CH 10. How Cells Divide Flashcards
Cell Division in Prokaryotes
- Called binary fission
-DNA replicated-prokaryotes possess single, circular chromosomes
Cell Division in Eukaryotes
Two Types:
Mitosis- produces genetically identical diploid cells
Meiosis- produces genetically unique, haploid cells
Chromosome
A threadlike structure of nucleic acids and proteins found in the nucleus of most living cells, carrying genetic information in the form of genes.
Chromatin
The material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed. It consists of protein, RNA, and DNA.
Chromosome Replication
Chromosome replication and segregation are key events during the microbial cell cycle that must be completed before a cell divides. To reproduce successfully, every cell must replicate its chromosome(s) and distinguish nascent sister chromosomes from one another.
Ploidy
The number of sets of chromosomes in the cells of an organism
Diploid
Two sets of chromosomes (2n)
Haploid
One set of chromosomes (1n or n)
Somatic vs Gamete
Somatic (Body) Cells- Contains DNA but it is not the DNA that is passed to offspring
Gamete (Sex) Cells- Are usually haploid (e.g Sperm and Eggs), Have one sets of chromosomes
Gametes have one set of chromosomes
For humans: n=23
Chromosomes and Chromatid numbers at various points
Similarly, in humans (2n=46), there are 46 chromosomes present during metaphase, but 92 chromatids. A quick tip: notice that during the stages of meiosis and mitosis, the chromatid count never changes. Only the number of chromosomes changes (by doubling) during anaphase when sister chromatids are separated.
Purpose and products of Mitosis
-Cell division that creates somatic cells (body cells)
-One division to create two daughter cells
-Cells produced are diploid (2n)
-Cells produced are genetically identical
-New cells used for growth, wound repair, and cell replacement
-Some eukaryotes (mostly single-celled) reproduce asexually by mitosis
The Cell Cycle
Cell cycle is the name we give the process through which cells replicate and make two new cells. The cell cycle has different stages called G1, S, G2, and M.
Interphase
Period when a cell is not actively dividing
G1 Phase
Cell groups and serves its function
-Most time is spent in this phase
-Upon receiving a signal to divide, the cell prepares by making key proteins
S Phase
DNA synthesis (DNA Replication)
-Chromosomes replicated to produce sister chromatids connected at centromeres
G2 Phase
Cell finishes preparing for division and checks for proper DNA replication
G0 Phase
Some cells never divide
-For example: Neurons, cardiac, muscle cells
M Phase
Period of cell division
Centromere
The region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division.
Sister Chromatid
Sister chromatids are duplicated copies of a single chromosome that are attached to each other and are identical
Kinetochore
These are large protein assemblies that connect chromosomes to microtubules of the mitotic and meiotic spindles in order to distribute the replicated genome from a mother cell to its daughters.
Phase 1: Prophase
-Chromosomes condense into chromatids
-Start forming spindle apparatus
-Nuclear envelope breaks down
Phase 2: Prometaphase
-Microtubules of spindle apparatus bind them to kinetochores on each sister chromatid
