Flashcards in Chapter 8 Deck (33):
Why can a eukaryotic cells not simply split into two?
Because then only one daughter cell would inherit the nucleus and the DNA. A cell's cytoplasm only splits after its DNA has been copied and packaged into more than one nucleus.
What is Mitosis?
Mitosis is a nuclear division mechanism that occurs in somatic (body) cells of multicelled organisms.
What is Meiosis?
The basis of sexual reproduction, in humans and mammals gametes (sperm and eggs) develop from immature reproductive cells.
Functions of Mitosis cytoplasm division (4).
In all multicelled eukaryotes, the basis of three processes:1. Increases in body size during growth2. Replacement of dead or worn-out cells3. Repair of damaged tissuesIn single-celled and many multicelled species, also thebasis of asexual reproduction
Function of Meiosis cytoplasm division.
In single-celled and multicelled eukaryotes, the basis of sexual reproduction; precedes gamete formation or spore formation.
Function of Prokaryotic fission.
In bacteria and archaeans alone, the basis of sexual reproduction.
What are Sister Chromatids?
Two attached molecules of DNA (attached as one chromosome)
What are Histones?
"Spools" of proteins. Under a microscope appears as beads on a string.
What are Nucleosomes?
A "bead" of a histone, the smallest unit of structural organization in eukaryotic chromosomes.
What is a Centromere?
The constricted region of a sister chromatid.
What are Kinetochores?
Binding sites for microtubules that tether the chromatids.
What is a Cell Cycle?
A series of events from one cell division to the next. Consists of: mitosis, cytoplasmic division, and interphase.
What is Interphase?
Interphase consists of three stages that increases the mass, doubles the cytoplasmic components, and duplicates the DNA of a cell.
What are the three stages of Interphase?
1. G1 - Interval (Gap) of cell growth and activity before the onset of DNA replication.2. Time of "Synthesis" (DNA replication).3. G2 - Second interval (Gap) after DNA replication where the cell prepares for division.
What is the Chromosome Number?
The sum of all chromosomes in a cell of a given type.
What are the four stages of Mitosis?
1. Prophase2. Metaphase3. Anaphase4. Telophase
What is the Bipolar Spindle?
A dynamic network of microtubules the grows from opposite poles of the cell during prophase.
What does "Mitos" mean?
Comes from the Greek word "thread".
What happens to two sister chromatids during prophase?
The duplicated chromosomes condense and become threadlike, and then rod-shaped. New microtubules assemble.
What is a Centrosome?
A region near the nucleus that will organize microtubules while they are forming.
When is the Centrosome duplicated?
Just before prophase.
What happens in the early stages of prophase?
Mitosis begins. DNA and its associated proteins have started to condense. Two chromosomes were inherited from the female parent. Theother two are their counterparts,inherited from the male parent.
What happens in the late stages of prophase?
The duplicated chromosomescontinue to condense. Newmicrotubules move one of twopairs of centrioles to the opposite side of the nucleus. The nuclear envelope starts to break up.
What happens during the transition from prophase to metaphase?
Microtubules penetrate the nuclear region and collectively form a bipolar spindle. Some tether one sister chromatid of each chromosome to a spindle pole. Others overlap at the spindle equator.
What happens during metaphase?
All of the chromosomes have become lined up midway between the spindle poles. At this stage of mitosis, the chromosomes are in their most tightly condensed form.
What happens during anaphase?
Sister chromatids separate as motor proteins moving along spindle microtubules drag them to opposite spindle poles. Other microtubules push the poles farther apart.
What happens during telophase?
There are two clusters of chromosomes, which now decondense. Patches of new membrane fuse to form a new nuclear envelope. Mitosis is over.
What results at the end of mitosis?
After cytoplasmic division, there are two daughter cells. Each is diploid: Its nucleus has two of each type of chromosome, just like the parent cell.
What are Kinases?
A class of enzymes that can activate other molecules by transferring a phosphate group to them. When DNA is broken or incomplete, kinases can activate certain proteins that eventually lead to cell death or stopping the cell cycle.
What are Growth Factors (checkpoints)?
Checkpoint proteins that activate genes that stimulate cells to grow and divide.
How is a tumour formed?
When a cell's continually dividing descendants are not stopped by a checkpoint protein and abnormal mass is formed.
What are Neoplasms?
Moles and other tumours, or abnormal masses of cells that lost control over how they grow and divide.