Exam 2 Review Session - Biology

Exam 2 Review Session Material Covers: Ch.10 (Photosynthesis), Ch.12 (Mitosis), Ch.13 (Meiosis), and Ch.14 (Genetics) Ch. 10 Photosynthesis Photosynthesis = converts solar energy into chemical energy (CO2 becomes reduced to glucose, and H2O becomes oxidized to O2)...

Exam 2 Review Session Material Covers: Ch.10 (Photosynthesis), Ch.12 (Mitosis), Ch.13 (Meiosis), and Ch.14 (Genetics) Ch. 10 Photosynthesis Photosynthesis = converts solar energy into chemical energy (CO2 becomes reduced to glucose, and H2O becomes oxidized to O2) Cellular Respiration = converting sugar into energy (Glucose becomes oxidized to CO2, and O2 becomes reduced to H2O)  Chloroplasts & Photosynthesis Chloroplasts are found mainly in cells of the mesophyll, and each mesophyll contains about 30-40 chloroplasts Leaves are the major locations of photosynthesis Stomata - CO2 enters the stomata and O2 exits the leaf through microscopic pores (of stomata) Thylakoids are connected sacs in the chloroplast and are the location of  Photosynthesis Light H2O CO2 Photosynthesis consists of: Light reaction (the photo part) – NADP+ light needed to produce organic energy molecules ATP and NADPH ADP Converts light energy into chemical + LIGHT Pi CALVIN energy of ATP and NADPH CYCLE REACTIONS Light used to split water and later release O2 into the atmosphere ATP Stroma Thylakoid Dark Reaction/ Calvin cycle (the NADPH synthesis part/light independent/”dark”) – no light needed Use ATP and NADPH to convert CO2 to Chloroplast the sugar G3P O2 [CH2O] Return ADP, inorganic phosphate, and (sugar) NADP to the light reactions Light reaction is carried out by molecules in the thylakoid space  Photosystems  Photosystem II (PS II) 4 Electron functions first 7 Electron transport Primary transport  Best at absorbing a Primary chain acceptor chain wavelength of 680 nm acceptor Pq e Fd (the reaction-center 2 e e 8 NADP+ chlorophyll a of PS II 2H + H2O e Cytochrome − − − NADP+ + H+ is called P680 + − complex reductase 3 ½ O2 Pc NADPH e −e P700  Photosystem I (PSI) 1 P680 5 functions second − Light Light  Best at absorbing a 6 wavelength of 700 nm ATP (the reaction center chlorophyll a of PS I is Pigment called P700 molecules Photosystem I Photosystem II (PS I) (PS II)  Cyclic Electron Flow (CEF) to produce ATP Electrons cycle back from Fd (ferredoxin, which acts Primary acceptor as an electron carrier), to Primary Fd acceptor Fd cytochrome complex & NADP Pq back to the PS I reaction NADP + + + H+ center Cytochrom e reductas NADP Uses only Photosystem I & complex e H Pc produces ATP (called cyclic photophosphorylation) Photosystem Photosystem ATP I No NADPH II No NADPH or No oxygen O2 Produces ATP Plant shifts to use the cyclic electron flow when ATP levels drop and NADPH levels rise Non-Cyclic vs Cyclic Photosynthesis Non-Cyclic Photosynthesis Cyclic Photosynthesis (CP): (NCP) Use only PS I formation of ATP & NADPH Only some ATP is produced electrons flow from H2O to PSII No splitting of water to PSI to NADPH Electrons only come from Make O2 from splitting H2O light harvesting complex. Make ATP from H+ gradient  The Calvin Cycle: uses the chemical energy of ATP & NADPH to reduce CO2 to sugar H2O CO2 For every 3 molecules of CO2 Light that enter the cycle, the net output is 1 G3P (3 carbon) NADP+ ADP 2 molecules of G3P are required to make 1 glucose CALVIN LIGHT G3P is monomer for making CYCLE REACTIONS glucose ATP Cycle needs to make 6 turns → NADPH 2 G3P molecules → 1 Glucose Calvin cycle uses 18 ATP & 12NADH to produce 1 Glucose O2 [CH2O] (sugar)  Input 3 CO2, entering one per cycle The Calvin Cycle: 3 Phases Phase 1: Carbon fixation Rubisco 1. Carbon fixation – 3 P P catalyzed by rubisco, 3P P 6 3-Phosphoglycerate P RuBP 6 ATP the most abundant 6 ADP enzyme on earth 3 ADP Calvin 3 ATP Cycle 6 P P 1,3-Bisphosphoglycerate 2. Reduction – 6 NADPH Phase 3: formation of G3P, or Regeneration 6 NADP+ 6 Pi glyceraldehyde 3 of RuBP G3P 5 P 6 P G3P Phase 2: phosphate Reduction 3. Regeneration of the CO2 acceptor **The RuBPCalvin cycle uses 18 ATP and 1 P Glucose & G3P other organic 12 NADH to produce 1 Glucose Output compounds  Photorespiration Consumes O2 and organic sugars, releases CO2 without making any ATP or sugar Allows plants to reduce buildup of O2 without opening their stomata Rubisco adds more oxygen to RuBP as temperature rises. Plants cannot undergo photosynthesis efficiently in C4 Plants – minimize photorespiration costs hot, dry areas. by making CO2 into four-carbon Photorespiration can drain up to 50% compounds Examples: Sugarcane plants of a plant’s carbon that was fixed via the Calvin Cycle CAM Plants – takes stored CO2 from the nighttime and undergoes the Calvin Cycle C4 and CAM plants have adaptions during the day (open their stomata at night) that allow them to live in hot and dry Examples: Pineapple plants Ch. 12 & 13 Mitosis and Meiosis  Terminology All the DNA in a cell constitutes the cell’s genome DNA molecules in a cell are packaged into chromosomes Eukaryotic chromosomes consist of chromatin Somatic cells are non-reproductive cells and have two sets of chromosomes Gametes are reproductive cells (sperm and eggs) and have one set of chromosomes A karyotype is an image that reveals an orderly arrangement of chromosomes Homologous chromosomes are matching pairs of chromosomes that can contain different versions of the same genes (alleles) Human Genome There are 46 total chromosomes in each cell Somatic Cells (non-reproductive) are diploid (2n) because they have 2 sets of chromosomes Therefore, Gametes (reproductive cells) are haploid (n) and have half as many chromosomes as somatic cells Sex chromosomes determine the sex of an individual (called X and Y) Human females have a homologous pair of X chromosomes (XX) Human males have one X and one Y chromosome (XY); Sex in humans is determined by the presence of the Y chromosome The remaining 22 pairs of chromosomes are called autosomes  G1 phase – cells grow and bio synthetic pathways resume Cell Cycle (cellular respiration, replicating organelles, making proteins) The cell cycle consists of: S phase – genetic information is duplicated (homologous Mitotic (M) phase (mitosis chromosomes duplicate) & cytokinesis) G2 phase – cell grows; G2 Interphase Checkpoint – cell cycle stops Interphase (about 90% of until MPF (promoting factor) is released to trigger the passage the cell cycle) can be divided of the cell into the M phase into sub-phases G1 phase (“first gap”) S S phase (“synthesis”) (DNA synthesis) G2 phase (“second gap”) s e si k in s G1 to G2 si y ito C (MM) ITOT M PHAIC SE Cell Death and Growth Controlled v. Uncontrolled Cell Death Growth – Cancer Cells Necrosis - Anchorage dependence: cells Low oxygen must attach to a surface to Random fragmentation survive, grow, and divide inflammation Density-dependent: cells grow to a limited density and can no Apoptosis (programmed longer grow cell death) - Cancer cells do not need growth No inflammation factors to grow and divide Chromatin condensation, because they make their own; they do not respond normally to membrane blabbing, the body’s control mechanisms single cell death Cancer cells do not exhibit neither type of regulation for cell division  Mitosis Part of the cell cycle when replicated chromosomes are separated into two new nuclei Results in two daughter cells that are identical to each other and have the same genetic information Used in multicellular organisms for: Development from a fertilized egg – once the egg is fertilized, the cells divides multiple times to accumulate cells that will differentiate into different parts of the body Growth – your body grows as new cells are formed; as mitosis occurs, cell count increases by one because one parent makes two daughter cells Repair – if something becomes damaged inside of the body, cells rush to the area and begin dividing to create new cells to  Centromere = part of Made of microtubules that control chromosomes that helps the cell chromosome movement in mitosis divide during division G2 of Interphase Prophase Prometaphase Centrosomes Chromosomes Early mitotic Fragments Nonkinetochore (with centriole (duplicated, Aster of nuclear spindle microtubules pairs) uncondensed) Centromere envelope Plasma Nucleolus Two sister chromatids Kinetochore Kinetochore Nuclear membrane of one chromosome microtubule envelope Nuclear membranes Chromosomes condense Chromosomes duplicate break apart and become visible Spindles interact with Spindles form the chromosomes  Metaphase Anaphase Telophase and Cytokinesis Metaphase Cleavage Nucleolus plate furrow forming Daughter chromosomes Nuclear Spindle Centrosome at envelope one spindle pole forming Chromosome copies align in Chromosomes separate and Nuclear membranes from the middle of the spindles move to the opposite end of the around each of the sets of cell chromosomes Spindles break down Meiosis Chromosomes duplicated during Interphase The sister chromatids become closely associated by their lengths, called sister chromatid cohesion (sister chromatids are held together by proteins called cohesions) The chromatids are  MEIOSIS I: Separates MEIOSIS II: Separates homologous chromosomes sister chromatids Telophase I Telophase II Prophase I Metaphase I Anaphase I and Prophase II Metaphase II Anaphase II and Cytokinesis Cytokinesis Centrosome Centromere (with (with centriole kineto- Sister pair) chore) chromatids Sister remain chroma- Chiasmata Meta- attached tids phase Spindle plate Sister Haploid chromatids daughter Homologous Cleavage separate cells Homo- chromo- furrow forming logous somes chromo- separate somes Fragments of nuclear Microtubules envelope attached to kinetochore Mitosis End products of mitosis is two 2n (diploid) cells Meiosis End products of meiosis is four n (haploid) cells  Nondisjunction: members of a chromosome pair fail to separate at anaphase, producing gametes with an incorrect number of chromosomes NONDISJUNCTION IN MEIOSIS I NONDISJUNCTION IN MEIOSIS II Abnormal Meiosis I egg Homologous cell with chromosomes fail extra n+1 to separate. chromoso me Meiosis II Extra Sister chromatids Normal fail to sperm separate. cell Gametes Abnormal n (normal) zygote with extra n+1 n+1 n–1 n–1 n+1 n–1 n n chromosome 2n + 1 Abnormal Abnormal Normal Aneuploids =  Difference between Mitosis and Meiosis Mitosis (deals with non-reproductive or somatic cells) Each cell (n) has one copy of each chromosome, and then they duplicate during the S phase during the cell cycle, and make sister chromatids Each cell is created genetically identical to the parent cell Crossing over does not occur One diploid (2n) makes two new diploid (2n) cells Meiosis (deals with reproductive cells or gametes) Each cell (2n) has two copies of each chromosome, and then they duplicate during the S phase, and each make sister chromatids Cells are genetically different from each other and parent cells Crossing over occurs in Prophase I Cells divide twice The number of chromosome sets is reduced from two diploid (2n) to Crossing Over During Prophase I After interphase, the sister chromatids are held together by cohesions, called sister chromatid cohesion The non-sister chromatids are broken at precisely corresponding positions A zipper-like structure called the synaptonemal complex holds the homologs tightly together DNA breaks are repaired, joining DNA from one non- sister chromatid to the corresponding segment of Genetic Variation = the difference in DNA sequences between individuals within a population, which results in different alleles of genes Crossing Over – produces Natural Selection – results in recombinant chromosomes the accumulation of genetic (recombination and exchange of variations better adapted to genetic material between the environment; better paternal/maternal chromosomes) competition, survival, and Contributes to genetic reproduction variation by combining DNA Mutations – changes in an from two parents into a single organism’s DNA chromosome Occurs when: errors during DNA Independent Assortment of replication, exposure to environmental factors, instability Chromosomes – each pair of of purines and pyrimidine bases chromosomes sorts maternal and In humans, there is an average of paternal homologs into daughter 64 new mutations per generation cells independently of the other pairs Random Fertilization – adds to Ch. 14 Genetics Terms -  Genetics: the study of heredity Heredity: the transmission of traits from one generation to the next  Gregor Mendel: studied the inheritance patterns in pea plants  - he first recognized there are certain traits which are passed on to descendants  Phenotype: physical appearance (ex. Hair color, height, etc.) Genotype: genetic makeup (ex. RR, Rr, rr)  Phenotype and genotype do not always match!!  P Generation: parental generation  F1 Generation: hybrid offspring of the parental generation  F2 Generation: offspring of a cross between two F1 plants  Genetics: the scientific study of heredity Gregor Mendel- Studied Dominant Recessive Dominant Recessive Flower Pod shape inheritance patterns in pea color Purple White Inflated Constricted Pod plants Flower position color Green Yellow Crossing different plants to see Stem length what the offspring produced Seed Axial Terminal flower color, flower position, Yellow Green color Tall Dwarf Seed seed color, seed shape, pod shape Round Wrinkled shape, pod color and stem length. Monohybrid Cross: cross between purebred parent plants that differ in only 1 character/trait - Hybrids are the offspring of two P Generation Genetic makeup (alleles) different purebred varieties Purple flowers White flowers F2 Generation Sperm from Alleles PP pp (hybrids) F1 plant carried P p by parents All P All p Gametes P Eggs from PP Pp F1 plant F1 Generation p (hybrids) Pp pp Purple flowers Alleles All Pp Genotypic ratio Phenotypic ratio segregate 1 1 p 1 PP : 2 Pp : 1 pp 3 purple : 1 white Gametes 2 P 2 Phenotype- physical appearance Genotype- genetic makeup  If we know the parent’s genotypes, then we can figure out the probability of a child inheriting a P Generation Genetic makeup (alleles) certain trait Parental (P) – PP (purple) x pp (white) - F1 – all offspring are Pp (purple) Purple flowers White flowers Alleles PP pp Self-fertilization of F1 carried - Pp (purple) x Pp (purple) by parents F2 Genotypic Ratio – 1 PP (purple): 2 Pp (purple): All P All p Gametes 1 pp (white) F2 Phenotypic ratio – 3 Purple: 1 White There is a 75% chance of getting a purple flower in the F1 Generation F2 and a 25% chance of getting a white flower in F2. (hybrids) Purple flowers The result of this mono hybrid cross proved the Law of Alleles All Pp Segregation! segregate During gamete formation, the allele of each gene 1 1 p Gametes 2 P 2 segregate from each other so that each gamete carries only 1 allele for each gene When fertilization occurs the new organism will have two copies of each trait, one from each parent Punnett Square Example 1. Mate the parental generation RR (red) x rr (white) Potential Outcome: all red flowers (Rr) 2. Self the F1 cross Rr (red) x Rr (red) ¾ red flowers: ¼ white flower 1 RR: 2 Rr: 1 rr  Dihybrid Cross – Cross between two traits  P generation: RRYY Dihybrid crosses proved the (yellow, round) x rryy Law of independent (green, wrinkled) Assortment.  F1 Generation: All Genes for different traits can RRYY (all yellow and segregate independently of round) the other genes during the formation of gametes  Self Fertilization of F1 - If there was no independent — RrYy x RrYy (yellow assortment, we would see all of and round) the yellow peas as rounded  F2 Phenotypic Ratio and all of the green peas as — 9 round yellow, 3 wrinkled. round green, 3 wrinkled yellow, 1 wrinkled green  (a) Hypothesis: (b) Hypothesis: Dependent assortment Independent assortment P Generation RRYY rryy RRYY rryy Gametes RY ry Gametes RY ry F1 Generation RrYy RrYy F2 Generation Sperm 1 1 1 1 4 RY 4 rY 4 Ry 4 ry Sperm 1 1 1 2 RY 2 ry 4 RY RRYY RrYY RRYy RrYy 1 2 RY 1 4 rY Eggs RrYY rrYY RrYy rrYy 9 Yellow Eggs 1 ry 16 round 2 1 Ry 4 RRYy RrYy RRyy Rryy 3 Green 16 round 1 4 ry 3 Yellow Predicted results RrYy rrYy Rryy rryy 16 wrinkled (not actually seen) Actual results 1 Green (support hypothesis) 16 wrinkled 36  Dominance Incomplete Dominance Codominance F1 offspring have a DIFFERENT F1 offspring gets a phenotype phenotype from the two parents that shows both of the parents’ traits. Red (RR) flower x White (rr) Red (RR) flower x White (WW) flower flower F1 Pink flowers F1 Red and White spotted flower  Pleiotropy and Polygenic Inheritance Pleiotropy: One gene affects multiple traits. If there is a mutation in the gene Pleiotropy Multiple that controls sickle cell, it also causes Single traits gene (e.g., sickle- many other issues cell Ex: Sickle-cell disease) Mutation: Beta-globin mutation (a single gene) Polygenic Effect: sickle shaped blood cells, inheritance which leads Polygenic to Inheritance: The Single trait Organ additive failure effects of many genes onto (e.g., height) one trait. paralysis Often there are TONS of Multiple genes that give a tiny effect to one genes trait (ex. Height, skin color, eye color, Other phenotype affecters Multiple Alleles: There are more than two alleles of a gene present in a population, but each person can only have two of these alleles. This is an example of Codominance. Blood groups Three potential alleles: A, B, and O Possibilities: AA, BB, AB, AO, BO, OO O is recessive. Environment: The environment can influence many human characteristics Diet, Climate, Illness, Stress Linkage: Genes that are located close to one another on a chromosome are usually inherited together (in autosomal) Sex Chromosome genes Sex Linkage: A gene located on a sex chromosome (usually the X). Usually (but not always) recessive Females need two copies to get the recessive disease (one on each X). Males only have one X chromosome (Expressed more frequently in males than females) Ex. Color blindness, hemophilia, muscular dystrophy Sex-Influenced: A gene located on an autosomal chromosome that are influenced by sex. A male needs one copy to express the trait, but females need both recessive copies to show the same trait. Male Pattern Baldness  Sex Linked Punnett Square Affected Male X Unaffected Affected Male X Carrier Female Female X X Y Y n n XN= Normal X X X N XN X X N n Y N Xn= Affected X X X NX XN X Y= Normal Y N n Y n Outcomes Males: All normal Females: All are carriers  Sex Linked Punnett Square Affected Male X Unaffected Affected Male X Carrier Female Female X X Y Y n n XN= Normal X X X N XN X X X N XN X N n Y N n Y Xn= Affected X X X NX XN X Xn X Xn Y= Normal Y N n Y n n Y Outcomes Outcomes Males: All normal Males: 1/2 unaffected: 1/2 Females: All are carriers affected Females: 1/2 carriers: 1/2 affected Test Cross = crossing an individual of an unknown genotype to an individual of a homozygous recessive genotype Ex. Unknown genotype of black dog. Only needs one dominant allele in order to be black. Can be BB or Bb, so we perform a test cross. B_ x bb BB x bb Bb (black) Bb x bb Bb (black) or bb (brown) Lethal Recessive/Dominant Lethal Recessive – must be Lethal Dominant – can be homozygous dominant or homozygous recessive in heterozygous to get the order to get the disease disease (example – RR, (example – rr) Rr) Most human genetic disorders Only need one dominant are recessive allele to get the disease People who are heterozygous Lethal dominant is much are known as carriers, and do more rare than lethal not have the disease recessive disease If two carriers mate, they There are no carriers (you have a 25% chance of passing the disease onto their child (if either have it or you don’t) autosomal) Examples: Huntington’s, Examples: Cystic Fibrosis, Tay Marfan’s Syndrome, Sachs, Sickle-Cell Progeria Questions??? Makeup quiz – email answers to [email protected] Once you take the quiz, you are free to go!!