Unit 3 Part 3 Flashcards
D2.1
Mitosis overview
Produces two identical genetic cells (daughter)
- Used for growth and repair
- Most cells In body replicate using mitosis
Meiosis overview
Produces sex cells only (gametes)
- Produces 4 daughter cells
- each daughter cell has dif combination of hereditary info from parent cell
What is cell division?
The process of producing two cells from one
What does cell division do?
Makes sure genetic info is passed on to future cells including copies of all organelles necessary to make cell function
Parent/ mother cells
Produce a copy
What are daughter cells?
Two new cells that are generated from parent cells
How do prokaryotic cells divide?
Binary fission
Why do prokaryotes divide by binary fission?
B/c they have a single chromosome of DNA to replicate
What happens during binary fission?
- DNA is copied
- 2 Daughter chromosomes become attached to Dif regions on plasma membrane
- Cell divides into two genetically identical daughter cells
Cytokineses
A process that splits a cell’s cytoplasm and membranes in two ones it reaches a certain size
Cytokineses in animal cells
Inwards pinching of fluid plasma membrane to form cleavage furrows
Cytokineses in plant cells
Has a rigid cell wall and form a cell plate
Cleavage furrows?
A groove along the cell membrane
Cell plate?
Built up by vesicles that collect midway between the two poles of cell and lay down cell membrane and cell wall cells
Oogenesis?
Unequal sharing of parent cell resources in production of eggs
What do cell daughters have?
An equal number of chromosomes as the parent cell and same genome
Before cells divide what must take place?
DNA replication
DNA replication?
When a complete copy of the cell’s DNA has been made
- Happens during the S phase ( synthesize phase)
What are the two sister chromatids attached to?
The centrome
How does the process of condensation work?
Involves DNA being wrapped around histone proteins
How are coils stacked on top of each other?
It’s coiled up and then supercoiled and form a compact pair of chromatids
Chromatin?
When DNA is associated w/ histone proteins
What does a centrosome do?
Makes microtubule spindle fibres that are needed to guide chromosomes to the right place before cell division
Motor proteins?
Specialized molecules that push or pull objects around a cell
What do motor proteins use to produce what?
They use ATP to produce conformational change ( a change in shape) that moves microtubules
Microtubules and motor proteins during cell division
Astral microtubule: Reach out from centrome
Kinetochore microtubules: Attach to centrome of chromosome
Overlap microtubules: Pass beside chromosomes
Motor proteins: sandwiched between overlap microtubules
What is it called when a cell is not undergoing cell division?
Interphase
Phases of mitosis?
Prophase
Metaphase
Anaphase
Telaphase
Prophase?
- Chromatin fibres coil up tightly forming chromosomes
- Envelope disintegrates, nucleoli disapears
- Mitotic spindles form
- Kinetochores attach to spindles
- Centrosomes move towards opposite cell poles due to microtubule lengthening
Metaphase?
- Chromosomes move to metaphase plate
- Centromes of chromosomes align on the plate
- Centrosomes move to opposite poles
Anaphase?
Chromosomes move towards opposite poles of cell as a result of motor proteins
Why do centromeres move towards the poles first in anaphase?
B/c they are attached to microtubules
Telophase?
- Set of chromosomes at each pole
- Nuclear envelope begins to reform around each set
- Chromosomes start to elongate
- Nucleoli reappears
- Spindle apparatus disappears
What kind of division is meiosis?
Reduction
Prophase 1
- The nuclear envelope breaks down. The chromatin condenses into chromosomes.
- Homologous chromosomes pair up.
- “crossing over occurs” which creates genetic variation
Metaphase 1
- Homologous chromosomes line up across the cell’s metaphase plate, are randomly orientated.
- Nuclear membrane disintegrates
Anaphase 1
Spindle fibers attach to chromosomes and pull them to opposite poles of cell
Telophase 1
- Spindles and spindle fibers disintegrate
- chromosomes uncoil and new nuclear membranes form
Prophase 2
- DNA re-condenses into visible chromosomes
- New meiotic spindle fibers are produced
Metaphase 2
- Nuclear membrane disintegrates
- Individual chromosomes line up along metaphase plate
- Spindle fibers form opposite poles attach to each of sister chromatids at centromeres
Anaphase 2
- The chromatids split at the centromere
- Migrate along the spindle fibers to opposite poles
- Chromosomes can be pulled towards either of newly forming daughter cells
Telophase 2
- The cells pinch in the center and divide again
- Chromosomes unwind their strands of DNA
- Nuclear envelopes form around each of the four new nuclei
What does the extra chromosome arise from
A phenomenon called Non-disjunction
- Can happen at different times and on different chromosomes
Crossing over in meiosis
When sections of 2 homologous but non-sister chromatids break at same point, twist around each other, and then each connects to the other’s initial position
Meristems?
Areas of special tissue found in plant cells
Meristematic cells?
Undifferentiated cells that can divide rapidly allowing growth in plants
2 Types of meristematic tissue?
Apical and lateral
Apical meristematic tissue
Occurs in root tips and at tips of branches, enables a plant to lengthen
Lateral meristematic tissue
Occurs in stem cells and enables the stems to grow in width
Zone of cell division?
Area where new, undifferentiated cells are formed
Cyclins?
Group of proteins that control the cells pregression through the cell cycle
- They bind to cycling dependent protein kinases
Phosphorylation?
When a phosphate group is attached to a molecule and is a common way to activate enzymes
What does the mitotic cyclin do?
Tell the cell to start making the microtubules that will form the spindle fibers for mitosis
Ancogenes?
Sections of genes that can mutate or can be expressed at abnormally high levels
Proto-oncogene?
A gene that can turn into an oncogene
Apoptosis?
A programmed death that breaks down the material of dead cells and recycles them in the organism
Tumor suppressor genes?
Specialized genes in healthy cells that code for proteins that can regulate the cell cycle
