1.
Gametes must be haploid because ___.
Correct Answer
C. Two gametes will unite during fertilization to create a diploid cell
Explanation
Gametes must be haploid because during fertilization, two gametes, each containing a haploid number of chromosomes, unite to create a diploid zygote. If gametes were not haploid, the resulting zygote would have double the number of chromosomes, leading to an abnormal chromosome count in the offspring. Therefore, to maintain the correct chromosome number, gametes must be haploid.
2.
What ratio of the offspring from the cross shown will be homozygous recessive for the trait of tallness?
Correct Answer
A. 0 in 4
Explanation
Based on the given information, the ratio of the offspring that will be homozygous recessive for the trait of tallness is 0 in 4. This means that none of the offspring from the cross shown will have the genotype for tallness.
3.
What is the probability that a heterozygous black-fur rabbit will produce white-fur offspring if its mate is a homozygous recessive rabbit?
Correct Answer
B. P = 1/2
Explanation
When a heterozygous black-fur rabbit (Bb) mates with a homozygous recessive rabbit (bb), there is a 50% chance that the offspring will inherit the recessive allele (b) from the homozygous recessive parent and therefore have white fur. This is because the heterozygous black-fur rabbit can pass on either the dominant allele (B) or the recessive allele (b) to its offspring, while the homozygous recessive rabbit can only pass on the recessive allele (b). Therefore, the probability of producing white-fur offspring is 1/2.
4.
The picture shows a student’s experiment with a common aquatic plant. Which change in this experiment is most likely to increase the volume of oxygen gas that accumulates in the top of the tube?
Correct Answer
C. Move the light source closer to the beaker
Explanation
Moving the light source closer to the beaker is most likely to increase the volume of oxygen gas that accumulates in the top of the tube. This is because the aquatic plant undergoes photosynthesis, where it uses light energy to convert carbon dioxide and water into oxygen and glucose. By moving the light source closer, the plant receives more light energy, which increases the rate of photosynthesis and therefore the production of oxygen gas.
5.
Both male and female rats have genotype Bb. Based on a Punnett square, Carol concluded that the phenotypic ratio of the monohybrid cross is 2:1:1. What mistake did Carol make?
Correct Answer
C. The ratio should be 3:1
6.
In which phase of meiosis would certain gene segments of the homologous pairs of chromosomes "cross over" and exchange genetic information?
Correct Answer
C. PropHase I
Explanation
During Prophase I of meiosis, homologous pairs of chromosomes come together and align next to each other. This close proximity allows for the exchange of genetic information between the chromosomes through a process called crossing over. This exchange of genetic material results in genetic variation and ensures that each gamete produced during meiosis is unique. Therefore, Prophase I is the phase of meiosis where certain gene segments of the homologous pairs of chromosomes "cross over" and exchange genetic information.
7.
All the individuals of a species that live in a particular area are called a ___.
Correct Answer
A. Population
Explanation
A population refers to all the individuals of a species that are living in a specific area. It represents a group of organisms of the same species that share a common habitat and can potentially interbreed. This term is used to describe the collective presence and characteristics of a species within a defined geographical location.
8.
The total permanent disappearance of a species from Earth is called ___.
Correct Answer
A. Extinction
Explanation
Extinction refers to the complete disappearance of a species from the Earth. It occurs when the last individual of a species dies, and there are no more individuals left to reproduce and continue the species. Extinction can be caused by various factors, including habitat destruction, climate change, overhunting, and competition with other species. Once a species goes extinct, it is gone forever, and its unique genetic and ecological characteristics are lost.
9.
What is the term for a molecule that combines with enzymes, undergoes a chemical reaction, and changes into new substances?
Correct Answer
A. Substrate
Explanation
A substrate is a molecule that combines with enzymes and undergoes a chemical reaction, resulting in the formation of new substances. Enzymes act as catalysts, facilitating and speeding up these reactions. The substrate binds to the active site of the enzyme, allowing the enzyme to modify the substrate and produce the desired products. Therefore, substrate is the correct term for a molecule that undergoes a chemical reaction with enzymes.
10.
DNA is composed of nucleotide subunits, each of which contains a ___.
Correct Answer
B. pHospHate group
Explanation
DNA is composed of nucleotide subunits, each of which contains a phosphate group. The phosphate group is an essential component of the nucleotide structure, along with a sugar molecule (deoxyribose in DNA) and a nitrogenous base (adenine, thymine, cytosine, or guanine). The phosphate group forms the backbone of the DNA molecule, providing stability and linking the nucleotides together through phosphodiester bonds. Therefore, the presence of a phosphate group in each nucleotide is a fundamental characteristic of DNA.
11.
Which process produces the greatest amount of ATP?
Correct Answer
A. Aerobic respiration
Explanation
Aerobic respiration produces the greatest amount of ATP. This process occurs in the presence of oxygen and involves the complete breakdown of glucose molecules to produce energy. It takes place in the mitochondria of cells and involves a series of reactions, including glycolysis, the Krebs cycle, and the electron transport chain. Through these reactions, aerobic respiration produces a total of 36-38 ATP molecules per glucose molecule. In comparison, fermentation and anaerobic respiration produce a much smaller amount of ATP, and photosynthesis is a process that produces glucose rather than ATP.
12.
In the ladder-like model of DNA, the vertical “backbones” consist of ___.
Correct Answer
D. Sugar and pHospHate groups
Explanation
In the ladder-like model of DNA, the vertical "backbones" consist of sugar and phosphate groups. These sugar and phosphate groups alternate along the length of the DNA molecule, forming the structural backbone of the DNA double helix. The nitrogen bases, on the other hand, are attached to the sugar molecules and project inward, forming the rungs of the DNA ladder. ATP, although important for cellular energy metabolism, is not a component of the DNA molecule itself. Nucleotides, which consist of a sugar, a phosphate group, and a nitrogen base, make up the building blocks of DNA, but they are not the vertical backbones themselves.