Exam Review Notes

Genetics with Mendel

• Gregor Mendel: The father of genetics, discovered the basic mechanics of how genetics work.

• Character: A heritable feature (e.g., hair color).

• Trait: A variant of a character (e.g., curly hair, straight hair). A subclass of characters. A trait is the variant that one has.

• Example: Blood type is a character; type A, B, AB, or O are the traits.

• Mendel experimented with plant hybridization, specifically with peas.

• Peas have different characters like flower color (purple or white), flower position (axial or terminal), and seed shape.

• Phenotypic Ratio: The ratio of visible traits in offspring.

  • Example: Crossing a heterozygous (Aa) with a homozygous recessive (aa) parent.

  • Punnett Square:

    • Top row: A, a

    • Side column: a, a

    • Resulting genotypes: Aa, aa, Aa, aa

  • Phenotypic Ratio: One to one (1:1).

  • 50% heterozygous, 0% homozygous dominant, 50% homozygous recessive.

• Chance of having a boy: 50%

  • Mother can only pass on X chromosomes.

  • Father passes on 50% X and 50% Y chromosomes.

Laws of Inheritance

• Law of Segregation: Alleles separate during meiosis.

• Law of Independent Assortment: Allele pairs of different genes arrange themselves independently. This is related to metaphase I of meiosis.

  • During metaphase I, chromosomes line up differently in germ cells.

  • The way one pair of alleles (e.g., A/a) lines up has no impact on how another pair (e.g., P/p) lines up.

  • Crossover also independently arranges things.

• Analogy: Choosing between a dollar and a hundred-dollar bill in one hand, and a gold coin and a silver coin in another. The outcome of each choice is independent.

• Genes on the same chromosome can also assort independently due to crossover events, which shuffles the deck of cards.

Mendel's Discoveries

• Mendel's discoveries were huge for science and are foundational to genetics.

  • Example test question: "Who is considered the father of genetics?"

Calculating Probabilities

• Chance of a couple having three boys in a row:

  • Chance of one boy: 50% (0.5)

  • Independent events: multiply the probabilities.

  • 0.5 \times 0.5 \times 0.5 = 0.125 (12.5% or one in eight chance).

• Chance of independent events happening together: multiply their probabilities.

  • Example: 50% chance of Joe showing up and 50% chance of Sam showing up. Chance of both showing up is 25% (0.5 * 0.5).

Incomplete Dominance

• Two dominant traits are not fully expressed, resulting in a blended phenotype.

• Notation: Use capital letters with subscripts (e.g., C^R for red allele, C^W for white allele).

• Example: Red flower C^R C^R crossed with white flower C^W C^W yields pink flower C^R C^W.

• Incomplete dominance is not a mutation, but different alleles arise from past mutations.

• Mutations: Mistakes that change the DNA code.

  • Example: DNA sequence changes from AT to TA.

Codominance

• Both alleles are fully expressed.

• Example: AB blood type. A and B alleles are dominant, O allele is recessive.

  • Type A: I^A I^A or I^A i

  • Type B: I^B I^B or I^B i

  • Type AB: I^A I^B

  • Type O: ii

• In AB blood type, both A and B tags are fully expressed on the blood cells.

Molecular Level*: Corn kernel example
*Homozygous recessive (shriveled kernel): sweet corn that we eat, soft corn.
*Heterozygote: dominant trait, but on a molecular level the corn kernel shows codominance.
*A gene codes for a protein, the dominant A is a functional protein that turns sugar into starch. The recessive protein will still be fully expressed as a protein, even though its enzyme is broken.

• The scale determines whether we call it a dominant recessive trait or a codominant.

• Analogy: Having two kits for patching holes in a boat. Having two functional patch kits = patching holes, while there may be faulty patch kits, the boat will still float.

  • Light-colored eyes results from a mutation that does not work anymore.

• People with brown eyes = related in a sense, depends recently the common ancestor was/how close the relationship is.

Other Concepts

• X-linked traits: Genes located on the X chromosome.

  • Notation: Use X with superscript (e.g., X^A or X^a).

  • Females: X^A X^A, X^A X^a, X^a X^a

  • Males: X^A Y, X^a Y

• Definitions:

  • Monohybrid cross: Looking at one single gene of one individual and the gene of the same gene of another individual.

  • Dihybrid cross: Looking at two genes simultaneously.

  • To figure out what alleles are gonna end up in the gametes, each allele has an equal chance of being passed down.

  • Chance of getting a big P: 50%

    • There is a 50% change the end of the allele will get a little P.

    • "Since the P's and Y's are independent of each other, there is a 50% chance of getting the big Y and 50% chance of getting the little Y."

      • If I was to ask: What's the chance of the gamete having a big P and a little Y?

        • Chance of both things happening together = 50% x 50% = 25%.

*Given: Individual that has big A, heterozygous for B gene and homozygous dominant for C gene, what is the chance of you ending up with the gamete that looks like this: big A, little B?
To figure this out:
*What's the chance of getting the big A?* 50%
What's the chance of getting the little B? 50%
What's the chance of getting the big C? 100%
What's the change what getting all of those together? 50%. You multiply:
50% x 50% x 1% = 25%

Cell Structures

• Robert Hooke: Discovered cells and microorganisms, developed microscopes (father of microscopy).

• Electron microscope has the best resolution by far, can literally see atoms.

  • Two types of electron microscopes: TEM (transmission electron microscope), higher resolution picture.

Test Breakdown:

• First four to five questions focuses on finding the structure of a cell.
  *Possible answers:
  *A structure found in all cells
  *A structure found in prokaryotic cells and not eukaryotic cells
  *Found in eukaryotic cells and not prokaryotic
  *Found in a plant cell, not animals

Common Structures in All Cells

• Ribosomes: Involved in making proteins.

• Plasma membrane: Border of the cell.

• Cytosol/Cytoplasm: Cytosol is the fluid around the organelles.

  • Cytoplasm: All the stuff inside the cell, including the organelles.

• DNA: The common code used for all life.

• chromosomes

Prokaryotic vs. Eukaryotic Cells (Found in Eukarya Domain)

Prokaryotic Cell Characteristics

• Nucleoid: Prokaryotic structure, not found in eukaryotic cells.

• Capsule: Prokaryotic structure, not found in eukaryotic cells.

• Pili: Prokaryotic structure

• Small in overall-size compared to the eukaryotic cell/structure.

• Key distinguishing characteristic: Do not have organelles that have a membrane around them.

• Cell walls made of peptidoglycan (bacterial cell wall).

Eukaryotic cells

• Function: Pili assist in attachment to surfaces and in conjugation, which is the transfer of genetic material between bacterial cells.

• Cell walls made of cellulose: plant structure (cellulose cell wall = plant structure)

• Have membrane bound organelles.

Animal Structures

• Centrioles. Don't find them in plants, involved in cell division

• Microvilli: Increase the surface to absorb food.

*Eukaryotic cell = plant and animals, fungus, protist
*There are three domains of life = eukarya, bacteria, archaea
*Eukarya = the only one that has eukaryotic cells
*Bacteria and archaea have prokaryotic cells. Both don't form big complex organism.
Arechar is present in harsh environments
If you can see it with your naked eye, its gonna be eukaryotic
Lysosomes digests thingS within the cell

Flagellum

• Uses to move.

Lysosome

• Functions to digest things within the cell

plants

• Chloroplasts: Organelles that convert sunlight into energy through photosynthesis.

• Vacuoles: Storage organelles that maintain cell turgor and store nutrients.

• Mitochondria: Organelles that produce energy in the form of ATP by breaking down glucose during cellular respiration.

• Cell Wall: A rigid outer layer that provides structure and support to plant cells, helping to maintain their shape.

Key Notes:

• Many of the plant structures will usually say the word "plast." Plant structures have P.L.A
  Example: Tonoplast, leukoplast, chromoplast, versaplast, nataplast

Those include: tonoplast, cell walls, pasmodesmata

Example: if you saw tonoplast, its got plast on the end! It's a plant structure. Chloroplasts are for photosynthesis.
Tonoplast is the membrane around the central vacuole (big giant container inside the cell.)

Nucleus

• You find a nucleus in eukaryotic cells. Eukaryotic cells include animals, plants and fungus.

• What is the main job of the nucleus? What is it storing?
  *It is storing DNA.

• Chromatin = DNA.

*It's a double membrane structure = two membranes
*Pore complexes = big doorway to the nucleus
*What is a pore complex used for? Its for opening like to for making proteins = Like a giant doorway.
*Its a way to transport from the nucleus to the outside and vice-versa

Fibers and Nuclear Structures

• Cytoskeleton are all the different fibers and filaments and microtubes.

  • A part of that includes, microtubules and microfilaments. The microfilaments are made of actin.

• Nuclear lamina = made of intermediate filaments only.
  *Also note: Intermediate filaments are never involved in any type of movement. They mostly are structural.
  Microtubues have things to allow the flagella to flap.
  *Mirco fillaments the actin. They pinch the side of the cell to form to create cleavage furrows.
  The chromosomes are moving by the microtubules

Endomembrane System

Key Notes:

• All this internal membranous stuff that's all throughout the cell.
  It includes
  *endoplasmic reticulum
  *nuclear envelope
  *Golgi apparatus
  Vacoules and vesicles. Those that aren't would be the mitochondria or even cholorplasts.
  *The reason its the endomembrane system. A direct connection between the pieces of membrane through the transporting. So many pieces of the endoplasmic membrane will pop of and get transported to be apart of gogli body

*Rough ER= has ribosomes all over the surface of the membrane, so rough Er is for protein production
Smooth Er= has no ribosomes on it so that means, no proteins.
The smoothie or can help contribute to various things in membrane structures. Its also involved in detoxification
If you have a chemical that is Hydrophobic, it can take more processing

*Golgli Apparatus: Cis face what the ER comes into, so it's receiving the supplies.
*Gogli Apparatus: The trans fase is shipping the product out.
Receiving is Cis = what the ER comes into
Is to transport it to the outside. Trans = to transport to the outside (shipping) If you are on same side you are cis and if you are cross over to he other then are trans.