Cell Cycle, Mitosis, and Meiosis Overview Wk13

What distinguishes living organisms from nonliving matter?

The ability of organisms to produce more of their own kind.

What is the continuity of life based on?

Cell division.

How do prokaryotes reproduce?

By binary fission.

What are the steps of binary fission in prokaryotes?

Chromosome replication, movement of daughter chromosomes apart, and inward pinching of the plasma membrane to divide the cell.

What are the three main reasons multicellular eukaryotes depend on cell division?

Reproduction, growth, and repair.

What are the requirements for cell division?

Receipt of a signal to divide, DNA replication, DNA distribution (mitosis), and cytokinesis.

What are the phases of interphase in the cell cycle?

G1 phase (first gap), S phase (synthesis), and G2 phase (second gap).

What occurs during the S phase of interphase?

Chromosome duplication.

What is the mitotic (M) phase?

The phase that includes mitosis and cytokinesis.

What is the outcome of most cell divisions in terms of DNA?

Daughter cells typically have identical DNA.

How does meiosis differ from mitosis in terms of DNA content?

In meiosis, daughter cells have half the DNA content (n) compared to parental cells (2n).

What is a genome?

A genome can consist of a single DNA molecule (prokaryotes) or several DNA molecules (eukaryotes).

What role do cohesins play during cell division?

Cohesins are proteins that attach chromatids together.

What is the function of centromeres?

Centromeres are linking DNA sequences that hold sister chromatids together.

What is the mitotic spindle?

A structure that controls chromosome movement during cell division, made of microtubules.

What are the three types of microtubules in the mitotic spindle?

Kinetochore microtubules, polar microtubules, and astral microtubules.

What is the 'Pac-man' mechanism in chromosome movement?

Motor proteins on kinetochores walk chromosomes along microtubules during anaphase.

What are the two motor proteins involved in mitosis?

Kinesins (move from center to periphery) and dyneins (move from periphery to center).

What is the process of cytokinesis in animal cells?

Cytokinesis occurs by cleavage, forming a cleavage furrow.

How does cytokinesis differ in plant cells?

In plant cells, a cell plate forms during cytokinesis.

What are the five stages of mitosis?

Prophase, prometaphase, metaphase, anaphase, and telophase.

What happens during telophase?

Chromatids reach opposite poles and the nuclear envelope begins to reform.

What is the significance of the centrosome in cell division?

The centrosome is the microtubule-organizing center that replicates during interphase.

What regulates the Eukaryotic Cell Cycle?

A molecular control system driven by cytoplasmic signaling.

How does the frequency of cell division vary?

It varies with the type of cell due to molecular regulation.

What happens to cancer cells in relation to the cell cycle?

Cancer cells escape the usual controls on the cell cycle.

What are the two alternatives to cell division?

Highly specialized cells commit to G0 and never divide, while some cells can be called back into the cell cycle by external cues.

What is the G0 phase?

A non-dividing state that cells enter if they do not receive the go-ahead signal.

What are growth factors?

Substances like Platelet-derived growth factor (PDGF) that stimulate other cells to divide.

What is density-dependent inhibition?

A process where crowded cells stop dividing.

What is anchorage dependence?

The requirement for cells to be attached to a surface/substance to divide.

What is the significance of Hayflick's Limit?

It refers to the limit of about 50 doublings before cells become senescent.

What is cell senescence?

The process where cells stop dividing due to the shortening of DNA telomeres.

What is telomerase?

An enzyme that catalyzes the addition of lost telomere DNA sequences, active in stem cells and most cancer cells.

What is a karyotype?

An ordered display of chromosomes.

How many pairs of chromosomes do human somatic cells have?

23 pairs of chromosomes (2n = 46).

What are homologous chromosomes?

Chromosomes that share the same structure and sequence of genes but are not genetically identical.

What is the diploid number for humans?

46 (2n = 46).

What is the outcome of meiosis?

It reduces the number of chromosome sets from diploid to haploid.

What are gametes?

Reproductive cells (sperm and eggs) that result from oogenesis and spermatogenesis.

What occurs during recombination in meiosis?

Sister chromatids remain attached while homologues pair.

What is the role of external cues in the cell cycle?

They can call certain cells back into the cell cycle from G0.

What is the relationship between cancer cells and growth factors?

Cancer cells may not need growth factors to grow and can produce their own or convey signals without their presence.

What is the significance of the statement '1 in 3 US citizens will develop cancer'?

It highlights the prevalence of cancer in the population.

What is the primary difference between somatic cells and cancer cells in terms of cell cycle control?

Cancer cells have an abnormal cell cycle control system and are released from normal controls.

What is the result of meiosis compared to mitosis?

Meiosis results in 4 daughter cells, while mitosis generates 2 daughter cells.

What are the two key events in meiosis?

Crossing over and independent assortment.

What occurs during crossing over in Prophase I?

Sister chromatids exchange genetic material at points called chiasmata.

What is the significance of independent assortment in meiosis?

It allows alleles of different genes to be sorted into gametes independently, increasing genetic diversity.

How many possible combinations of maternal and paternal chromatids can be formed in a gamete with 23 sets of chromosomes?

8,324,608 possible combinations.

What is the total possible combination of alleles for genes in humans?

Approximately 70,368,744,177,664 combinations.

Who is recognized as the father of modern genetics?

Gregor Mendel.

What organism did Gregor Mendel use for his genetic experiments?

Garden peas.

What terms did Mendel coin in his studies?

Recessive and dominant.

What does dominance describe in genetics?

How the protein products of alleles interact in the phenotype.

What is a pedigree used for in genetics?

To show human traits and calculate the probability of specific phenotypes in offspring.

What is an example of a recessive inherited disorder?

Sickle-cell disease.

What is an example of a dominant inherited disorder?

Achondroplasia.

What is nondisjunction in meiosis?

It is when homologous chromosomes or sister chromatids do not separate normally during meiosis.

What is the result of nondisjunction in humans?

Aneuploidy, which can lead to conditions like Turner syndrome and Down syndrome.

What is polyploidy and in which organisms is it common?

Polyploidy is having more than two complete sets of chromosomes and is common in plants.

What are mutations in the context of genetics?

Mutations are changes in DNA that can be a source of genetic variation.

What does an organism's phenotype include?

Its physical appearance, internal anatomy, physiology, and behavior.

What is the difference between mitosis and meiosis in terms of chromosome separation?

In mitosis, sister chromatids separate; in meiosis, homologous chromosomes separate in Meiosis I and sister chromatids separate in Meiosis II.

What is the role of chiasmata during meiosis?

Chiasmata are points where crossing over occurs between homologous chromosomes.

How does meiosis contribute to genetic diversity?

Meiosis allows for novel combinations of traits through crossing over and independent assortment.

What is the outcome of meiosis II?

It results in four haploid daughter cells, each with n chromosomes.

What is the difference between identical daughter cells produced by mitosis and the daughter cells produced by meiosis?

Mitosis produces identical daughter cells, while meiosis produces genetically diverse daughter cells.