Chapter 7: Cell cycle, Mitosis and Meiosis Flashcards
Cell Division
A process by which a parent cell duplicates its genetic material and then divides into two similar cells
What are the two basic strategies for organisms to reproduce themselves?
Asexual reproduction and sexual reproduction
Asexual reproduction
Is a rapid and effective mean of making new individuals. The offsprings are clones of the parent organism and are genetically identical to each other and the parent
Binary Fission
It is a method, in which a cell simply copies its DNA and then splits in two, giving a copy of its DNA to each “daughter cell,” is used by bacteria and archaebacteria.
Mitosis
one nucleus produces two daughter nuclei, each containing the same number of chromosomes as the parent nucleus and the products are identical to each other
Why is mitosis necessary?
It is necessary because it replaces dead cells, damaged cells, or cells that have short life spans.
Sexual Reproduction
two haploid gametes—usually one from each parent—unite in fertilization to form a genetically unique diploid zygote that has a considerable genetic variation
Gamete
A mature sexual reproductive cell: an egg or a sperm
Meiosis
A process of cell division resulting in daughter cells with only half the genetic material of the original cell. It goes through a two-step division process
Daughter Cell
are produced after a single cell undergoes cell division
Somatic cells
Are cells that are not specialized for reproduction. They contain two sets of chromosomes
Zygote
Formed when two haploid gametes fuse
Reproductive Signals
Are signals that initiate cell division and may originate from inside or outside the cell
DNA Segregation
It is a process where a cell must distribute the replicated DNA tp each of the two new cells
Cytokinesis
Is the process where the cytoplasm must divide to form the two new cells, each surrounded by a cell membrane and a cell wall in organisms that have one
What are the steps of cell division for Prokaryotes by binary fission?
Reproductive Signals
DNA Replication
DNA Segregation
Cytokinesis
DNA Replication in Prokaryotic Cells?
Almost all prokaryotic genetic information is carried on one single chromosome
Single-celled Eukaryotes can also reproduce by binary fission, but what is a better method to reproduce itself?
A better way for single-celled eukaryotes to reproduce is by mitosis because they have multiple chromosomes that require a more elaborate way to properly separate between daughter cells
In eukaryotic cells, what are the two main phases of cell cycle?
- Interphase and mitotic phase (M)
What happens during the interphase of a cell cycle?
The cell grows and makes a copy of its own DNA and it has three phases.
What happens during the mitotic phase (M)
The cell separates its DNA into two sets and divides its cytoplasm, forming two new cells
What are the three phases of the interphase of a cell cycle?
- G1 phase (G = gap 1)
- S phase (S = synthesis)
- G2 phase (G = gap 2)
What happens in the G1 phase of the interphase of a cell cycle?
During G1 phase, also called the first gap phase, the cell grows physically larger, copies organelles, and makes the molecular building blocks it will need in later steps
What happens in the S phase of the interphase of a cell cycle?
In S phase, the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome. The centrosomes help separate DNA during M phase
What happens in the G2 phase of the interphase of a cell cycle?
During the second gap phase or G2 phase, the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis. G2 phase ends when mitosis begins
cyclin-dependent kinases (CDKs)
It controls the cell cycle
cell cycle checkpoints
Are several different CDKs functions at specific stages of the cell cycle (signaling pathways regulate the progress of the cell cycle)
Where are the four checkpoints in cell division?
There are three in the interphase and one in the mitosis phase
What are the three checkpoints in the interphase of cell division?
- The Restriction Point (R)checkpoint (G1/S transition)
- The S/G2 transition checkpoint
- The G2/M transition checkpoint
What does the Restriction Point (R)checkpoint (G1/S transition) do?
It checks for many things including cell size, nutrients, growth factors, DNA damage
What does the S/G2 transition checkpoint do?
It checks for DNA damage, incomplete replication.
What does The G2/M transition checkpoint do?
It checks for DNA damage, replication, and completeness
What is the checkpoint in the mitosis phase and what does it do?
The Spindle checkpoint checks for chromosome attachment to spindles at metaphase plate
What is cancer?
Cancer is an uncontrolled cell division
Centrosome
“central body”, an organelle in the cytoplasm near the nucleus. It consists of a pair of centrioles and is also known as the Microtubule Organizing Center (MTOC)
Centrioles
hollow tubes formed by 9 triplets of microtubules
What are the five phases of the continuous mitosis process?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What happens in prophase of Mitosis?
- Chromosomes start to condense
- mitotic spindle begins to form
- The nucleolus (or nucleoli, plural) membrane disappears
What happens in Prometaphase (late Prophase)
- The chromosomes finish condensing
- The nuclear envelope breaks down, releasing the chromosomes
- The mitotic spindles grows more, and some of the microtubules start to “capture” chromosomes.
What happens in Metaphase of Mitosis?
- All the chromosomes align at the metaphase plate
2. the microtubules connect to chromosome
What happens in Anaphase of Mitosis?
- The protein “glue” that holds the sister chromatids together is pulled apart. The chromosomes of each pair are pulled towards opposite ends of the cell.
What happens in telophase of Mitosis?
- The mitotic spindle is broken down into its building blocks
- Two new nuclei form, one for each set of chromosomes. Nuclear membranes and nucleoli reappear
- The chromosomes begin to decondense and return to their “stringy” form.
What happens in cytokinesis of Mitosis?
the division of the cytoplasm to form two new cells and is the final stage of mitosis
Ploidy level
Is DNA content
sister chromatids
Are the two halves of a duplicated chromosome
Homologous chromosomes
are chromosome pairs (one from each parent) that are similar in length, gene position, and centromere location
What happens in Prophase I of Meiosis?
- DNA is condensed
- homologous chromosomes pair together
- Crossing over occurs
- MTOC migrate to poles
- Nuclear membrane breaks down
What is crossing over in meiosis?
It’s when homologous chromosomes swap their genes
What happens in Metaphase I of Meiosis?
The homologous pairs line up at the metaphase plate
chiasmata
is a cross-shaped structures where homologues are linked together.
What happens in Anaphase I of Meiosis?
the homologues are pulled apart and move apart to opposite ends of the cell.
What happens in Telophase I of meiosis?
the chromosomes arrive at opposite poles of the cell
Meiosis II
The cells that enter meiosis II are the ones made in meiosis I. These cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids. In meiosis II, the sister chromatids separate, making haploid cells with non-duplicated chromosomes.
Random orientation of homologue pairs
The random orientation of homologue pairs in metaphase I allow for the production of gametes with many different assortments of homologous chromosomes
What is the product of meiosis for a cell?
The product is 2N = 6
Nondisjunction
Failure of chromosomes to separate correctly in mitosis or meiosis
Aneuploidy
When cells have the wrong number of chromosomes
