Nokea
Which genetic descriptor refers to an organism's actual appearance?
- A. Phenotype
- B. Genotype
- C. Homozygote
- D. Karyotype
Correct Answer: A
Rationale: Phenotype refers to the observable characteristics or traits of an organism, including physical appearance, behavior, and physiological properties. It is influenced by the organism's genotype and environmental factors. Genotype, on the other hand, represents the genetic makeup of an organism, while homozygote refers to an individual having two identical alleles for a particular gene. Karyotype, on the other hand, refers to the complete set of chromosomes in an individual.
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What cellular appendage enables cells to move through their environments?
- A. Flagellum
- B. Cell membrane
- C. Transport protein
- D. Receptor
Correct Answer: A
Rationale: The flagellum is a whip-like appendage found in certain cells like sperm cells and some bacteria, enabling them to move through their environments. It plays a crucial role in locomotion by allowing cells to swim or propel themselves in liquids, aiding in their movement and navigation.
Each species has a characteristic chromosome number and most of their cells have a complete set of these chromosomes. However, in the life cycle of humans, only sperm and eggs have which number of chromosomes?
- A. Diploid.
- B. Polyploid.
- C. Haploid.
- D. Monoploid.
Correct Answer: C
Rationale:
Which process is the movement of particles from a high concentration to a low concentration?
- A. Diffusion.
- B. Filtration.
- C. Osmosis.
- D. Facilitation.
Correct Answer: A
Rationale: Correct Answer: A (Diffusion)
Rationale:
1. Diffusion is the movement of particles from areas of high concentration to low concentration.
2. This process occurs due to random movement of particles until equilibrium is reached.
3. Filtration is the movement of particles through a barrier due to pressure differences.
4. Osmosis is the movement of water molecules across a semi-permeable membrane.
5. Facilitation involves the assistance of carrier proteins in the movement of particles.
Summary:
Diffusion is the correct answer as it aligns with the movement of particles from high to low concentration. Filtration, osmosis, and facilitation involve different mechanisms and are not specifically related to concentration gradients.
Why can animal cells use a contractile ring but plant cells cannot?
- A. Plant cells can use both methods to divide.
- B. Animal cells divide faster, requiring them to pinch apart.
- C. Plant cells are too rigid to utilize a contractile ring.
- D. Plant cells have a cell wall that hinders the formation of a contractile ring.
Correct Answer: D
Rationale: Plant cells have a rigid cell wall surrounding their cell membrane, which prevents the formation of a contractile ring during cell division. The contractile ring is a structure composed of actin filaments responsible for pinching the cell in two during cytokinesis. Since plant cells cannot form a contractile ring due to the presence of the cell wall, they rely on other methods such as cell plate formation to complete cell division.
What enzyme is used to catalyze the elongation of the DNA strand during replication?
- A. DNA polymerase
- B. Primase
- C. DNA Ligase
- D. Helicase.
Correct Answer: A
Rationale: Correct Answer: A: DNA polymerase
Rationale:
1. DNA polymerase is responsible for adding nucleotides to the growing DNA strand during replication.
2. It catalyzes the formation of phosphodiester bonds between incoming nucleotides.
3. DNA polymerase also possesses proofreading abilities to ensure accuracy.
4. Primase is responsible for synthesizing RNA primers, not elongating the DNA strand.
5. DNA ligase joins Okazaki fragments and seals nicks in the DNA backbone.
6. Helicase unwinds the DNA double helix during replication, not involved in elongation.