cell continuity

What is a chromosome?

A strand of DNA containing many genes and histone proteins.

What does diploid mean?

Having two sets of chromosomes (2n).

What does haploid mean?

Having one set of chromosomes (n).

What are autosomes?

Chromosomes not involved in sex determination.

What are sex chromosomes?

Chromosomes involved in sex determination.

What are the three main stages of the cell cycle?

Interphase, mitosis, and cytokinesis.

What occurs during interphase?

The cell enlarges, develops organelles, and prepares for division.

What are the three phases of interphase?

G1 (gap 1), S (synthesis), and G2 (gap 2).

What happens during the G1 phase?

Intense cellular synthesis occurs, increasing the number of organelles and proteins.

What occurs during the S phase?

DNA semi-conservative replication takes place, resulting in two chromatids held together by a centromere.

What is the function of the G2 phase?

Some cell growth occurs, mitochondria divide, and chromosomes are checked for errors.

What is the purpose of checkpoints in the cell cycle?

To ensure conditions are favorable and all stages have occurred without error before the cell divides.

What happens if cyanide is injected during interphase?

Mitosis does not occur, and there is no cell division because ATP is not produced.

What is the role of checkpoint proteins?

They monitor criteria to determine if the cell can proceed to the next stage of the cell cycle.

What is a benign tumor?

A tumor that is encapsulated, usually stops growing, and does not spread to other locations.

What is a malignant tumor?

A tumor that continues to grow unchecked and can spread to form secondary tumors.

What is chemotherapy?

The use of drugs to treat cancer by targeting processes within the cell cycle.

What are antimetabolites?

Drugs that act as S phase inhibitors, preventing DNA synthesis.

What is the function of vincristine?

It prevents the formation of microtubules, stopping chromatids from pulling apart during mitosis.

What is the significance of the centromere? It holds the two chromatids together after DNA replication.

What is a locus?

The specific position of a gene on a chromosome.

What happens at the G1 checkpoint?

The cell checks for growth, size, and DNA damage before proceeding to DNA synthesis.

What occurs at the G2 checkpoint?

The cell checks if DNA has been fully replicated and if there is any DNA damage.

What is the metaphase checkpoint?

It ensures all chromosomes are properly attached to spindle fibers before proceeding with mitosis.

What is the outcome of mutations in checkpoint proteins? Cells may undergo uncontrolled division, leading to tumor formation.

What is the role of ATP in the cell cycle?

ATP is produced and stored during interphase to provide energy for cell division.

What is the significance of the surface area to volume ratio in cell growth? Increasing cell size would decrease this ratio, making diffusion insufficient for cell needs.

What are chromosomes composed of in eukaryotic cells? Chromosomes are composed of DNA supported by histone proteins.

What is a nucleosome?

A nucleosome is DNA wrapped around a group of histone molecules.

What is the role of histones in chromosome structure? Histones provide support for DNA during chromatin condensation to form visible chromosomes.

What is a karyogram?

A photograph of chromosomes.

What is a karyotype?

The set of chromosomes in an organism.

What is the structure of centrioles?

Centrioles have a 9x3 microtubule structure.

What is the function of centrioles?

Centrioles are involved in the formation of the spindle fiber.

What are spindle fibers made of?

Spindle fibers are made of microtubules containing the protein tubulin.

What is the role of spindle fibers during mitosis? Spindle fibers attach to chromatids by their centromeres, facilitating their separation.

What occurs during prophase of mitosis?

Chromosomes condense, centrioles move to opposite poles, and the spindle begins to form.

What happens during metaphase?

Chromosomes line up along the equator and attach to the spindle by their centromeres.

What occurs during anaphase?

Centromeres split, and sister chromatids are pulled towards opposite poles.

What happens during telophase?

Nuclear envelopes form around each group of chromosomes, and chromosomes decondense.

What is cytokinesis?

Cytokinesis is the division of the cytoplasm following mitosis.

How does cytokinesis differ in animal and plant cells?

In animals, a cleavage furrow forms; in plants, a cell plate forms.

What is the role of the Golgi apparatus in plant cytokinesis?

The Golgi apparatus produces vesicles that fuse to form the cell plate.

What is the significance of mitosis?

Mitosis results in genetic stability and is crucial for growth, repair, and asexual reproduction.

What are the two main reasons daughter cells are genetically identical to the parent cell? DNA replication during S phase and the arrangement of chromosomes along the equator in metaphase.

What is the function of microfilaments during animal cytokinesis?

Microfilaments pull the membrane in along the equator to form a cleavage furrow.

What are the key points on mitosis?

Mitosis occurs for growth, repair, and asexual reproduction in somatic cells.

What is the difference in the presence of centrioles and asters between plant and animal cells? Centrioles and asters are present in animal cells but not in plant cells.

What is the final outcome of mitosis?

At the end of mitosis, there are two new nuclei that are genetically identical to the parent nucleus.

What is the role of the centromere during mitosis? The centromere joins sister chromatids and splits during anaphase.

What type of cells does meiosis occur in?

Meiosis takes place in diploid cells.

Where does meiosis occur in humans and plants?

In humans, meiosis occurs in the reproductive organs (testes and ovaries); in plants, it occurs in pollen grains and ovules.

What is the end result of meiosis in terms of daughter cells?

Meiosis results in 4 haploid daughter cells that are genetically different from each other.

What happens during the first meiotic division?

The first meiotic division involves the separation of homologous chromosomes.

What happens during the second meiotic division?

The second meiotic division involves the separation of chromatids.

What is crossing over in meiosis?

Crossing over occurs in prophase I when homologous chromosomes pair up (synapsis) and exchange genetic material at points called chiasmata.

What is a bivalent in meiosis?

A bivalent is a homologous pair of chromosomes containing 4 chromatids lying side by side.

What is the significance of chiasmata in meiosis?

Chiasmata are points where chromatids may break and swap places, resulting in genetic recombination.

What is independent assortment in meiosis?

Independent assortment occurs during metaphase I when homologous pairs line up randomly at the equator, affecting the genetic composition of the resulting gametes.

What occurs during prophase I of meiosis?

In prophase I, chromosomes condense, homologous chromosomes form bivalents, chiasmata are formed, and the spindle begins to form.

What happens during metaphase I of meiosis?

During metaphase I, bivalents line up along the equator and attach to spindle fibers by their centromeres.

What occurs during anaphase I of meiosis?

In anaphase I, homologous chromosome pairs are separated and pulled towards opposite poles.

What is the outcome of telophase I in meiosis?

In telophase I, the chromosomes reach opposite poles, and a nuclear envelope forms around each group, resulting in 2 nuclei.

What happens during prophase II of meiosis?

In prophase II, a new spindle forms at right angles to the old spindle, and chromosomes may condense.

What occurs during metaphase II of meiosis?

During metaphase II, chromosomes line up along the equator and attach to the spindle by their centromeres.

What happens during anaphase II of meiosis?

In anaphase II, centromeres split, and sister chromatids are pulled towards opposite poles.

What is the outcome of telophase II in meiosis?

In telophase II, the two groups of chromosomes reach opposite poles, a nuclear envelope forms, and cytokinesis follows.

What is the significance of meiosis in terms of genetic variation?

Meiosis results in genetic variation because each gamete is genetically different and fertilization is random.

What is produced as a result of meiosis?

Meiosis produces 4 genetically different haploid daughter cells, also known as a tetrad.

What is the role of centrioles during meiosis?

Centrioles move towards opposite poles during both meiotic divisions to help form the spindle apparatus.

What is the difference between homologous chromosomes and sister chromatids?

Homologous chromosomes are pairs of chromosomes containing the same genes but may have different alleles; sister chromatids are identical copies of a single chromosome.

What is the role of the spindle fibers during meiosis?

Spindle fibers attach to centromeres of chromosomes to facilitate their movement during cell division.

What is the significance of the random alignment of chromosomes during metaphase I?

The random alignment leads to independent assortment, contributing to genetic diversity in gametes.