Bio Unit 5 & 6

*UNIT 5 Q 9* In pea plants, purple flower color is dominant to red flower color and long pollen grains are dominant to round pollen grains. Researchers crossed two pure-breeding lines of the pea plants to investigate whether the genes controlling flower color and pollen shape segregate independently. The procedure for the genetics experiment is summarized in Figure 1. Which of the following tables best shows the expected values in the F2 generation for a chi-square goodness-of-fit test for a model of independent assortment?

1199 400 400 133

*UNIT 5 Q20* If the woman and a man with normal clotting function have children, what is the probability of their children exhibiting hemophilia A?

50 percent for sons, 0 percent for daughters

*UNIT 5 Q21* Which of the following is most likely the immediate cause of the first appearance of Huntington's disease in a person?

An allele with more than 39 CAG repeats was inherited by the affected person.

*UNIT 5 Q8* For this condition, which of the following modes of inheritance is most consistent with the observations?

Autosomal dominant

*UNIT 6 Q23* Based on the information in Figure 1, which type of mutation explains the nature of the change in DNA that resulted in cystic fibrosis in the affected individual?

Deletion, because a thymine is missing, which changes the reading frame.

*UNIT 6 Q5* Labeled nucleotides were supplied to a cell culture before the cells began DNA replication. A simplified representation of the process for a short segment of DNA is shown in Figure 1. Labeled DNA bases are indicated with an asterisk (*). Which of the following best helps explain how the process represented in Figure 1 produces DNA molecules that are hybrids of the original and the newly synthesized strands?

Each newly synthesized strand remains associated with its template strand to form two copies of the original DNA molecule.

*UNIT 6 Q11* Which of the following statements best explains the role of Enzyme 1 in the DNA replication process?

Enzyme 1 is a topoisomerase that relieves tension in the overwound DNA in front of a replication fork.

*UNIT 6 Q24* Nucleotide base pairing in DNA is universal across organisms. Each pair (T−A; C−G) consists of a purine and a pyrimidine. Which of the following best explains how the base pairs form?

Hydrogen bonds join a double-ringed structure to a single-ringed structure in each pair.

*UNIT 6 Q21* Which of the following best explains how this model illustrates DNA replication of both strands as a replication fork moves?

I is synthesized continuously in the 5′ to 3′ direction, and III is synthesized in segments in the 5′ to 3′ direction.

*UNIT 6 Q2* Which of the following best explains how the pattern of DNA arrangement in chromosomes could be used, in most cases, to determine if an organism was a prokaryote or a eukaryote?

Prokaryotic DNA - Single circular chromosome Eukaryotic DNA - Multiple linear chromosomes

*UNIT 6 Q19* All cells must transcribe rRNA in order to construct a functioning ribosome. Scientists have isolated and identified rRNA genes that contribute to ribosomal structure for both prokaryotes and eukaryotes. Figure 1 compares the transcription and processing of prokaryotic and eukaryotic rRNA. Which of the following statements provides the best explanation of the processes illustrated in Figure 1 ?

Sections of the pre-rRNA are removed, and the mature rRNA molecules are available to combine with proteins to form the ribosomal subunits.

*UNIT 6 Q20* A woman develops Huntington's disease. Her father had the disorder. Her mother did not, and there is no history of the disorder in the mother's family. Which of the following best explains how the woman inherited Huntington's disease?

She inherited an allele with more than 40 CAG repeats in the HTT gene from her father.

*UNIT 6 Q22* Which claim is most consistent with the information provided by the diagram and current scientific understanding of gene regulation and expression?

Some sequences of DNA can interact with regulatory proteins that control transcription.

*UNIT 5 Q6* Based on the data in Figure 1, which of the following is the best prediction of the mode of inheritance of red eyes in Japanese koi?

The allele for red eyes is inherited in an autosomal dominant pattern.

*UNIT 5 Q7* Using a significance level of p=0.05, which of the following statements best completes a chi-square goodness-of-fit test for a model of independent assortment?

The calculated chi-square value is 3.91, and the critical value is 7.82. The null hypothesis cannot be rejected.

*UNIT 6 Q10* A cell needs to metabolize the substrate illustrated in Figure 1 for a vital cellular function. Which of the following best explains the long-term effect on the cell of splicing that yields only enzyme C mRNA?

The cell will die because it is unable to metabolize the substrate without enzyme A, which is structurally specific for the substrate shown.

*UNIT 5 Q16* Which of the following statements best explains how the fur color can be different in Himalayan rabbits raised under different temperature conditions?

The environment determines how the genotype is expressed.

*UNIT 6 Q7* Which of the following best predicts what will happen when a normal cell is exposed to a retrovirus?

The reverse transcriptase will produce DNA from the viral RNA, which can be incorporated into the host's genome and then transcribed and translated.

*UNIT 6 Q8* Exposure to ultraviolet (UV) radiation is the leading cause of skin cancer in humans. Figure 1 shows a model of how UV exposure damages DNA. Which of the following statements best explains what is shown in Figure 1 ?

UV photons cause dimers to form, leading to misshapen DNA, which results in replication and transcription errors.

*UNIT 6 Q9* Which of the following evidence best supports a claim that tryptophan functions as a corepressor?

When trpR is mutated, the trp operon is transcribed regardless of tryptophan levels.