Mitosis Flashcards
What is chromatin?
Chromatin is a loose combination of DNA and proteins that is present during interphase (phase of mitosis). The primary functions of the chromatin are the following:
- Package DNA into a more compact, denser shape.
- Reinforce the DNA macromolecule to allow mitosis.
- Prevent DNA damage.
- Control gene expression and DNA replication.
What is a chromatid?
A chromatid is one half of a duplicated chromosome and it is still joined to the original chromosome by a single centromere.
What is a chromosome?
A chromosome is a long, continuous thread of DNA that consists of numerous genes and regulatory information. Genes are specific regions of DNA that code for a particular protein and lead to the expression of hereditary character.
What is a centromere?
A centromere is a region of a condensed chromosome that looks pinched; where spindle fibers attach during meiosis and mitosis. Actually, the centromere links a pair of sister chromatids.
What are telomeres?
Telomeres are regions of repetitive nucleotide sequences (organic molecules) at each end of a chromosome. They protect the end of the chromosome from deterioration, from fusion with neighbouring chromosomes and they help prevent the loss of genes.
Explain the terms “haploid” and “diploid.”
The term “haploid” describes a cell that has only one copy of each chromosome (1n). Example: egg cell, sperm cell
The term “diploid” describes a cell that has two copies of each chromosome, one from an egg and one from a sperm. Example: embryo, skin cell
What is mitosis and what is its function?
In cell biology, mitosis is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. As mentioned above, mitosis is the process by which a cell divides its nucleus and contents.
What are the different stages of mitosis?
The stages of mitosis are the following:
Before the four stages of mitosis >Interphase: It plays an important role in preparing the cell to divide. By the end of interphase, an individual cell has two full sets of DNA, or chromosomes, and is large enough to divide. During interphase, the chromosomes are not visible.
The cell copies its DNA and grows in preparation for division. The DNA is loosely organized during interphase.
- Prophase: DNA and proteins condense into tightly coiled chromosomes. The nuclear envelope breaks down, centrioles begin to move to opposite poles, and spindle fibers form.
- Metaphase: Spindle fibers attach to each chromosome. They align the chromosomes along the cell equator.
- Anaphase: Chromatids separate to opposite sides of the cell. Cytokinesis usually begins in late anaphase or telophase.
- Telophase: Nuclear membranes start to form, chromosomes begin to uncoil, and the spindle fibers fall apart.
What is cytokinesis?
Cytokinesis is the process which divides cytoplasm between two daughter cells, each with a genetically identical nucleus. The cells enter interphase and begin the cell cycle again.
REMEMBER!
Cells divide during mitosis and cytokinesis!
Chromosomes condense at the start of mitosis!
Mitosis and cytokinesis produce two genetically identical daughter cells!
What is DNA?
DNA is a double-stranded molecule made of four different subunits called nucleotides. A nucleotide is made of three parts: a sugar, a phosphate group, and a nitrogen-containing molecule called a base. When the sugars and phosphate groups bond, they form the backbones of the long chains called nucleic acid.
If the DNA would be stretched out straight and laid end to end, it would be about 3 metres (10 feet) long in just one of your cells.
How does the DNA fit inside the nucleus of a microscopic cell?
DNA wraps around proteins that help organize and condense it.
Interphase: DNA is loosely organized.
Mitosis: Chromosomes are tightly condensed.
What is crucial during interphase and mitosis?
During all of interphase, proteins must access specific genes for a cell to make specific proteins or to copy the entire DNA sequence. During mitosis, the duplicated chromosomes must condense to be divided between two nuclei.
What would probably happen if chromosomes remain stringy during mitosis?
Perhaps a cell would get two copies of one chromosome and no copies of a different one.
What are histones?
Histones are a group of proteins. At almost all time during the cell cycle, our chromosomes are associated with histones. DNA wraps around histones at regular intervals, parts of the histones interact with each other further compacting the DNA. >Interphase (chromatin).
