Biology - Mitosis/Meiosis/Cancer Flashcards
Defining Mitosis Meiosis and Cancer
Is a big cell always better?
- If a cells size is doubled then it would require 8x more nutrients and have 8x more waste to excrete
- Surface area increases by 4x
- Plasma membrane would not have enough surface area to allow oxygen, nutrients, and wastes to diffuse
- Cells would either die from their own waste or starve to death
Cell size:
- Limited in size
- Female egg is the largest cell in the human body (can be seen without a microscope)
Structure of eukaryote chromosomes
During most of cells life cycle, the chromosomes exist as CHROMATIN (strands of DNA wrapped around protein)
Chromosomes
When cell enters mitosis, chromatin coils up into the form of chromosomes
Chromosomes structure
- Consists of DNA wrapped
around proteins (Histones) - DNA & histone molecules form bead like structures called NUCLEOSOMES
- Nucleosomes fold DNA and become tightly packed to form chromosomes during mitosis
Two Copies
- Due to DNA replication in the S phase, each chromosomes has an identical copy
The Cell Cycle
- Cells go through to two general periods
- Interphase is the growth period (growing)
- Mitosis is the period of division (÷ of nucleus)
- Most of the cells life is spent carrying out the activities of interphase.
What is cytokinesis ?
When the chromosome membrane splits
What are the roles of cell division ÷
- Un unicellular organisms
+ Method of Reproduction - Multi cellular organisms
+ Growth
+ Maintenance
+ Replacement
What are spindles and what stage of the cell cycle are they found?
- Found in the Metaphase stage
- Football shaped structure consisting of thin fibers made of micro-tubes
- Separates sister chromatids
What is a chromatid
- Esch sister chromatic is attached to its own spindle fiber
- Ensures that each new cell will get an identical and complete set of chromosomes
What is Cytokinesis and what cells is it found in?
- Found in animal cells
- Toward the end of telophase the plasma membrane pinches in along the equator to creat two separate cell identical to the original
What happens to plant cells?
- PLasma membrane doesn’t pinch in. Instead, a cell plate is formed and is place across the cells equator. (Picture a line down the center of the cell)
What is contacts inhibition?>
- Cell to cell communication
- Cells communicate w/ each other by producing band secreting chemical signals
- When changes occur in the genetic control of these chemicals - cancer can result.
What is the structure and function of DNA?
- DNA is made up of nucleotides
- Each. Nucleotide contains:
+ Deoxyribose (sugar)
+ a phosphate group
+ a nitrogen base
What are the 4 bases of nucleotides?
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
(A & T go together and C & G go together)
What 2 bases are purines?
Adenine and guanine
What 2 bases are pyrimidines?
Cytosine and thymine
What are Chargaff’s rules?
- the % of guanine and cytosine in a cell are =
- the % of adenine and thymine are =
- The amount of purines = the amount of pyrimidines
Structure of DNA
- 2 chains of nucleotides in DNA are joined by hydrogen bonds between bases
- Covalent bonds join the sugar and phosphate sides together
How does Mitosis reproduce?
- Asexual (Clones)
- single parent (only 1 cell needed)
- Passes all genes from 1 parent
- Offspring is genetically identical
How does Meiosis reproduce?
- Sexual (Variation)
- 2 parents
- Each parents passes down half of their genes
- Offspring have unique genetic combination
How many rounds or meiosis are there?
2 rounds of cell ÷:
What happens in Meiosis 1?
- Prophase 1
- Métaphase 1
- Anaphase 1
- Telophase 1 & cytokinesis
What happens in Meiosis 2?
- Prophase 2
- Metaphase 2
- Anaphase 2
- Telophase 2 and cytokinesis
What happens in Prophase 1?
- Crossing over occurs (introduces genetic diversity)
- Forms a tetrad
- Homologous chromosomes pair up & form tetrads
- Can exchange portions of their chromatids
- Results to produce new genetic combinations
What is the result of Meiosis 2?
- Produces 4 genetically different cells
Males: 4 sperm cells
Females: 1 egg & 3 polar bodies (Polar bodies don’t participate in reproduction)
What is genetic recombination?
- Peas have 7 pairs of chromosomes
+ pease can form up to 128 different kinds of sperm - Humans have 23 pairs of chromosomes
- They can form up to 8 million different kinds of sperm or eggs.
What is Interphase?
- Nucleus is still visible
- DNA is in loose strand of chromatin
- G1: Cell grows
- S: DNA replication
- G2: Preparation for Mitosis
What happens in Prophase?
- Chromatin coils into chromosomes and becomes visible
- Centrioles separate and move to poles
- Nucleolus disappears
- Nuclear envelope breaks down
What happens in Metaphase?
Chromosomes line up along the middle (equator) of the cell
What happens in Anaphase?
- Centromeres separate
- Sister chromatids separate into chromosomes
- Chromosomes move to opposite poles
What happens in Telophase?
- Chromosomes reach poles and begin to uncoil
- Nuclear envelope re-forms
- Spindle breaks apart
- Nucleus becomes visible
What happens in Cytokinesis?
- Division of the cytoplasm
- Plants develop a cell plate
