Genetics and Cell Division Quiz

A type of cell division that produces two daughter cells genetically identical to the parent cell. It is involved in growth, repair, and asexual reproduction.

A type of cell division that produces four daughter cells with half the number of chromosomes as the parent cell. It is crucial for sexual reproduction.

Mitosis occurs in all multicellular organisms during growth, development, and repair. It also happens in many unicellular organisms for asexual reproduction.

Meiosis occurs only in organisms that reproduce sexually. It takes place in the reproductive organs to create gametes (sperm and egg cells).

Mitosis occurs throughout the body, in all tissues and organs that need new cells.

Meiosis occurs in specialized tissues of the reproductive organs, like ovaries in females and testes in males.

Mitosis ensures that each daughter cell receives a complete and identical copy of the parent cell's DNA, allowing for growth, repair, and asexual reproduction.

Meiosis generates genetic diversity by shuffling the parental chromosomes and reducing the chromosome number by half, creating gametes for sexual reproduction.

Bananas are primarily propagated through asexual reproduction, where new plants are grown from cuttings of existing ones. This results in genetically identical offspring, leading to a lack of genetic diversity.

Fusarium wilt is a fungal disease that affects banana plants, particularly the Gros Michel variety, which was the dominant banana cultivar before 1950. It causes wilting, yellowing, and eventual death of the plant.

Since asexual reproduction creates genetically identical offspring, a disease or pest that affects one plant can wipe out an entire population, as there's no genetic variation to confer resistance.

The Cavendish banana is the current dominant cultivar, replacing the Gros Michel banana after the latter was devastated by Fusarium wilt. While it's more resistant to the wilt, it is still vulnerable to other diseases and pests due to its lack of genetic diversity.

Sexual reproduction introduces genetic variation in crops, allowing for greater resilience to disease, pests, and environmental changes. This ensures the survival of the species and provides a foundation for developing superior cultivars through selective breeding.

Genetic variation is preserved within a population through natural processes like random mating, crossing over, and independent assortment.

Crossing over is a genetic process where homologous chromosomes exchange segments of genetic material during meiosis, creating new allele combinations.

Independent assortment occurs during meiosis where chromosomes are randomly sorted into gametes, ensuring individual genes are inherited independently.

A population bottleneck is a drastic reduction in population size, often due to natural disasters or catastrophic events. This results in a significant decrease in genetic diversity.

Non-random mating refers to mating patterns where individuals preferentially mate with specific individuals, leading to changes in allele frequencies.

Alleles are alternative forms of a gene, found at the same locus (position) on a chromosome. They represent different versions of the same genetic information.

Homologous chromosomes are pairs of chromosomes that carry the same genes, but may have different alleles for those genes, one inherited from each parent.

Organisms that undergo sexual reproduction have a greater ability to adapt to harsh environments because it reshuffles genes, promoting variation and potentially beneficial traits.

The cell cycle includes four main stages: G1 (growth), S (DNA synthesis), G2 (growth), and M (mitosis). G0 represents a quiescent state where the cell is not actively dividing.

Checkpoints, like G1/S, G2/M, and M, are control mechanisms that ensure proper progress through the cell cycle. They prevent errors in DNA replication or chromosome segregation.

Flow cytometry uses fluorescent DNA binding dye to analyze the DNA content of cells. This allows scientists to determine the proportion of cells in different stages of the cell cycle based on their fluorescence.

Cells in G1 have 1x DNA content, cells in G2 have 2x DNA content, and cells in S phase have DNA content between 1x and 2x.

The size of the peak in flow cytometry data represents the number of cells in a particular stage. For example, a smaller peak in G2/M may indicate a checkpoint is preventing cells from transitioning to mitosis.

Phosphorylation, the addition of a phosphate group, plays a vital role in controlling the cell cycle. Kinases, enzymes that add phosphate groups, regulate the activity of proteins involved in cell cycle progression.

Cdks are enzymes that are constantly present in the cell. Their activity is regulated by cyclins, proteins that accumulate and degrade at specific times during the cell cycle. This ensures Cdks are active only when needed.

Cyclin-dependent kinases (Cdks) rely on cyclins to become active. Cyclins are proteins that bind to Cdks, enabling them to phosphorylate other proteins and drive the cell cycle forward.

Cyclins bind to and activate Cdks. Once activated, Cdks phosphorylate target proteins, triggering events that lead to cell cycle progression.

M-cyclin levels fluctuate during the cell cycle, regulating the activity of M-Cdk. M-Cdk is crucial for the processes that occur during mitosis (M phase).

Different cyclins control specific stages of the cell cycle by activating different Cdks. This ensures that events happen in the correct order and that the cell cycle progresses smoothly.

The location of active Cdk/cyclin complexes within the cell determines their activity during the cell cycle. This ensures that events happen at the right time and place.

Multiple regulatory mechanisms ensure that Cdk activity is tightly controlled. This protects against errors and ensures that the cell cycle progresses correctly.

Cdk activity is controlled through several mechanisms: cyclin ubiquitination (degradation), phosphorylation/dephosphorylation, and inhibitors.

If regulatory mechanisms fail, Cdk activity may become uncontrolled, leading to errors in cell division and potentially cancer development.

p53 is a tumor suppressor gene that regulates the cell cycle. It acts as a checkpoint protein, preventing cells with damaged DNA from replicating.

If DNA damage is detected, p53 activates genes that halt the cell cycle, allowing time for repair. If the damage is too severe, p53 triggers apoptosis (programmed cell death).

p21 is a protein that acts as a CDK inhibitor. It binds and inhibits cyclin-dependent kinases (CDKs), preventing them from phosphorylating targets necessary for cell cycle progression.

p21 is activated by p53. It inhibits CDK activity, leading to a pause in the cell cycle, allowing time for DNA repair or apoptosis.

A mutated p53 is unable to function properly. Damaged cells continue to replicate unchecked, leading to uncontrolled cell growth and potential cancer development.

The high rate of p53 mutations in cancer underscores its crucial role in tumor suppression. Its inactivation allows cancer cells to escape normal cell cycle regulation, leading to uncontrolled growth.

The initiation of DNA synthesis (S phase) is regulated by the origin recognition complex (ORC). In G1, Cdc6 helps load the helicase at the origin of replication. S-Cdk activates the helicase, assembles replication proteins at the fork, and phosphorylates Cdc6, preventing reassembly of the replication complex.

The entry into mitosis is controlled by M-Cdk (M-phase promoting factor). Cdc25 removes inhibitory phosphates from M-Cdk, activating it. Wee1, on the other hand, adds inhibitory phosphates to M-Cdk.