Topic 8 Flashcards
Binary fission
Bacteria have a single, circular DNA molecule, and replicate via binary fission
The chromosome is replicated, and the two products are partitioned to each end of the cell prior to the actual division of cell
Bacteria cell division replication and division as a concerted process, while in Eukaryotic cell division DNA replication occurs early in division, and chromosomes separate occur much later
Mitosis
is the phase of the cell cycle in which the spindle apparatus assembles, binding to the chromosomes, and moves the sister chromatids apart, and is essential for separation of the two daughter genomes. It is subdivide into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.
Meiosis
is a special form of division, that occurs in the formation of gametes, that results in the production of cells with half the normal number of chromosomes
Stages of Meiosis
Meiosis I: This stage is divided into five sub-stages:
Prophase I: The chromatin condenses into discrete chromosomes, and homologous chromosomes pair up and exchange genetic information through a process called crossing-over
Metaphase I: The homologous chromosome pairs align at the metaphase plate, and the spindle fibers attach to the kinetochores of each chromosome
Anaphase I: The homologous chromosomes separate and move towards opposite poles of the cell
Telophase I: The chromosomes reach the opposite poles of the cell, and the cell undergoes cytokinesis, resulting in two haploid daughter cells
Interkinesis: This is an optional stage that occurs between meiosis I and meiosis II. During this stage, the cell undergoes a period of rest, and the chromosomes may partially decondense
Meiosis II: This stage is divided into four sub-stages:
Prophase II: The chromosomes condense again, and the spindle fibers begin to form
Metaphase II: The chromosomes align at the metaphase plate, and the spindle fibers attach to the kinetochores of each chromosome
Anaphase II: The sister chromatids separate and move towards opposite poles of the cell
Telophase II: The chromosomes reach the opposite poles of the cell, and the cell undergoes cytokinesis, resulting in four haploid daughter cells
Cell Cycle
is divided into five phases, based on the key events of genome duplication and segregation
Prophase
It is a part of M phase
Chromatin condenses, forming visible chromosomes
Duplicate chromosomes (sister chromatids) are held together by a centromere
Centrosomes – start making microtubules, mitotic spindle, asters
Golgi and ER are dispersed, and Nuclear envelop breaks down.
Prometaphase
Is typically said to be a part of prophase
Chromosomes attach to microtubules at the kinetochores
Each chromosome is oriented such that the kinetochores of sister chromatids are attached to microtubules from opposite poles
Chromosomes move to equator of the cell
Metaphase
Is part of M phase
Centromeres of chromosomes are precisely aligned at cell’s equator
The imaginary plane midway between poles is called metaphase plate
Chromosomes are attached to opposite poles and are under tension.
Anaphase
is part of M phase
Shortest of all phases
Centromeres of chromosomes splits simultaneously each sister chromatid now becomes a separate chromosome
Chromosomes are pulled toward their respective poles by motor proteins of kinetochores
One Chromosome of each original pair goes to opposite poles
Telophase
Is part of M phase
Begins when chromosome movement stops.
Each set of chromosomes (at opposite ends of cell) uncoils to form chromatin
New nuclear membranes form around each chromatin mass
Nucleoli reappear
Spindle disappears
G1 phase (gap phase 1)
Part of Interphase
is the primary growth phase of the cell, the term gap phase refers to its filling the gap between cytokinesis and DNA synthesis. For most cells this is the longest phase.
G2 phase (gap phase 2)
Is part of interphase
is the second growth phase, and preparation for separation of the newly replicated genome. This phase fills the gap between DNA synthesis and the beginning of mitosis. During this phase microtubules begin to reorganize to form a spindle.
S phase
Is part of interphase
is the phase in which the cell synthesizes a replica of the genome
Before a cell can divide the genome must be replicated first in S phase.
M Phase
Mitosis – is the phase of the cell cycle in which the spindle apparatus assembles, binding to the chromosomes, and moves the sister chromatids apart, and is essential for separation of the two daughter genomes. It is subdivide into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.
Interphase
is the portion of the cell cycle between cell division (G1, S, and G2)
Cytokinesis
is the phase of the cell cycle when the cytoplasm divides, creating two daughter cells. In plant cells, a plate forms between dividing cells forming a cell wall
Begins during late anaphase and continues through mitosis
Ring of actin microfilaments contracts to form cleavage furrow
Two daughter cells are pinched apart
G0 phase
no further division occurs
is a “resting phase” in which the cell is paused in G1 phase, and remain in this phase for days to years before resuming cell division.
Understand the difference between binary fission and Mitosis
binary fission and mitosis are two different processes of cell division that occur in different types of cells. Binary fission is a type of asexual reproduction that occurs in prokaryotes, while mitosis is a process of cell division that occurs in eukaryotes
binary fission does not involve spindle fibers, and the DNA is not packaged into chromosomes
Mitosis results in what type of daughter cells?
2 genetically identical diploid daughter cells
Meiosis results in what type of daughter cells?
4 unique haploid daughter cells
Define: Karyotype, Diploid, Haploid, Chromosome, and Chromatin, and list the number of Chromosomes found in different organisms.
Karyotype – is the array of chromosomes/normal set an individual organism possess.
Diploid (2n) – is the total number of chromosomes in a cell (2 sets of chromosomes)
Haploid (n) – is one complete set of chromosomes necessary chromosomes for that organism
Chromosome - made up of DNA and proteins and carry our genetic information in the nucleus.
Chromatin - a complex of DNA that condenses to form chromosomes
there is a chart on slide 7 showing the # of chromosomes in different organisms
chromatid
One half of a replicated chromosome
Chromosomes are copied in preparation for cell division, and the two identical copies are called sister chromatids
somatic cells
diploid cells that are not sperm or egg cells, meaning they have two sets of chromosomes and can be affected by DNA mutations but not passed on to offspring
gametes
haploid sex cells, specifically sperm and egg
The subsequent fusion of two of these cells ensures a consistent chromosome number from one generation to the next
cleavage furrow
A cleavage furrow is an indentation of the cell’s surface that begins the process of cell division.
It occurs when the cell is preparing to split into two daughter cells by pinching its cell membrane and cytoplasm down the middle.
crossing over
Genetic recombination also called crossing over, and random orientation of chromosomes on the metaphase plate, increase genetic diversity in the gametes, thus resulting in increase rate of genetic diversity.
homologous chromosomes
Homologous chromosomes are pairs of chromosomes that come from each parent. Containthe alleles of the same genetype in the same locations . Homologous chromosomes carry the same genes, one from each parental source, and are responsible for genetic variation in offspring. Each homologous pair consists of one paternal and one maternal chromosome
Cyclin-dependent kinases
class of enzymes that are responsible for the phosphorylation of other key enzymes in the cell cycle, and Cdks will become activated when forming a complex with Cyclin – called MPF (Mitosis-promoting factor)
are proteins that are activated or deactivated by cyclins producing Cyclin-Cdk complex, that initiates enzymatic cascades needed for cell division.
are destroyed after mitotic cell division, and process begins again, by MPF activity during M phase
Maturation-promoting factor (MPF)
Maturation-promoting factor (MPF) is a complex cellular protein that stimulates cell division in eukaryotic cells. It is also called mitosis-promoting factor or M-Phase-promoting factor 1. MPF is a protein complex that includes the protein cyclin, which accumulates during interphase and triggers mitosis or meiosis
cdk and cyclin complex
Cancer
the malignant growth due to uncontrolled cell division
Missense mutations that multiply over time, leading to cell cycle disruption and the formation of tumors.
Daughter cells with too many or too few chromosomes, a feature known as aneuploidy.
Errors at any point in the process of mitosis can introduce errors into cells’ genetic programming that lead to cancer or other diseases.
proto-oncogenes
A proto-oncogene is a healthy gene found in the cell that is responsible for making a protein involved in cell growth, division, and other processes. Most of the time, these genes do their jobs without problems. However, if an error (mutation) occurs in a proto-oncogene, the gene can become turned on when it isn’t supposed to be. If this happens, the proto-oncogene can turn into a malfunctioning gene called an oncogene. Cells will start to grow out of control, which leads to cancer
tumor suppressor genes
Tumor suppressor genes are normal genes that slow down cell division or tell cells to die at the right time. They are among the most common genes protecting the body from cancer. When tumor suppressor genes don’t work properly, cells can grow out of control, which can lead to cancer
