, intermediate characteristics, that for each trait with two alternates, one was expressed in the F1 generation, that an expression of traits segregated among progeny of a cross, and that an expression of traits produced a 3:1 Mendelian ratio.
6. That parents transmit factors that provide information about traits, each individual contains two factors for each trait (diploid), not all copies of a factor are identical (alleles), alleles from each parent do not influence one another (do not blend), and that the presence of a factor does not ensure its expression.
7. A dihybrid cross involves two characteristics.

8. A test cross involves the breeding of a dominant trait individual with a recessive individual, in order to determine the zygosity of the former one by analyzing proportions of offspring with the recessive phenotype.

9. Codominance is when neither allele is completely dominant over the other allele; they are expressed equally. An example of that are blood types.
10. Incomplete dominance is when alternative alleles are not dominant or recessive. An example is when red flowers crossed with white flowers produce pink flowers.
11. It states that alternative forms of a gene are encoded by discrete alleles.
12. It states that alternative alleles separate at random along metaphase plate.
13. Pleiotropy is the production by a single gene of two or more apparently unrelated effects. An example is Sickle-Cell Anemia.
14. The gene interaction in which one gene modifies the expression of other genes. An example is the coat color in Labrador retrievers.
15. Continuous variation is a small range of differences like seen with height and weight that is exhibited by most traits that reflect the action of polygenes (genes that act sequentially or jointly).
16. The norm of reaction is the phenotypic range of a genotype which is phenotypic ratio of a genotype influenced by the environment
17. In humans, males are XY and females are XX. The X and Y chromosomes are called sex chromosomes and all of your other chromosomes are called autosomes. You have 22 pairs of autosomes plus your sex chromosomes.
18. In humans, sex is determined by a specific set of chromosomes.
19. Yes, genes located on the same chromosome assort independently during meiosis. Crossover in meiosis disrupts gene linkage.
20. The record of descent of an animal, showing it to be purebred.
21. A genetic abnormality is passed to offspring from parents, and it is a condition that is a deviation from the usual or average but is not life threatening, a genetic disorder is passed to offspring from parents, and it is a condition that causes medical problems, and a syndrome is a set of symptoms that characterize a particular disorder.
22. An example of a trait that is autosomal recessively inherited is