Cell Division Flashcards
Diploid
definition
Referring to cells that contain two sets of chromosomes (i.e. pairs of homologous chromosomes). One set of chromosomes is inherited from the mother and the other set is inherited from the father. Diploid cells are 2n. Somatic and germ cells are diploid.
Homologous
definition
Refers to two chromosomes that are a matched pair in a diploid cell. A matched pair of chromosomes are the same length and contain genes for the same characteristics at the same position on them. For each homologous pair, one chromosome is inherited from the mother and the other is inherited from the father.
Sister Chromatid (definition)
One of two identical copies of a chromosome duplicated during the S phase of the cell cycle. A centromere connects two sister chromatids together. When joined together sister chromatids compose one chromosome, and chromatids are separated from each other during mitosis or meiosis.
Gamete
definition
A haploid, sex cell (egg or sperm) produced from germ cells that have undergone meiosis. When two gametes join in fertilization the resulting zygote is a complete diploid cell.
Homologue
definition
Refers to one of the other of a homologous pair of chromosomes. Each is considered the homologue of the other.
Somatic Cell (definition)
Any nonreproductive cell found in multicellular organisms. That is, any cell except a germ cell or gametes (sperm and egg cells) found in a muticellular organism. Examples are lung and heart cells, nerve cells, and blood cells.
Gene
definition
A segment of DNA that carries specific information, ultimately coding for a protein, which determines certain traits in an organism. The gene is the basic unit of inheritance. It is a segment of DNA with instructions for protein synthesis. Genes are located on DNA stands, and each gene is composed of a specific nucleotide sequence that codes for the amino acid sequence of a protein.
Karyotype
definition
Diagrammatic representation of an organism’s genome. An image of the chromosomes of a cell in metaphase where the chromosomes are arranged in pairs by centromere position and size. Karyotypes are used to count and analyze the chromosomes of an individual and can also be used in the determination of chromosomal abnormalities.
Zygote
definition
The newly formed diploid cell that is produced when two haploid gametes unite. In animals this occurs when a sperm fertilizes an egg.
Germ Cell (definition)
A cell that in the body of a sexually reproducing organism that produces gametes (eggs or sperm) through meiosis. Germ cells are immature reproductive cells. In humans, germ cells are found in the testes of men and ovaries of women.
Meiosis
definition
A type of cell division in which a single, diploid germ cell is divided into four, haploid gamete cells. Meiosis only occurs in organisms that sexually reproduce and results in the production of sperm in males and eggs in females.
Haploid
definition
Cells that contain only one set of chromosomes. Haploid cells are referred to as “1n”. Gametes (sperm and eggs) are haploid. In human haploid gametes contain 23 chromosomes.
Mitosis
definition
A type of cellular division in which a single, diploid, somatic cell is divided into two genetically identical daughter cells. Mitosis along with cytokinesis compose the mitotic (M) phase of the cell cycle.
Genome
definition
All the genetic information in an organism. The complete DNA sequence of one set of chromosomes from an organism.
Allele
definition
An alternative form of a gene. An example would be genes that encode eye color -some encode blue eyes (one allele), while others encode brown, green or hazel eye colors (other alleles).
Anaphase
definition
A stage within the mitosis phase of cell division (also known as cell reproduction). Anaphase starts when sister chromatids separate from each other and ends when each set of separated, sister chromatids arrives at the opposite poles of the cell.
Centrioles
definition
The place where the microtubules originate from during mitosis. Centrioles are contained within the centrosomes.
Cytokinesis
definition
The division of the cytoplasm of a cell at the end of mitosis to form two separate daughter cells. In animals cells, this occurs through the pinching of the membrane at the center of the parental cell while in plants, this occurs through the formation of a cell plate as new cell wall forms to separate the daughter cells.
Interphase
definition
The stage of the cell cycle when division (mitosis) does not occur. During interphase, the cell grows, acquires nutrients, and replicates both its chromosomes as well as its organelles. Interphase consists of the G1 (chromosomes condense), S (DNA duplicates), and G2 (DNA integrity checked and repaired) phases of the cell cycle. Cells spend the majority of their time in interphase.
Kinetochore
definition
Proteins on the centromere where microtubules attach. These attached microtubules are called kinetochore microtubules.
Metaphase
definition
This is a stage of mitosis where the sister chromatids connected by centromeres are lined up along the plane of the cell’s center (called the metaphase plate).
Microtubules
definition
One type of fiber that makes up the cytoskeleton of a eukaryotic cell. Microtubules consist of proteins called tubulins. Microtubules aide in cell structure and movement and are also responsible for moving the chromosomes during mitosis and meiosis.
Prophase
definition
This is the first stage of mitosis. In prophase, the nucleus is broken down, the chromosomes (duplicated during the S phase of the cell cycle) condense, and the mitotic spindles form.
Telophase
definition
This is the final stage of mitosis. In telophase, new nuclear envelopes form around the separated chromosomes at each pole of the cell, the chromosomes unfold back into chromatin, nucleoli reappear, and the cell continues to elongate.
