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Biology 1001A
Tom Haffie

*No lab reports in first year Bio *Spend 6-10 hours per week on Bio *Labs/tutorials start week of Sept. 19 *Look up Synthia *Homework quiz 24 hours before each class – ends when class begins *Doc called Outcomes posted on WebCT – what you are expected to know Cell Biology Group ON Oil & Water Don’t Mix - What is the structure of water?  Water is polar, molecules attract - What is the structure of oil?  Oil is a non-polar hydrocarbon, insoluble in water - What is more electronegative, carbon or hydrogen?  Carbon - How does EN affect bonding between molecules?  Molecules with higher EN will be more closely attracted to each other - How does H bonding result in the separation of oil and water mixtures?  Water undergoes very strong H bonding - Why doesn’t mayo separate when it is made from canola oil and water?  Look at the third major ingredient (eggs) – they contain molecules that are amphiphilic (have both hydrophobic and hydrophilic regions)  Eggs provide phospholipids, which contain polar and non-polar parts  Phospholipids stabilize the structure  Phospholipids assemble into bilayer when added to an aqueous liquid – hydrophobic fatty acids aggregate while polar head groups associate with water  Mayo and the origin of life – membranes are formed by phospholipid bilayers, which contain both hydrophobic and hydrophilic portions Membranes  Comparing Types of Membrane Transport – pg. 102 Table 5.1 - By acting as a selectively permeable barrier, the plasma membrane allows for nutrient uptake and waste elimination while maintaining a protected environment in which metabolic processes can occur - “Fluid mosaic model” – says membrane is fluid and asymmetrical - Small, uncharged, polar molecules and hydrophobic molecules (Oxygen, Nitrogen, Carbon dioxide) cross membranes easily through passive transport without expending energy – simple diffusion and facilitated diffusion - Diffusion is driven by an increase in entropy (high concentration  low concentration) - Entropy is at its maximum when equilibrium is reached - Rate of diffusion increases with the size of the gradient – even when the concentration is equal, molecules/ions move constantly from one side to the other = dynamic equilibrium - Water crosses membranes through osmosis – if a cell is in a hypotonic solution, water will enter and cause swelling; if a cell is in a hypertonic solution, it must constantly expend energy to make up for water lost by osmosis - In most cases, cells exist in isotonic atmospheres and try to maintain this state by constantly pumping Na ions from the inside to the outside - Because the membrane is impermeable to charged molecules or simply because of their large size, ions, proteins, large molecules (glucose) are transported across membranes by wither facilitated diffusion (powered by concentration gradient) or active transport (against concentration gradient, requires energy) through specific protein channels - Primary active transport – same protein transports AND creates energy to fuel the transport of positively charged ions - Secondary active transport – concentration gradient of ions built up by primary transport fuels transport of ions and organic molecules (symport and antiport) - Eukaryotic cells import and export larger molecules by endocytosis and exocytosis - Endocytosis imports proteins, larger molecules, and whole cells into the cytoplasm by means of endocytic vesicles (pinching off of a plasma membrane bulge) – includes pinocytosis and phagocytosis - Exocytosis exports secretory proteins and waste materials to the cell’s exterior by means of secretory vesicles - Combined workings of endocytosis and exocytosis constantly cycle membrane segments between the internal cytoplasm and the cell surface, a balance that maintains the surface area of the plasma membrane - Membrane structure is very complex - Unsaturated hydrocarbons are fluid at room temperature because of their kinks and bends (ie. phospholipid bilayer of the membrane) - Phospholipids are amphiphilic and consist of 2 nonpolar fatty acid chains linked to several types of alcohols or amino acids by a polar phosphate group - Membranes must be kept in a fluid state so they do not become too stiff (viscous) or too fluid (liquid) – at normal temperatures, fluid state is a combination of saturated and unsaturated hydrocarbon fatty acids - If the temperature is too low permeability will be inhibited; if it s too high, there will be membrane leakage and an imbalance of ions - Fluidity of membrane must be maintained at lower temperatures – need an increase double bonds to create more kinks – desaturase enzyme activity increases and converts saturated hydrocarbons into unsaturated hydrocarbons – as temperature decreases, the number of desaturases increases; sterols can also increase fluidity by disrupting fatty acids from associating at low temps. - Fluidity of membrane must also be maintained at higher temperatures – sterols restrict movement of lipids at high temps. Bacteria, Archaea, and Eukarya  Prokaryotic Cell Structure – pg. 33 Fig. 2.15  Eukaryotic Cell Structure – pg. 35 Fig. 2.18 - Cell Theory 1. All organisms are composed of one or more cells – even unicellular prokaryotes are capable of carrying out all life activities; in multicellular organisms, cells specialize for different activities but individual cells can still survive if isolated 2. The cell is the smallest unit that has the properties of life 3. Cells arise only from the growth and division of preexisting cells - Diversity of Cells – every living thing is composed of cells; cells are the fundamental units of life - Bacteria and archaea are prokaryotic (have no membrane-bound organelles) - Archaea are found in extreme conditions - Eukarya are eukaryotic (have a membrane-bound nucleus) - Bacteria, Archaea, and Eukarya have a common ancestor - Chemical origins of life – Earth forms  Prokaryotes  Increase in atmospheric oxygen  Eukaryotes  Animals  Land plants  Extinction of dinosaurs  Humans - This process occurred over ~ 4.6 billion years - Protobionts were the first cells to develop – abiotically produced organic molecules that are surrounded by a membrane-like structure - Membrane allowed internal environment to evolve that was different from the external environment – internal molecules could become more concentrated and attain more order - DNA and proteins evolved from RNA molecules and are able to do the respective jobs of info storage and catalysis much better than RNA does itself - Proteins are more versatile and diverse than RNA molecules; they are the dominant structural and functional molecules in the cell - DNA is also much more complex than RNA – nucleotides may have been produced by the random removal of oxygen from the ribose in RNA which, at some point, paired with RNA molecules and assembled into complementary copies - DNA is much more stable because it contains deoxyribose, can be repaired, and has a complementary strand to fix damaged strand in case of mutation - Reactions to harness energy and early ETCs eventually developed and ATP became the primary source of energy for cells - Prokaryotes have properties of life common to all cells - Plasma membrane surrounding a cytoplasm that is composed of cytosol containing organelles - Plasma membrane containing protein complexes that allow controlled transport of material into and out of cells - ETCs to synthesize ATP are similar to the energy transduction machinery of eukaryotes - DNA organized into chromosomes - DNA localized in central region - Transcription and translation that rely on ribosomes for the synthesis of proteins from an RNA template - Prokaryotes display remarkable diversity, even though they are 10x smaller than eukaryotes and have no internal membrane organization - Metabolic flexibility – ability to use a variety of substances as energy and carbon sources and to synthesize almost all their required organic molecules from inorganic materials - Biochemical versatility - Live successfully in extreme regions and vastly outnumber all other types of organisms - Evolution of oxygenic photosynthesis resulted in an explosion of life – led to the evolution of proks that can undergo aerobic respiration and then to euks - Endomembrane system of euks (nuclear envelope, the ER, and the Golgi complex) is derived from the plasma membrane - Nuclear envelope – movement of proteins and RNA into and out of the nucleus - ER and Golgi complex – protein synthesis and transport, lipid synthesis, detox processes - Theory of endosymbiosis suggests that mitochondria and chloroplasts are descendants of free-living prokaryotic cells that were engulfed by larger prokaryotic cells, formed a symbiosis, and eventually became the same organism - Ancestral eukaryotes acquired aerobic prokaryotes - Ancestral plants acquired photosynthetic prokaryotes (ex. cyanobacteria) - Mitochondria and chloroplasts are similar to prokaryotes in their morphology, reproduction (both must be derived from preexisting ones and divide by binary fission), genetic information (contain their own set of DNA), the processes of transcription and translation (able to synthesize the proteins encoded by their DNA), and ETCs to generate energy in the form of ATP Eukaryotic Animal Cell Eukaryotic Plant Cell - Eukaryotes are distinguished from proks because they: - Are larger – surface area of a cell must be able to supply its volume with the necessary metabolic requirements - Are internally compartmentalized – membrane-bound compartments have specialized functions - Have DNA separated from the cytoplasm by a nuclear envelope - Have highly specialized motor proteins that move cells and internal cell parts - Have rod-shaped chromosomes, while proks have circular chromosomes The Cytoskeleton - Important in cell division because it supports and moves cell structures - Contains 3 major types of structural elements 1. Microtubules – microscopic hollow tubes composed of tubulin 2. Intermediate Filaments – fibres composed of keratin that occur in parallel bundles and interconnected networks 3. Microfilaments – thin fibres consisting of 2 rows of actin subunits wound in a spiral - Animals have all 3 types; plants only have microtubules and microfilaments - Eukaryotic cell movements - One end of a motor protein is firmly fixed and the other “walks” along microtubules or microfilaments in swiveling motion using energy from ATP - Microtubules and their motor proteins produce the whipping motions of sperm tails - Microfilaments are responsible for amoeboid motion, cytoplasmic streaming, and muscle contraction - In cell division, chromosomes divide by microtubules and cytoplasm divides by microfilaments Synthia - Species of microplasma - Venter and his research group synthesized the entire genome of one bacterial Synthia and put it into another (different species of microplasma) - Named “synthetic life” – only synthetic part was DNA - First cell in history that didn’t have another cell as a parent Group On Dividing Synthia - What organelles are in prokaryotic cells?  Chromosomes, membrane, ribosomes - What are they made of?  DNA, fatty acids, phospholipids, protein, RNA - Where does this material come from?  Biochemical reactions, other ribosomes - Venter put DNA into cell that already had ribosomes (didn’t synthesize ribosomes) - Ribosomal RNA and every kind of RNA comes from transcription DNA Replication  DNA Replication Process – pg. 284 Fig. 3.12 - Explained by complementary base pairing - DNA has a double helical structure with 2 antiparallel backbones - DNA replication is semiconservative - Proposed by Watson and Crick and determined by Meselson and Stahl - H bonds between strands break - Helicase unwinds DNA to expose template strands in a Y-shaped replication fork - Strands are kept apart by SSBs - Each strand acts as a template for the synthesis of its partner strand - RNA primers (assembled by primase) provide the starting point for DNA polymerase - 2 double helices are produced – each has one parental strand and one newly synthesized strand - Double helices have identical base-pair sequence as parent - DNA polymerases are the primary enzymes of DNA replication – assemble nucleotides into complementary chains - DNA polymerases can add a nucleotide only to the 3’ end of an existing nucleotide chain - All complementary base pairing is antiparallel - DNA is assembles in the 5’  3’ direction (template strand read in the 3’  5’ direction) - Replication forks replicate one strand continuously, one discontinuously - Only one template strand runs in a direction that allows continuous replication in the direction of unwinding - DNA strand synthesized in opposite direction to unwinding is made discontinuously in Okazaki fragments that are later linked covalently by DNA ligase - DNA synthesis is bidirectional - Replication bubble arises from two forks created at one origin - Replication proceeds on both sides on the origin - Direction of leading/lagging strand depends on the fork (there are leading and lagging strands on the top and the bottom of the bubble) - Distinct 3’ and 5’ ends confer “polarity” on DNA backbones - 3’ end has free hydroxyl, 5’ end has free phosphate Cell Division and Cell Cycles Inheritance of Sameness - Sameness – daughter cells the same as parent cells - Organelle replication and partitioning - Stable double helix - Base pairing – replication process of DNA (daughter cells get the same genome as parents) - Checkpoints in cell cycles - Cytoskeleton Bacterial Cell Cycle Bacterial Cell Division Stem Cells - Self-renewing population - Progeny are progressively more differentiated - Controversial and promising research - Ex. Haematopoietic stem cells – give rise to all mature blood cells - Humans have 3 billion base pairs vs. Synthia at ~ 4000 - Stem cells in eukaryotes must replicate 3 billion base pairs - ** Large, linear, euk chromosomes have multiple replication origins that are fired simultaneously - Chromosome number varies depending on genome of specific organism – just because an animal is more complex does not mean it has more chromosomes Cell – Nucleus – Chromosome – DNA - Cell division, nuclear division, chromosome division, DNA replication - Pull ideas together Replicated Chromosome - When somatic cells replicate, number of chromosomes in the cell does not increase ONE Chromosome TWO Chromatids Checkpoints of the Cell Cycle - Most cells most of the time are not in the cycle (0n G carrying out their specific functions) - Checkpoint btwn G 1nd S (G c1eckpoint) – is there any DNA damage? - Checkpoint btwn G 2nd Prophase (G ch2ckpoint) – is the cell ready to go through mitosis and divide? - Checkpoint btwn Metaphase and Anaphase – cells will not proceed beyond metaphase until all chromosomes are attached to the microtubule - Checkpoints are there to ensure daughter cell is properly/identically replicated - Cells can come out of 0 and re-enter the cell cycle (ex. wart) - Cancer cells do not leave 0 Mitosis PROPHASE - DNA (in the form of chromatin) begins to condense into visible, rod-shaped chromosomes PROMETAPHASE - Nuclear membrane dissolves and spindle enters the former nuclear area - Microtubules invade fragmented nucleus - Sister chromatids of each chromosome make connections to opposite spindle poles - Each chromatid has a kinetochore that attaches to spindle microtubules METAPHASE - Chromosomes, moved by the spindle microtubules, align at metaphase plate ANAPHASE - 2 chromatids are pulled apart by spindle and moved to opposite poles - Kinetochores of chromatids are pulled by motor proteins toward pole along microtubule TELOPHASE AND CYTOKINESIS - Microfilaments and spindles are active - More are present spindles than chromosomes; spindles from opposite poles find each other and push against each other, pushing poles apart - Cells are pushed apart with chromosomes in opposite cells - Chromosomes decondense and return to extended interphase state - Nuclear envelop reforms - Cytokinesis, the division of the cytoplasm, produces 2 daughter cells - Cytoskeleton plays a very important role in ensuring that all of the chromosomes get into the daughter cells Group On Purpose of Actively Cycling Cells - When/where are cells actively cycling in you?  Reproductive organs – testicles (gamete production)  Bone marrow – active stem cells (tissue replacement)  Damaged areas that need to be regenerated  Stomach lining  Skin  Areas of growth and development (esp. childhood) - When/where are cells actively cycling in a tree?  Meristem tissue  Root tips, shoot/stem tips (up and down growth)  Under the bark (outward growth) - Most cells most of the time are in 0 -When/where might cells be programmed to die (apoptosis)?  Infected by a virus  Grotesque mutation (ex. UV damage)  White blood cells (die after removing something from the blood system)  When there are too many (tail and webbed feet lost from embryo before birth)  When their function is as a dead cell (xylem cells in a tree) Prokaryotic Recombination Importance of the Inheritance of Difference - Genetic recombination allows “jumping genes” to move, inserts some viruses into their host chromosomes, underlies the spread of bacterial antibiotic resistance, and lies at the heart of eukaryotic meiosis - Rare mutations may change DNA sequence of a gene, giving it a new allele - Inheritance of sameness ensures that the same basic organism is being reproduced; in reality, DNA is not exactly the same - Mutations are not bad, they are essential - Genetic diversity results from mutation – increases likelihood of survival - If DNA replication were 100% accurate and there was no recombination, all offspring would be identical clones of their parent and there would be no diversity for evolution to work on - Sectored colonies arise when daughter cells are different - Synthia was the first organism whose genome was a product of the human mind Lederberg Experiment - Proved bacteria could engage in inheritance of difference - Used 2 multiple-mutant strains of auxotrophic bacteria Strain 1: bio met leu thr thi + + + - - - Strain 2: bio met leu thr thi - Both strains could not grow separately on minimal medium - When put together, several hundred colonies grew even though none of the original cells carried the allele needed for growth; recombination produced prototrophic cells (genetically different from either parent strain) - Bacteria have a kind of sexuality in their reproduction process - Sexuality is recombination, not reproduction F plasmid transfers from F+ donor to F- recipient cells - Bacterial conjugation brings DNA into close proximity - Each cell has a single, circular chromosome - Instead of fusing, bacterial cells conjugate – contact each other through a long, tubular sex pilus and form a cytoplasmic bridge through which a copy of DNA moves into the other cell - Once DNA enters, genetic recombination can occur and a prokaryotic kind of recombination is facilitated - Sexuality – DNA coming into close proximity and crossing over to make new combinations of alleles - Recombination enzymes cut and paste both DNA backbones in one recombination event – responsible for exchange of alleles and transfer of bacterial genes - Plasmid – small, circle of DNA - F factor (fertility plasmid) carries genes that code for its own replication and transfer into a recipient cell, as well as genes encoding the sex pilus proteins - F plasmid transfers itself from donor to recipient during conjugation or down generations during the usual process of cell division - F factor replicates using “rolling circle” replication – a single strand moves through the cytoplasmic bridge into the recipient and the remaining strand rolls like a spool while DNA synthesis fills in complementary bases in both donor and recipient cells - Recipient cells become F+, but no chromosomal DNA is transferred between cells – genetic recombination has not yet occurred - Sometimes F factor comes into close proximity with the host, lines up in a short region of homology, and undergoes a recombination event - F factor is now integrated in chromosome of host and host is now called Hfr cell (high frequency of recombination) - F factor can bring chromosomal genes from the donor into the recipient – uses the conjugation mechanism by which DNA from one parent is brought into close proximity with DNA from another parent - Sets up possibility for recombination and for DNA of 2 parents to be exchanged - Conjugation bridge usually breaks before the entire donor chromosome is transferred Transformation and Transduction  Transduction pg. 207 Fig. 10.7 - Other ways that DNA can transfer from one bacterial cell to another - Like conjugation, these mechanisms transfer DNA in one direction and create partial diploids in which recombination can occur between alleles in homologous DNA regions - Enable recipient cells to recombine with DNA obtained from dead donors - Transformation – bacteria take up pieces of DNA that are released into the environment as cells disintegrate - Linear DNA fragments taken up from virulent cells recombine with the chromosomal DNA of virulent cells – recombination introduces allele for capsule formation into nonvirulent cells, making the cell and all of its descendants virulent - Transduction – DNA transferred from donor to recipient inside the head of an infecting bacterial virus/bacteriophage - New phages assemble in an infected bacterial cell and fragments of host DNA are sometimes incorporated with the viral DNA - When the host is killed, released phages may attach to another cell and inject bacterial DNA rather than infective viral DNA Transposition - Transposons can send a copy of themselves onto a plasmid (“jumping genes”) - Transposons can replicate and recombine to send a copy into target sequence through transposition - Plasmids can carry resistance genes (in transposons) to recipient cells (ex. bacterial antibiotic resistance) Inheritance of Difference in Bacteria through 4 Mechanisms - Mutation and binary fission - Conjugation - Transformation - Transduction - Transposition Eukaryotic Recombination - Purpose of eukaryotes in life is to bring parental DNA into close proximity as a zygote and later provide this parental DNA - Genetic recombination in meiosis allows for diverse populations - Sexual reproduction is dependent on meiosis - Meiosis – specialized process of DNA division that recombines DNA and produces cells with half the number of chromosomes in somatic cells – meiosis changes chromosome number and DNA sequence - At fertilization, egg and sperm cells fuse to produce a zygote cell – without halving the number of chromosomes, fertilization would double the number of chromosomes each generation - Homologous chromosomes carry the same genes, but different alleles - Different alleles of a gene have similar but distinct DNA sequences – encode variations of given RNA and protein gene product - Humans have 23 pairs of sister chromatids – one chromatid of pair maternal, other paternal - Homology allows different DNA molecules to line up and recombine precisely - Cutting and pasting 4 DNA backbones results in one recombination event - Each cell produced by meiosis carries only one member of each homologous pair – meiosis produces 4 genetically different daughter cells Meiosis  Meiosis vs. Mitosis pg. 219 Fig. 10.13 - Meiosis I – synapsis takes place (homologues find their chromosomes and pair lengthwise), recombination occurs during this intimate pairing, members of each pair are separated into one of two daughter cells, each with half the number of chromosomes (still 2 sister chromatids) - Chromosome number is reduced from diploid (2n) to haploid (n) - Meiosis II – sister chromatids are separated into different cells with haploid number of chromosomes and a novel collection of alleles - Cells divide to give products with “1C” amount of DNA - Chromosome number doesn’t change, amount of DNA is cut in half - C for concentration - Prophase I – homologous chromosomes pair and recombine; point when sexual recombination occurs during meiosis, spindle forms in cytoplasm - Synapsis of tetrads occurs – fully paired homologues consist of 4 sister chromatids - “Crossing over” is recombination – doesn’t only occur between inside chromatids as illustrated in most books, actually occurs along all 4 chromatids in different places - Chromatids exchange segments - Prometaphase I – nuclear envelope breaks down, spindle enters former nuclear area, 2 chromosomes of each pair attach to kinetochore microtubules leading to opposite spindle poles - 2/4 sister chromatids of each homologue to each pole  haploid - Metaphase I and Anaphase I – spindle microtubules align recombined tetrads on the equatorial plane (metaphase plate) between spindle poles and 2 chromosomes of each pair move to each pole - Alignment of one homologous pair is independent of others – independent assortment during metaphase I - Can line up many different ways giving different cells going into meiosis II - Telophase I and Interkinesis – little/no change in the chromosomes, some species develop new nuclear envelope, spindle area disassembles and microtubules reassemble into 2 new spindles - Prophase II, Prometaphase II, and Metaphase II – occurs in reproductive tissue, chromosomes condense and spindle forms, nuclear envelope breaks down, spindle enters former nuclear area, spindle microtubules attach to kinetochore, chromosomes come to rest on the metaphase plate - Anaphase II and Telophase II – sister chromatids move to opposite spindle poles, chromatids decondense to the extended interphase state, spindles disassemble, nuclear envelope forms around chromatin - Women undergo first part of meiosis (recombination) as a fetus before they are born, then go into meiotic arrest until egg matures - Men start meiosis when they are sexually mature - Gametes fuse together randomly to produce a staggering combination of different zygotes - Parents do the recombination that give rise to offspring – organisms do not do their own recombination, instead do the recombination for their offspring Meiosis Occurs at Different Places in Different Organismal Life Cycles - In animal life cycles, the zygote divides by mitosis - Animal life cycle is predominantly spent in the diploid phase and has a reduced haploid phase – animals are only haploids as sperm and eggs - No mitotic divisions occur during the haploid phase - Function of organism is to get parental DNA together and put it in different combinations - Meiosis is followed directly by gamete formation - Plants and fungi alternate between haploid and diploid generations - Either generation can dominate life cycle depending on the organism - Mitotic divisions occur in both phases - Fertilization produces a diploid generation of sporophytes - Not everything that comes from meiosis is gametes – in plants, full-grown sporophytes go through meiosis to produce haploid, reproductive spores, NOT gametes - Spores do not fuse together with other spores, but germinate and divide by mitosis to produce haploid generation of gametophytes - Gametophytes produce gametes by mitosis - Fusion of gametes produces diploid zygote that divides to produce sporophytes again - Sporophyte generation is generally the most visible part of the plant - Although humans spend most of life cycle as diploids, not all organisms are diploid - Some fungi have haploid body cells - Immediately after fertilization, zygote undergoes meiosis to produce haploid phase - 2 haploid gametes fuse to form diploid nucleus, which produces 4 haploid cells through meiosis – cells develop into haploid spores after a few mitotic divisions - Mitotic divisions occur only in haploid phase - Spores germinate to produce haploid gametophytes  mitotic divisions  differentiation into + and – gametes - All gametes are genetically identical Nondisjunction and Misdivision Change the Number of Chromosomes - Nondisjunction results when homologues fail to separate in meiosis I - In meiosis II, they separate normally but give rise to gametes that have unbalanced chromosome count (too many or too few) - One pole receives both chromosomes of a homologous pair - Produces 2 gametes with missing chromosomes and 2 gametes with an extra chromosome - Misdivision occurs when chromatids fail to separate in meiosis II - Both chromatids go to the same pole - Produces 2 normal gametes, one gamete with an extra chromosome, one gamete with a missing chromosome - Fertilization by these gametes produces an individual with extra or missing chromosomes called aneuploids (vs. euploids with a normal set) Other Chromosomal Alterations - Deletion – broken segment is lost from a chromosome - Duplication – segment broken from one chromosome is inserted into its homologue; the alleles in the inserted fragments are added to the ones already present in the receiving homologue - Translocation – broken segment is attached to a different, non-homologous chromosome - Inversion – broken segment reattaches to the same chromosome from which it was lost, but in the reversed orientation, so that the order of genes is reversed - Individuals with an atypical number of chromosomes or a structural abnormality in one or more chromosomes are said to have chromosomal anomalies – seen in aneuploidy, deletion, duplication, translocation, and inversion - Be able to identify from karyotype Inheritance of Difference in Animals through 4 Mechanisms - Genetic recombination - Differing combinations of maternal and paternal chromosomes segregated to poles during Anaphase I - Differing combinations of recombinant and non-recombinant chromatids segregated to poles during Anaphase II - Particular sets of male and female gametes that unite in fertilization Case Study of Mary Jane - Needs new kidneys; testing reveals she cannot be the mother of 2 of her 3 children - Pedigree follows a trait of interest through familial generations; shows normal family relationships for Mary Jane’s relatives - Karyotype uses chromosome painting to identify homologues as different colours; Mary Jane and all her family members are karyotypically normal - Cell nucleus in interphase is very ordered so karyo
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