1.
DNA and RNA have many structural similarities. Which structure in DNA and RNA is similar?
Correct Answer
A. Purine bases
Explanation
DNA and RNA both contain purine bases, which are a type of nitrogenous base. Purine bases include adenine (A) and guanine (G). These bases are responsible for forming the genetic code and are involved in the pairing of nucleotides in DNA and RNA molecules. Therefore, the similarity in the structure of purine bases is a common feature between DNA and RNA.
2.
What occurs during metaphase I of meiosis?
Correct Answer
C. Homologous chromosome pairs line up along the cell’s equator.
Explanation
Metaphase I = homologous chromosomes are pulled to the middle of the cell
3.
When comparing 2 populations of animals, which statement most likely indicates that they are the same species?
Correct Answer
A. They produce fertile offspring.
Explanation
The statement "They produce fertile offspring" most likely indicates that the two populations of animals are the same species. This is because the ability to produce fertile offspring is a key characteristic of members of the same species. If two populations can successfully mate and produce offspring that can also reproduce, it suggests that they share enough genetic similarity to be considered the same species. The other statements, such as inhabiting the same area, having similar outward appearance, or consuming the same type of diet, may be indicative of similarities between populations but do not necessarily confirm that they are the same species.
4.
Persons A and B have similar mRNA sequences with the exception of 1 nucleotide.
Person A: AUGGUUACUAAGGGCUGA
Person B: AUGGUUACUGAGGGCUGA
The genetic code chart to determine how this difference affects the sequence of amino acids in the resulting protein.
Correct Answer
A. Lys in Person A is replaced with Glu in Person B.
Explanation
The given answer correctly states that Lysine (Lys) in Person A is replaced with Glutamic acid (Glu) in Person B. This is evident from the difference in the mRNA sequences, where the nucleotide 'U' in Person A is replaced with 'G' in Person B at the corresponding position, resulting in the change in the codon from AAA (Lys) to GAA (Glu). This substitution leads to a change in the amino acid sequence of the resulting protein.
5.
Which example best illustrates Mendel's law of independent assortment?
Correct Answer
C. A tall prurple-flowered pea plant and a short white-flowered pea plant are crossed, producing offspring including tall white-flowered pea plants.
Explanation
This example best illustrates Mendel's law of independent assortment because the traits for plant height and flower color are segregating independently during the cross. The fact that the offspring includes tall white-flowered pea plants indicates that the tall trait and the white-flower trait are not linked and are inherited independently of each other. This supports Mendel's observation that different traits are inherited independently and are not influenced by each other's presence.
6.
How does the regulation of gene expression lead to cell specialization?
Correct Answer
B. Methylation of some regions of DNA prevents transcription.
Explanation
Methylation of certain regions of DNA prevents transcription by adding a methyl group to the DNA molecule, which can inhibit the binding of transcription factors and RNA polymerase. This prevents the gene from being transcribed into RNA, ultimately leading to a decrease or complete halt in the production of the corresponding protein. This regulation of gene expression is crucial for cell specialization as different cells in the body need to express different sets of genes to perform their specific functions.
7.
In humans, pigmented skin is dominant to non-pigmented skin (albinism). What is the genotype of an individual with albinism?
Correct Answer
D. Homozygous recessive
Explanation
An individual with albinism has a genotype of homozygous recessive. This means that both of their alleles for the pigmentation gene are recessive, resulting in the absence of pigmentation in their skin.
8.
Two black guinea pigs bred and produced 3 black offspring and 2 albino offspring. Assuming no mutations, which guinea pigs must be heterozygous?
Correct Answer
D. Both parents
Explanation
If both parents produced black offspring and albino offspring, it suggests that both parents have the genetic material for both black and albino traits. This means that they must be heterozygous for the black trait. If they were homozygous for the black trait, they would only produce black offspring. Therefore, both parents must be heterozygous.
9.
Jeanine inherited 2 alleles for round eye shape and has round eye shape. Her brother inherited 1 allele for round eye shape and 1 allele for almond eye shape and has almond eye shape. What type of trait is round eye shape?
Correct Answer
C. Recessive
Explanation
Round eye shape is a recessive trait. This is evident from the fact that Jeanine inherited 2 alleles for round eye shape and has round eye shape, while her brother inherited 1 allele for round eye shape and 1 allele for almond eye shape and has almond eye shape. Since Jeanine's round eye shape is dominant over her brother's almond eye shape, it indicates that the almond eye shape allele is recessive.
10.
In humans, red-green color blindness is a recessive, sex-linked trait. The chromosomes and alleles associated with color blindness are represented in this chart.
Which child could NOT be born to these parents; a female (XBXb) and a male (XBY)?
Correct Answer
A. Color-blind daughter
Explanation
Since red-green color blindness is a recessive trait, it can only be expressed if an individual has two copies of the color-blind allele (Xb). The mother in this case is a carrier of the color-blind allele (XBXb) and the father is not color blind (XBY). The only way for a child to be color blind is if they inherit the color-blind allele from both parents. Since the father does not have the color-blind allele, a color-blind daughter cannot be born to these parents.
11.
What characteristic of early autotrophs gave them an advantage over early heterotrophs?
Correct Answer
C. They made their own food.
Explanation
Early autotrophs had an advantage over early heterotrophs because they were able to produce their own food. Autotrophs are organisms that can synthesize organic compounds from inorganic substances, such as carbon dioxide and sunlight. This ability allowed them to survive and thrive in environments where there may have been limited or no external food sources available. In contrast, heterotrophs rely on consuming other organisms for their energy and nutrients, making them more dependent on the availability of other living organisms. By being able to produce their own food, early autotrophs had a greater advantage in terms of survival and reproduction.
12.
The genotype of F1 individuals from a dihybrid cross is AaBb x AaBB. What is the expected ratio of AaBb individuals in the F2 generation?
Correct Answer
B. 4/16
Explanation
In a dihybrid cross, the F1 generation is produced by crossing two individuals that are heterozygous for two different traits. In this case, the F1 individuals have the genotype AaBb x AaBB. When these individuals are crossed in the F2 generation, there are four possible genotypes that can be produced: AaBB, AaBb, AABb, and AABB. Since the AaBb genotype is one out of the four possible genotypes, the expected ratio of AaBb individuals in the F2 generation is 1/4 or 4/16.
13.
Alkaptonuria is a genetic disorder of protein metabolism.
The disorder is determined by 2 alleles at 1 locus.
What is the genotype for Individual 1 in the diagram?
Correct Answer
C. Aa
Explanation
Individual 1 in the diagram has the genotype Aa. This is because the disorder is determined by 2 alleles at 1 locus, meaning there are two possible versions of the gene that can be present in an individual. In this case, Individual 1 has one copy of the A allele and one copy of the a allele, resulting in the genotype Aa.
14.
Which example best illustrates the process of natural selection?
Correct Answer
B. Giraffe necks varied in length, and the shorter-necked giraffes were at a disadvantage.
Explanation
The example that best illustrates the process of natural selection is when giraffe necks varied in length, and the shorter-necked giraffes were at a disadvantage. This scenario demonstrates the key elements of natural selection, where there is variation in a population, and certain traits provide a disadvantage or advantage for survival and reproduction. In this case, the shorter-necked giraffes would struggle to reach food, while the longer-necked giraffes would have better access to resources, increasing their chances of survival and passing on their genes to the next generation.
15.
Most male crickets produce a mating song by rubbing together their curved wings. In a certain geographic area, parasitic flies detected male crickets singing and deposited their larvae into them, which killed the crickets. Eighteen generations later, the number of males with flat wings has increased to 90%. The flat-winged crickets do not sing, but are still able to mate with females, and parasitic flies cannot detect them.
Which type of selection is occurring in this cricket population?
Correct Answer
B. Directional
Explanation
In this cricket population, directional selection is occurring. This is because the frequency of a particular trait, flat wings, has increased over generations. The selection pressure is favoring the flat-winged crickets because they are not detected by the parasitic flies, allowing them to survive and reproduce. As a result, the percentage of flat-winged males has increased to 90%.
16.
Horse skeleton fossils indicate that the size of horses increased over time. Which statement best explains this fossil record?
Correct Answer
D. Larger horses produced a slightly greater number of surviving offspring.
Explanation
The fossil record indicates that the size of horses increased over time. This suggests that larger horses had a reproductive advantage and produced a slightly greater number of surviving offspring. Over generations, this led to the gradual increase in the average size of horses. There is no evidence or mention of smaller horses breeding with larger horses, a fatal virus affecting smaller horses, or larger horses consuming the food supply of smaller horses in the given information.
17.
Cytochrome C is a protein used in the electron transport chain. This table shows short sections of Cytochrome C's amino acid sequences in 5 organisms, using single letter abbreviations.
Use this data to determine which organism most likely shares the most recent common ancestor with humans.
Correct Answer
A. Organism 1
Explanation
Based on the given information, it can be inferred that the organism with the most similar amino acid sequence to humans in the short sections of Cytochrome C is Organism 1. Therefore, Organism 1 is most likely to share the most recent common ancestor with humans.
18.
Which event of meiosis reveals the mechanism for understanding Mendel's laws of segregation and independent assortment?
Correct Answer
B. The arrangement of homologous chromosomes during metapHase I varies from cell to cell.
Explanation
The arrangement of homologous chromosomes during metaphase I varies from cell to cell. This event in meiosis is known as independent assortment, which is one of Mendel's laws. It explains how different traits are inherited independently of each other. During metaphase I, homologous chromosomes line up at the equator of the cell in pairs, and the orientation of each pair is random. This random alignment leads to the formation of different combinations of alleles in the gametes, resulting in genetic variation. Therefore, the arrangement of homologous chromosomes during metaphase I is the event that reveals the mechanism for understanding Mendel's laws of segregation and independent assortment.
19.
Maria wanted to rid her home of cockroaches. She applied pesticide and after 1 day she found many dead cockroaches. Days later, she observed a few live cockroaches. She reapplied the pesticide, but she continued to see some live cockroaches. What best explains the continuing presence of live cockroaches?
Correct Answer
A. A few cockroaches exhibited pesticide resistance due to natural variability within the population.
Explanation
A few cockroaches exhibited pesticide resistance due to natural variability within the population. This means that within the population of cockroaches, there is a natural variation in their ability to resist the pesticide. Some cockroaches may have genetic traits that make them less susceptible to the pesticide, allowing them to survive and reproduce. Over time, this can lead to an increase in the number of cockroaches with pesticide resistance, explaining why Maria continues to see live cockroaches even after reapplying the pesticide.
20.
Dr. Romero is raising 3 types of damselfishes in separate aquariums: 2 from the Atlantic Ocean and 1 from the Pacific Ocean. This table summarizes the information she gathered through observations and breeding experiments.
Based on the most commonly accepted definition of a species, how many different species of damselfishes is Dr. Romero raising, and which fish are they?
Correct Answer
C. 2 species: Fish A and C are a single species; Fish B is a separate species
Explanation
Dr. Romero is raising two different species of damselfishes. Fish A and C belong to the same species, while Fish B is a separate species. This conclusion is based on the most commonly accepted definition of a species, which states that individuals belong to the same species if they can interbreed and produce fertile offspring. Since Fish A and C can interbreed and produce fertile offspring, they are considered to be the same species. On the other hand, Fish B cannot interbreed with Fish A or C, indicating that it is a separate species.