64 terms

Cell Reproduction

Rod-shaped, structures made of DNA and proteins. The DNA in a eukaryotic cell's nucleus is coiled into these very compact structures.
Each chromosome is a single DNA molecule with its associated proteins
In between cell divisions, the DNA is not so tightly coiled and forms this complex
Each half of the chromosome
The constricted area of each chromatid
Sex Chromosomes
chromosomes that determine the sex of an organism.
all of the other chromosomes in an organism.
Homologous Chromosomes
The two copies of each autosome
A photomicrograph of all of the chromosomes in a dividing cell of an individual
Chromosomes in Humans
the 46 chromosomes exist as 22 homologous pairs of autosomes and 2 sex chromosomes.
Cells having two sets of chromosomes and have both chromosomes for each homologous pair, and they have two sex chromosomes.
Cells having only one set of chromosomes. Human sperm and egg cells are haploid. They have half the number of chromosomes so that when they combine during sexual reproduction, the new cell will be diploid
Somatic Cells
all of the cells in an organism except for the sex cells, egg and sperm. (Diploid)
Sex Cells
egg and sperm, or any cells that develop into egg and sperm.
Two kinds of cell division in eukaryotes
Mitosis and Meiosis
cell division which results in new cells with genetic material that is identical to that of the original cell. Form diploid cells (2n).
cell division which results in cells with half the chromosome number of the original cell. Form haploid cells (1n).
Cell Cycle
the ordered sequence of events that extends from the time a eukaryotic cell is first formed from a dividing parent cell until its own division into two cells.
Cell Division
one phase of the cell cycle.
The time between cell divisions. Divided into three phases
The division of the cell happens in two phases
Mitosis is the division of the nucleus in eukaryotic cells.
Cytokinesis is the division of the cytoplasm in eukaryotic cells.
First growth (G1) phase
a cell grows rapidly and carries out its routine functions.
Synthesis (S) phase
A cell's DNA is copied during this phase.
Second growth (G2) phase
preparations are made for the nucleus to divide.
(M phase) Mitosis
The process during cell division in which the nucleus of a cell is divided into two nuclei
the process during cell division in which the cytoplasm divides
(G0) phase
During this phase, cells have exited from the cycle and do not copy their DNA and do not prepare for cell division. They just do their normal functions as a cell.Usually occurs after G1
made up of protein microtubules that help move chromosomes
structures shaped like cans that anchor the spindle at the end of the cell.
-first stage of mitosis
- the nuclear envelope dissolves
- the chromosomes tightly coil
- and a spindle forms.
- the chromosomes move to the center of the cell
- and line up along the equator.

This is the stage when karyotypes are typically made.
- the chromatids split at the centromere
- and then move toward opposite poles of the dividing cell.
- the spindles disassemble
- the chromosomes become
less tightly coiled
- a nuclear envelope and nucleolous forms
- cytokinesis occurs.
is the process when the cytoplasm divides by pinching inward and the cell grows to enclose each new cell.
Cleavage Furrow
a shallow groove on the cell's surface
Cell Plate
In plant cells, a membrane-bound cell wall is formed
Roles of Mitosis
- Growth
- Cell Replacement
- Asexual Reproduction
a disease of the cell cycle. Cells do not respond to the cell cycle control system.
- Divide excessively
- Can invade other body tissues
an abnormally growing mass of cells that is found within normal tissue.
Benign Tumor
If the tumor remains at the original site
Malignant Tumor
If the tumor spreads into neighboring tissues or other parts of the body
Binary Fission
the division of a prokaryotic cell into two offspring cells.
Three Stages of Binary Fission
1. DNA is copied. The cell grows until it is approximately twice the original size.
2. Cell begins to divide by forming a cell wall between the two chromosomes.
3. Two identical haploid cells are created.
the union of the nucleus of the sperm cell with the nucleus of an egg cell, producing a zygote.
a fertilized egg, which is diploid, that results from the union of sperm and egg.
Egg and sperm cells
the process of meiosis ensures that the next generation will have
- the diploid number of chromosomes
- a combination of traits that differs from that of either parent.
The period of time between meiosis I and meiosis II
Prophase I
the spindle appears while the nuclear envelope fragments and the nucleolus disappears. Because DNA replicated during interphase prior to meiosis I, the homologous chromosomes each have two sister chromatids.
Metaphase I
homologous pairs are aligned at the metaphase plate.
Anaphase I
homologous chromosomes separate and move to opposite poles of the spindle. Each chromosome still consists of two chromatids.
Telophase I
nuclear envelopes may reform and nucleoli may reappear.
Prophase II
a spindle appears while the nuclear envelope disassembles and the nucleolus disappears.
Anaphase II
sister chromatids separate, becoming daughter chromosomes that move into the daughter nuclei.
Telophase II
the spindle disappears as nuclear envelopes reform.
Cytokinesis after Meiosis II
the plasma membrane furrows to give two complete cells, each with the haploid number of chromosomes
Meiosis I
separates homologous chromosomes
Meiosis II
separates sister chromatids
Two Sources of Genetic Recombination
1. crossing-over of nonsister chromatids and
2. independent assortment of homologous chromosomes.
Crossing Over
the exchange of segments between chromatids of homologous chromosomes during synapsis in Prophase I of meiosis.
the pairing of homologous chromosomes during Prophase I.
Independent Assortment
when homologous chromosome line up during metaphase I of meiosis, the maternal and paternal chromosomes randomly line up.
occurs when members of a homologous chromosome pair (meiosis 1) or sister chromatids (meiosis II) do not separate.
A pair of homologous chromosomes lined up next to each other during prophase I of meiosis