Honors Biology - CUMULATIVE 2 REVIEW

(� TOPIC: Cellular Structure and Function) What are the basic components of all cells?

• Ribosomes → small structures that synthesize proteins through translation

• Cell Membrane (Plasma Membrane) → acts as a phospholipid bilayer that surrounds the cell and controls what enters and exits

• Cytoplasm → jelly-like fluid inside the cell where chemical reactions occur (most metabolism occurs here); it contains organelles (in eukaryotic cells)

• DNA → universal genetic code or hereditary material

• eukaryotic cells have a nucleus while prokaryotic cells do NOT

(� TOPIC: Cellular Structure and Function) Describe the structure and function of key organelles (ER).

• ER → series of membranes that allows material to travel through the cell

(� TOPIC: Cellular Structure and Function) Describe the structure and function of key organelles (Golgi).

• Golgi → packages and prepares materials to be sent and secreted out of the cell

(� TOPIC: Cellular Structure and Function) Describe the structure and function of key organelles (mitochondria).

• Mitochondria → supplies energy through cellular respiration and creates ATP

(� TOPIC: Cellular Structure and Function) Describe the structure and function of key organelles (lysosomes).

• Lysosomes → contains enzymes that digest food, old cell parts, and bacteria

(� TOPIC: Cellular Structure and Function) Describe the structure and function of key organelles (nucleus).

• Nucleus → contains the genetic material (DNA)

(� TOPIC: Cellular Structure and Function) Why are cell membranes important for homeostasis?

• Every cell is enclosed in a cell membrane to maintain an internal environment separate from the external environment. The cell membrane is a selectively permeable nonpolar barrier that maintains homeostasis by controlling movement into and out of the cell. 

  • This means that cells are not just physical building blocks that make up organisms, but that each individual cell performs the life processes (regulation, reproduction, cellular respiration, nutrition, synthesis, growth, excretion, and transport) in order to maintain HOMEOSTASIS! In multicellular organisms, the cells also work together to help the entire organism maintain HOMEOSTASIS!

(� TOPIC: Cellular Structure and Function) What roles do transmembrane proteins play in the cell membrane?: TRANSPORT PROTEINS

• Transport Proteins → Proteins that help move substances across membrane (includes protein channels and protein carriers and protein pumps)

(� TOPIC: Cellular Structure and Function) What roles do transmembrane proteins play in the cell membrane?: ENZYMES

• Enzymes → Proteins that catalyze reactions inside the cell (active site faces the cytoplasmic side)

(� TOPIC: Cellular Structure and Function) What roles do transmembrane proteins play in the cell membrane?: IDENTITY MARKERS

• Identity Markers → These have carbohydrate “antenna” used to detect surroundings for “cell-to-cell” recognition, which enables them to determine things as “self vs. non-self”:

  • GLYCOPROTEINS - short sugar chains attached to a protein

  • GLYCOLIPIDS - short polysaccharide attached to a phospholipid

(� TOPIC: Cellular Structure and Function) What roles do transmembrane proteins play in the cell membrane?: RECEPTORS

• Receptors → Receptor proteins are in the membrane and receive external chemical signals, called ligands (like hormones or neurotransmitters). The chemical signal activates the receptor, which in turn, activates a SIGNAL TRANSDUCTION PATHWAY (a series of specific reactions in the cell). 

(� TOPIC: Cellular Structure and Function) What roles do transmembrane proteins play in the cell membrane?: CELL JUNCTIONS

• Cell Junctions → Proteins that connect one cell to another (some proteins act as rivets to hold cells together in tissues)

(� TOPIC: Cellular Structure and Function) What roles do transmembrane proteins play in the cell membrane?: STRUCTURE

• Structure → Proteins (including peripheral proteins) can provide structure by attaching to the cytoskeleton (microfilaments) and extracellular matrix (outside of cell) to help maintain cellular shape and assist in movement

(� TOPIC: Cellular Structure and Function) How does the surface area to volume ratio impact cell efficiency?

• Ideally, cells should have a HIGH surface area to volume ratio. Small cells have a larger SA (lots of membrane) and smaller volume (less cytoplasm): This allows a more efficient exchange rate with the environment. 

• The larger the SA:V ratio, the more efficient the cell is. As cells get bigger, the SA:V ratio decreases (which decreases the efficiency). 

• To remain efficient, cells may:

  • DIVIDE into smaller cells.

  • Make more organelles to maintain a high level of efficiency inside the cell

  • Some cells have specialized folds microvilli, alveoli

• Otherwise… the cell will eventually starve to death. 

(� TOPIC: Cellular Structure and Function) Explain the difference between active and passive transport across the membrane. (Including Osmosis, Diffusion, Facilitated Diffusion) - PASSIVE TRANSPORT

• PASSIVE TRANSPORT: does NOT require energy to move substance across membrane (down the gradient) from high to low concentration

  • SIMPLE DIFFUSION: small, uncharged, nonpolar (hydrophobic, lipid soluble) molecules that can pass through membrane easily

    • Examples: O₂, CO₂, steroid hormones (lipids)

  • FACILITATED DIFFUSION: “Medium” Size, charged ions & polar molecules use protein channels or carriers to get through membrane (inside of channel is hydrophilic/charged)

    • Examples: K⁺, Na⁺, Cl^- (any ion), amino acids, glucose

  • OSMOSIS: movement of water through the membrane using aquaporins (protein channels)

• As molecules move down the gradient, energy is released. Entropy increases! This energy is often used to do work inside the cell!

(� TOPIC: Cellular Structure and Function) Explain the difference between active and passive transport across the membrane. (Including Osmosis, Diffusion, Facilitated Diffusion) - ACTIVE TRANSPORT

• ACTIVE TRANSPORT: requires ENERGY (ATP) to move ions or bulk substances across membrane from low to high concentration (*NO GRADIENT REQUIRED)

  • PROTEIN PUMPS

  • BULK TRANSPORT

(� TOPIC: Cellular Structure and Function) Recall that in dialysis tubing, the size of the membrane pores is critical in determining the movement of molecules.

• Dialysis tubing is a semipermeable membrane, meaning it allows certain molecules to pass while blocking others based on size.

  • Small molecules (water, glucose, ions) can diffuse through the pores.

  • Larger molecules (proteins, starches, DNA) cannot pass through due to their size.

(� TOPIC: Cellular Energy) Why can’t cells use glucose directly for energy?

• Glucose  would release too much energy at once. Metabolic pathways evolved to slowly release and store the energy.

• ATP holds and releases smaller “packets” of energy so none is wasted (energy efficient)

• Glucose is too big of a molecule to travel around efficiently. 

(� TOPIC: Cellular Energy) Describe the ATP cycle and its role in cellular processes.

• ATP consists of adenine (a nitrogenous base), ribose (a five-carbon sugar), and three phosphate groups. ATP provides the energy for 3 types of cellular work: chemical (like synthesis reactions: DNA synthesis, protein synthesis), mechanical (like the movement of cilia or flagella, muscles), and transport (like movement of ions against the gradient).    

• The ATP Cycle:

  • ATP Hydrolysis (Energy Release):

    • ATP → ADP + Pi + energy

    • When cells need energy, ATP is broken down (hydrolyzed) into ADP (adenosine diphosphate) and Pi (inorganic phosphate).

  • ATP Synthesis (Energy Storage):

    • ADP + Pi → ATP

    • To regenerate ATP, cells add a phosphate group to ADP. This process requires energy, which comes from: Cellular respiration (in mitochondria) & Photosynthesis (in chloroplasts of plant cells)

      

(� TOPIC: Cellular Energy) Compare and contrast photosynthesis and cellular respiration. Which organisms perform each process?

Feature	Photosynthesis	Cellular Respiration
Overall Purpose	Converts light energy into chemical energy (glucose)	Breaks down glucose to release chemical energy as ATP
Type of Organism	Autotrophs; Plants, algae, cyanobacteria	All eukaryotes (plants, animals, fungi, protists), and many prokaryotes (bacteria)
Cell Organelle	Chloroplasts (contains chlorophyll)	Mitochondria (site of aerobic respiration)
Energy Source	Sunlight	Chemical energy in glucose
Type of Process	Anabolic (builds glucose molecules)	Catabolic (breaks down glucose)
Main Goal	To store solar energy in glucose molecules	To produce usable energy (ATP) for cellular work
Reactants (Inputs)	Carbon dioxide (CO2), Water (H2O), Sunlight	Glucose (C6H12O6), Oxygen (O2)
Products (Outputs)	Glucose (C6H12O6), Oxygen (O2)	Carbon dioxide (CO2), Water (H2O), ATP (energy)
Overall Balanced Equation	6CO2 + 6H2O + light energy → C6H12O6 + 6O2	C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
Stages or Steps	1. Light-dependent reactions (thylakoids) 2. Calvin Cycle (stroma)	1. Glycolysis (cytoplasm) 2. Krebs Cycle (matrix) 3. Electron Transport Chain (inner membrane)
Location in Cell	Chloroplast (mainly in leaf mesophyll cells)	Starts in cytoplasm (glycolysis); continues in mitochondria
Electron Carriers Involved	NADP+ → NADPH	NAD+ → NADH and FAD → FADH2
Energy Transformation	Light energy → Chemical energy (in glucose)	Chemical energy (glucose) → Chemical energy (ATP)
Relationship to Each Other	Provides glucose and oxygen for respiration	Provides CO2 and water for photosynthesis

(� TOPIC: Cellular Energy) In general happens during aerobic vs. anaerobic respiration – what are the reactants and overall products? (Intermediate steps or numbers of products/ intermediates are NOT required) - AEROBIC RESPIRATION

• AEROBIC RESPIRATION:

  • uses “free” oxygen (O₂)

  • most energy efficient

  • Releases maximum amount of energy by completely oxidizing glucose (all of the bonds will be broken)

  • occurs in most organisms

  • Starts with: Glucose & O₂

  • Results in: ~ 32 ATP (net), 6 CO₂ 6 H₂O (60% of energy is lost to heat!)

  • PATHWAYS INVOLVED IN AEROBIC RESPIRATION:

    • Glycolysis

    • Pyruvate Oxidation

    • Citric Acid Cycle (Krebs Cycle) 

    • Oxidative Phosphorylation

(� TOPIC: Cellular Energy) In general happens during aerobic vs. anaerobic respiration – what are the reactants and overall products? (Intermediate steps or numbers of products/ intermediates are NOT required) - ANAEROBIC RESPIRATION

• ANAEROBIC RESPIRATION:

  • does not use O₂

  • very little energy released

  • Glucose is only partially oxidized (only a few bonds will be broken)

  • occurs in some small, unicellular organisms (and in O₂ deprived muscle, bacteria, yeast)

  • Starts with: Glucose

  • Results in: 2 ATP (net) 

    • various products depending on the organism (CO₂, alcohol, lactic acid, vinegar)

  • PATHWAYS INVOLVED IN ANAEROBIC RESPIRATION:

    • Glycolysis

    • Fermentation

(� TOPIC: Cellular Energy) How do light, pigments, and wavelength affect photosynthesis? Know how to read an absorption spectrum, and what that means for energy absorption/ reflection. - LIGHT

• LIGHT:

  • Light energy refers to sunlight radiation that travels in waves, but acts like particles of energy we refer to as PHOTON (a discrete bundle of electromagnetic energy).

(� TOPIC: Cellular Energy) How do light, pigments, and wavelength affect photosynthesis? Know how to read an absorption spectrum, and what that means for energy absorption/ reflection. - PIGMENTS

• PIGMENTS:

  • Pigments are substances that capture light energy. All photoautotrophs contain photosynthetic pigments (cyanobacteria, plants, some protists). Chlorophyll a is the main photosynthetic pigment (most abundant) in plants and is contained within the membranes of the chloroplast.

  • ACCESSORY PIGMENTS are other pigments found in plants, including: chlorophyll b (yellow-green), xanthophylls (yellow), and carotenes (orange). Accessory pigments absorb some wavelengths of light that chlorophyll a cannot absorb. 

    • This allows a wider range of wavelengths to be absorbed, and therefore maximizes the amount of energy used for photosynthesis.

  •  More pigments means more energy absorbed which means more photosynthesis which means more glucose.

(� TOPIC: Cellular Energy) How do light, pigments, and wavelength affect photosynthesis? Know how to read an absorption spectrum, and what that means for energy absorption/ reflection. - WAVELENGTH

• WAVELENGTH:

  • A wavelength is the distance between the crests (or troughs) of a wave.

  • Longer wavelength (longer λ photons) means lower energy and shorter wavelength (shorter λ photons) means higher energy.

(� TOPIC: Cellular Energy) How do light, pigments, and wavelength affect photosynthesis? Know how to read an absorption spectrum, and what that means for energy absorption/ reflection. - Answer the following questions using the Absorption Spectrum of Chlorophyll a, Chlorophyll b, and Carotenes.

(� TOPIC: Ecology) What is the difference between energy flow and nutrient cycling in ecosystems?  Which organisms are involved in decomposition and recycling?

• Chemicals (like carbon, nitrogen, and water) cycle through the environment in biogeochemical cycles and are reused over and over again by organisms while energy (from the sun) flows in one direction through ecosystems and is not recycled (it is lost as heat at each trophic level instead). 

• Decomposers (like fungi and bacteria) break down dead organisms and return nutrients to the soil.

(� TOPIC: Ecology) Explain trophic levels and the 10% energy rule.

• In every ecosystem, organisms are organized into trophic levels, which describe their position in the flow of energy. Producers (like plants and algae) are at the base of the energy pyramid. They use sunlight to make their own food through photosynthesis. All other organisms are consumers. 

• Energy passes from primary producers (autotrophs) →  primary consumers (herbivores) → secondary consumers (carnivores) → tertiary consumers (carnivores who eat other carnivores). 

• Only about 10% of the energy is transferred to the next trophic level. Most of it is used for life processes (metabolism) like movement, growth, and lost as heat.

(� TOPIC: Ecology) Know how to read a food web and to determine which trophic levels organisms will be considered.

• A food web is more realistic and ACCURATE and shows many interconnected food chains and interconnected relationships between different species. It reflects how organisms often eat more than one type of food.

(� TOPIC: Ecology) Understand the consequences of removal of an organism from an ecosystem/ food web.

• If a predator is removed, its prey population may grow out of control, which can lead to overgrazing or depletion of other organisms. 

• If a prey species disappears, predators may struggle to find food and decline or shift their diets, affecting other parts of the food web. This kind of disruption can lead to a chain reaction called a trophic cascade, where the effects spread through multiple levels of the food web.

•  Some organisms, like pollinators and decomposers, provide essential services such as plant reproduction and nutrient recycling. Without them, ecosystems can become less productive and less stable. 

• If a keystone species is removed, the entire ecosystem could collapse. The loss of one species can also cause other dependent species to decline, reducing biodiversity and making the ecosystem more vulnerable to future stresses like disease or climate change.

(� TOPIC: Ecology) Define and give examples of symbiotic relationships (mutualism, commensalism, parasitism).

Symbiotic Relationship	Definition	Example
Mutualism  (+/+)	both organisms benefit	Acacia trees and ants → ants clear the area at the base of the acacia tree (obligate) Bees and flowers → bees get nectar and flowers get pollinated
Commensalism (+/o)	one species benefits, the other is unaffected	Barnacles ride on whales to get around, and the whale isn’t harmed
Parasitism (+/-)	one benefits, the other is harmed	Tapeworms in bear; a tick feeds on a dog’s blood and can cause disease

(� TOPIC: Ecology) What is biomagnification, and why are top predators at risk?

• Biomagnification is the process where toxic substances, like mercury or DDT, become more concentrated in organisms as they move up the food chain. These chemicals are fat-soluble and non-biodegradable, meaning they build up in animal tissues and don’t get broken down. 

• Top predators are most affected, as they eat many contaminated organisms below them. For example, Bald eagles suffered eggshell thinning and population declines due to DDT buildup from eating contaminated fish.

(� TOPIC: Ecology) How does human interventions, like deforestation and logging impact ecosystems and biodiversity?

• Habitat Loss —- the homes of plants and animals are destroyed.

• Biodiversity Loss —- many species die or go extinct.

• Disrupted Water Cycles —- less transpiration —> reduced waterfall.

• Disrupted Food Webs —- loss of a species will affect predators and prey.

• Soil Erosion —- trees can no longer hold the soil, leading to landslides and nutrient loss.

• Climate Change —- trees absorb CO₂, so by cutting them down, greenhouse gases are increased.

(� TOPIC: Cell Cycle and Cell Division) Terms to know: chromosomes

• tightly coiled, condensed form of DNA that is X-shaped when duplicated or rod-like when single

• present during cell division (mitosis or meiosis)

• ensures accurate DNA separation during cell division

(� TOPIC: Cell Cycle and Cell Division) Terms to know: chromatid

• one of the two identical halves of a chromosome that has been replicated in preparation for cell division

• the two “sister” chromatids are identical strands of DNA that are held together by a centromere

(� TOPIC: Cell Cycle and Cell Division) Terms to know: homologous chromosomes

• pairs of chromosomes that carry the same genes, one inherited from each parent

• they have the same size and shape, and their genes are arranged in the same order, although the specific versions (alleles) of those genes may differ

(� TOPIC: Cell Cycle and Cell Division) Terms to know: diploid (2n)

• have TWO copies of each chromosome—one set from each parent

• these are the kinds of cells that make up most of our body (except reproductive cells)

  • we call these SOMATIC cells

• these have homologous pairs

(� TOPIC: Cell Cycle and Cell Division) Terms to know: haploid (n)

• have only ONE copy of each chromosome

• sex cells/reproductive cells/GAMETES

  • sperm in males and eggs in females

• do not have homologous pairs

(� TOPIC: Cell Cycle and Cell Division) Terms to know: gametes

• sex cells made during meiosis

• haploid

(� TOPIC: Cell Cycle and Cell Division) Terms to know: zygote

•  a fertilized egg

• diploid

(� TOPIC: Cell Cycle and Cell Division) Terms to know: somatic cell

• body cells

• diploid

• made during mitosis

(� TOPIC: Cell Cycle and Cell Division) Terms to know: Law of Independent assortment

• when homologous pairs line up in the middle of the cell, they assort independently - in other words, the alignment of one chromosome pair does not influence the alignment of another chromosome pair

  • this means that we must consider all the possible arrangements of the chromosomes

(� TOPIC: Cell Cycle and Cell Division) Terms to know: crossing over

• when homologous pairs come together to form a tetrad, crossing over occurs

• an equal exchange of genetic material between homologous chromosomes

• also known as genetic recombination

(� TOPIC: Cell Cycle and Cell Division) Terms to know: fertilization

• the process where male and female gametes fuse to form a zygote, which then develops into a new organism

• restores the diploid number of chromosomes, which was halved in the gametes

(� TOPIC: Cell Cycle and Cell Division) Terms to know: karyotype

• a picture or diagram of all the chromosomes in a cell, arranged in pairs and ordered by size and shape (largest to smallest)

• it shows the complete set of chromosomes for an individual, which has 46 chromosomes in humans (23 pairs)

• sex chromosomes are always last

(� TOPIC: Cell Cycle and Cell Division) Terms to know: nondisjunction

• the failure of chromosomes to separate properly during cell division (mitosis or meiosis), resulting in daughter cells with an abnormal number of chromosomes)

• leads to various chromosomal abnormalities, such as trisomy (an extra chromosomes) or monosomy (a missing chromosome

(� TOPIC: Cell Cycle and Cell Division) Terms to know: sex chromosomes

• 2 chromosomes (1 pair)

• code for chromosomal sex/gonadal development

  • these do not determine gender identity or sexual orientation

• female sex chromosomes are XX and male sex chromosomes are Xy

(� TOPIC: Cell Cycle and Cell Division) Terms to know: autosomes

• 44 chromosomes (22 homologous pairs)

• code for all body traits and physiological functions (everything except sex)

(� TOPIC: Cell Cycle and Cell Division) Understand the Cell Cycle: Interphase vs. Mitosis - INTERPHASE

• INTERPHASE: A cell spends most of its life cycle in interphase; during this time the cell grows and performs its normal metabolic function — it’s doing its job! The cell is NOT dividing during Interphase! When the cell needs to divide, it will prepare for cell division and replicate its chromosomes. The phases of Interphase include G0, G1, S, and G2. In Interphase, the DNA is in CHROMATIN form (because it is a metabolically active cell) and it is contained in the nucleus.

(� TOPIC: Cell Cycle and Cell Division) Understand the Cell Cycle: Interphase vs. Mitosis - MITOSIS

• MITOSIS: Mitosis is the type of cell division that helps the body grow, heal, and replace cells. It makes identical body cells (same number of chromosomes) and results in 2 identical cells (called daughter cells).

(� TOPIC: Cell Cycle and Cell Division) Understand the Cell Cycle: Interphase vs. Mitosis - MITOSIS: STAGES OF MITOSIS IN ANIMAL CELLS (these cells have centrosomes)

1. Chromatin coils into chromosome form & the nuclear membrane disintegrates.

2. The spindle fibers form from the centrosome and attach to the chromosomes at the centromere.

3. The spindle fibers push/pull chromosomes until they align in the middle of the cell (sometimes called the “metaphase plate” or at the “equator of the cell”).

4. The spindle fibers start to shorten, which pulls apart the sister chromatids move them to opposite poles of the cell.

5. Once the single-stranded chromosomes reach opposite ends, they begin to uncoil back into chromatin form, and a new nuclear membranes forms around each nucleus.

6. During the last phase of mitosis, the cell undergoes CYTOKINESIS - “splitting of the cytoplasm”: In animal cells, a CLEAVAGE FURROW is formed, which is the pinching in of the cell membrane, creating two new cells.

7. The two identical cells return to INTERPHASE.

(� TOPIC: Cell Cycle and Cell Division) Understand the Cell Cycle: Interphase vs. Mitosis - MITOSIS: STAGES OF MITOSIS IN PLANT CELLS (these cells do not have centrosomes)

1. Chromatin coils into chromosome form & the nuclear membrane disintegrates.

2. The spindle fibers attach to the chromosomes at the centromere and align them in the middle of the cell.

3. The sister chromatids pull apart at the centromere and move to opposite poles of the cell.

4. Once the chromosomes reach opposite ends, they begin to uncoil back into chromatin form, and new nuclear membranes form.

5. The cell undergoes CYTOKINESIS: a CELL PLATE is formed, which eventually grows to become a complete cell wall made of cellulose.

(� TOPIC: Cell Cycle and Cell Division) Describe the purpose and outcomes of mitosis and meiosis. - MITOSIS

• MITOSIS:

  • Mitosis occurs for GROWTH of an organism (from a single cell/Zygote to adulthood), to replace dying or damaged cells, and to keep cells small (HIGH surface area to volume ratio) in order to stay energy efficient.

  • Creates 2 identical diploid daughter cells

(� TOPIC: Cell Cycle and Cell Division) Describe the purpose and outcomes of mitosis and meiosis. - MEIOSIS

• MEIOSIS:

  • Meiosis occurs at puberty and beyond in order to make SEX CELLS (GAMETES) for sexual reproduction!

    • Sperm cells + egg cells (Haploid cells)

  • Creates 4 unique haploid daughter cells 

  • Multiple divisions

(� TOPIC: Cell Cycle and Cell Division) Know which type of cells are diploid and haploid. - DIPLOID

• Body cells (somatic cells) such as skin cells, muscle cells, and nerve cells are diploid.

• Zygotes are also diploid.

(� TOPIC: Cell Cycle and Cell Division) Know which type of cells are diploid and haploid. - HAPLOID

• Gametes (sex cells) which are sperm in males and egg in females are haploid cells.

(� TOPIC: Cell Cycle and Cell Division) How can mutations in the cell cycle lead to cancer?

• There are various, important CHECKPOINTS in the cell cycle → these are control points where “stop” and “go” signals regulate the cycle. These are critical for proper cell division!

  • If these cell cycle checkpoints fail, it could lead to TUMORS and CANCER.

    • DNA undergoes “TRANSFORMATION” (mutation) which leads to Uncontrolled Cell Division. The body’s immune system normally recognizes a transformed cell and destroys it. (The cell undergoes cell death, called APOPTOSIS)

(� TOPIC: Cell Cycle and Cell Division) How can mutations in the cell cycle lead to cancer? - The Steps

• The Steps:

  • The cell cycle controls fail!

    • Mutations in the cell cycle mean that cancer cells will ignore cellular signals even in the absence of growth factors that tell them to stop dividing and will continue to divide even at high densities.

  • Cells stop functioning → they do not perform normal life functions or metabolism

  • Repeated & rapid cell division of non-functioning cells occurs

  • The cells stop dividing at random points in the cell cycle.

(� TOPIC: Cell Cycle and Cell Division) When is DNA duplicated in the cycle, and why?

• DNA is duplicated (doubles, an exact copy is made) in the S phase of Interphase.

  • This occurs because each new cell needs a complete set of DNA to function properly.

  • Before a cell divides, it must first copy all of its DNA so that one complete copy can go to each daughter cell.

(� TOPIC: Genetics and Inheritance) What is a karyotype and how can it identify genetic disorders?

• A karyotype is a picture or diagram of all the chromosomes in a cell, arranged in pairs and ordered by size and shape (largest to smallest). It shows the complete set of chromosomes for an individual. 

• It can identify genetic disorders because geneticists can look at a karyotype and see if there are problems with any of the chromosomes; for example, a monosomy (lack of one chromosome) or trisomy (extra chromosome).

  

(� TOPIC: Genetics and Inheritance) What is the expected genotypic and phenotypic ratio for multiple types of genetic crosses: Monohybrid

• crosses involving ONE trait/gene (Aa x Aa)

• set up a Punnett Square for ratios

(� TOPIC: Genetics and Inheritance) What is the expected genotypic and phenotypic ratio for multiple types of genetic crosses: Dihybrid

• involving TWO different genes on TWO different chromosomes (BbCc x BbCc)

• Crosses involcing more than one chromosomes must consider: THE LAW OF INDEPENDENT ASSORTMENT

• 9 dominant dominant : 3 dominant recessive : 3 recessive dominant : 1 recessive recessive

(� TOPIC: Genetics and Inheritance) What is the expected genotypic and phenotypic ratio for multiple types of genetic crosses: Incomplete dominance

• when both alleles contribute equally to the phenotype of a heterozygous individual, resulting in a 3^rd phenotype with a “blended” appearance (RR x WW)

• For incomplete dominance gene interactions, we use 2 DIFFERENT CAPITAL LETTERS to show the allele combinations

• set up a Punnett Square for the ratios

(� TOPIC: Genetics and Inheritance) What is the expected genotypic and phenotypic ratio for multiple types of genetic crosses: Multiple Alleles

• genes that have three or more forms that exist in a population (2 upper case letters with a superscript and one lowercase letter)

• But remember, individuals can only have 2 alleles at a time…one from each parent

• set up a Punnett Square for the ratios

(� TOPIC: Genetics and Inheritance) What are sources of genetic variation in sexually reproducing organisms?

• CROSSING OVER during gamete formation

• The LAW of INDEPENDENT ASSORTMENT during gamete formation

• RANDOM FERTILIZATION of sperm and egg creates even more variations (trillions of possibilities) during sexual reproduction!

(� TOPIC: Genetics and Inheritance) How do independent assortment and crossing over contribute to genetic diversity? - INDEPENDENT ASSORTMENT

• INDEPENDENT ASSORTMENT: When homologous pairs line up in the middle of the cell, they ASSORT INDEPENDENTLY - in other words, the alignment of one chromosome pair does not influence the alignment of another chromosome pair.

  • This means that we must consider all the possible arrangements of the chromosome, giving humans a limitless number of different gametes during meiosis.

(� TOPIC: Genetics and Inheritance) How do independent assortment and crossing over contribute to genetic diversity? - CROSSING OVER

• CROSSING OVER: When homologous pairs come together to form a tetrad, CROSSING OVER occurs. It is an equal exchange of genetic material between homologous chromosomes (GENETIC RECOMBINATION).

  • This results in new combinations of genes.