AP Biology Unit 5: Heredity

Explain why some haploid cells formed after meiosis in this experiment will have only one fluorescent marker.

The scientists then investigated whether attaching individual kinetochore proteins to a specific DNA sequence present in a known crossing-over hotspot on chromosome 8 affected the frequency of crossing over at this location. In their first experiment, they examined three groups of yeast cells containing the modified chromosome 8. Group 1 contained no kinetochore proteins attached to the hotspot, group 2 contained the kinetochore protein CTF attached to the hotspot, and group 3 contained the kinetochore protein IML attached to the hotspot. For each group, the scientists determined the frequency of crossing over between the RFP and GFP genes. To determine the frequency, the scientists added the number of cells emitting both red and green light to the number of cells that emitted no light and divided by the total number of cells (Figure 2).

Based on Figure 2, describe the effect on the frequency of crossing over when CTF is attached to the chromosome 8 hotspot compared with the effect when IML is attached to the hotspot.

Predict the effect on the number of copies of chromosome 8 likely to be present in the resulting daughter cells when CTF is attached to the hotspot.

Provide reasoning to justify your prediction.

Explain how the presence of hotspots (Figure 1) could increase the likelihood that a population will survive in the presence of selective pressures.

Write your responses to this question only on the designated pages in the separate Free Response booklet. If there are multiple parts to this question, write the part letter with your response.

Identify the genotypes of the male and female flies used in cross 2.

Identify the cross in which the female parent was most likely heterozygous.

The researchers hypothesize that crossing any unaffected female and an affected male will result in a 0\% chance of producing an affected male offspring. Evaluate the validity of the hypothesis.

Explain how the results exclude the possibility that the trait is encoded by a mitochondrial gene.

PAGE FOR ANSWERING QUESTION 6

Using the template in the space provided for your response, construct an appropriately labeled graph that represents the data in Table 1. Determine which species show(s) a difference in the number of mitochondria between normal and elevated levels of $\mathrm{CO}_{2}$.

Based on the data in Table 1, describe the relationship between the level of $\mathrm{CO}_{2}$ and the average number of mitochondria per unit area of a cell.

The leaves of a particular plant species are typically green, but scientists notice a plant in which the leaves have white stripes. They determine that the stripes result from a mutation in mitochondrial DNA that interferes with the development of chloroplasts. The scientists crossed plants using pollen from the plant with white-striped leaves and ovules from a plant with green leaves. Predict the phenotype(s) of the leaves of offspring produced from this cross. Provide reasoning to justify your prediction. Explain why plants with the same genotype are able to differ in the structure and/or number of certain organelles in response to changes in atmospheric levels of $\mathrm{CO}_{2}$.

Write your responses to this question only on the designated pages in the separate Free Response booklet.