D2.1 Cell and Nuclear Division

What is cytokinesis?

Cytokinesis is the splitting of cytoplasm in the parent cell between daughter cells.

How does cytokinesis occur in animal cells?

A cleavage furrow forms from the constriction belt made of actin and myosin

How does cytokinesis occur in plant cells?

A cell plate forms from fused vesicles to create a new cell wall between daughter cells.

What is equal cytokinesis?

Equal cytokinesis is the division of cytoplasm and organelles into two daughter cells, where each must receive at least one mitochondrion.

What is unequal cytokinesis?

Unequal cytokinesis refers to the unequal distribution of organelles and cytoplasm during reproduction, such as in yeast budding and oogenesis.

What roles do mitosis and meiosis serve in eukaryotes?

Mitosis is for maintaining chromosome number and genome continuity, while meiosis reduces chromosome number and increases diversity.

What happens during DNA replication?

DNA replication occurs before mitosis and meiosis during the S phase of interphase, resulting in sister chromatids connected by a centromere.

Kinetochores

Protein structures assembled on the centromere

Role of microtubules

Attach to kinetochores on the centromere and move the chromosomes to opposite poles

What are the phases of mitosis?

The phases of mitosis are prophase, metaphase, anaphase, and telophase.

What is the difference between diploid and haploid organisms?

Diploid organisms have two sets of chromosomes (2n), while haploid organisms have one set of chromosomes (n).

What is nondisjunction and its potential consequences?

Nondisjunction is the uneven splitting of homologous chromosomes or sister chromatids, which can lead to conditions like Down syndrome.

How does meiosis lead to genetic variation?

Meiosis leads to variation through random orientation of bivalents and crossing over during prophase 1.

What is cell proliferation?

Cell proliferation is the rapid increase in the number of cells through rapid cell division.

What are the phases of the cell cycle?

The cell cycle consists of mitosis, G1, S, and G2 phases.

What occurs in G1?

The cell undergoes active growth and regular functioning

What occurs in S?

DNA synthesis/copying of chromosomes

What occurs in G2?

Preparations for mitosis (growth, production of organelles, DNA packing as chromatin)

Function of cell checkpoints

Cell cycle checkpoints hold cells until it is appropriate for them to proceed to the next phase + adequate amount of cyclins present

What is the role of cyclins in the cell cycle?

Cyclins are proteins that regulate the cell cycle by ensuring checkpoints are met before moving to the next phase.

G1 Checkpoint

Ensures there is adequate room in the environment for more cells and enough energy and materials available

G2 Checkpoint

Ensures there is enough energy and materials available and DNA has been completely replicated and checked for errors

M Checkpoint

Checks that all chromosomes are attached to microtubules

Maturation Promotion Factors (MPFs)

Regulates G2 checkpoint (made of cyclin, CDK and phosphate)

What are the consequences of mutations in checkpoint regulation?

Mutations can lead to uncontrolled cell division and tumor formation.

Proto-oncogenes

Promotes cell proliferation

What distinguishes benign tumors from malignant tumors?

Benign tumors are not serious and removable, while malignant tumors can metastasize and invade other tissues.