GENETICS VOCABULARY

 

GENE – A location on a chromosome that codes for a general trait (protein).  Example:  Plant Height Gene

 

ALLELES – Different forms of the same gene.  Examples:  A and a.

 

PHENOTYPE – The physical appearance of an organism due to its genetics.  Examples: Tall and Dwarf.  PHENOTYPIC RATIO: 3:1 Tall:Dwarf

 

GENOTYPE – The genetic combination of alleles in an individual.  GENOTYPIC RATIO: 1:2:1  AA: Aa: aa.  3 Basic Genotypes:

1. HOMOZYGOUS DOMINANT – both alleles are dominant – AA

2. HOMOZYGOUS RECESSIVE – both alleles are recessive – aa

3. HETEROZYGOUS – the alleles are different from one another - Aa

Thursday 11/21/13 Gregor Mendel and Monohybrid Crosses

Gregor Mendel- (1850's) Often called "Father of Genetics" Austrian monk, Worked with pea plants. (Plant pass down genes in the same way that animals, so this worked out.) Identified seven traits within pea plants to work with.

• Flower color, position, plant height, pod color, pod shape, pea color and seed shape

I. The Monohybrid Cross- cross between parents that have different characteristics for 1 trait.

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Parental (P)              True-breeding Tall(M)    x    True-breeding dwarf(F)  (Truebred is like purebred)

1st Filial (F1)                                             All Tall

2nd Filial (F2)                                        Tall : Dwarf
(Inbreeding of F1's)                                    3 : 1 ratio
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Key:                               P       Male plant (TT)      x       Female plant (tt)    

T = Tall plant                             Sperm ~~(T)                         Egg (t)
t = Dwarf plant
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                                     F1      Male offspring (Tt)    x    Female offspring (Tt)
- - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - -
                                     F2                  Punnet Square

Genetics

I. Probability

Product Rule- The probability of 2 or more independent events occurring together is the product of those events.

Take the odds of each event and multiply them together, this will give you your probability

Sum Rule- When there are more than one combination of ways to get an event, the probability is the sum of those combinations.

Meiosis - 2 divisions that result in 4 haploid cells (sperm/egg cells).

I.   The 9 phases of Meiosis.
        
      A. Interphase - DNA is duplicated
         
      B. Prophase I - Chromosomes appear; the nuclear envelope breaks down.
          The chromosomes form tetrads;  two homologous chromosomes
          connected.
                       - In the tetrad, Crossing-Over takes place.  Random bits of
                         information are exchanged between the two homologous         
                         chromosomes. This accounts for the genetic-variability in
                         Gametes.

      C. Metaphase I - Tetrads line up at equator.

      D. Anaphase I - Homologues split apart from 1 another and move toward 
         the poles.

      E. Telophase I - Cytokinesis.  Cell divides into 2 intermediate cells.  This is
           a know as Reduction Division.
                          -Reduction Division has its name because the chromatids 
                           remain together. This means that the amount of genetic
                           information in each of the new cells is significantly reduced.

                    
      F. Prophase II - DNA doesn't replicate again, and no tetrads form
          therefore no cross-over occurs.



      G. Metaphase II - Chromatid Pairs line up at the equators.

      H. Anaphase II - Chromatids split apart and move toward the poles.

       I. Telophase II - Cytokinesis divides the 2 cells into 4 unique haploid 
         cells.

5. Cancer- There are 2 types  of Genes that, if mutated, can potentially lead to cancer:
     A. Proto-Oncogene- encode for proteins that, when ready, stimulate cell division. If mutated, they are Oncogenes- automatically signal cell division.
     B. Tumor Suppressor Gene- encode proteins that inhibit cell division. Cell will continue onto the Cell Cycle w/o inhibition if these genes are mutated

P53- is a tumor suppressor gene that 1) either repairs the DNA to allow the Cell Cycle to continue, or 2) triggers PCD if DNA is irrepairable.

Meiosis- Cell Division that results in the formation of 4 genetically unique haploid cells (sperm and egg).

1. 2 Divisions and 9 Phases 
    A. Interphase- Includes the G1, S, and G2 Phases and their checkpoints. Same as Mitosis.
DNA Replication: S-phase









Homologues- have the same genes, but not necessarily the same alleles.
Chromatids- 2 exact copies of DNA.

IV. Controlling the Cell Cycle- 3 "checkpoints"
    A. G1 Checkpoint- at end. Is it ready to replicate the DNA?
    B. G2 Checkpoint- at end. Had the DNA replicated correctly?
    DNA polynerases (enzymes) assess and repair "damage" to DNA.
    C. M Checkpoint- Had the DNA separated correctly? If yes, Cytokinesis finishes the process; if no, the cell/s will undergo a programed cell death.
V. Cancer and the Cell Cycle- an uncontrolled growth of cells is a cancerous tumor. 2 types:
    A. Benign- Encapsulated- contained within a membrane. Most can be surgically removed.
    B. Malignant- Non-encapsulated- invasive- can spread into ANY part of the body- Metastis- when the malignancy spreads to another tissue or organ.
    C. Mutations in 2 types of genes are dangerous in term of Cancer.
        1. Proto-oncogene- Code for proteins that simulate cell division. Activated, or not, at the G1 Checkpoint. If mutated they might become Oncogenes- Automatically be activated no matter what. (Bad)
        2. Tumor-suppressor Genes- Inhibit cell division
          P53- Monitors the integrity of DNA. If the protein is damaged, the protein stops cell division and stimulated repair. Will simulate PCD (programed cell death) if the damage is beyond repair. (Good if it isn't mutated)

11/6 Cell Division cont.

(Chapters 9-10)

II. Mitosis- Cyclic (never stops). The Cell Cycle:
    A. G1 Phase- ("1st growth") Cell elongates and becomes "normal" size.
    B. S Phase- ("Synthesis" of DNA) DNA is replicated in this phase.
    C. G2 Phase- ("2nd growth") Organelles are "doubled."
    (Collectively these three phases are called Interphase)
    D. M Phase- ("Mitosis") When the cell undergoes division.
    E. C Phase- ("Cytokinesis") When the cell/s re-form membranes and other cytoskeletal structures. This starts in the M Phase. Cell divides completely here.

III. M-Phase
    A. Interphase (G1, S, G2)- DNA replicates here but this process is invisible, because the DNA is in the form of Chromatin- DNA is "uncondensed" and not wrapped around histames. The DNA is going from 46 pieces to 92 pieces of DNA.
    B. Prophase- DNA condenses around its histomes and forms Chromosomes (visible). In chromosomes, two identical pieces of DNA called Chromatids, are joined by a small bead called a Centromere. The Nuclear membrane breaks down and the Chromatid pieces spread randomly through the cell. 2 Centrioles break from the Centrosome and move to the poles of the cell.
    C. Metaphase- Chromatid pairs line up at the equator of the cell, and spindle fibers (made from microfiliments) develop from the centrioles and attach to them.
    D. Anaphase- Chromatin pairs separate and are pulled apart by the spindle and begin moving towards the poles.
    E. Telophase- Chromosomes reach the poles and Cytokinesis begins (the actual division of the cell)