Cell Division (Chapter 16) Flashcards
What are the three main reasons for cell division?
- Growth/Differentiation:
Mitosis enables organisms to grow from a single-celled zygote into a mature organism that might contain hundreds of trillions of specialized cells - Maintenance:
New cells produced to replace worn out/dead cells - Repair:
They can regenerate damaged tissues (finger cut → new skin). Some organisms can regenerate entire body parts.
True or False…
There is no new combination of cellular material as a result of single cell reproduction
True; all new cells contain same DNA as original cell
Where does asexual reproduction occur?
Occurs in all somatic (body) cells, unicellular organisms, and simple multicellular organisms (budding, runners)
What are the five levels DNA is organized into?
- DNA Molecule
- Histones (DNA wraps around histones forming a bead-like structure)
- Chromatin Strands (the bead-like structure is packed tightly, producing chromatin strands)
- Chromatin Fibres: Stands from loops which are attached to a supporting protein scaffold
- Chromosomes: Protein scaffold folds further to condense the genetic material into chromosomes (duplicate during replication)
True or False…
Chromosomes may be found as individual chromatids (during late stages of cell division) or as paired/sister chromatids (connected at the centromere)
True
Fill in the Blank:
Sister chromatids are _________ to each other
Sister chromatids are IDENTICAL to each other
How many pairs of chromosomes do humans have?
23 pairs (46 total)
Define: Homologs
- Homologous chromosomes carry the same genes, in the same order
- Despite this, homologous chromosomes often have slightly different DNA sequences resulting in different alleles (different form of the same gene)
- Share several other characteristics including: length, centromere location, and banding pattern
What is the cell cycle?
Refers to the life cycle of a cell where it alternates between haploid and diploid form
What are the two MAIN parts of the cell cycle?
- Cell division (mitosis): division of genetic material & nucleus
- Interphase: cell growth and synthesis stages
What are the 3 stages of interphase?
- G1 (first cell growth stage): cell grows (organelle replication)
- S (synthesis phase): Cell DNA is replicated
- G2 (second cell growth stage): cell grows, rebuilds energy reserves, and prepares for mitosis
What are the five stages of cell division?
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
What are the five stages of cell division?
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
Define: mitosis
Cell division in somatic cells
True or False…
All of the cells produced by mitosis are identical in genetic makeup to the original cells
True
Define: alleles
A alternative form of the same gene caused by slight variations in DNA base sequences
The appearance and functionality of a cell is a result of…
a) difference in cellular content
b) difference in the way that content is expressed
Answer: B
The unique appearance and functionality found in different cells of the body is NOT due to difference in cellular content, but instead, a difference in the way that content is expressed (differentiation)
Define: differentiation
The process during which young, immature (unspecialized) cells take on individual characteristics and reach their mature (specialized) form and function
Explain the steps of prophase in cell division
- Nuclear envelope breaks down and the contents of the cell’s nucleus becomes visible
- DNA strands shorten and thicken, causing chromatin to condense into visible chromosomes
- Centrioles move to opposite poles of cell and begin growing spindle fibres
Explain the steps of metaphase in cell division
- Chromosomes move to center of cell
- Centromeres align across equator
- Spindle fibres attach to the centromeres
Explain the steps of anaphase in cell division
- Spindle fibres shorten and start pulling the sister chromatids apart
- Chromatids separate at centromeres
- Chromatids move to opposite poles of cell (same number of single-copy chromosomes should be at each pole)
Explain the steps of telophase in cell division
- Chromosomes at opposite ends of cell
- Chromosomes un-condense to form chromatin
- Nuclear envelope and nucleolus reappears
Explain the steps of cytokinesis in cell division
- Division of the cytoplasm
- In plant cells, a cell-plate forms first, separating two cells by forming cell wall
- In animal cells, cell membrane pinches in at the cleavage furrow to form two distinct daughter cells
Define: Stomaic Cells
- Somatic cells are found all throughout the body, except in cells that divide by meiosis to produce gametes (sperm and eggs)
- Somatic cells are diploid cells
- They have DNA from maternal and paternal sides combined
Define: Gamete Cells
- Gametes (sperm or eggs) are haploid cells
- They only hold half the DNA from somatic cells from which they came
- When an ovum is fertilized by a sperm, the original number of chromosomes (46 = 2n) is restored, forming a zygote
Define: Zygote
A diploid cell that results from the fusion of two haploids gametes
What is the purpose of meiosis?
Creates gamete cells by reducing the number of chromosomes from 46 to 23 by copying chromosomes once, but dividing twice
What is separated during Meiosis I?
Homologous chromosome
What is separated during Meiosis II?
Sister chromatids