Biology Unit 4 Final

Biology Cellular Reproduction, Stem Cells, Cancer

Chromosomes

Chromosomes are DNA-packed structures in the cell nucleus that carry genes. 46 chromosomes (23 pairs)

Benign

Tumors that are non-cancerous and do not spread to other parts of the body.

Carcinogen

A carcinogen is a substance or agent that can cause cancer by damaging DNA or disrupting normal cell processes.

Metastasize

To metastasize means to spread cancer cells from the original site to other parts of the body through the blood or lymph system.

Centromere

The centromere is the central region of a chromosome where the two sister chromatids are joined.

Somatic cell

A somatic cell is any cell in the body except reproductive cells

Stem cells

Stem cells are special cells that can develop into many different types of cells in the body

Malignant

Malignant means cancerous and harmful.

Mitosis

Mitosis is the process of cell division where a single somatic cell divides to produce two identical daughter cells.

Cell Cycle

The cell cycle is the series of events a cell goes through to grow, replicate DNA, and divide into two daughter cells

Chromatid

A chromatid is one half of a duplicated chromosome, formed during DNA replication.

Zygote

A zygote is the first cell formed when a sperm fertilizes an egg.

Stages of Cell Cycle

• G1 phase: Cell grows, makes proteins, and prepares for DNA replication.

• S phase: DNA is replicated (each chromosome becomes two sister chromatids).

• G2 phase: Cell grows more, checks DNA, and prepares for mitosis.

• M phase: Mitosis + cytokinesis → nucleus and cytoplasm divide, forming two identical daughter cells.

Cancer

Cancer is a disease where abnormal cells grow uncontrollably and can spread (metastasize) to other parts of the body

Tumor

A tumor is an abnormal mass of cells that forms when cells grow and divide uncontrollably.

Meiosis

Meiosis is the type of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes (haploid) compared to the parent cell.

Homologous

Homologous refers to chromosome pairs that are similar in size, shape, and gene content

Chromatin

Chromatin is the complex of DNA and proteins (mainly histones) found in the nucleus of eukaryotic cells.

Gamete

A gamete is a haploid reproductive cell (sperm in males, egg in females) that carries half the number of chromosomes of a normal body cell.

Stages of Mitosis

• Prophase: Chromosomes condense, spindle fibers form, and the nuclear envelope begins to break down.

• Metaphase: Chromosomes align at the cell’s equator (metaphase plate).

• Anaphase: Sister chromatids are pulled apart to opposite poles of the cell.

• Telophase: Nuclear membranes reform around each set of chromosomes; chromosomes begin to decondense.

• Cytokinesis: Cytoplasm divides, producing two identical daughter cells.

haploid

A haploid cell has one complete set of chromosomes (n), instead of the two sets found in diploid cells.

histones

Histones are proteins in the nucleus that help package DNA into a compact, organized structure.

Why must our bodies use cell division for growth, repair, and replacement?

Cell division allows organisms to grow by increasing cell number, repair damaged tissues, and replace old or dead cells with new ones.

Why is cell differentiation important to the development of multicellular organisms?

Differentiation ensures cells develop specialized structures and functions, allowing complex organisms to form tissues and organs that work together.

Compare and contrast sexual and asexual reproduction.

• Sexual reproduction: Involves gametes, produces genetically diverse offspring.

• Asexual reproduction: Involves one parent, produces genetically identical offspring.

What changes does DNA go through during the cell cycle?

DNA is replicated during the S phase, condensed into chromosomes during mitosis, and distributed equally into daughter cells.

Describe the structure of a chromosome.

A chromosome is a tightly coiled DNA molecule wrapped around histone proteins, consisting of two sister chromatids joined at a centromere.

What are the stages of the cell cycle?

G1 phase, S phase, G2 phase (interphase), M phase (mitosis), and cytokinesis.

What events occur during each stage of the cell cycle?

• G1: Cell grows and makes proteins.

• S: DNA is replicated.

• G2: Cell prepares for mitosis.

• Mitosis: Nucleus divides (prophase, metaphase, anaphase, telophase).

• Cytokinesis: Cytoplasm divides, forming two daughter cells.

What are the defining characteristics of stem cells?

• They can divide and make more stem cells.

• They can develop into specialized cell types (muscle, nerve, blood, etc.).

How do embryonic stem cells differ from adult stem cells?

• Embryonic stem cells: Derived from early embryos, pluripotent (can become almost any cell type), unlimited division potential, but raise ethical concerns.

• Adult stem cells: Found in tissues like bone marrow and fat, multipotent (limited to certain cell types), mainly used in therapies like bone marrow transplants

Describe the number and cell type produced by mitosis.

Mitosis produces two diploid daughter cells that are genetically identical to the parent cell. These are somatic (body) cells, used for growth, repair, and replacement.

Explain how DNA is divided during mitosis.

During mitosis, duplicated chromosomes (sister chromatids) condense and align at the cell’s equator. Spindle fibers attach to the centromeres and pull the chromatids apart during anaphase, ensuring each daughter cell receives a complete set of DNA.

Describe how cancer affects the human body.

Cancer disrupts normal cell growth and division, leading to uncontrolled cell proliferation. It can form tumors, invade tissues, weaken organ function, and spread to other parts of the body, ultimately interfering with vital processes.

How can exposure to certain environmental factors increase the chance for cancer-causing mutations?

Environmental factors like tobacco smoke, UV radiation, chemicals, and certain viruses can damage DNA. These mutations may disrupt genes that control cell growth and division, increasing cancer risk.

Distinguish between benign and malignant tumors.

• Benign tumors: Non-cancerous, grow slowly, do not spread, usually less harmful.

• Malignant tumors: Cancerous, grow rapidly, invade nearby tissues, and can metastasize.

Define metastasis

Metastasis is the process by which cancer cells break away from the original tumor, travel through blood or lymph, and form new tumors in other parts of the body.

How can factors external and internal to the cell increase the risk for cancer?

• External factors: Carcinogens (chemicals, radiation, viruses), lifestyle choices (diet, smoking, alcohol).

• Internal factors: Genetic mutations, inherited predispositions, errors in DNA replication, and malfunctioning cell cycle checkpoints.

Describe the number and cell type produced by meiosis.

Meiosis produces four haploid gametes (sex cells: sperm or egg), each genetically unique and containing half the number of chromosomes compared to the parent cell.

Explain how DNA is divided during meiosis.

• Meiosis I: Homologous chromosomes pair up, exchange DNA through crossing over, and then separate into two cells. Each cell receives one chromosome from each homologous pair.

• Meiosis II: Sister chromatids separate, similar to mitosis, resulting in four haploid cells with distinct DNA combinations.