Intro to Biology: Cells and Macromolecules

Basics of Biology

• Macromolecules are large molecules like proteins, nucleic acids, lipids, and carbohydrates.
• Monosaccharides form polysaccharides (carbohydrates).
• Fatty acids form fats/lipids.
• Amino acids are the building blocks of proteins; there are 20 different amino acids. Some amino acids are hydrophobic, while others are hydrophilic, allowing them to bind and loop.
• Enzymes are proteins that facilitate chemical reactions.
• Prions are proteinaceous infectious agents that trigger other proteins to misfold, causing disease.
• Nucleotides form nucleic acids.

Eukaryotic vs. Prokaryotic Cells

• Eukaryotes are multicellular organisms like plants and animals with a nucleus and membrane-enclosed organelles.
• Organelles are specialized parts of a cell performing unique jobs.
  • Cytoplasm is the part of the cell outside the nucleus but inside the plasma membrane.
  • The endoplasmic reticulum (ER) is the site of protein synthesis (translation), a network of channels and tubes for molecule shuttling.
  • Mitochondria produce and store energy and regulate programmed cell death (apoptosis). Apoptosis is a cell's active suicide program, characterized by DNA fragmentation, nuclear condensation, and shrinkage.
  • The plasma membrane is the outer membrane, separating the cell from its environment, featuring a hydrophobic layer between two hydrophilic layers. Proteins traverse the membrane as receptors or transporters.
  • Hydrophobic substances are water-repelling and not water-soluble, like lipids.
  • Hydrophilic substances are water-loving and soluble in water
• Prokaryotes are single-celled organisms (e.g., bacteria, protists) without a nucleus or membrane-enclosed organelles.

Molecules and Bonding

• A molecule is a structure of covalently bonded atoms (e.g., carbon, hydrogen, sulfur, oxygen).
• A covalent bond is a strong bond between atoms; double bonds are stronger and harder to break.

Cell Cycle

• G1 (Gap 1): The cell grows, carries out normal functions, and prepares for DNA replication.
• S (Synthesis): DNA replicates, resulting in each chromosome consisting of two sister chromatids.
• G2 (Gap 2): The cell continues to grow, producing proteins necessary for cell division and checking for DNA replication errors.
• M (Mitosis): Cell division occurs, chromosomes are separated, and the cell divides into two daughter cells.

Building DNA

• DNA (deoxyribonucleic acid) is a linear, double-stranded polymer composed of deoxyribose nucleotides, carrying genetic information.
• RNA (ribonucleic acid) is a linear, single-stranded polymer composed of ribose nucleotides, synthesized by transcribing DNA or copying RNA.
• Nucleotide: Basic DNA/RNA building blocks consisting of a phosphate group, sugar (deoxyribose/ribose), and nucleic base
• Nucleotides consist of:
  • A phosphate group links with the sugar through covalent bonds, connecting each nucleotide and forming the DNA helix backbone.
  • Deoxyribose sugar is a 5-carbon sugar molecule forming part of the backbone
  • Ribose backbone: Covalently bonded molecules of ribose or 2-deoxyribose that form the backbone of DNA or RNA
  • A nucleoside is a nucleic base plus a sugar that attach via hydroxyl groups (OH).
  • A nucleic base is a nitrogen-containing ring compound with either a purine or pyrimidine base making up the "rungs" of the DNA ladder.
  • Purines (adenine, guanine) bind to pyrimidines (thymine, cytosine) to form base pairs.
• A DNA molecule consists of two DNA strands held together by hydrogen bonds between paired bases. Each strand has two ends (5’ and 3’) with opposite polarity.
• A base pair is the association of two complementary nucleotides between DNA or RNA strands stabilized by hydrogen bonding. G-C has 3 hydrogen bonds, making it stronger than A-T with only 2.

DNA Replication

• DNA replication, facilitated by DNA polymerase, results in a second copy of double-stranded DNA.
• Helicase unwinds and separates the double helix strands by breaking hydrogen bonds between nucleic base pairs, creating a replication fork.
• Primase adds bases for a small section at the beginning of the strand, creating a "primer" to indicate the starting point, then DNA polymerase finishes.
• DNA Polymerase (POL I) adds matching bases only in the 5’ to 3’ direction.
• For the lagging strand, this enzyme works in short bursts (Okazaki fragments), then DNA ligase joins them together. It also has a proofreading function, where another polymerase fills in gaps and checks for misplaced nucleotides.
• DNA clamps are proteins that move down the strand, helping to hold polymerase in place (e.g., sliding clamp).

Nucleosome

• A nucleosome is the basic structural unit of DNA packing and is a section of DNA wrapped around a core of histones.
• Chromatin is a dynamic complex of DNA and proteins that makes up the chromosome. Its shape and tightness facilitate transcription.
• Histones are a group of proteins that DNA coils around to form a nucleosome, specifically histones H2A, H2B, H3, and H4, with two of each in a nucleosome (8 total).

Gene

• A gene is a unit of biological inheritance; a DNA segment on a chromosome contains information to make a protein.
• The gene structure includes exons that code for proteins (coding sequences), introns which are non-coding sequences between exons, and regulatory elements (promoter at the 5’ end; termination region at the 3’ end) that control gene expression level.
• Terminology
  • The gene locus is the gene location on a chromosome.
  • An allele is any of the alternative forms of a gene at a given gene locus.
  • Genotype is the genetic makeup of an organism, which can be determined through genotyping analysis.
  • Phenotype is the visible/measurable characteristics resulting from the interaction of an organism's genotype and the environment.
  • A somatic cell is any cell in the body except germ cells (egg and sperm).
  • Diploid (2N) cells have two copies of each chromosome (somatic cells).
  • Haploid (1N) cells have the same number of chromosomes as a gamete (germ cell), half as many as a somatic cell.
  • An autosomal chromosome is any one of 22 pairs of chromosomes not related to sex.

Retroviruses

• A retrovirus uses RNA (instead of DNA) and inserts its genetic material into a host cell’s DNA using reverse transcriptase to convert RNA into DNA.
• Human Endogenous Retroviruses (HERVs) are ancient viral DNA sequences incorporated into the human genome over millions of years. When retroviruses infected human ancestors (likely germ cells), their genetic material became a permanent part of the host’s DNA instead of being cleared.
• Most HERVs are inactive and don’t cause disease, but some still have functional roles.
• Mobile genetic elements include LINES/SINES, retroviral-like elements, and DNA-only transposons, all components of DNA that have multiplied in our genome by replicating and inserting new copies in different positions.

RNA Transcription

• Transcription converts genetic information from a gene to messenger RNA (mRNA) and occurs in the nucleus.
• The promoter region is a DNA sequence immediately upstream from a gene's start site where RNA polymerase and transcription factors bind to induce transcription, determining its initiation site.
• A transcription factor is a protein that binds to specific genes (based on the gene promoter sequence) and induces or represses gene transcription with other accessory proteins.
• RNA polymerase is the enzyme that facilitates RNA transcription from DNA.
• The enhancer region DNA sequences enhance the transcription of nearby genes by interacting with specific transcription factors, increasing gene expression.
• Messenger RNA (mRNA) is a sequence of RNA generated during transcription complementary to the coding DNA strand, transferring the DNA code into instructions for protein synthesis.
• A stop codon (UAA, UGA, or UAG) tells the RNA polymerase to stop reading the gene.
• Overview:
  • RNA polymerase, with transcription factors, binds to the DNA promoter region.
  • Helicase unwinds DNA, and RNA polymerase adds complementary RNA nucleotides to the DNA template strand, forming mRNA.
  • Enhancer regions can regulate this process, boosting transcription activity.
  • Once transcription is complete, mRNA is processed and leaves the nucleus to be translated into protein. A 5’ methylated cap and a poly-A tail are added to either end of the mRNA, making it easier to leave the nucleus, protect from degradation, and connect with other organelles later in the process. RNA splicing (spliceosome cuts out extra information, becomes exon).
  • Genes can be transcribed with different efficiencies, allowing the amount of protein A to be much greater than that of protein B if gene A is transcribed and translated more efficiently.

Regulation of Gene Expression via Transcription Factors

• Transcription factors regulate gene expression by binding to specific DNA sequences (regulatory elements) within genes, controlling the initiation and rate of transcription.
  • The promoter is where general transcription factors and RNA polymerase assemble.
  • Regulatory sequences are binding sites whose presence on the DNA affects the rate of transcription; they can be located next to the promoter, upstream, or downstream.
  • DNA looping involves transcription factors binding at any position to interact with the proteins that assemble at the promoter.
  • Gene regulatory proteins and binding site locations differ for each gene relative to the promoter.
• E.g., the Aryl Hydrocarbon Receptor (AhR) Signaling Pathway displays high AhR levels in cancer.

Regulation of Gene Expression via Short Interfering RNA (siRNA or RNAi)

• Short interfering RNA (siRNA) are short, double-stranded RNAs that mediate RNAi, silencing specific genes by targeting and degrading their mRNA, preventing protein synthesis. a. Double-stranded RNA molecules (dsRNA) originating from viruses, transposons, or experimentally introduced RNA bind to a protein complex, Dicer. b. Dicer cleaves the dsRNA into smaller fragments. c. One of the RNA strands is loaded into another protein complex, RISC, and links it to a sequence on a target mRNA through base pairing d. mRNA is cleaved and degraded by nucleases.
• Terminology:
  • RNAi is the silencing of gene expression triggered by the presence of double-stranded RNA homologous to portions of a gene, which can degrade or block translation of target mRNA.
  • Dicer is an enzyme that catalyzes the formation of double-stranded RNA (either siRNA or miRNA) that interacts with the RISC complex.
  • RNA-dependent RNA polymerase (RdRP) is an enzyme that synthesizes RNA by copying the viral RNA genome (in contrast to RNA polymerase, which uses DNA as the template), amplifying the signal of siRNAs/miRNAs by producing double-stranded RNA using the products of the Dicer reaction as primers.
  • The RNA-induced silencing complex (RISC) is a ribonucleoprotein complex containing single-stranded guide RNA and an endonuclease (Argonaut), which directs either the cleavage of the mRNA target or the suppression of translation of the mRNA target.

Regulation of Gene Expression via Endogenously Encoded Micro RNA (miRNA/miR)

• MicroRNA (miRNA or mIR) is a short segment of RNA with a complementary sequence to a target mRNA, regulating gene expression by binding to target mRNA molecules, leading to their degradation or inhibiting translation.
• The process.
  • Dicer cuts the pre-miRNA into short, double-stranded RNA fragments in the cytoplasm, one strand is incorporated into the RISC complex.
  • miRNA within the RISC complex binds to complementary sequences on target mRNA to repress translation or degrade mRNA.
• Disease-associated miRNAs can be metastatic, oncogenic, or tumor suppressors.

siRNA vs miRNA

siRNA:

• Exogenous (viruses or experimentally inserted into the cell)
• Double-stranded RNA
• Specific for single mRNA sequence
• mRNA degradation
• Present in lower animals

miRNA:

• Endogenous (DNA encoded)
• Single-stranded RNA with hairpin turn
• Targets several genes
• mRNA degradation and translation inhibition (interferes with ribosomes, blocks reading of mRNA)
• Present in all animals, including humans and plants
• Both use Dicer and the RNA-induced silencing complex (RISC).

Regulation of Gene Expression via Epigenetics

• Protein (histones) or DNA-associated protein modifications.

RNA Translation

• Translation converts genetic information from messenger RNA into protein.
  • tRNA serves as the bridge between nucleic acids and proteins, double-stranded in some places, forming loops due to complementary base bonding.
• Process:
  1. Initiation occurs when a ribosome assembles around mRNA, and the first tRNA binds to the start codon on mRNA.
  2. Elongation: involves the ribosome moving along the mRNA, reading each codon while tRNA molecules bring corresponding amino acids that are added to the growing polypeptide chain; the ribosome shifts and this process repeats for each codon
  3. Termination occurs once the ribosome reaches a stop codon; the ribosome releases the newly synthesized protein, which folds into a functional shape (structure helps determine function).
• Terminology
  • Transfer RNA (tRNA) is a looped segment of RNA that recognizes a specific amino acid on one end and a specific codon on the other.
  • A codon is a sequence of three nucleotides on mRNA, coding for a specific amino acid.
  • An anticodon is the three nucleic base sequence on an external loop of tRNA complementary to the mRNA sequence.
• Mutations can cause a frame shift (genetic mutation caused by the insertion or deletion of nucleotides in a DNA sequence, which shifts the reading frame of the codons, can result in a completely altered and nonfunctional protein) or monogenic disorder (disorders caused by a mutation in a single gene).

Gene Editing with CRISPR/Cas9

• CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9 are molecular tools that modify DNA by directing the Cas9 enzyme to a specific genetic sequence.
• Guide RNA (gRNA) is a short RNA segment designed to match a specific target DNA sequence and directs the Cas9 enzyme to the location for cleavage.
• The Cas9 enzyme is a bacterial enzyme with helicase activity (enables the unzipping of double-stranded DNA, allowing gRNA access) and nuclease activity to snip DNA at specific sequences.
• Process:
  1. Guide RNA (gRNA) directs the Cas9 enzyme to the exact location where editing is needed.
  2. Cas9 enzyme unzips the DNA and cuts it, allowing gRNA to bind to the DNA.
  3. The cell’s natural repair mechanisms then kick in.
• E.g., knocking out the Aryl Hydrocarbon Receptor (AhR), which recognizes environmental chemicals to suppresses the immune system and allows tumors to grow rapidly, tumors completely stop growing when knocked out in mice.

Detecting and Manipulating DNA - Restriction Enzymes

• Restriction enzymes recognize and cut DNA at specific sequences in double-stranded DNA at a restriction site.
• This process allows manipulation and analysis of genetic material (genetic engineering), enable cutting DNA exactly where needed based on sequence knowledge
• This enzymes can create blunt (straight down) or sticky ends (non-straight, base sequences sticking out on either side)
• Serve as Bacterial defense against bacteriophages (viral DNA). Incoming phage DNA is cleaved biochemically cleaved at recognition sites (specific base pair sequence), then degraded into smaller fragments.

DNA Denaturation/Renaturation with Heat

• Denaturation uses heat to break hydrogen bonds and denature DNA (separate into two strands) or proteins which is commonly used in techniques like PCR
• Renaturation occurs when the denatured DNAs are cooled in suitable conditions, then two single strands reconnect to form double helix again

Polymerase Chain Reaction (PCR)

• PCR is a technique used to amplify specific DNA sequences and rapidly produce millions of copies of a targeted region for analysis.
  • A DNA primer is a short sequence that forms base pairs with a complementary template strand functioning as the starting point for nucleotide addition. These primers may come in the form of oligonucleotides (short molecules)
  • Polymerase copies a strand of DNA to make the complementary strand, forming a new double-stranded DNA molecule.
• Molecular process:
  1. Denaturing : A double-stranded DNA sample is heated, separated into two strands
  2. Annealing: Temperature drops so short DNA primers bind to the single stranded DNA at the start/end of the target sequence
  3. Extension: Temp raises so Taq DNA polymerase extends primers and synthesize new strands of DNA complementary to the original strands
• Note: heat-insensitive DNA polymerase is made by hemophilic bacteria.
• The process is repeated for 20-40 cycles, leading to exponential amplification of the target DNA sequence.

RNA Sequencing using Reverse Transcriptase

• This method involves using reverse transcriptase to convert RNA into complementary DNA (cDNA) that can be sequenced.
  • Reverse transcriptase is an enzyme that synthesizes a DNA from an RNA template. It is often found in retroviruses
  • Complementary DNA (cDNA) is DNA molecule copied from an mRNA molecule by reverse transcriptase, so it lacks the introns present in genomic DNA
• Process:
  1. Total RNA is isolated from a sample during RNA extraction .
  2. During reverese transcription, reverse transcriptase binds to RNA and creates a cDNA strand.
  3. After strand synthesis, once first cDNA strand is synthesized, second strand of cDNA is created to form double-stranded molecule, and is done using DNA polymerase and other enzymes
  4. Using amplification and sequencing, the resulting cDNA is amplified (using PCR or other methods) and then sequenced using technologies that determine the exact sequence of nucleotides in the cDNA, providing insight into gene expression
• Semi-Quantitative Reverse Transcription-PCR uses traditional PCR methods (reverse transcription turns RNA into cDNA, then PCR amplifies to estimate the relative amount of a specific mRNA in a sample). The more mRNA present in the cell, the faster the sequence will be amplified, and the fewer rounds of PCR will be required.

Real-Time Quantitative PCR

• Real-time PCR (Quantitative PCR/RT-qPCR) quantitatively measures the amplification of DNA or RNA in real time, providing precise data on the initial amount of mRNA in a sample, and differs from traditional PCR, which only provides a final product at the end of the amplification cycle.
• Process:
  1. Amplification: Target DNA is amplified in each cycle
  2. Fluorescent detection: During amplification, a fluorescent signal is created by adding dye or using sequence-specific probes; emit fluorescence when they bind to DNA
  3. Quantification: fluorescence intensity correlates with amount of DNA present
• It can be used for relative quantification (comparing gene expression between different samples) or absolute quantification (determining exact number of copies of a target gene in the sample). Its how SARS CoV-2 is detected because when fluorescence reaches certain level, the virus is present in sample

Traditional PCR vs RT-qPCR

• How the amplification process is monitored and quantified is the main factor
• Traditional PCR
  • Detection: amplifies target DNA so detection is at end of process
  • Quantification: provides qualitative data
  • Efficiency: Focus is on amplification rather than monitoring DNA quantity throughout process
  • RT-qPCR
  • Detection: monitors amplification process in real-time
  • Quantification: Precise measurement of quantity is available because it measures fluorescence intensity
  • Efficiency: more sensitive, gives accurate measurement of gene expression levels

DNA Extraction based on Hydrophobicity

• Because water and DNA are polar, DNA easily dissolves in water
• Process:
  1. Detergent is used to prepare a solution to break open cell membrane
  2. Precipitate DNA with cation/alcohol solution: add monovalent cations (e.g., sodium acetate) and ethanol (alcohol to facilitate neutralization)
  3. Ethanol causes DNA to clump together into visible strands, that can then be collected
• Monovalent cations help neutralize charge of DNA so that the (+ charged Na associates with – charged phosphates), thus charge reductions reduce solubility
• Ethanol facilitates association between Na and Phos, so when they come together, DNA precipitate out

Bulk DNA/RNA Sequencing

• Method that sequences and analyzes large amounts of DNA or cDNA from a sample to get an overview of the entire genome or transcriptome
  • Genome: total genetic information carried by a cell or organism
  • Genomic DNA (gDNA): Natural DNA produced by all somatic cells
  • Transcriptome: allows you to determine gene activity for all RNA transcripts in a cell/tissue at a given time
  • cDNA Library: collection of all the DNA generated by reverse transcription of mRNA from a sample
• Process:
  1. DNA is extracted from sample
  2. Break DNA into smaller pieces
  3. After DNA fragments are processed fragments by library prep (attaching adapters)
  4. Amplification of DNA fragments to increase quantity
  5. Sequencing Technology is used to read the nucleotide sequence of each fragment
  6. Sequences are analyzed and aligned and aligned to genomes
• This process allows sequencing of large volumes of DNA quickly and efficiently Bulk RNA sequencing involves extracting and converting mRNA to cDNA and the undergoing a similar process.

Restriction Fragment Length Polymorphism (RFLP)

• RFLP detects variations in DNA sequences by analyzing differences in the lengths of DNA fragments produced by restriction enzyme digestion due to mutations.
• Molecular Process:
  1. DNA is isolated from cells
  2. Treat with restriction enzymes that cleave DNA at specific sequences
  3. Electrophoresis uses gels to separate DNA fragments by size
  4. A membrane is used to expose probes that bind to DNA fragments with the target
  5. The pattern of restriction fragment lengths (polymorphisms) is visualized based on the probe's location.
• Electrophoresis: Electrophoresing applies an electric field through a gel to move molecules (DNA, RNA, or proteins) based on sizes/charge
  • Charged molecules go to the opposite charge.
  • Smaller fragments move faster through gel. Separated molecules can be stained with dye and seen under UV light

Applications of DNA-based technologies

• Can do tumor treatment, forensics or suss out potential to aquire a disease

Quantifying Differential Gene Expression (Transcriptomes) using Microarrays

• Differential gene expression (DGE) compares gene activity by measuring how much of each gene's DNA/RNA binds to probes.
• Differentially expressed genes (DEGs) are determined often with bulk RNA/cDNA sequencing.
• Bulk RNA sequencing allow comparison of two cell populations with bulk RNA sequencing vs single cells (single cell RNA sequencing)
• A DNA microarray, which contains 100-1000s of gene probes and used to analyze cell or tissue transcriptomes, allows you to Hybridize DNA or RNA samples to any known gene sequence
• Using the probes (radioactive/flourescent labeled short DNA segments) allows for a read.
• Process to read RNA:
  1. RNA is extracted
  2. cDNA creation w/dye labels.
  3. cDNA application and binding.
  4. Chip Washing/laser scanning to remove unbound cDNA and detect fluorescence
  5. Gene levels based on amount of the fluorescence detected that determines level, up/down regulation by heat map

Single Cell RNA Sequencing

• SIngle Cell RNA-seq(scRNA-seq): Measure mRNA to determine distinct expression profile of a gene at the single cell level
  • Process: isolate cells, extract RNA, convert to cDNA then sequence

FISH

• A probe that uses visualization of fluorescently labeled probes to detect and determine locations of specific DNA/RNA. FISH expression can visualize gene expression

Cloning

• DNA cloning is a technique used to create identical copies of a DNA fragment by inserting it into a cloning vector and then replicating it within a host organism.

• Key aspects:

  • Recombinant DNA (rDNA): DNA molecule made when fragments from two different sources are joined

  • Cloning vector: A DNA molecule, such as a plasmid or virus, used to carry and replicate foreign DNA within a host cell during the process of DNA cloning.

    • Bacteriophage: DNA virus that infects bacteria

    • Plasmid: Small, circular DNA molecules found in bacteria

  • Clone: Group of identical cells that contain the same recombinant DNA molecule

• Process:

  1. Cut target gene/DNA fragment using restriction enzymes
  2. Prepare a plasmid vector: cut with the same enzyme to create sticky ends.
  3. Using DNA ligase (enzyme tht joints DNA together) insert target DNA fragment into plasmid vector
  4. Transfrom Recombinant plasmid into bacterium cells
  5. Select bacteria that are able to do this through anti-biotics.
  6. Bacteria make more after replicates

Transfection

• Experimentally introducing foreign DNA into cells in culture

• Overview:

  1. Prepare genetic material for delivery
  2. Induce them into the cells (chemicals/ electroporation)
  3. Integrate gene into genome
  4. Foreign mateiral is expressed within cells

Transduction

• Introducing new material by introducing vectors in virus. This makes cloned DNA expressionable for for protien (expression vector)

• Transgene: Any gene that is artificially transferred into a cell of interest

• Overview:

  • Transduction: Adenovirus: Direct delivery so it does not intergate into the host genome

  • Transduction Lentivirus: Virus infected host cell into DNA

Transfection vs Transduction

• Transduction is high efficiency while transfection does not intergrate the material.

Gene Therapy

• Virus delivery into the blood stream or cell based delivery outside then in by injection

CAR T cells

• CAR T cells (Chimeric Antigen Receptor T cells): genetically modified T lymphocytes that express a synthetic antigen receptor designed to recognize and target specific proteins on the surface of cancer cells, allowing the immune system to attack tumors

CRISPR-Mediated Gene Knockout in Mice

• Gene knock-out: deletion of a specific gene through CRISPR/Cas9 or other form of gene editing

• Gene knock-in: addition of a specific gene through CRISPR/Cas9 or other form of gene editing

• Transgenic: animal in which a transgene has been introduced into germ cells (egg or sperm) and now expresses the transgene in one or more organs, gets passed down through generations

Protein Technologies

• ELISA - antigen to proteins, western to quantify cells

Genomics

Genomics overview

• Darwin theory selection
• Positive selection (aka Darwinian selection): Process by which beneficial traits or genetic variations that enhance an organism's survival and reproduction become more common in a population over generations
• Haemophilus infulenzae (first sequenced )
• Human Genome Project (Congressional order - health and radiation)

Approaches to Sequencing a Genome

1. Contiguous mapped cloning (Location of cloned genes; sequenced) -Process: broken DNA to bacteria, know fragements locations then sequence them
2. Shotgun - break sequence individually without maps (line up using software IT resources)

Contiguous vs Shot Gun

Easier tracking versus needing software (Time versus accuracy)

Outcomes of Human Genome project

Find gene expressions - codons + dna - noncoding is regulatory ethical concerns raised

Eugenics

Improve genetic pop through dna alteration ethics is the gateway

Comparative Genomics

Similiaries with other species like C.elegans for its apoptotic properties.

Genomics Variability - Transposons

• lines and sines for chromosomes
• polymorphism is common nucleotide sequence

Cell Division

• Mitosis and Meisos
• Karyotype to see complete sets of chromosomes

###Epigenetics Heritable change in gene expression or fx

• Epigenome is for changes in heritable structure

Epigenetic Factors

Histone acetylation/methylation + chromatin structure alters gen expression.