Unit 6 Cell Growth, Division and Reproduction Chapter 10 (and 11.4)

What are the parts of a chromosome (chromatid and centromere)?

-Histome, protein molecule around which DNA is tightly coiled in chromatin -Chromatid, one of two identical "sister" parts of a duplicated chromosome -Centromere, area where the chromatids of a chromosome are attached

Zygote

A fertilized egg.

Gametes

A sex cell. A mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote.

Carcinogens

A substance capable of causing cancer in living tissue.

Explain why cell division is important to the life functions of any organism.

All life begins and thrives through cellular processes, and cell division is the process of development and transformation. In multicellular organisms, cell division is responsible for the growth of the organism and the replacement of old or worn-out cells.

Explain the importance of surface area to volume (why can cells only grow to a certain size?).

As cells get larger, volume increases more rapidly than surface area. Since cells exchange materials and molecules across their membranes, a large cell has more difficulty transporting enough materials.

Prophase 2

As the cells enter Prophase 2, their chromosomes- each consisting of two chromatids- become visible.

Malignant

As tumors grow and become malignant, however, they gain the ability to break through these boundaries and invade adjoining tissues.

Describe cancer in terms of cell division (how do cancer cells differ from other cells?).

Cancer is considered a disease because when control over the cell cycle has broken down, cancer cells begin to form. Cancer cells do not respond to signals that regulate the growth of most cells. As a result, the cells divide uncontrollably.

How do cells become specialized for different functions?

Cell differentiation is how generic embryonic cells become specialized cells. This occurs through a process called gene expression. Gene expression is the specific combination of genes that are turned on or off (expressed or repressed), and this is what dictates how a cell functions.

What is the role of chromosomes in cell division?

Chromosomes carry all the genetic information (DNA)

Describe homologous chromosomes, and state their relationship to each other.

Chromosomes in which one set comes from the male parent and one set comes from the female parent.

Crossing-over

Crossing over is when genetic material is exchanged between homologous pairs, and occurs during prophase in meiosis.

Cancer

Disorder in which some of the body's cells lose the ability to control growth.

Cytokinesis

Division of the cytoplasm to form two separate daughter cells.

Anaphase 1 (Meiosis)

During anaphase 1, spindle fibers pull each homologous chromosome pair toward opposite ends of the cell. Third part of meiosis.

Anaphase

During anaphase the two chromatids of each chromosome separate and move to opposite poles, as if pulled along the spindle fiber, by the centromeres.

Interphase

During interphase the chromosomes are dispersed in the nucleus and appear as a network of long, thin threads of the chromatin. At some point before prophase begins, the chromosomes replicate themselves to form pairs of identical sister chromatids.

Metaphase 1 (Meiosis)

During metaphase 1 of meiosis, paired homologous chromosomes line up across the center of the cell. Second part of meiosis.

For each phase of mitosis, describe changes in chromosomes and other cell parts.

During prophase, the genetic material inside the nucleus condenses and the duplicated chromosomes become visible. Outside the nucleus, a spindle starts to form. During metaphase, the centromeres of the duplicated chromosomes line up across the center of the cell. Spindle fibers connect the centromere of each chromosome to the two poles of the spindle. During anaphase, the chromosomes separate and move along spindle fibers to opposite ends of the cell. During telophase, the chromosomes, which were distinct and condensed, begin to spread out into a tangle of chromatin.

Prophase

During prophase, the two chromatids remain attached to one another at the centromere, and the nuclear envelope breaks down and disappears. The spindle begins to form. In animal cells the centrioles separate and move apart, and asters appear around them. The spindle fibers run from one centriole to the other. In plant cells the spindle forms without centrioles.

Telophase

During telophase new nuclear envelopes from around the two groups of daughter chromosomes. The new nucleoli begin to appear, and eventually, as the formation of the two daughter nuclei is completed, the spindle fibers disappear. The chromosomes uncoil for dispersed distribution within the interpolated nucleus.

Benign

During the early stages of cancer, tumors are typically benign and remain confined within the normal boundaries of a tissue.

State two ways that meiosis allows for increased variety of genetic combinations.

Each member of a homologous pair came from each parent, and code for the same traits.Genetic material is exchanged between the pairs, this results in genetic recombination. When homologous pairs are separated during anaphase I, they do so independent of each other. Each new cell gets some of the maternal chromosomes and some of the paternal chromosomes.

Cytokinesis (Meiosis)

Follows telophase 1, forming two new cells. Fifth part of meiosis.

Contrast cytokinesis in plant and animal cells.

In animal cells, the cell membrane is drawn inward until the cytoplasm is pinched into two nearly equal parts. Each part contains its own nucleus and cytoplasmic organelles. In plant cells the cell membrane is not flexible enough to draw inward because of the rigid cell wall that surrounds it. Instead, a structure known as the cell plate forms halfway between the divided nuclei. The cell plate gradually develops into cell membranes that separate the two daughter cells. A cell wall then forms between the two new membranes, completing the process.

Contrast mitosis and meiosis. Include both differences in the process and in the end result.

In mitosis, when the two sets of genetic material separate, each daughter cell receives one complete set of chromosomes. In meiosis, homologous chromosomes line up and then move to separate daughter cells. Mitosis does not normally change the chromosome number of the original cell. This is not the case for meiosis, which reduces the chromosome number by half. Mitosis results in the production of two genetically identical diploid cells, whereas meiosis produces four genetically identical diploid cells.

Prophase 1 (Meiosis)

In prophase 1 of meiosis, each replicated chromosome pairs with its corresponding homologous chromosome. First part of meiosis.

Telophase 1 (Meiosis)

In which a nuclear membrane forms around each cluster of chromosomes. Fourth part of meiosis.

Describe how the cell cycle is regulated; give examples of internal and external regulators.

Internal and External Regulatory proteins. Internal regulators respond to events occurring inside a cell where external regulators respond to events outside of the cell.

State, in order, the parts of the cell cycle

Interphase, Mitosis, Anaphase, Telephase, and Cytokinesis

Tumor

Mass of rapidly dividing cells that can damage surrounding tissue.

Give examples of structures in which meiosis occurs (for both plants and animals).

Meiosis only occurs in sexual organs... testes, ovaries, flowers.

What is the difference between mitosis and cytokinesis?

Mitosis and cytokinesis differ in that mitosis the process in which a duplicated genome within a cell separates into identical halves, while cytokinesis involves the division of cellular cytoplasm into two daughter cells.

Cyclin

One of a family of proteins that regulates the cell cycle in eukaryotic cells.

Growth Factors

One of a group of external regulatory proteins that stimulate the growth and division of cells.

Mitosis

Part of eukaryotic cell division during which the cell nucleus divides.

Metaphase

Phase of mitosis in which the chromosomes line up across the center of the cell.

Meiosis

Process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.

Apoptosis

Process of programmed cell death.

Asexual reproduction (and examples)

Process of reproduction involving a single parent that results in offspring that are genetically identical to the parent. Asexual reproduction is the primary form of reproduction for single-celled organism as the archaea, bacteria, and protists. Many plants and fungi reproduce asexually as well.

Centromere

Region of a chromosome where the two sister chromatids attach.

Cell cycle

Series of events in which a cell grows, prepares for division, and decides to form two daughter cells.

Spindle fibers

Spindle fibers form a protein structure that divides the genetic material in a cell. The spindle is necessary to equally divide the chromosomes in a parental cell into two daughter cells during both types of nuclear division: mitosis and meiosis. During mitosis, the spindle fibers are called the mitotic spindle.

What is the importance of stem cells?

Stem cells may make it possible to develop a new field of regenerative medicine, in which undifferentiated cells are used to repair or replace damaged cells and tissues.

Tetrad

Structure containing four chromatids that form during meiosis.

Centrioles

Structure in an animal cell that helps to organize cell division.

Chromatin

Substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones.

Haploid

Term used to refer to a cell that contains only a single set of genes.

Diploid

Term used to refer to a cell that contains two sets of homologous chromosomes.

Homologous

Term used to refer to chromosomes in which one set comes from the male parent and one set comes from the female parent.

Metaphase II, Anaphase II, Telophase II, and Cytokinesis

The final four stages of meiosis II are similar to those in meiosis 1. However, the result is four haploid daughter cells.

Sexual reproduction

The genetic material from two individuals is combined to form a new being (zygote). Egg + Sperm = Zygote This fusion of gametes (sex cells) is called fertilization.

Meiosis 2

The two cells now enter a second meiotic division. Unlike the first division, neither cell goes through a round of chromosome replication before entering meiosis 2.

Stem Cells

The unspecialized cells from which differentiated cells develop. Sit at the base of a branching "stem" of development from which different cell types form. Stem cells are found in the early embryo, but they are also found in many places in the adult body.

Chromosome

Threadlike structure of DNA and protein that contains genetic information; in eukaryotes, chromosomes are found in the nucleus; in prokaryotes, they are found in the cytoplasm.

Chromatids

Two identical "sister" parts of a duplicated chromosome.

Metastasis

— literally meaning "new place" — In this stage, cancerous cells enter the bloodstream or the lymphatic system and travel to a new location in the body, where they begin to divide and lay the foundation for secondary tumors.