-
Fermentation
A process that results in the partial degradation of sugars or other organic fuel without the use of oxygen.
-
Aerobic Respiration
Oxygen is consumed as a reactant along with the organic fuel.
Done by most eukaryotic and prokaryotic organisms.
Some prokaryotes use substances other than oxygen as reactants in a similar process called anaerobic respiration.
-
Cellular Respiration
Technically includes aerobic and anaerobic processes but refers mostly to aerobic respiration.
C6H12O6+ 6O2 -> 6CO2 + 6H2O + Energy (ATP+Heat)
Process is exergonic (negative ^G change, spontaneous)
Includes: oxidation and reduction
-
Redox Reactions
~Also called: Oxidation-Reduction Reactions
~Transfer of one or more electrons from one reactant to another.
- ~The loss of electrons from one substance is called OXIDATION.
- ~The addition of electrons to another substance is called REDUCTION
- ~Reducing Agent: Electron donor
- ~Oxidixing Agent: Electron acceptor
~Oxidation and Reduction ALWAYS go hand in hand
~Not all redox reactions involve the complete transfer of electrons from one substance to another
~Oxygen is one of the most potent oxidizing agents because it's so electronegative
~Energy MUST be added to pull an electron away from an atom
-
Reducing Agent
&
Oxidizing Agent
- Electron Donor
- &
- Electron Acceptor
-
NAD+
- An electron carrier, functioning as an oxidizing agent during respiration
- A coenzyme
- Can cycle easily between oxidized (NAD+) and reduced (NADH) states
-
Electron Transport Chain
- In cristae of mitrochondrion
- Consists of a number of molecules (mostly proteins) built into the inner membrane of the mitochondria of eukaryotic cells
- Respiration uses an ETC to break the fall of electrons to oxygen into several energy-releasing steps
- Thousands in each mitochondrion
- Does not generate ATP
-
Glycolysis
- Occurs in the cytosol
- Begins the degradation process by breaking glucose into two molecules of pyruvate
- Carbon (6-carbon sugar) is split into two 3-carbon sugars, then oxidized, then rearranged to form two molecules of pyruvate
- Two phases: energy investment phase (ATP spent) and energy payoff phase (ATP gained)
-
Citric Acid Cycle
- Functions as a metabolic furnace that oxidizes organic fuel derived from pyruvate
- Catabolic - Oxidizing acetyl CoA and using energy to synthesize ATP
-
Oxidative Phosphorylation
- Mode of ATP synthesis powered by the redox reactions of the electron transport chain
- Adds an inorganic phosphate to ADP
-
Substrate-Level Phosphorylation
Mode of ATP synthesis that occurs when an enzyme transfers a phosphate group from a substrate molecule to ADP,
-
Acetyl CoA
- Acetyl Coenzyme A
- Pyruvate converted to Acetyl CoA in step linking glycolysis and the citric acid cycle
-
How many ATP molecules produced per glucose molecule? How many during glycolysis? How many during the citric acid cycle?
- 4 ATP Molecules
- 2 during glycolysis
- 2 during citric acid cycle
-
How many CO2 needed to produce 1 G3P?
3 CO2 (Each completing cycle alone; 3 Calvin Cycles)
-
How many times must the Calvin Cycle take place for one G3P?
Three times (3 CO2)
-
Cytochromes
- Proteins
- Most of the remaining electron carriers between ubiquinone and ozygen in ETC
-
ATP Synthase
- Protein complex
- The enzyme that makes ATP from ADP and inorganic phosphate
- Works like an ion pump running in reverse
- Populates inner membrane of the mitochondrion or prokaryotic plasma membrane
- Uses the energy of an existing ion gradient to power ATO synthesis
-
Chemiosmosis
- Process in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work
- Example: the synthesis of ATP
- The flow of H+ across a membrane
-
Proton-Motive Force
The potential energy stored in the form of a proton electrochemical gradient, generated by the pumping H+ across a biological membrane during chemiosmosis
-
Energy flow during respiration
Glucose -> NADH -> ETC -> Proton-Motive Force -> ATP
*ETC: Electron Transport Chain
-
Fermentation & Types
- A way of harvesting chemical energy w/o using either oxygen or any ETC (w/o cellular respiration)
- Alcohol and Lactic Acid
-
Alcohol Fermentation
- Pyruvate converted to Ethanol in two steps
- Step 1: Release CO2 from pyruvate, which is converted to the 2-carbon compound acetaldehyde
- Step 2: Acetaldehyde is reduced by NADH to ethanol (regenerates supply of NAD+ needed for glycolysis)
- Many bacteria carry out AF under anaerobic (w/o air) conditions
-
Lactic Acid Fermentation
- Pyruvate reduced directly by NADH to form lactate w/ no release of CO2
- Certain fungi/bacteria used by dairy industry to make cheese and yogurt
- Used by human muscle cells to make ATP when oxygen is scarce (during strenuous exercise)
-
-
Aerobic
Cellular Respiration
-
Differences between Fermentation and Cellular Respiration
- -Both use glycolysis to oxidize glucose and other organic fuels to pyruvate
- -Cellular respiration produces much more ATP
- -Fermentation Final Electron Acceptor: Pyruvate
- -Cellular Respiration Final Electron Acceptor: O2
-
Biosynthesis
- The body uses small molecules to build other substances
- Small molecules may come directly from food, from glycolysis, or from the citrci acid cycle
-
Photosynthesis
- The conversion from solar to chemical energy
- Most plants, algae, some prokaryotes, and some unicellular eukaryotes
-
Autotrophs
Heterotrophs
- Autotrophs: Sustain themselves w/o eating anything derived from other organisms (plants)
- Heterotrophs: Obtain their organic material from other organisms; Consumers (humans)
-
Photoautotrophs
- Plants
- Organisms that use light as a source of energy to synthesize organic substances
-
Chloroplasts
- All green parts of a plant have chloroplasts
- Found mainly in the mesophyll (tissue in the interior of the leaf)
- Has an envelope of two membranes surrounding a dense fluid called the stroma
-
What is the major site of photosynthesis?
Leaves (in most plants)
-
Mesophyll
- The tissue in the interior of the lead
- Has about 30-40 chloroplasts, 2-4um by 4-7um
-
Stomata
- Microscopic pores
- Oxygen exits the leaf through the stomata
-
Stroma
- A envelope of two membranes surrounding a dense fluid
- Contains membrane system made up of sacs, called thylakoids, which segregates the stroma from the thylakoid space inside the sacs
-
Thylakoids
- Sacs that segregate the stroma from the thylakoid space inside these sacs
- In some places, they are stacked in columns called grana (singular granum)
- Chlorophyll found here
-
Grana (singular name?)
- Columns of thylakoids
- Singular: granum
-
Chlorophyll
- The green pigment that gives leaves their color
- Found in the thylakoid
-
Chemical Equation for Photosynthesis
- 6CO2 + 6H2O + Light Energy -> C6H12O6 + 6O2
- 6CO2 + 12H2O + Light Energy -> C6H12O6 + 6O2+6H2O
-
What are the two stages of photosynthesis?
- 1- Light Reactions (photo)
- 2- The Calvin Cycle (synthesis)
-
Light Reactions
- The steps of photosynthesis that convert solar energy to chemical energy
- Water is split (providing electrons & protons)
- O2 released
- No sugar produced
-
Photophosphorylation
Process in which ATP is generated by using chemiosmosis to power the addition of a phosphate group to ADP
-
The Calvin Cycle
- Anabolic - Building carbs from smaller molecules and consuming energy
- Incorporates CO2 from the air into organic molecules already present in the chloroplast (called Carbon Fixation)
- The fixed carbon is then reduced to carbohydrates by the addition of electrons
- 3 Phases: Carbon Fixation, Reduction, Regeneration of the CO2 Acceptor
-
Carbon Fixation
The initial incorporation of carbon into organic compounds
-
Wavelength
- The distance between the crests of electromagnetic waves
- Range from less than a nanometer to more than a kilometer
-
Electromagnetic Spectrum
- The entire range of radiation
- Less than a nanometer-More than a kilometer
- Segment most important to life: 380nm-750nm
-
What segment of the electromagnetic spectrum is most important to life?
- 380nm-750nm
- Called visible light
-
Visible Light
- 380nm-750nm
- Segment of the electromagnetic spectrum most important to life
- Can be detected as various colors by the human eye
-
Photons
- Discrete particles
- Not tangible objects, but act like objects in that each of them has a fixed quantity of energy
-
What is the relationship between the amount of energy and wavelength of the light?
- The amount of energy is inversely related to wavelength of light
- The shorter the wavelength of light, the greater the energy of each photon of that light
-
What radiation drives photosynthesis?
Visible Light
-
Absorption Spectrum
A graph plotting a pigment's light absorption versus wavelength
-
Chlorophyll a
The key light-capturing pigment that participates directly in the light reactions
-
Chlorophyll b
The accessory pigment
-
Carotenoids
- Separate group of accessory pigments
- Hydrocarbons that are various shades of yellow and orange because they absorb violet and blue-green light
- May broaden the spectrum of colors that can drive photosynthesis
- Some function as photoprotectors - Absorb and disspate excessive light energy that would otherwise damage chlorophyll or interact with oxygen, forming reactive oxidative molecules that are dangerous to the cell
-
Action Spectrum
- Profiles the relative effectiveness of different wavelengths of radiation in driving the process
- Prepared by illuminating chloroplasts with light of different colors, then plotting wavelength against some measure of photosynthetic rate
-
What happens when chlorophyll and other pigments absorb light?
The colors corresponding to the absorbed wavelengths disappear from the spectrum of the transmitted and reflected light (but energy cannot disappear)
-
A green plant reflect what color?
Green
-
Photosystem
- Composed of a reaction-center complex surrounded by several light-harvesting complexes
- Photosystem I and Photosystem II
- Each photosystem functions in the chloroplast as a unit
- Converts light energy to chemical energy, which will ultimately be used for the synthesis of sugar
-
Reaction-Center Complex
- An organized association of proteins holding a special pair of chlorophyll a molecules
- Contains a molecules capable of accepting electrons and becoming reduced (primary electron acceptor)
-
Light-Harvesting Complex
- Consists of various pigment molecules (may include chlorophyll a, b, and multiple carotenoids) bound to proteins
- Enables a photosystem to harvest light ove a larger surface area and a larger portion of the spectrum than any single pigment alone
-
Primary Electron Acceptor
A molecule capable of accepting electrons and becoming reduced
-
What is the first step of light reactions?
The solar-powered transfer of an electron from the reaction-center chlorophyll a pair to the primary electron acceptor
-
What is a redox reaction?
As soon as the chlorophyll electron is excited to a higher energy level, the primary electron acceptor captures it
-
Photosystem II (PSII)
- Functions 1st in light reactions
- P680
-
Photosystem I (PSI)
- Functions 2nd in light reactions
- P700
-
Linear Electron Flow
- A flow of electrons through the photosystems and other molecular components built into the thylakoid membrane
- Occurs during the light reactions of photosynthesis
- Generates ATP and NADPH
-
Cyclic Electron Flow
- Uses photosystem I only
- No production of NADPH or oxygen
- Generate ATP
- Occurs in photosynthetic bacteria with one photosystem (PSII or PSI)
- Can occur in photosynthetic organisms with both photosystems
-
Chemiosmosis in Mitochondrion
Chemiosmosis in Chloroplasts
- in Mitochondrion: Chemical Energy (from food) transfer to ATP
- in Chloroplasts: Light energy transforms to Chemical Energy of ATP
-
-
G3P
- Glyceraldehydr 3-Phosphate
- The carbohydrate produced directly from the Calvin Cycle
- 3-Carbon Sugar
- For the net synthesis of one molecule of G3P, the cycle must take place 3 times (3 CO2)
-
How many molecules of ATP and NADPH are consumed by the Calvin Cycle for one G3P?
-
How many molecules of ATP and NADPH are consumed by the Calvin Cycle for one molecule of glucose?
-
How many Calvin Cycles needed for one molecule of glucose?
6 (6CO2)
-
C3 Plants
- Plants that use the Calvin Cycle for the initial steps that incorporate CO2 into organic material, producing 3-Phosphoglycerate
- Examples: Rice, Wheat, Soybeans
-
C4 Plants
- Plants in which the Calvin Cycle is preceded by reactions that incorporate CO2 into a 4-carbon product
- Examples: Sugarcane, Corn
-
CAM Plants
- Plants that use crassulacean acid metabolism*
- Examples: Pineapple
*An adaptation for photosynthesis in arid conditions
-
Crassulacean Acid Metabolism
An adaptation for photosynthesis in arid conditions
-
Bundle-Sheath Cells
Arranged into tightly packed sheaths around the veins of the leaf
-
Photorespiration
- A process that occurs in the light and consumes O2 while producing CO2
- Uses ATP
- Produces no sugar
- Decreases photosynthesis output
-
Cell Division
Reproduction of cells
-
Cell Cycle
- The life of the cell from the time it is first formed during division of a parent cell until its own division into two daughter cells
- Crucial Function: Passing identical genetic material to cellular offspring
-
Genome
- A cell's genetic info
- Prokaryotic genomes - single DNA molecule
- Eukaryotic genomes - a number of DNA molecules
-
Chromosomes
- Structures containing DNA molecules
- # in Human Somatic Cells: 46 (2 sets of 23)
- # in Human Gametes: 23 (one set)
-
Genes
- The units of info that specify an organism's inherited traits
- Program the specific traits that emerge as we develop from fertilized eggs into adults
- Written in the language of DNA
-
Chromatin
- The entire complex of DNA and proteins that is the building material of chromosomes
- Varies in its degree of condensation during cell division
-
Somatic Cells
All body cells except the reproductive cells
-
How many chromosomes in human cells nuclei?
- 46 chromosomes
- Two sets of 23 (one set inherited from each parent)
-
Gametes
- Reproductive Cells
- Sperm and Eggs
- One set of chromosomes (half as many somatic)
- In humans: one set of 23 chromosomes
- The vehicles that transmit genes from one generation to the next
-
Sister Chromatids
- Joined copies of the original chromosome
- Initially attached all along their lengths by protein complexes called cohesins
-
Cohesins
Protein complexes that initially attach sister chromatids along their lengths
-
Chromatid Cohesin
The attachment of sister chromatids to each other
-
Mitosis
- The division of the genetic material in the nucleus
- Usually followed by cytokinesis (the division of the cytoplasm)
-
Phases of the Cell Cycle
- Mitotic (M) Phase
- Interphase (Sub-phases: G1 Phase, S Phase, G2 Phase)
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
-
Interphase
- Accounts for 90% of the cell cycle
- Includes sub-phases: G1 Phase, S Phase, and G2 Phase
- A cell grows by producing proteins and cytoplasmic organelles such as mitochondria and endoplasmic reticulum
-
S Phase
- Sub-phase of interphase
- Duplication of the chromosomes occurs entirely
-
Mitotic Spindle
- Consists of fibers made of microtubules and associated proteins
- Begins to form in the cytoplasm during prophase
- Includes: The centrosomes, The spindle microtubules, and the asters
-
G2 Phase
- A nuclear envelope (double membrane) encloses the nucleus
- Two centrosomes have formed by duplication of a single centrosome
- Each centrosome contains two centrioles
-
Prophase (mitosis)
- The chromatin fibers become more tightly coiled
- The nucleoli disappear
- Each duplicated chromosome appears as two identical sister chromatids joined at their centromeres
- The mitotic spindle begins to form
- The centrosomes move away from each other
-
Prometaphase (mitosis)
- The nuclear envelope fragments
- The microtubules extending from each centrosome can now invade the nuclear area
- The chromosomes have become even more condensed
- Each of the two chromatids of each chromosome now has a kinetochore (specialized protein structure at center of centromere)
- Some of the microtubules attach to kinetochores, becoming "kinetochore microtubules," which kerl the chromosomes back and forth
-
Metaphase (mitosis)
- The centrosomes are now at opposite poles of the cell
- The chromsomes have all arrived at the metaphase plate (a plane equidistant between spindle's two poles)
- For each chromosome, the kinetochores of the sister chromatids are attached to kinetochore microbtubules coming from opposite poles
-
Anaphase (mitosis)
- Shortest stage of mitosis
- Begins when the cohesin proteins are cleaved, allowing the two sister chromatids of each pair to part suddenly (each chromatid becomes a full-ledged chromosomes)
- The two liberated sister chromosomes begin moving toward opposite ends of the cell
- The cell elongates as the nonkinetochore microtubules lengthen
- By the end of this stage, the two ends of the cell have equivalent (and complete) collections of chromosomes
-
Telophase (mitosis)
- Two daughter nuclei form in the cell
- Nuclear envelopes arise from the fragments of the parent cell's nuclear envelope
- Nucleoli reappear
- The chromosomes become less condensed
- Any remaining spindle microtubules are depolymerized
- Mitosis is complete
-
Cytokinesis (mitosis)
The division of the cytoplasm is usually well under way by the late telophase, so the two daughter cells appear shortly after the end of mitosis
-
Centrosomes
- A subcellular region containing material that functions throughout the cell cycle to organize the cell's microtubules
- A pair of centrioles at center
-
Aster
- A radial array of short microtubules
- Extends from each centrosome
-
Kinetochore
A structure made of proteins that have assembled on specific sections of DNA at each centromere
-
Metaphase Plate
- A plane midway between the spindle's two poles
- Imaginary plate
-
Cleavage Furrow
- A shallow groove in the cell surface near the old metaphase plate
- The 1st sign of cleavage
- Deepens until the parent cell is pinched in two, producing two separate cells
- Animal cells, not plant cells
-
Cleavage
- Process by which cytokinesis occurs
- 1st Sign: Cleavage Furrow
-
Cell plate
- Produced in plant cells when vesicles from the Golgi move along microtubules to the middle of the cell, where they coalesce (come together)
- Enlarges until its surrounding membrane fuses with the plasma membrane along the perimeter of the cell
-
Binary Fission
- "Division in Half"
- Refers to the process and asexual reproduction of single-celled eukaryotes (bacteria)
-
Cell Cycle Control System
- A cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle
- Proceeds on its own, according to a built in "clock"
- Regulated at certain checkpoints by internal and external adjustment
-
Checkpoint
- A control point in the cell cycle where stop and go-ahead signals can regulate the cycle
- Three important checkpoints found in G1, G2, and M Phases
-
Cyclin
- Protein
- Cyclically fluctuating concentration in the cell
-
Cyclin-dependent Kinases (Cdks)
- Enzymes that activate or inactivate other proteins by phosphorylating them
- Activity rises and falls with changes in the concentration of its cyclin partner
-
Which checkpoint is most important? Why?
- G1 Checkpoint
- If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the G1, S, G2, and M phases and divide
- If a cell does not receive a go-ahead signal at the G1 checkpoint, it may exit the cycle, switching into a nondividing state called the G0 phase
-
G0 Phase
- Nondividing state
- The result of not receiving a go-ahead signal at G1 checkpoint
- Most cells of human body at this phase
-
Growth Factor
- A protein released by certain cells that stimulates other cells to divide
- Different cell types respond specifically to different growth factors or combinations of growth factors
-
Density-Dependent Inhibition
A phenomenon in which crowded cells stop dividing
-
Anchorage Dependence
- To divide, cells must be attached to a substratum
- Signaled to the cell cycle control system via pathways involving plasma membrane proteins and elements of the cytoskeleton linked to them
-
Benign Tumor
- Most do not cause serious problems
- Most can be removed by surgery
- A mass of abnormal cells within otherwise healthy tissue that remains at the original site (too few genetic and cellular changes to survive at another site)
-
Malignant Tumor
- A mass of abnormal cells within otherwise healthy tissue whose genetic and cellular changes enable them to spread to new tissues and impair the functions of one or more organs
- "Cancer"
-
Metastasis
Spread of cancer cells to locations distant from their original site
-
Heredity
- Transmission of traits from one generation to the next
- Also called inheritance
-
Variation
Differences between members of the same species
-
Genetics
Scientific study of heredity and hereditary variation
-
Locus
- A gene's specific location along the length of a chromosome
- Plural: loci
-
Asexual Reproduction
- A single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes
- Example: Single-celled eukaryotic organisms,
- Some multicellular organisms
-
Sexual Reproduction
- Two parents give rise to offspring that have unique combinations of genes inherited from the two parents
- Offspring vary genetically from their siblings and parents
- Variations not replicas
-
Life Cycle
- The generation-to-generation sequence of stages in the reproductive history of an organism
- Conception to own reproduction
-
How many chromosomes in each somatic cell?
46 Chromosomes
-
How many chromosomes of each type?
- Each chromosome has two pairs
- 23 x 2 = 46
-
Karyotype
- Ordered display of chromosomes
- Starts with longest
-
Homologous Chromosomes
- Also called homologs
- A pair of chromosomes of the same length, centromere position, and staining pattern
- Possesses genes controlling the same inherited characteristics
- Exception: X and Y Chromosomes
-
Human females have XX or XY chromosomes?
XX
-
Human males have XX or XY chromosomes?
XY
-
XY or XX Chromosomes
- Sex chromosome
- Males: XY
- Females: XX
-
Homologs
- Also called homologous chromosomes
- A pair of chromosomes of the same length, centromere position, and staining pattern
- Possesses genes controlling the same inherited characteristics
- Exception: X and Y Chromosomes
-
Autosomes
Chromosomes that are not sex chromosomes
-
Diploid Cell
- Any somatic cell with two chromosome sets
- Has a diploid number of chromosomes, abbreviated 2n
- Humans: Diploid # = 46 (2n=46)
-
Haploid Cell
- Any gamete with one chromosome set
- Has a haploid number of chromosomes, abbreviated n
- Humans: Haploid # = 23 (n=23)
-
Fertilization
- The union of gametes
- Result: Zygote, fertilized egg
-
Zygote
- Fertilized egg
- Diploid because it contains two haploid sets (paternal and maternal copy of chromosomes)
-
What are the only cells not produced by mitosis?
Gametes
-
Where are gametes developed?
- In germ cells, in the gonads
- Ovaries and Testes
-
Meiosis
- Type of cell division involved in gamete formation
- Occurs in germ cells (in the gonads)
- Reduces the number of sets of chromosomes from two to one in the gametes, counterbalancing the doubling that occurs at fertilization
- Meiosis I and Meiosis II
-
Alternation of Generations
- Plants and some species of algae
- Includes both diploid and haploid stages that are multicellular
- Sporophyte: Muticellular Diploid Stage
- Gametophyte: Muticellular Haploid Stage
- The sporophyte generation produces a gametophyte as its offspring, and the gametophyte produces the next sporophyte
-
How many stage of Meiosis are there?
- Two
- Meiosis I and Meiosis II
-
What results from Meiosis I and Meiosis II?
4 daughter cells, each with only half as many chromosomes as the parent cells
-
Stages of Meiosis
- Meiosis I: Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis
- Meiosis II: Prophase II, Metaphase II, Anaphase II, Telophase II, Cytokinesis
-
Prophase I (meiosis)
- Centrosome movement, spindle formation, and nuclear envelope breakdowns
- Chromosomes condense progressively
- Each chromosome pairs with its homolog, aligned gene by gene, and crossing over occurs
- Each homologous pair has one or more X-shaped regions called chiasmata, where crossovers have occured
- Microtubules from one pole or the other will attach to the two kinetochores (one at the centromere of each homolog)
- The homologous pairs will then move toward the metaphase state
-
Metaphase I (meiosis)
- Pairs of homologous chromosomes are now arranged at the metaphase plate, each pair facing its own pole
- Both chromatids of one homolog are attached to kinetochore microtubules from one pole
-
Anaphase I (meiosis)
- Breakdown of proteins that are responsible for sister chromatid cohesion along chromatid arms allows homologs to separate
- Homologs move toward opposite poles
- Sister chromatid cohesion persists at the centromere, causing chromatids to move as a unit toward the same pole
-
Telophase I and Cytokinesis (meiosis)
- Each half of the cell has a complete haploid set of duplicated chromosomes
- Cytokinesis usually occurs simultaneously with telophase I, forming two haploid daughter cells
- In animal cells, a cleavage furrow forms
- In some species, chromosomes condense and nuclear envelopes form
- No chromosome duplication occurs between Meiosis I and Meiosis II
-
Prophase II (meiosis)
- Spindle apparatus forms
- Chromosomes move toward metaphase II plate
-
Metaphase II (meiosis)
- The chromosomes are positioned at the metaphase plate
- Because of crossing over in meiosis I, the two sister chromatids of each chromsome are not genetically identical
- The kinetochores of sister chromatids are attached to microtubules extending from opposit poles
-
Anaphase II (meiosis)
- Breakdown of proteins holding the sister chromatids together at the centromere allows the chromatids to separate
- The chromatids move toward oppiste poles as individual chromosomes
-
Telophase II and Cytokinesis (meiosis)
- Nuclei form, the chromosomes begin decondensing, and cytokinesis occurs
- The meiotic division of one parent cell produces four daughter cells (each w/ haploid set of chromosomes)
- The four daughter cells are genetically distinct from each other and the parent cell
-
Synaptonemal Complex
- Zipper-like structure
- The formation of which holds one homolog tightly to the other
-
Synapsis
During - The DNA breaks are closed up so that each broken end is joined to the corresponding segment of the nonsister chromatid
-
What are the two sources of variation among offspring?
- Independent Assortment of Chromosomes
- Crossing Over
-
Character
- A heritable feature that varies among individuals
- Example: Flower color
-
Trait
- Each variant for a character
- Example: Purple or white color for flowers
-
True-Breeding
Organisms produce offspring of the same variety over many generations of self-pollination
-
Hybridization
- The crossing of two true-breeding varieties
- P Generation: true-breeding parents
- F1 Generation: hybrid offspring of P Generation
- F2 Generation: offspring from F1 Generation
-
P Generation
Two true-breeding parents
-
F1 Generation
Hybrid offspring of P Generation
-
F2 Generation
Offspring of F1 Generation
-
Alleles
Alternative versions of a gene
-
What are the four related concepts that make up Mendel's Model?
- Alternative versions of genes account for variations in inherited characters.
- For each character, an organism inherits two copies (two alleles) of a gene, one from each parent.
- If the two alleles at a locus differ, than one (the dominant allele) determines the organisms appearance; the other (the recessive allele) has no noticeable effect on the organisms appearance
- The two alleles for a heritable character segregate during gamete formation and end up in different gametes (The Law of Segregation)
-
The Law of Segregation
- States that the two alleles for a heritable character segregate during gamete formation and end up in different gametes
- An egg or a sperm gets only one of the two alleles that are present in the somatic cells of the organism making the gamete
-
Punnett Square
A diagrammatic device for predicting the allele composition of offspring from a cross between individuals of known genetic makeup
-
Homozygous
Name for an organism that has a pair of identical alleles for a character
-
Heterozygous
- Name for an organism that has two different alleles for a gene
- Not true-breeding
-
Homozygous Recessive
Name for an organism that has a pair of identical recessive alleles for a character
-
Phenotype
- An organism's appearance or observable traits
- Example: PP and Pp (purple vs white colored petals) have the same phenotype, which is the purple petals
-
Genotype
- An organism's genetic makeup
- Example: PP and Pp (purple vs white colored petals) have different genotypes, PP vs Pp
-
Testcross
- Breeding an organism of unknown genotype with a recessive homozygote
- Can reveal the genotype of the unknown organism
-
Monohybrids and Monohybrid Cross
- Monohybrid: An organism is heterozygous for one particular character
- Monohybrid Cross: A cross between two heterozygous organisms with a single differing character
-
Dihybrids and Dihybrid Cross
- Dihybrid: An organism heterozygous for two characters
- Dihybrid Cross: A cross between two heterozygous organisms with two differing characters
-
Law of Independent Assortment
- Two or more genes assort independently - each pair of alleles segregates independently of each other pair of alleles - during gamete formation
- Only applies to genes located on different chromosomes or to genes that are very far apart on the same chromosome
-
What is the probability scale of Mendelian Genetics?
0-1
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Multiplication Rule
To determine the probability that two or more independent events will occur together in some specific combination: Multiply the probability of one event by the probability of the other event
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Addition Rule
The probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual probablities
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Incomplete Dominance
- Neither allele is completely dominant
- Example: Red and White flower mate - Produce Pink offspring
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Complete Dominance
- The phenotype of the heterozygote and the dominant homozygote are indistinguishable
- Example: Red and White flower mate - Produce dominant colored offspring
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Codominance
- Two alleles each affect the phenotype in separate, distinguishable ways
- Example: Red and White flower mate - Produce Red and White speckled offspring
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Tay-Sachs Disease
- An inherited disorder in humans
- Brain cells cannot metabolize certain lipids because a crucial enzyme does not work properly
- Symptoms: Seizures, blindness, degeneration of motor/mental performances, and death
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Pleiotropy
- Multiple phenotypic characters
- Most genes have this property
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Epistasis
Phenotypic expression of a gene at one locus alters that of a gene at a second locus
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Quantitative Characters
Example: human skin color
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Polygenic Inheritance
- An additive affect of two or more genes on a single phenotypic character
- Example: Height. Over 180 genes affect height
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Multifactorial
Characters that have many factors, both genetic and environmental, influence phenotype
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Pedigree
A family tree describing the traits of parents and children across generations
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Carriers
Heterozygotes that may transmit the recessive allele for a genetic disorder to their offspring
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Cystic Fibrosis
- Most common lethal genetic disease in the US
- 1/2500 people
- Can cause death by 5 years old
- Abnormally high concentration of extracellular chloride, which causes mucus coating certain cells to become thicker and stickier
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Sickle-Cell Disease
- Most common inherited disorder among people of African descent
- 1/400 African-Americans
- Red blood cells sickle-shaped
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Amniocentesis and Chorionic Villus Sampling
Techniques that can determine whether the developing fetus has Tay-Sachs disease
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