Bio1 Cell Cycle and Cell Division + PCV: Mitosis

How do prokaryotic cells divide? How do eukaryotic cells divide?

Prokaryotic cells divide through binary fission.

Eukaryotic cells divide through mitosis and meiosis.

What is created in mitosis?

two daughter cells that are identical to and have the same chromosome number as the parent cell

Describe what occurs before mitosis.

In interphase, the cell prepares for division by replicating the centrosome and the DNA in the nucleus.

What is created in DNA replication?

sister chromatids, two identical copies of a chromosome that are connected by a centromere

What are Centrosomes? Describe structure and what they do.

Microtubule organizing centers that guide the movement of chromosomes during mitosis

Each centrosome contains a pair of centrioles.

Describe all the stages of mitosis in order.

Prophase

• chromatin coils and condenses, resulting in compacted chromosomes (that can be seen with a microscope)

Prometaphase

• nuclear envelope breaks down

• A kinetochore forms in the centromere of each chromosome

• Spindle microtubules form from the centrosomes and attach to the kinetochores

Metaphase

• the chromosomes are aligned by the spindle fibers at the cell’s equator

Anaphase

• the centromere splits and the sister chromatids separate

• The separated sister chromatids are now individual chromosomes. The individual chromosomes move toward opposite poles of the cell

Telophase

• the chromosomes reach the poles

• the spindle fibers break down

• the nuclear envelopes reform

• the chromatin unravel and decondense (becomes diffuse)

• Cytokinesis begins

What is cancer? What causes it?

Cancer is uncontrolled cell division, which can be caused by DNA mutations.

Chromosomes are made of what macromolecule?

DNA

All cell division (in both prokaryotes and eukaryotes) requires… (4 pts)

• Signal to reproduce

• Replication of DNA and vital cell components

• Segregation of DNA to each new cell

• Cytokinesis

What causes prokaryotic cells to divide?

triggered by an external or internal signal such as having plenty of food or when the cell is starting to age

What causes eukaryotic cells to divide?

Why do they divide? (4 pts)

triggered by internal signals, which often work by affecting the cell cycle

Eukaryotic cells divide for animal reproduction, animal development, plant growth and development, and immunology (animal defense systems).

What is the cell cycle?

the process a cell goes through before and during cell division

Describe the presence/absence of cyclin and cyclin-dependent kinases (CDK) throughout the cell cycle?

Discuss the function of cyclin.

CDK protein is always present but its active site is not exposed (inactive form).

Cyclin is only created at a certain point in the cell cycle. When cyclin binds to CDK, the active site of CDK is exposed (allosteric activation).

After the specific phase is complete, cyclin will break down and CDK returns to its inactive form.

What is a chromosome?

What is chromatin?

What are homologous chromosomes?

A chromosome is a single piece of DNA.

Chromatin is DNA wound around its associated proteins.

Homologous chromosomes (“homologs”) are 2 chromosomes that are similar and contain the same genes in the same order), but are not identical and can have different alleles of those genes.

How many chromosomes do humans have? How many of those are sex chromosomes?

Humans have 23 pairs of chromosomes (46 total). One of those pairs are sex chromosomes (2).

When it comes to DNA segregation, what complicating factors do eukaryotes that prokaryotes do not?

Eukaryotes have a nucleus, can be diploid, and can have multiple chromosomes

How many cells does cytokinesis create in prokaryotes vs eukaryotes?

In prokaryotes, cytokinesis always results in two cells.

In eukaryotes, cytokinesis can result in two cells (mitosis) or four cells (meiosis).

What is the goal of meiosis (in humans)?

to produce gametes (egg or sperm) that have half the DNA or the original cell

Describe the ploidy (and designation) of gametes vs somatic cells.

Gametes are haploid (n ploidy designation) and only have one copy of each chromosome.

Somatic cells are diploid (2n ploidy designation) and have two copies of each chromosome (one from each parent).

Diplontic vs Haplontic vs Haplodiplontic Life Cycle

Which do humans have?

A diplontic life cycle features a dominant diploid stage where meiosis produces haploid gametes. Most of the life cycle is spent as diploid.

A haplontic life cycle features a dominant haploid stage where one single-celled zygote is created during the diploid phase. Most of the life cycle is spent as haploid.

Haplodiplontic organisms spend significant amounts of their lives diploid or haploid.

Humans have a diplontic life cycle.