Biology 1406: Exam 3

A human somatic cell has a total of 46 chromosomes. Half of these chromosomes, 23, come from the father and the other half also come from the mother. Therefore, the correct answer is 46 chromosomes in total, with 23 coming from each parent.

Violet color has greater energy compared to red color in the electromagnetic spectrum. This is because violet light has a shorter wavelength and higher frequency than red light. According to the wave-particle duality of light, higher frequency corresponds to higher energy. Therefore, violet light carries more energy per photon than red light.

If the other pigments in a plant were lost but chlorophyll remained, the plant would only be able to absorb the wavelengths of light that chlorophyll can absorb. This is because chlorophyll is responsible for capturing light energy for photosynthesis. Without the other pigments, the plant would not be able to capture a broader range of wavelengths, limiting its ability to convert light energy into chemical energy. Therefore, the statement is true.

Cytokinesis is the stage of the cell cycle during which the cytoplasm divides to form two cells. This process occurs after the nuclear division (mitosis or meiosis) and ensures that each daughter cell receives a complete set of genetic material. During cytokinesis, the cytoplasmic components, including organelles and cytosol, are evenly distributed between the two daughter cells, resulting in the formation of two separate cells. It is an essential step in cell division and plays a crucial role in the growth and development of organisms.

In stage 2 of the Calvin cycle, ATP and NADH are used to form glyceraldehyde 3-phosphate from phosphoglyceric acid. This step is crucial for the production of glucose during the cycle. ATP provides the necessary energy, while NADH acts as a reducing agent to convert phosphoglyceric acid into glyceraldehyde 3-phosphate. This conversion is an important intermediate step in the overall process of glucose synthesis.

The cell below contains 6 chromosomes, and each chromosome has double copies. This means that there are a total of 12 copies of chromosomes in the cell.

After meiosis II is complete, each nucleus will have 12 chromosomes. This is because meiosis II is the second division of meiosis, where the sister chromatids separate and move to opposite poles of the cell. In this organism, the original cell had 24 chromosomes (2n = 24), and after meiosis I, the resulting cells have 12 chromosomes each. Therefore, after meiosis II, each nucleus will also have 12 chromosomes.

In non-cyclic photophosphorylation, water is hydrolyzed to release oxygen gas as a byproduct. This process occurs in the thylakoid membrane of the chloroplast during photosynthesis. Oxygen is essential for aerobic respiration and is also released into the atmosphere, contributing to the oxygen levels in the environment.

The production of ATP is a common event in both non-cyclic and cyclic photophosphorylation. In both processes, light energy is used to generate ATP molecules through the phosphorylation of ADP. In non-cyclic photophosphorylation, ATP is produced through the movement of electrons in a linear pathway, while in cyclic photophosphorylation, ATP is produced through a cyclic pathway. Therefore, the production of ATP is present in both types of photophosphorylation.

Chlorophyll is the green pigment found in plants and other photosynthetic organisms. It is responsible for capturing light energy and converting it into chemical energy through the process of photosynthesis. Chlorophyll is essential for plants to carry out photosynthesis and is what gives them their green color.

Meiosis involves two divisions, known as meiosis I and meiosis II. In meiosis I, the cell undergoes a reduction division, resulting in two daughter cells with half the number of chromosomes as the parent cell. In meiosis II, each of these daughter cells divides again, resulting in a total of four daughter cells. These four daughter cells are genetically different from each other and from the parent cell, allowing for genetic diversity.

The diploid number of chromosomes in a mouse is 40, which means that each cell has two sets of chromosomes. Since a sperm cell is a haploid cell, it only contains one set of chromosomes. Therefore, the number of chromosomes in a sperm cell of a mouse would be half of the diploid number, which is 20.

Animal cells typically achieve cytokinesis by forming a cleavage furrow that pinches the cell into two. During cytokinesis, the cytoplasm of the cell divides, resulting in the formation of two daughter cells. In animal cells, a contractile ring made of actin and myosin filaments forms around the equator of the cell. This ring contracts, causing the plasma membrane to invaginate and form a furrow. The furrow deepens until it pinches the cell into two separate daughter cells. This process is known as cleavage furrow formation and is the most common method of cytokinesis in animal cells.

In oogenesis, the first polar body and the secondary oocyte undergo meiosis II. This process results in the production of two polar bodies and one haploid ovum. The term "upon" indicates that this event occurs either before or at the moment of fertilization. Therefore, the correct answer is "upon."

The separation of the pair of homologous chromosomes is unique to meiosis. This event, also known as homologous chromosome disjunction, occurs during meiosis I. It is the process in which the two homologous chromosomes, one from each parent, separate and move to opposite poles of the cell. This separation is crucial for the formation of haploid cells with a unique combination of genetic material. In mitosis, sister chromatids separate, but homologous chromosomes do not pair up and separate as they do in meiosis.

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The chromosomes in egg cells and sperm cells are located in the nucleus. The nucleus is a membrane-bound organelle within the cell that contains the genetic material, including the chromosomes. The chromosomes carry the DNA that contains the instructions for the development and functioning of an organism. Therefore, the nucleus is the correct location for the chromosomes in both egg and sperm cells.

In anaphase, the sister chromatids of each chromosome separate and move towards opposite poles of the cell. In the given options, only cell C shows the separation of sister chromatids, with each chromatid moving towards opposite poles. Therefore, cell C illustrates anaphase.

During the S phase of interphase, the DNA is doubled. This is because S phase stands for synthesis phase, where DNA replication takes place. In this phase, the cell prepares to divide by duplicating its DNA, ensuring that each daughter cell will have a complete set of genetic information. The S phase is a crucial step in the cell cycle and is followed by the G2 phase, where the cell prepares for mitosis or cell division.

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The given answer is 4 because during mitosis, the parent cell undergoes replication of its DNA, resulting in two identical sets of chromosomes. Each set contains the same number of chromosomes as the parent cell. Since the answer is asking for the number of chromosomes in the parent cell, it is equal to the number of chromosomes in one set, which is 4.

The correct answer is X. In the figure, the X part represents the phase of cell division called mitosis. During mitosis, the nucleus divides into two daughter nuclei, each containing a complete set of chromosomes. This process ensures that each new cell formed during cell division receives the correct number of chromosomes. Therefore, X is the correct answer as it represents the division of the nucleus into two.

The part labeled B in the illustration of a chloroplast is the stroma. The stroma is the fluid-filled region within the chloroplast where various metabolic reactions, including the synthesis of carbohydrates through photosynthesis, take place. It is surrounded by the inner membrane of the chloroplast and contains enzymes, DNA, ribosomes, and other components necessary for the functioning of the chloroplast.

In a cell with 46 double copy chromosomes, each chromosome consists of two sister chromatids. Therefore, the total number of sister chromatids would be 46 multiplied by 2, which equals 92.

The correct answer is B. In telophase II, the chromosomes have already separated into two sets during anaphase II, and they are now moving towards opposite poles of the cell. In telophase II, the nuclear envelope reforms around each set of chromosomes, and the chromosomes begin to decondense. In the given cell, the chromosomes are clearly separated and moving towards opposite poles, indicating telophase II.

Interkinesis refers to the short period of rest that occurs between meiosis I and meiosis II. During this time, the cell does not undergo DNA replication, and there is no pairing of homologous chromosomes. Instead, the cell prepares for meiosis II by synthesizing new proteins and replenishing energy stores. This period allows the cell to recover before proceeding to the second round of division.

Crossing over between homologous chromosomes takes place during prophase I of meiosis. This is the stage where the homologous chromosomes pair up and exchange genetic material through a process called crossing over. This genetic exchange increases genetic diversity and results in the shuffling of alleles between homologous chromosomes. This process is crucial for the proper segregation of chromosomes during meiosis and the production of genetically diverse gametes.

In a human somatic cell, there are two sets of chromosomes, one set inherited from the mother and one set inherited from the father. This is because somatic cells are diploid, meaning they have two complete sets of chromosomes. On the other hand, in a human gamete (sperm or egg), there is only one set of chromosomes. Gametes are haploid, meaning they have only one complete set of chromosomes, which is necessary for sexual reproduction when the sperm and egg combine to form a new individual with two sets of chromosomes.

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In the light-dependent reactions of photosynthesis, NADP is converted to NADPH and ADP + Pi is converted to ATP. This occurs in the thylakoid membrane of the chloroplasts, where light energy is captured and used to generate chemical energy in the form of ATP and NADPH. These energy-rich molecules are then utilized in the light-independent reactions (also known as the Calvin cycle) to convert carbon dioxide into glucose. Therefore, the correct answer is light-dependent reactions.

The chlorophyll is located in the thylakoid in the chloroplast in the mesophyll cell in the leaf. This statement accurately describes the location of chlorophyll, which is a pigment responsible for capturing light energy during photosynthesis. Chlorophyll is specifically found within the thylakoid membranes, which are located inside the chloroplasts. The chloroplasts themselves are present within the mesophyll cells of the leaf, where they perform photosynthesis.

During mitosis, the parent cell divides into two identical daughter cells. In this case, the parent cell has 10 chromosomes (2n = 10), so each daughter cell will also have the same number of chromosomes as the parent cell. Therefore, there will be 10 chromosomes in each of the two daughter cells.

After completion of meiosis I, a daughter cell could be haploid. Meiosis I is the first division in meiosis, where the homologous chromosomes separate, resulting in two daughter cells with half the number of chromosomes as the parent cell. This is because during meiosis I, the homologous chromosomes pair up and exchange genetic material through crossing over, leading to genetic variation. Therefore, the daughter cells produced after meiosis I are haploid, containing only one set of chromosomes. The letter C represents haploid in the given options.

The checkpoint that checks if the chromosomes are properly attached to the spindle fibers is located in part Y in the figure.

During anaphase, the sister chromatids separate and move towards opposite poles of the cell. Each chromatid contains one centromere. Therefore, if there are 20 centromeres in a cell at anaphase, it means that there are 20 sister chromatids. After cytokinesis, the cell divides into two daughter cells. Each daughter cell will receive half of the sister chromatids, resulting in 10 chromosomes in each daughter cell.

If a cell has 46 double copy chromosomes, it means that there are 46 pairs of chromosomes in the cell. Each pair of chromosomes consists of two identical molecules of DNA. Therefore, the total number of molecules of DNA in the cell is equal to the number of pairs of chromosomes, which is 46. Hence, the correct answer is 46, not 92.

In non-cyclic photophosphorylation, the lost electron in PS II is replaced by electrons coming from water. During photosynthesis, water molecules are split in a process called photolysis, releasing electrons, protons, and oxygen. The electrons from water replace the lost electrons in PS II, allowing the electron transport chain to continue and generate ATP. This process is crucial for the production of energy-rich molecules in plants.

In C4 plants, CO2 fixation by PEP carboxylase occurs in mesophyll cells, while CO2 fixation by RuBisCO occurs in bundle sheath cells. This is because C4 plants have a specialized carbon fixation pathway that allows them to minimize photorespiration and maximize efficiency in low CO2 environments. In this pathway, mesophyll cells initially fix CO2 using PEP carboxylase to form a four-carbon compound. This compound is then transported to bundle sheath cells, where it is decarboxylated to release CO2, which is then fixed by RuBisCO. This spatial separation of CO2 fixation in different cell types allows C4 plants to efficiently concentrate CO2 around RuBisCO, enhancing photosynthetic efficiency.

The correct answer is D because in anaphase II, the sister chromatids are separated and pulled towards opposite poles of the cell. In the given cell D, the chromatids are clearly separated and moving towards the poles, indicating anaphase II.

In the mitotic phase of the cell cycle, the division of the nucleus and the division of the cytoplasm occur. This is known as mitosis, where the nucleus divides into two identical sets of chromosomes, and then the cytoplasm divides to form two separate daughter cells. However, the duplication of DNA actually occurs in the S phase of the cell cycle, which is before the mitotic phase. During the S phase, the DNA is replicated to ensure that each daughter cell receives a complete set of genetic material. Therefore, the correct answer is that the duplication of DNA does not happen in the mitotic phase.

The first step of binary fission in bacteria is the duplication of the DNA. This process involves the replication of the bacterial chromosome to ensure that each daughter cell receives a complete copy of the genetic material. Once the DNA is duplicated, the cell can proceed with division, where the cells split into two, followed by cell elongation and septum formation to complete the process of binary fission.

The dark reactions, also known as the Calvin cycle, are a series of chemical reactions that occur in the stroma of chloroplasts. These reactions use the energy from ATP and the reducing power of NADPH (derived from NADH) to convert carbon dioxide (CO2) into glucose through a process called carbon fixation. Therefore, the inputs of the dark reactions are ATP, NADH, and CO2.

After telophase II of meiosis, each daughter cell is haploid, meaning it contains half the number of chromosomes as the parent cell. Additionally, the chromosomes in each daughter cell are in a single copy, meaning they are not paired with homologous chromosomes as they were in the parent cell.

In CAM (Crassulacean Acid Metabolism) plants, CO2 fixation by PEP carboxylase occurs at night time in mesophyll cells. This is because CAM plants have a unique adaptation where they open their stomata at night to minimize water loss through transpiration. During the night, CO2 is fixed into organic acids using PEP carboxylase in the mesophyll cells. These organic acids are stored in vacuoles. During the day, when the stomata are closed to conserve water, the stored organic acids are broken down, releasing CO2 for the Calvin cycle in the bundle sheath cells.

Meiosis is the process of producing haploid egg cells and sperm cells. It is a type of cell division that reduces the chromosome number by half, resulting in the formation of gametes. During meiosis, DNA replication occurs followed by two rounds of cell division, resulting in the formation of four genetically unique haploid cells. This process is essential for sexual reproduction and ensures genetic diversity in offspring.

The haploid number represents the number of chromosomes in a cell that contains only one set of chromosomes. In a normal somatic cell, the number of sister chromatids is double the number of chromosomes. Therefore, if there are 32 sister chromatids, the haploid number for that cell would be half of that, which is 16.

The reducing agent is the substance that donates electrons and gets oxidized in a redox reaction. In this reaction, 6H2O is being oxidized to form 6O2. Therefore, 6H2O is the reducing agent because it is losing electrons and getting oxidized.

The correct answer is A because during metaphase II, the chromosomes align at the equatorial plate of the cell. In the given figure, only cell A shows chromosomes aligned at the equatorial plate, indicating that it is undergoing metaphase II.

In non-cyclic photophosphorylation, electrons from chlorophyll in PS II replace the lost electron in PS I. This process occurs during the light-dependent reactions of photosynthesis. PS II absorbs light energy and uses it to excite electrons, which are then transferred to PS I through an electron transport chain. The electrons from PS II replace the lost electron in PS I, allowing it to continue the flow of electrons and generate ATP.