Unit 3 Flashcards
Blastema cells
Divide up to 50x faster than human cells.
All cells on earth
Come from other cells
Purpose of cell division
Expanding populations, and replacing cells lost to wear and tear
Cells in multicellular organisms
No meant to divide immediately
Binary fission
Prokaryotic cells reproducing. Double in size, replicate chromosomes, and split. Includes a B, C, D period
B period
DNA synthesis and cell enlargement
C period
Chromosomes seperated on opposite sides of the cell
D period
Membrane pinches and 2 daughter cells are made
Bacteria and archaea use
A single circular packet of DNA
In an abundance of nutients
Bacteria and archaea do not have a B period
Segregation
Proposed by François Jacob. 2 chromosomes attach to the plasma membrane and are pulled apart, passive replication
Origin of replication (Ori)
Where chromosomes replicate. In the center and then moves to the poles
Cytoplasmic division
Inward constriction of cytoskeletal proteins. The cell wall and plasma membrane forms and divides. Only works with one chromosome
Eukaryotic missing a chromosome
Bad, often lethal
Chromatid
Eukaryotes adaptation to hold 2 double stranded DNA
Binary fission and evolution
Variation proving intermediates in the evolutionary pathway. Some nuclear membranes dissociate while others don’t
Mitosis
Daughter cells are identical to the parent (clones)
Mitosis occurs because of 3 things
- Master programing allows for orderly and timely progression
- DNA is copied almost perfectly
- Cables and motors of the cytoskeleton divide chromosome
Meiosis
Different than the parent. 1/2 the chromosomes of a normal cell, makes gametes and spores
Chromosome
Nuclear units of genetic info divided by mitotic cell division. Made up of DNA and proteins
Diploid 2n
Most eukaryotes. Have 2 of each chromosome (46)
Haploid, n
23, one copy of each chromosome
Ploidy
Multiples of n bigger than 2
Sister chromatid
2 copies of a chromosome held together by sister chromatid cohesion until segregation
Chromosome segregation
Equal separation of sister chromatids
Interphase
Longest phase and is comprised of G1, G2, G3 phases
G1 phase
Cell function, some growth, some cells go to G0. Varies in length. Chromosomes are organized and lightly packed
G2 phase
DNA replication and chromosome duplication. 10-12 hr
G3 phase
More cell growth, 4-6 hours
Mitosis length
Less than an hour
G0 phase
Cells can reenter G1 to start dividing or just live the rest of their lives.
Internal mechanisms
Regulate mitotic processes. Effected by hormones and growth factors
Stages of mitosis
Prophase, prometaphase, metaphase, anaphase, telophase
Prophase
Chromosomes become chromatin, nucleolis becomes smaller and eventually disapears, mitotic spindles form between the centrosomes, microtubules radiate from the spindle poles
Chromatin
Compact rod shaped DNA. Appears like thin threads under a microscope
Prometaphase
Starts when the nuclear envelope breaks down. Some spindle fibers attach to the chromosomes
Centromere
Kinetochore that holds chromatids together
Kinetochore
A complex of proteins
Kinetochore microtubules
Attach to kinetochore and therefore determine the outcome of mitosis
Metaphase
Spindle fibers move the chromosomes to the spindle midpoint (metaphase plate) and condensation is completed.
What is formed in metaphase
A karyotype
Karyotype
An arrangement of chromosomes according to size and shape
Anaphase
Chromatids move to opposite polls. Movement starts at the centromeres. Daughter chromosomes are now on either side of the cell
Telophase
Spindle fibers disappear and chromosomes decondense. Nuclear envelope and nucleolus reform. 1 cell with 2 separate nucleus’ exists
Cytokinesis
The division of the cytoplasm starting in telophase resulting in 2 daughter cells. The nucleus is in G1 of interphase
Cytokinesis in animals, fungi, and protists
The furrow gridles the cell and eventually cuts it
Cytokinesis in plants
A cell plate grows through the cytoplasm dividing it and making a new cell
Furrowing
Spindle fibers stretch out from the spindle midpoint across the cell, microfilaments form a belt inside the plasma membrane that condenses using motor proteins until the cell pinches into 2 cells
Cell plate formation
Microtubules act as a guide for vesicles from the ER and Golgi complex. The vesicles fuse and span the spindle midpoint. When they are all the way across the cell, the 2 cells separate
Mitotic spindle
Made of microtubules and their proteins
Mitotic spindles in mitosis
Microtubules disassemble from cytoskeleton and reorganize to become spindle , filling almost the whole cell
2 pathways for mitotic spindles
Centromere or no no centromere. The results are almost identical
Microtubule organizing center
The centrosome. Anchors the cytoskeleton and positions the organelles during interphase
Centrioles
1 pair/centrosome. They exist 90 to each other. The generate microtubules for flagella and cilia
Centrioles do not
Construct mitotic spindles
Centrioles in mitosis
Duplicate in the s phase. During M phase centrosome with centriole centers separate and microtubules lengthen and increase in number
Late prophase
Centrosomes are fully separate. Spindles continue to grow and fill the cytoplasm
Asters
Centrosomes at the spindles tip. Makes sure each daughter cell gets a centriole
When there is no centrosome
Microtubules form spindles from many directions with many MTCs.
Spindles form from
100-1000’s of microtubules
2 types of microtubules
Kinetochore and nonkinetochore. They work separate but coordinated during anaphase
Kinetochore microtubules
Connenct chromosomes to spindle poles
Non kinetochore microtubules
Extend between spindle poles without connecting to a chromosome.
Current chromosome division theory
Chromosomes walk to the poles on stationary microtubules. Use kinetochore motor proteins. The kinetochore microtubules disassemble as they go
Experiment proving 1/2 of division
Bleached kinetochore microtubules section did not move during anaphase
Other part of the chromosome division theory
Motor proteins pull kinetochore microtubules poleward, disassembling them into tubulin sub units
Nonkinetochore microtubules
Spindles are lengthened and push each other generated by microtubules sliding over each other because of proteins. The cell become a long oval
