Exam IV Study Guide Flashcards
Know the definition of cell division and describe the two important requirements of this process
The Process by which one cell becomes two daughter cells
Requirements:
1. Each daughter cell must receive the full complement of genetic material from the parent cell
2. The parent cell must be large enough to divide in two and provide sufficient cytoplasmic components to the daughter cells
Know the process of Binary fission and the type of cell in which this process occurs
The Process whereby Prokaryotic Cells undergo division is called “Binary fission”
Compare cell division in eukaryotes vs prokaryotes
Eukaryotes:
- DNA in nucleus
- Genome Larger and Linear
Prokaryotes:
- genome small and circular
- DNA in Cytoplasm
Know and Describe the two distinct phases of the cell cycle; including which stage a cell spends the majority of it’s time in.
For Eukaryotic Cells, there are two distinct stages
- M-Phase: The Time where the parent cell splits into two, daughter cells
A. Mitosis: Division of DNA
B. Cytokinesis: Separation of cytoplasmic Organelles. - Interphase: The Time between “M-Phases”
* This is the longest phase — and the cell spends most of its time during it
A. Interphase lasts 10-14 hours.
• During Interphase, the Cell makes preparations for division:
◦ replication of DNA in the nucleus
◦ increase in cell size
Describe Interphase, including the four phases that comprise it.
Four Phases of Interphase
- G1 phase, first “Gap” Phase (Big Growth Phase for the Cell).y
• the size and protein content of the cell increases in preparation for the S phase
◦ regulatory proteins are made and activated - S phase
• the entire DNA content in the nucleus of the cell is replicated - G2 phase
• the cell prepares for mitosis and cytokinesis - G0 phase
• differs from G1 because there is no preparation taking place for cell division
◦ this phase is present in cell types that do not actively divide: liver and nerve cells
Describe how DNA is organized in Eukaryotic Cells
DNA is organized within histones and other proteins into chromosomes.
Cells in the human body contain 46 chromosomes (23 Pairs).
- Humans have 22 pairs of homologous chromosomes and 1 pair of sex chromosomes.
Compare Haploid and Diploid Cells
Haploid Cells: Only have 1 of a set of data. (Sperm / long egg)
Diploid Cells: Have 2 sets of complimentary data (zygote: Egg + Sperm, fertalized)
Know the Definition and function of: Centromeres, Chromatids, and Kinetochores
Centromeres: The middle area that binds sister chromatids together (Think of this as the binding site between the two — brining them together to form one).
Chromatids: If you were to take our X shaped chromosomes and split it town the middle into > / < , we would have two sister chromatids. So for every chromosome, we have two chromatids
Kinetochores: These are the binding sites on the actually Centromeres that the Microtubules filaments can bind to. Think of these as the “Anchor Sites” for the Microtubules. After binding to the Sister Chromatids, the Microtubules will be shortened — thus pulling the sister geomatics away from one another, separating them.
Know and Describe the 5 Stages of Mitosis:
- Prophase
• Microtubules are long chains of proteins that are emitted from Centrosomes.
◦ This stage is still Diploid, because we have two complete sets of genetic material
- Prometaphase
• Disintegration of the Nuclear Envelope.
• Then, the Microtubules (coming from Centrosomes), start to attach to the Chromosomes at their Kinetochores.
‣ Kinetochores are on the “Centromeres” of the Chromosomes
- Metaphase
• Chromosomes are going to line up in the Midline of the Cell
◦ Still Diploid
4. Anaphase • The Microtubules are going to Retract back towards the Centromere, shortening the Microtubules • This shortening is going to pull apart the Sister Chromatids, leaving both sides with 1 copy of their respective DNA.
• After being pulled apart, each Chromatid becomes a CHROMOSOME
In anaphase, the # of Chromosomes in a cell will double!
- Telophase
• In telophase, we are going to reform our Nuclear Envelope around our nearly formed Chromosomes.
• These chromosomes are going to de-condense, and become long and stringy.
Know and Describe the process of Cytokinesis
Also, compare them in Plant and Animal Cells
(In Animal Cells)
• Actin Filaments form a Contractile Ring, Perpendicular to the spindle axis; the ring contracts and pinches the cell into two
• As the Actin Filaments shorten and shorten, it will “pinch” off the cell — which will leave us with two, genetically identical daughter cells.
• Both Daughter Cells are Genetically Identical to the Parent Cell
(In Plant Cells)
* Formation of the cell plate which eventually becomes the cell wall. This cell plate separates the cytoplasm and distinguishes 2 unique cells
Know where meiosis is occurring and its basic properties
◦ Meiosis occurs in specialized germ cells that result in Sperm and Egg cells.
‣ Results in four daughter cells (genetically unique)
‣ Each daughter cell is a haploid (contains half of the chromosomes as the parent cell).
•Know and describe the processes of Meiotic Cell Division I and Meiotic Cell Division II, including all aspects of crossing over that occurs during Prophase I and the accounting of chromosomes at each stage
Meiosis 1: Results in 2 daughter cells, each with 23 paired chromosomes (46 Chromatids).
Meiosis 2: Results in 4 daughter cells, each with 23 unpaired chromosomes (because these cells are haploid, totaling 92 chromatids across all 4 daughter cells). Or 23 chromatids per cell.
•Compare cytokinesis in sperm and egg cells
• All 4 Daughter cells from Meiosis 2 are useful for Males
• 1 Egg will take the majority of the cytoplasm, resulting in 1 egg and 3 “polar bodies” as the daughter cells resulting from Cytokinesis.
◦ Only the Egg “Ooocyte” is helpful, the three polar bodies can’t be used
Describe how fertilization produces a diploid cell
Fertilization is quite literally the combination of two haploid cells. This results in a diploid Zygote, which gets 1/2 of its genetic material from both Papa Sperm and Momma Egg. (Diploid meaning that it now has 23 pairs of chromosomes).
Compare key similarities/differences between mitosis and meiosis
◦ Mitosis produces Diploid daughter cells (2), which are genetically identical to the parent
◦ Meiosis’s produced Haploid cells (4), which are genetically unique from the parent.
‣ MEIOSIS ALSO GOES THROUGH ITS STEPS TWICE!
Know and describe Cyclins and Cyclin Dependent Kinases and their role in regulating the cell cycle
Progression through the cell cycle is usually regulated by Cyclins. (Produced and degraded cyclically).
• Activate Cyclin Dependant Kinases (CDKs).
• Activation of CDKs promotes cell division
• CDKs are always present in the cell but are only active when bound to a Cyclin.
Know and compare the function of the G1/S Cyclin-CDK complex, S Cyclin-CDK complex, M Cyclin-CDK complex and know when each complex is acting during the cell cycle.
G1/S Cyclin-CDK Complex: Active at the end of G1, and it’s job is to prepare the cell for “S” Phase
S Cyclin-CDK Complex: Initiates DNA synthesis during the “S” Phase
◦ Also activates Protein complexes involved in DNA replication.
M Cyclin-CDK Complex: Active at the end of G2 and beginning of M,
◦ Initiates multiple events associated with mitosis.
Know and compare the DNA damage checkpoint, DNA replication checkpoint, and Spindle assembly checkpoint, including when they are occurring during the cell cycle
DNA Damage Checkpoint: Checks for Damaged DNA before entering the S phase
DNA Replication Checkpoint: Checks the presence of unreplicated DNA before the cell enters mitosis
Spindle Assembly Checkpoint: Checks for attachment of all chromosomes to the spindle before the cell progresses with mitosis.
Describe the role of p53 in the DNA damage checkpoint
P53 is responsible for bonding onto damaged DNA, which prevents it from being exported; giving the cell time to repair the damaged DNA and continue the cell cycle
Know the basic structure of DNA
• Sugar-Phosphate Backbone, Major Grooves and minor grooves for enzyme binding, Nitrogenous bases are held together through Hydrogen-Bonding.
