Chapters11-16 Flashcards
(163 cards)
Mitosis
Segregation and replication of the DNA in a Diploid cell.
A single nucleus gives rise to two nuclei that are geneticall identical to each other and to the parent nucleus. Accurate segregation of the eukaryotic cells multiple chromosomes into daughter nuclei.
Diploid Cell
diploid cell is a cell that contains two sets of chromosomes.
Chromatin
single strand of a chromosome, and it is the complex of DNA and proteins
Centromere
Is part of the chromosome that holds the two sister chromatids together.
Histones
Are proteins that are positively charged, and they help package the eukaryotic DNA. They are positively charged because of their high content of the basic amino acids lysine and arginine.
Nucleosomes
Is the basic unit of DNA packaging in Eukaryotes, consisting of a segment of DNA wound in sequence around four histone protein cores.
Centrosome
An organelle in the cytoplasm near the nucleus. It serves as the main microtubule organizing center. It usually consists of a pair of centrioles
Centrioles
A pair in each centrosome, Hollow tube formed by nine triplets of micotubules. The two tubes are right angles to each other.
How does the Centrosomes determine the plane of cell division?
During S phase the centrosome doubles to form a pair of centrosomes. G2 to M transition, two centrosomes separate from one another moving to opposite ends of the nuclear envelope. Positions of the centrosomes determine the plane at which the cell will divide.
What are microtubules and how are they formed?
Centrioles are surrounded by high concentrations of tubulin dimers these proteins then form the microtules that orchestrate chromosomal movement.
What happens in prophase in mitosis?
1) chromatin fibers become coiled into chromosomes with each chromosome having two chromatids that join at a centromere.
2) the mitotic spindle, composed of microtubules and proteins form in the cytoplasm (serves as a structure to which the chromosomes attach and act as a framework)
3) the two pair of centrioles move away from one another and it serves as a mitotic center(poles of the cell)
What is the Spindle?
Array of microtubules spreading out from both poles of a dividing cell during mitosis.
What are the two types of microtubules in the spindle?
Polar microtubules and kinetochore microtubules
What is a polar microtubule?
Acts as a frame work of the spindle, and runs from one pole to the other attaching to the centrosomes
What is a kinetochore microtubule?
Attach to the kinetochores on the chromosomes
What is a Kinetochore?
is the protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart
List the steps in Mitosis
Prophase, Prometaphase,Metaphase,Anaphase and telophase
What happens in Mitosis prometaphase?
The nuclear envelope breaks down and the compacted chromosomes attach to the kinetochore microtubules.
What happens in Mitosis Metaphase?
The microtubules pull the chromosomes to a equatorial position in the cell.
What happens in Anaphase in Mitosis?
The paired sister chromatids separate, and the new daughter chromosomes begin to move toward the poles. Separation occurs because on subunit of the cohesin protein holding the sister chromatids are hydrolyzed by an enzyme called protease but a specific variation of this enzyme called separase. After they separate the chromatids are called daughter chromosomes.
What happens in telophase in mitosis?
Occurs after the chromosomes have reached the poles, a nuclear envelope forms around each set of chromosomes, The chromatin decondenses.
What happens in Cytokinesis in a eukaryotic cell?
A single eukaryotic cell is divided to form two daughter cells. It begins with a pinch of the plasma membrane called a contractile ring. It is composed of microfilaments of actin and myosin, they pinch the cell in two.
Asexual reproduction.
Mitosis based, the offspring are clones, they are genetically identical to the parents.
Sexual reproduction
Consists of both mitosis and meiosis, the organism is not identical to its parents.