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Biology Chapter #13
BOX 1
| Question | Answer |
|---|---|
| What are the 3 main roles of DNA? | Storing, copying and transmitting genetic information in the cell |
| What as the primary role of DNA? | Storing information - it is the molecule of heredity - genes control patterns of development |
| How does DNA copy information? | Copies each of its genes before the cell divides (synthesis before mitosis) |
| How is DNA equally transmitted? | "When a cell divides, each daughter cell must receive a complete copy of the genetic info" - The loss of DNA might result in the loss of info for generations, permanently |
| What is a bacteriophage? | A virus that attacks bacteria, "bacteria eater" |
| How does a bacteriophage transmit genetic info? | It injects its own DNA into the bacterium - The genes then produce more bacteriophages within the bacterium, gradually killing it |
| What is the relationship between nucleic acids and nucleotides? | Nucleic acids are made up of nucleotides linked together to form chains |
| What are the basic components of DNA's nucleotides? | A 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base (A,G,C,T) |
| How are these nucleotides held together? | Covalent bonds between sugar and phosphate groups |
| Name the base pairs | Adenine-Thymine, Guanine-Cytosine (ANY SEQUENCE IS POSSIBLE) |
| What did Erwin Chargaff discover? [Chargaff's rules] | He discovered that the percentages of adenine and thymine were almost equal in every sample of DNA (as well as C,G) - [A] = [T] AND [G]=[C] |
| Rosalind Franklin | Used X-ray diffraction to reveal the X-shaped structure of DNA - strands of DNA coiled around each other like a spring |
| Watson and Crick | Created the double helix model after seeing Franklin's X-ray diffraction image of DNA - depicted two strands wound up around each other + base pairing |
| The Double-Helix Model | Explained Franklin's X-ray pattern and Chargaff's rules of base pairing and how the two strands of DNA are held together |
| Antiparallel Strands | In the double helix model, the two strands of DNA run in opposite directions - allows the nitrogenous bases to meet at the center of the molecule |
| Hydrogen bonding | Form between nitrogenous base pairs to hold the molecule together - Weak Hydrogen bonds are important, as it allows the two strands of the helix to easily separate (for replication) |
| DNA polymerase | an enzyme that joins individual nucleotides (and thus complementary strands) to produce a new strand of DNA - also "proofreads" each new strand of DNA to ensure that it is a perfect copy of the original |
| Replication | The DNA molecule separates into two strands and then produces two new complementary strands following the rules of base pairing - The result of replication is two DNA molecules identical to each other and to the original molecule. |
| Telomeres | The tips of chromosomes - notoriously hard to properly replicate - DNA may actually be lost from telomeres each time a chromosome is replicated |
| Telomerase | An enzyme which adds short, repeated DNA sequences to telomeres, lengthening the chromosomes slightly and making it less likely that important gene sequences will be lost from the telomeres during replication |
| Replication in Prokaryotic Cells vs Eukaryotic Cells | Prokaryotic: only one point of origin - replication occurs in two opposing directions at the same time - takes place in the cell cytoplasm. Eukaryotic: multiple points of origin - use unidirectional replication - takes place within nucleus of the cell |
| Prokaryotic gene replication | Requires a trigger - regulatory proteins bind to a single starting point on the chromosome |
| Helicase/Primer complex | An enzyme that untwists the double helix of DNA at the replication forks. |
| Replication Fork | A Y-shaped point that results when the two strands of a DNA double helix separate so that the DNA molecule can be replicated |
| Leading strand (DNA) | New continuous complementary strand of DNA - synthesized in the 3' to 5' direction |
| Lagging/scumbag strand (DNA) | A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork. |
| RNA primase | An enzyme that creates an RNA primer for initiation of DNA replication. |
| RNA primer | A primer is a short nucleic acid sequence that provides a starting point for DNA synthesis. In living organisms, primers are short strands of RNA. |
| Okazaki fragment | short DNA nucleotide sequences are discontinuously synthesized and further associated by ligase enzyme which gives rise to the lagging strand at the time of DNA replication. |
| DNA ligase | is a DNA-joining enzyme. If two pieces of DNA have matching ends, ligase can link them to form a single, unbroken molecule of DNA. In DNA cloning, restriction enzymes and DNA ligase are used to insert genes and other pieces of DNA into plasmids. |
| DNA gyrase | Another enzyme called DNA gyrase actually binds to the DNA and decreases the stress involved with unwinding by introducing negative supercoils (helps helicase) |
| β sliding clamp (ligase complex) | secures DNA polymerase to the replication fork, increasing the processivity of nucleotide polymerization from tens of nucleotides per polymerase binding event to thousands of nucleotides per polymerase binding event |
| Nucleic acid (composition) | Phosphate group, 5-carbon, nitrogenous base |
| RNA vs DNA | (1) the sugar in RNA is ribose instead of deoxyribose, (2) RNA is generally single-stranded and not double-stranded, and (3) RNA contains uracil in place of thymine. |
| Function of RNA | RNA controls the assembly of amino acids into proteins. Each type of RNA molecule specializes in a different aspect of this job |
| Role of Messenger RNA (mRNA) | The RNA molecules that carry copies of these instructions are known as messenger RNA (mRNA): They carry information from DNA to ribosomes |
| Role of Ribosomal RNA (rRNA) | Reads the mRNA codons (3 at a time) and searches for the anti-codon tRNA to complete the amino acid - these ribosome subunits are made up of several ribosomal RNA (rRNA) |
| Role of Transfer RNA (tRNA) | When a tRNA recognizes and binds to its corresponding codon in the ribosome, the tRNA transfers the appropriate amino acid to the end of the growing amino acid chain. (Each tRNA has its corresponding amino acid attached to its end.) |
| Genetic code for one amino acid | a three-base, or triplet, code (CODON) |
| What is transcription? | Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). The major steps of transcription are initiation, promoter, elongation, and termination. |
| Initiation (transcription) | the phase during which the first nucleotides in the RNA chain are synthesized |
| Promoter | Promoters are signals in the DNA molecule that show RNA polymerase exactly where to begin making RNA. Similar signals in DNA cause transcription to stop when a new RNA molecule is completed. (polymerase binds to these regions) |
| Elongation | the stage when the RNA strand gets longer, thanks to the addition of new nucleotides. During elongation, RNA polymerase "walks" along one strand of DNA, known as the template strand, in the 3' to 5' direction |
| Termination | Termination once the polymerase transcribes a sequence of DNA known as a terminator |
| What is translation? | Translation takes place on ribosomes in the cell cytoplasm, where mRNA is read and translated into the string of amino acid chains that make up the synthesized protein. (mRNA to PROTEIN) |
| Introns | a segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes - are cut out and discarded by the spliceosome (removed in the nucleus in Eukaryotes) |
| Exons | a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence - remaining pieces of the RNA molecule are spliced back up |
| Pre-mRNA | Pre-mRNA is the first form of RNA created through transcription in protein synthesis. The pre-mRNA lacks structures that the messenger RNA (mRNA) requires. Does not leave the nucleus yet. (introns are yet to be removed) |
| What are mutations? | Mutations are heritable changes in genetic information. |
| Gene mutations | Those that produce changes in a single gene are known as gene mutations. (substitutions, insertions, deletions) |
| Chromosomal mutations | Those that produce changes in whole chromosomes are known as chromosomal mutations. (deletion, duplication, inversion, translocation) |
| Point mutations | Mutations that involve changes in one or a few nucleotides - If a gene in one cell is altered, the alteration can be passed on to every cell that develops from the original one. |
| Substitutions (gene) | In a substitution, one base is changed to a different base - usually affect no more than a single amino acid, and sometimes they have no effect at all. |
| Insertions/Deletions (gene) | One base is inserted or removed from the DNA sequence - the bases are still read in groups of three, but now those groupings shift in every codon that follows the mutation. AKA frameshift mutations - can alter a protein so much that t becomes unfunctional |
| Chromosomal deletion | Deletion involves the loss of all or part of a chromosome |
| Chromosomal duplication | Duplication produces an extra copy of all or part of a chromosome |
| Chromosomal inversion | Inversion reverses the direction of parts of a chromosome |
| Chromosomal translocation | Translocation occurs when part of one chromosome breaks off and attaches to another. |
| Effects of mutations | Often produce proteins with new or altered functions that can be useful to organisms in different or changing environments OR negatively disrupt gene function |
| Mutagens | Chemical: pesticides, plant alkaloids, tobacco smoke, environmental pollutants Physical: electromagnetic radiations (X-rays and UV light) |
| Harmful mutations | The defective proteins produced by these mutations can disrupt normal biological activities, and result in genetic disorders. (eg: Sickle cell disease - caused by a point mutation - long and pointed shape of red blood cells) |
| Beneficial mutations | Some mutations have enabled microorganisms to adapt to new chemicals in the environment. |
| Why are mutations necessary? | Without mutations, organisms cannot evolve, because mutations are the source of genetic variability in a species. |
| Polyploidy | Considered a beneficial mutation from an agricultural perspective - organism has extra sets of chromosomes - Polyploid plants are often larger and stronger than diploid plants. |
| Prokaryotic gene regulation | DNA-binding proteins in prokaryotes regulate genes by controlling transcription - To conserve energy and resources, prokaryotes regulate their activities, producing only those genes necessary for the cell to function |
| Regulatory proteins | Switch genes on and off (in response to changes in environment - the presence or absence of nutrients) |
| Operon | a group of genes that are regulated together and usually have related functions |
| The LAC Operon | The genes in the operon encode proteins that allow the bacteria to use lactose as an energy source. |
| When lactose is not present (LAC Operon) | the lac repressor binds to the O region, blocking the RNA polymerase from reaching the lac genes to begin transcription. |
| When lactose is present (LAC Operon) | lactose attaches to the lac repressor protein (binding site) and changes the shape of the repressor protein in a way that causes it to fall off the operator. - RNA polymerase can now bind to the promoter and begin transcription |
| Promoters and Operators (regulatory regions on one side of the operon) | Promoter: site where RNA-polymerase can bind to begin transcription Operator: where the DNA-binding protein known as LAC REPRESSOR can bind to DNA |
| Eukaryotic Gene Regulation | By binding DNA sequences in the regulatory regions of eukaryotic genes, transcription factors control the expression of those genes. |
| TATA box | binds a protein that helps position RNA polymerase by marking a point just before the beginning of a gene - short region of DNA in Eukaryotic cells |
| Transcription factors | proteins involved in the process of converting, or transcribing, DNA into RNA - initiate and regulate the transcription of genes. |
| Activators | boost a genes transcription |
| Repressors | decrease transcription |
| Enhancers | turn a gene on in specific parts of the body |
| Silencers | turn a gene off in specific parts of the body |
| Why is gene regulation in eukaryotes more complex than in prokaryotes? | Cell specialization- complex gene regulation in eukaryotes is what makes specialization possible |
| RNA interface (RNAi) | Blocking gene expression by means of an miRNA silencing complex |
| Dicer enzyme | Cuts small interfering RNA molecules (which had folded into double-stranded hairpin loops) into miRNA (these two strands then separate) |
| Master control genes | trigger particular patterns of development and differentiation in cells and tissue |
| Differentiation | Gene regulation helps cells become specialized in structure and function (differentiated) |
| Edward B. Lewis | First to discover "master control genes" - found that a mutation in homeotic genes resulted in a fly with a leg growing out of its head in place of an antenna |
| Homeotic Genes | code for transcription important transcription factors - control formation of proteins necessary for large scale development - organs in specific parts in the body |
| Homeobox | code for transcription factors that activate other genes that are important in cell development and differentiation - expressed in certain regions of the body, and they determine factors like the presence of wings or legs |
| Hox Genes | Group of homeobox genes - the master regulators of embryonic development for all animals, decide what body parts go where, mutations can be disasterous |
| Environmental influences on gene expression | Temperature, salinity, nutrient availability, EXTERNAL FACTORS |
| Metamorphosis | series of transformations from one life stage to another, such as the transformation of a tadpole to an adult bullfrog - regulated by a number of external and internal factors (drying pond, a high density of predators, low amounts of food may speed it up) |
| MicroRNA (miRNA) silencing complex | miRNA pieces attach to a cluster of proteins (silencing complex) - silencing complex then binds to and destroys any mRNA containing a sequence complementary to the miRNA |
| Internal factors on gene expression | hormones, gender, and metabolic activities |
| What is a karyotype? | shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size (46 chromosomes and 23 pairs) - photographed when cells are in mitosis as chromosomes are condensed |
| Sex chromosomes | 2/46 chromosomes determine an individual's sex - Males have XY and Females XX |
| Punnet Square | 1/2 of the zygotes will be male and 1/2 will be a female - a chart that allows you to easily determine the expected percentage of different genotypes in the offspring of two parents |
| Dominant Alleles | A dominant allele produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent. (will be expressed over the recessive allele if heterozygous) |
| Recessive Alleles | A type of allele that when present on its own will not affect the individual. Two copies of the allele need to be present for the phenotype to be expressed (homozygous) |
| X vs Y chromosomes | X: Contains more than 1200 genes, huge Y: Contains only about 140 genes, much smaller than X, most associated with male sex determination |
| Sex-linked Inheritance | The recessive phenotype of a sex-linked genetic disorder tends to be much more common among males than among females because they only have one copy of a specific chromosome |
| Barr Bodies (X-Chromosome Inactivation) | In female cells, most of the genes in one of the X chromosomes are randomly switched off, forming a dense region the nucleus known as a Barr body |
| Human Pedigrees | shows the presence or absence of a trait according to the relationships between parents, siblings, and offspring. - makes it possible to determine the nature of genes and alleles associated with inherited human traits. |
| Autosomal Inheritance | the gene in question is located on one of the numbered, or non-sex, chromosomes (can be dominant, recessive, or co-dominant) |
| Phenotype | a set of observable characteristics or traits of an organism |
| How do small changes in DNA affect human traits? | Changes in a gene’s DNA sequence can change proteins by altering their amino acid sequences, which may directly affect one’s phenotype (link between genotype and phenotype) |
| Sickle Cell Disease | Caused by defective allele of one allele for beta-globin - makes hemoglobin less soluble and this stick together - molecules clump into long fibers (recessive) |
| Cystic Fibrosis | Most cases result from the deletion of just three bases in the gene for a protein called CFTR (which normally allows chloride ions to cross cell membranes) - missing CFTR causes protein to misfold and destroy (recessive) |
| Huntington's Disease | Caused by dominant allele found in brain cells-The greater the number of codon repeats, the earlier the disease appears, and the more severe are its symptoms |
| Why are some disorders still around? | Genetic advantages during environmental change |
| Gamete | a reproductive cell of an animal or plant (sperm or egg cell) |
| Meiosis | a form of cell division which produces four non-identical, haploid sex cells or gametes |
| Nondisjunction in Meiosis | a pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cell - leading to a disorder of chromosome numbers |
| Trisomy | Three copies of a chromosome - EG: Trisomy 21 (down syndrome) |
| Turner's syndrome | Nondisjunction of the X chromosome - female only inherits one X chromosome - individuals are sterile and sex organs do not develop properly |
| Klinefelter's syndrome | Nondisjunction of the X chromosome in males - extra X chromosome usually prevents individuals from reproducing |
| Why cut DNA? | DNA molecules on their own are too large to be analyzed, so they must be split into smaller, more manageable pieces |
| Restriction enzymes | Produced by bacteria, cut DNA into RESTRICTION FRAGMENTS - every restriction enzyme is unique and each cuts a different sequence of nucleotides |
| "Sticky ends" | Single stranded overhangs left behind by restriction enzymes - bond to a DNA fragment with a complementary base sequence |
| Gel electrophoresis | an electric voltage is applied to the gel and DNA molecules (which are negatively charged) move towards the positive end of the gel. The smaller the fragment the faster it moves - results in pattern of bands based on fragment size (separated) |
| PCR | Polymerase Chain Reactions - uses separated bases as a template to make new DNA strands - When DNA synthesis is completed, the result is a series of color-coded DNA fragments of different lengths. |
| How is the sequence of bases determined after Gel electrophoresis and PCR? | The order of colored bands on the gel tells the exact sequence of bases in the DNA |
| Human Genome Project | The main goals of the project were to sequence all 3 billion base pairs of human DNA and identify all human genes |
| "Shotgun Sequencing" | a rapid sequencing method that involves cutting DNA into random fragments, then determining the base sequence in each fragment |
| SNP - single nucleotide polymorphisms | are the most common type of genetic variation among people. |
| Haplotypes | Groups of reoccurring SNPs |
| International HapMap Project | Main goal: to determine the common patterns of DNA sequence variation in the human genome and to make this information freely available in the public domain. |
| What is BIOINFORMATICS? | the application of tools of computation and analysis to the capture and interpretation of biological data |
| Sperm cell | 1/2 carry X chromosome 1/2 carry Y chromosome |
| Egg cell | Only carries X chromosome |
| Central Dogma of Biology | DNA to RNA (transcription ) RNA to PROTEIN (translation) |
| Homozygous alleles | refers to having inherited the same versions (alleles) of a genomic marker from each biological parent |
| Heterozygous alleles | refers to having inherited different versions (alleles) of a genomic marker from each biological parent |
| Bacterial Transformation | In transformation, the DNA (usually in the form of a plasmid) is introduced into a competent strain of bacteria, so that the bacteria may then replicate the sequence of interest in amounts suitable for further analysis and/or manipulation |
| Frederick Griffith's Experiments | Mixed heat-killed, S-strain bacteria with live, harmless bacteria from the R strain and injected the mixture into laboratory mice - mice died - concluded that a gene was the transforming factor |
| Avery's Experiments | extracted a mixture of various molecules from the heat-killed bacteria and treated this mixture of macromolecules with enzymes - When DNA was destroyed transformation did not occur, when DNA wasn't destroyed the opposite occured |
| Hershey-Chase Experiment | Injected bacteria with viruses containing P-32 (DNA) and S-35 (Protein coat) - all radioactivity was found from Phosphorus 32, meaning that the genetic material of the bacteriophage was DNA and not protein |
| What is an allele? | Different versions of a gene, which vary according to the nucleotide base present at a particular genome location (diploid cells are NOT identical even though 2 copies are made) |
| Define GENOME | The complete set of genes or genetic material present in a cell or organism. |
Created by:
Kaliimarz
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