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Big Idea 3: Living Systems store, retrieve, transmit and respond to information essential to life processes
Transcript of Big Idea 3: Living Systems store, retrieve, transmit and respond to information essential to life processes
Living Systems store, retrieve, transmit and respond to information essential to life processes 1. Genetic Information is stored in and passed to subsequent generations through DNA molecules and, in some cases, RNA molecules
2. Noneukaryotic organisms have circular chromosomes. while eukaryotic organisms have multiple linear although in biology there are exceptions to this rule
3. Prokaryotes, viruses and eukaryotes can contain plasmids, which are small extra-chromosomal, double stranded circular DNA molecules
4. The proof that SNA is the carrier of genetic information involved a number of important historical experiments. These include:
Contributions of Watson, Crick, Wilkins, and Franklin on the structure of DNA
Hershey-Chase Experiment 1. both have three components - sugar, phosphate and a nitrogenous base - which form nucleotide units that are connected by covalent bonds to form a linear molecule with 3' and 5' ends, with the nitrogenous bases perpendicular to the sugar-phosphate backbone
2. The basic structural differences include:
DNA contains deoxyribose (RNA contains ribose)
RNA contains uracil in liew of thymine in DNA
DNA is usually double stranded, RNA is usually single stranded
The two DNA strands in double-stranded DNA are antiparallel in directionality 3. Both DNA and RNA exhibit specific nucleotide base pairing that is conserved through evolution: Adenine pairs with Thymine or Uracil (A-T and A-U) and cytosine pairs with guanine (C-G)
Purines (G and A) have a double ring structure
Pyrimidines (C, T and U) have a single ring structure
4. The Sequence of the RNA bases, together with teh structure of the RNA molecules, determines RNA function
mRNA carries information fromt eh DNA to the ribosome
tRNA molecules bind specific amino acids and allow information in the mRNA to be translated to a linear peptide sequence
rRNA molecules are functional building blocks of ribosomes
The role of RNAi includes regulation of gene expression at the level of mRNA transcription DNA and RNA molecules have structural similarities and differences Essential Knowledge 3.A.1
DNA, and in some cases RNA, is the primary source of heritable information Genetic Information is transmitted from one generation to the next through DNA or RNA 5. DNA Replication ensures continuity of hereditary information.
Replication is a semiconservative process; that is; one strand serves as the template for a new, complementary strand.
Replication requires DNA polymerase plus many other essential cellular enzymes, occurs bidirectionally, and differs in the production of the leading and lagging strands.
6. Genetic Information in retrovirus is a special case and has an alternate flow of information: from RNA to DNA, made possible by reverse transcriptase, an enzyme that copies the viral RNA genome into DNA. This DNA integrates into the host genome and becomes transcribed and translated for the assembly of new viral progeny Genetic Information Flows from a sequence of nucleotides in a gene to a sequence of amino acids in a protein 1. The enzyme RNA-polymerase reads the DNA molecule in the 3' to 5' direction and synthesizes complementary mRNA molecules that determine the order of amino acids in the polypeptides
2. In eukaryotic cells the mRNA transcript undergoes a series of enzyme-regulated modifications
Addition of a poly-A tail 3. Translation of the mRNA occurs in the cytoplasm on the ribosome.
4. In prokaryotic organisms, transcription is coupled to translation of the message. Translation involves energy and many steps, including initiation, elongation and termination Phenotypes are determined through protein activities Enzymatic Reactions Genetic Engineering Techniques can manipulate the heritable information of DNA and, in special cases, RNA Polymerase Chain Reaction Products of Genetic Engineering Cloned Animals Essential Knowledge 3 B. 1 Gene regulation results in differential gene expression, leading to cell specialization. Essential Knowledge 3.A.2
In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization What does this mean? A. Both DNA regulatory sequences, regulatory genes, and small regulatory RNAs are involved in gene expression The cell cycle is a complex set of stages that is highly regulated with checkpoints, which determine the ultimate fate of the cell 1. Interphase consists of three phases: Growth, Synthesis of DNA, preparation of mitosis
2. The cell cycle is directed by internal controls or checkpoints. Internal and External signals provide stop-and-go signs at the checkpoints 1. DNA regulatory sequences- stretches of DNA that interact with regulatory proteins to control transcription
An example is a promoter. A promoter facilitates the transcription of a particular gene.
A promoter in plants is the Cauliflower mosaic virus 35S. It works through reverse transcription. It causes high levels of gene expression in plants.
2. Regulatory gene- DNA sequence encoding a regulatory protein or RNA Cancer Results from disruptions in cell cycle control 3, Cyclin and cyclin-dependent kinases control the cell cycle.
4. Mitosis alternates with interphase in the cell cycle
5. When a cell specializes, it often enters into a stage where it no longer divides, but it can reenter the cell cycle when given appropriate cues. Nondividing cells may exit the cell; or hold at a particular stage in the cell cycle Mitosis passes a complete genome from the parent cell to daughter cells 1. Mitosis occurs after DNA replication
2. Mitosis followed by cytokinesis produces two genetically identical daughter cells
3. Mitosis plays a role in growth, repair, and asexual reproduction
4. Mitosis is a continous process with observable structural features along the mitotic process. Evidence of student learning is demonstrated by knowing the order of the process
Replication, Alignment, Separation Meiosis, a reduction division, followed by fertilization ensures genetic diversity in sexually reproducing organisms 1. Meiosis ensures that each gamete receives one complete haploid (1n) set of chromosomes.
2. During meiosis, homologous chromosomes are paired, with one homologue originating from the maternal parent and the other from the paternal parent. orientation of the chromosome pairs is random with respect to the cell poles.
3. Separation of the homologous chromosomes ensures that each gamete receives a haploid (1) set of chromosomes compposed of both maternal and paternal chromosomes. B. Both positive and negative control mechanisms regulate gene expression in bacteria and viruses. 4. During meiosis, homologous chromatids exchange genetic material via a process called "crossing over", which increases genetic variation in the resultant gametes.
5. Fertilization involves the fusion of two gametes, increases genetic variation in population by providing for new combinations of genetic information in the zygote, and restores the diploid number of chromosomes 1. Inducers turn on the expression of specific genes.
2. Repressors can inhibit the expression of specific genes.
3. Both inducers and repressors are small molecules that interact with regulatory proteins and regulatory sequences. 4. Regulatory proteins inhibit gene expression by binding to DNA and blocking transcription (negative control).
5. Regulatory proteins bind to DNA and stimulate transcription (positive control) or bind to repressors to inactivate repressor function.
6. Some genes are always turned on. Essential Knowledge 3.A.3
The Chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring C. In eukaryotes, gene expression is complex and control involves regulatory genes, regulatory elements, and transcription factors. Rules of probability can be applied to analyze passage of single gene traits from parent to offspring Segregation and independent assortment of chromosomes result in genetic variation 1. Segregation and independent assortment can be applied to genes that are on different chromosomes
2. Genes that are adjacent and close to each other on the same chromosome tend to move as a unit; the probability that they will segregate as a unit is a function of the distance between them. 1. Transcription factors bind to specific DNA sequences and/ or other regulatory proteins.
2. Some transcription factors are activators (increase expression), while others are repressors (decrease expression).
3. The combination of transcription factors binding to the regulatory regions at any one time determines how much, if any, of the gene product will be produced. 3. The pattern of inheritance (monohybrid, dihybrid, sex-linked on the same homologous chromosomes) can often be predicted from data that gives the parent genotype/phenotype and/or the offspring phenotypes/genotypes Certain human genetic disorders can be attributed to the inheritance of singel gene traits or specific chromosomal changes, such as nondsjunction D. Gene regulation accounts for some of the phenotypic differences between organisms with similar genes This explains why you and your sibling have different hair or eye color. A variety of intercellular and intracellular signal transmissions mediate gene expression Essential Knowledge 3 B. 2 Example: Cytokines regulate gene expression to allow for cell replication and division.
Each cytokine has a matching cell-surface receptor. Subsequent cascades of intracellular signalling then alter cell functions. This may include the upregulation and/or downregulation of several genes and their transcription factors, resulting in the production of other cytokines, an increase in the number of surface receptors for other molecules, or the suppression of their own effect by feedback inhibition. A) Signal transmission within and between cells mediates gene expression. Example: HOX genes and their role in development.
Hox genes- A group of related genes that determine the structure and orientation of an organism.
They are critical for the proper placement of segment structures of animals in early embryonic development (legs, antennae, and wings in fruit flies or the different vertebrate ribs in humans). B) Signal transmission within and between cells mediates cell function. Essential Knowledge 3 C. 1 Changes in genotype can result in changes in phenotype. A) Alterations in a DNA sequence can lead to changes in the type or amount of the protein produced and the consquent phenotype. Sickle-Cell Anemia Down Syndrome Many ethical, social and medical issuessurround human genetic disorder 1. DNA mutations can be positive, negative or neutral based on the effect or
the lack of effect they have on the resulting nucleic acid or protein and the
phenotypes that are conferred by the protein. Essential Knowledge 3.A.4
The inheritance pattern of many triats cannot be explained by simple Mendelian genetics Many traits are the product of multiple genes and/or physiological processes 1. Patterns of inheritance of many triats do not follow ratios predicted by Mendel's laws and can be identified bny quantitative analysis, where observed phenotypic ratios statistically differ from teh predicted ratios Some traits are determined by genes on sex chromosomes in mammals and flies, the Y chromosome is fairly small Some Traits result from nonnuclear inheritance Cystic Fibrosis (Negative mutation)
This disease cripples children and leads to early death. It damages the lungs, digestive organs and, in the male, the vas deferens (spermatic duct). Its differing effects, from mild to severe, are in part due to different types of mutation affecting one key gene.
The biochemical basis is the mutation of a gene coding for a transmembrane protein regulating chloride ion transport across the cell membrane. This gene has 250,000 base pairs and is called the CFTR gene. It codes for a transmembrane protein of 1,480 amino acids. Research on this gene showed a mutation, delta-F508, occurring in most clinical cases of CF. This mutation is a deletion of three nucleotides.
Normal DNA . . . T ATC ATC TTT GGT GTT
Cystic Fibrosis DNA . . . T ATC AT- --T GGT GTT 1. Chloroplasts and mtochondria are randomly assorted to gametes and daughter cells; thus, traits determined by chloroplast and mitochondrial DNA do not follow simple Mendelian rules
2. In animals, mitochondiral DNA is transmitted by the egg and not by sperm; as such, mitochondrial-determined traits are maternally inherited Essential Knowledge 3. D. 1
Cell communication processes share common features that reflect a shared evolutionary history Communication
involves transduction of stimulatory or inhibitory signals from other cells, organisms or the environment B) Errors in DNA replication or DNA repair mechanisms, and external factors,
including radiation and reactive chemicals, can cause random changes, e.g.,
mutations in the DNA. Correct and appropriate signal transduction processes are generally under strong selective pressure In single-celled organisms, signal transduction pathways influence how the cell respond to its environment Use of pheromones to trigger reproduction developmental pathways 1. Whether or not a mutation is detrimental, beneficial or neutral depends on the
environmental context. Mutations are the primary source of genetic variation. In multicellular organisms, signal transduction pathways coordinate the activities within individual cells that support the function of the organism as a whole C) Errors in mitosis or meiosis can result in changes in phenotype. 1. Changes in chromosome number often result in new phenotypes, including
sterility caused by triploidy and increased vigor of other polyploids. DNA Repair Mechanisms 2. Changes in chromosome number often result in human disorders with
developmental limitations, including Trisomy 21 (Down syndrome) and XO
Down Syndrome results from nondisjunction of the 21st chromosome, so there are three copies of it.
Turner's syndrome results from part or all of the second sex chromosome is not transferred to the fetus. Essential Knowledge 3. D. 2
Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling Cell communicate by cell-to-cell contact Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell Signals released by one cell type can travel long distances to target cells of another cell type Insulin Immune cells interact by cell-cell contct, antigen-presenting cells (APCs), helper T-cells and killer T-cells Neurotransmitters 1. Endocrine signals are produced by endocrine cells that release signaling molecules, which are specific and can travel long distances through the blood to reach all parts of the body Human Growth Hormones Essential Knowledge 3. D. 3
Signaling begins with the recognition of a chemical messenger, a ligand, by a receptor protein Signaling begins with the recognition of a chemical messenger, a ligand, by a receptor protein Signal transduction is the process by which a signal is converted to a cellular response Insulin Ligand-gated ion channels 1. Many signal transduction pathways include:
Protein modifications (an illustrative example could be how methylation changes the signaling process)
Phosphorylation cascades in which a series of protein kinases add a phosphate group to the next protein in the cascade 1. Different receptors recognize different chemical messengers, which can be peptides, small chemicals or proteins, in a specific one-to-one relationship
2. A receptor recognizes signal molecules, causing the receptor protein's shape to change, which initiates transduction of the Turner's Syndrome Down Syndrome 1. Signaling cascades relay signals from receptors to cell targets, often amplifying the incoming signals, with the results of appropriate responses by the cell
2. Second messengers are often essential to the function of the cascade D) Changes in genotype may affect phenotypes that are subject to natural selection.
Genetic changes that enhance survival and reproduction can be selected by
environmental conditions. Sickle-cell anemia is an autosomal recessive genetic blood disorder characterized by red blood cells that have an abnormal, sickle shape.
To be affected by the disorder, you must have a homozygous recessive (aa) hemoglobin gene.
If you are a carrier, meaning heterozygous (Aa), you are malaria-resistant.
In areas stricken by malaria (Africa), the sickle cell trait is selected for. Ligand-gated ion channels Essential knowledge 3.D.4
Changes in signal transduction pathways can alter cellular response Conditions where signal transduction is blocked or defective can be deleterious, preventative or prophylactic Diabetes Heart Disease 1. Selection results in evolutionary change. Biological systems have multiple processes
that increase genetic variation. A) The imperfect nature of DNA replication and repair increases variation.
B) Transformation (uptake of naked DNA), transduction (viral transmission of DNA), conjugation (cell-to-cell transfer) and transposition (movement of DNA segments within and between DNA molecules) increase variation in prokaryotes. C) Sexual reproduction in eukaryotes involving gamete formation, including
crossing-over during meiosis and the random assortment of chromosomes during
meiosis, and fertilization serve to increase variation.
Viral replication results in genetic variation,
and viral infection can introduce genetic variation into the hosts. A) Viral replication differs from other reproductive strategies and generates genetic variation through various mechanisms. 1. Viruses have highly efficient replicative capabilities that allow for rapid evolution and acquisition of new phenotypes.
2. Viruses replicate via a component assembly model allowing one virus to produce many progeny simultaneously via the lytic cycle.
3. Virus replication allows for mutations to occur through usual host pathways. Essential Knowledge 3. C. 3: Essential Knowledge 3. C. 2: B) The reproductive cycles of viruses facilitate transfer of genetic information. 1. Viruses transmit DNA or RNA when they infect a host cell. 2. Some viruses are able to integrate into the host DNA and establish a latent infection. These not fully-developed viral genomes can result in new properties for the host. Individuals can act on information and communicate it to others. Essential Knowledge 3 E. 1: A. Organisms exchange information with each other in response to internal and external cues, which can change behavior. Fight or Flight Response
Theory: Animals react to threats with a general discharge of the sympathetic nervous system, priming the animal for fighting or fleeing.
The hormones adrenaline and noradrenaline facilitate the physical signs:
Digestion slows down
Dilation of pupils
Dilation of blood vessels in muscles
In the human fight or flight response in prehistoric times, fight was manifested in aggressive, combative behavior and flight was manifested by fleeing potentially threatening situations, such as being confronted by a predator. B. Communication occurs through various mechanisms. 1. Living systems have a variety of signal behaviors or cues that produce changes in
the behavior of other organisms and can result in differential reproductive success.
Territorial marking in mammals
Many mammals mark their territory by urinating on the perimeter of it. The urine describes their species, age, and sex. Males mark more than females. Many females usually mark the night before it ovulates. 2. Animals use visual, audible, tactile, electrical and chemical signals to indicate
dominance, find food, establish territory and ensure reproductive success.
Birds sing to impress potential mates and proclaim territories. at equilibrium (steady state, where concentrations are not changing) can define the rate of enzyme-substrate complex formation by using the equilibrium constants:
K1[E] [S] + K4 [E] [P] = [ES] (K2+K3) 2. Cooperative behavior tends to increase the fitness of the individual and the
survival of the population. Herd, flock and schooling behavior in animals
Colony and swarming behavior in insects
increases the liklihood of species survival because they have mates readily available and most predators will not attack a large group. C. Responses to information and communication of information are vital to natural selection and evolution. 1. Natural selection favors innate and learned behaviors that increase survival and reproductive fitness.
Parent and offspring interactions
Courtship and mating patterns Essential knowledge 3.E.2: Animals have nervous systems that detect external and internal signals, transmit and integrate information, and produce responses. A. The neuron is the basic structure of the nervous system that reflects function. 1. A typical neuron has a cell body, axon and dendrites. Many axons have a
myelin sheath that acts as an electrical insulator.
2. The structure of the neuron allows for the detection, generation, transmission
and integration of signal information.
3. Schwann cells, which form the myelin sheath, are separated by gaps of
unsheathed axon over which the impulse travels as the signal propagates along
the neuron. B. Action potentials propagate impulses along neurons. 1. Membranes of neurons are polarized by the establishment of electricalpotentials across the membranes.2. In response to a stimulus, Na+ and K+ gated channels sequentially open andcause the membrane to become locally depolarized.3. Na+/K+ pumps, powered by ATP, work to maintain membrane potential. Sodium-Potassium Pump C. Transmission of information between neurons occurs across synapses. 1. In most animals, transmission across synapses involves chemical messengers called neurotransmitters.
Epinephrine also known as adrenaline is a neurotransmitter and hormone essential to metabolism. It regulates attention, mental focus, arousal, and cognition. It also inhibits insulin excretion and raises the amounts of fatty acids in the blood. Epinephrine is made from norepinephrine and is released from the adrenal glands. Epinephrine Animation 2. Transmission of information along neurons and synapses results in a response.3. The response can be stimulatory (encourage development) or inhibitory (hinder growth). D. Different regions of the vertebrate brain have different functions. Right and left cerebral hemispheres in humans Cancer results from uncontrolled cell division in mitosis, and in the end it might kill the organism. Most cells have a fixed number of divisions (approximately 50) before they will die, but cancer cells do not have a limit. 4. RNA viruses lack replication error-checking mechanisms, and thus have higher rates of mutation.
5. Related viruses can combine/recombine information if they infect the same host cell.
6. HIV is a well-studied system where the rapid evolution of a virus within the host contributes to the pathogenicity of viral infection. a disease passed down through families in which red blood cells form an abnormal crescent shape Down syndrome is a genetic condition in which a person has 47 chromosomes instead of the usual 46. The have an extra 21st chromosome. Transgenic Animals enables researchers to produce millions of copies of a specific DNA sequence in approximately two hours. This automated process bypasses the need to use bacteria for amplifying DNA. A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual There are three major DNA repairing mechanisms: base excision, nucleotide excision and mismatch repair.
DNA's bases may be modified by deamination or alkylation. The position of the modified (damaged) base is called the "abasic site" or "AP site".
In E. coli, proteins UvrA, UvrB, and UvrC are involved in removing the damaged nucleotides (e.g., the dimer induced by UV light). The gap is then filled by DNA polymerase I and DNA ligase.
To repair mismatched bases, the system has to know which base is the correct one. In E. coli, this is achieved by a special methylase called the "Dam methylase", which can methylate all adenines that occur within (5')GATC sequences. Immediately after DNA replication, the template strand has been methylated, but the newly synthesized strand is not methylated yet. Thus, the template strand and the new strand can be distinguished. Neurotransmitters are the chemicals which allow the transmission of signals from one neuron to the next across synapses. They are also found at the axon endings of motor neurons, where they stimulate the muscle fibers. And they and their close relatives are produced by some glands such as the pituitary and the adrenal glands. In this chapter, we will review some of the most significant neurotransmitters. Insulin injection is used to control blood sugar in people who have type 1 diabetes (condition in which the body does not make insulin, so they cannot control the amount of sugar in the blood) or in people with type 2 diabetes ( the condition in which the blood sugar is too high because the body does not produce or use insulin normally) that cannot be controlled with oral medications alone. Insulin injection is used to take the place of insulin that is normally produced by the body. It works by helping move sugar from the blood into other body tissues where it is used for energy. It also stops the liver from producing more sugar. Growth hormone is produced by the pituitary gland, a pea-sized structure at the base of the brain, to fuel childhood growth and help maintain tissues and organs throughout life. Beginning in middle age, however, the pituitary gland slowly reduces the amount of growth hormone it produces. This natural slowdown has prompted an interest in the use of synthetic human growth hormone (HGH) to stave off the realities of old age. Ligand-gated ion channels are one type of ionotropic receptor or channel-linked receptor. They are a group of transmembrane ion channels that are opened or closed in response to the binding of a chemical messenger such as a neurotransmitter Diabetes is a lifelong (chronic) disease in which there are high levels of sugar in the blood. Heart disease is a broad term used to describe a range of diseases that affect your heart. The various diseases that fall under the umbrella of heart disease include diseases of your blood vessels, such as coronary artery disease; heart rhythm problems, heart infections; and heart defects you're born with. THANKS FOR WATCHING!
By: Julie and Amy