Science Assessment

Students are expected to know that:

1. In sexually reproducing organisms, only half of the genetic information of each parent is passed to each of its offspring.
2. During sexual reproduction, parents produce specialized cells called sex cells (e.g., eggs, sperm, pollen) that contain half as many DNA molecules (and, therefore, chromosomes) as are found in the other cells of the organism (body cells).
3. A sex cell from one parent merges with a sex cell from the other parent in a process called fertilization, and the fertilized egg cell has twice as many DNA molecules as the sex cell and the same number of DNA molecules (and, therefore, chromosomes) as the body cells of each parent.
4. The offspring that develop from the single cell that was formed from the combination of the two sex cells have traits of both parents because they have DNA from both parents.
5. In sexually reproducing organisms, traits that are acquired during the lifetime of an organism and affect its body cells (e.g. due to injuries, malnutrition, mutation, weight training) cannot be passed from parent to offspring. Only changes in the DNA of the sex cells of an organism can be inherited by offspring.
6. In asexually reproducing organisms (uni-cellular or multi-cellular), all of the inherited genetic information comes from one parent cell. The offspring’s DNA molecules (and therefore the offspring’s genes and chromosomes) contain the same information as the DNA molecules of the parent.
7. Following asexual reproduction, the genetic information contained in the DNA molecules in the resulting cells is the same as the genetic information in the DNA molecules of the original cell.
8. In both sexually and asexually reproducing organisms, there is no other mechanism by which genetic information is passed to offspring other than by the transfer of DNA.

Boundaries:

1. Students are not expected to know that sexual reproduction can involve self-fertilization by a single parent having both male and female sex cells.
2. Students are not expected to know that the amount of genetic material in a sex cell is not exactly half of that found in a body cell due to differences in the sizes of the different sex chromosomes and/or the transmission of the entire mitochondrial DNA molecule.
3. Students are not expected to know that environmental factors interact with DNA at the molecular level to affect the genetic information that is expressed.