Mastering biology chapter 17 the genetic code
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Flashcards Memorize Quiz Match Gravity. View Flashcards. Number of cards: All 1 2 3 4 5 6 7 8 9 10 11 Changes are done, please view the flashcard. Shuffle Cards. Front Back Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because A genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
C many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA. D certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors. E metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies. A genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway? A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation? A an accumulation of A and no production of B and C. If A, B, and C are all required for growth, a strain that is mutant for the gene encoding enzyme A would be able to grow on which of the following media?
A minimal medium B minimal medium supplemented with nutrient "A" only C minimal medium supplemented with nutrient "B" only D minimal medium supplemented with nutrient "C" only E minimal medium supplemented with nutrients "A" and "C". C minimal medium supplemented with nutrient "B" only. If A, B, and C are all required for growth, a strain mutant for the gene encoding enzyme B would be capable of growing on which of the following media?Figure From other considerations, they suspected that the metabolic pathway of arginine biosynthesis included the precursors ornithine and citrulline.
Their most famous experiment, shown here, tested both their one gene—one enzyme hypothesis and their postulated arginine pathway. In this experiment, they grew their three classes of mutants under the four different conditions shown in the Results section below. The three classes of mutants had different growth requirements. Because each of their mutants was mutated in a single gene, they concluded that each mutated gene must normally dictate the production of one enzyme.
Their results supported the one gene—one enzyme hypothesis and also confirmed the arginine pathway. Notice that a mutant can grow only if supplied with a compound made after the defective step. Precursor Precursor Precursor Precursor. Ornithine Ornithine Ornithine Ornithine. In a cell lacking a nucleus, mRNA produced by transcription is immediately translated without additional processing.
The nucleus provides a separate Polypeptide compartment for transcription. Start point Initiation. DNA transcript 2 Elongation. In the wake of Rewound transcription, the DNA strands re-form a double helix. RNA transcript 3 Termination. RNA polymerase. Newly made RNA. Protein 1 snRNA Other proteins. Domain 3. Domain 2 Domain 1. Amino Polypeptide acids. Hydrogen bonds. P Adenosine. AMP 4 Activated amino acid is released by the enzyme.
Small subunit. This is a model of a bacterial ribosome, showing its overall shape. The eukaryotic ribosome is roughly similar. A ribosomal subunit is an aggregate of ribosomal RNA molecules Figure This schematic ribosome will appear in later diagrams.
Next amino acid to be added to polypeptide chain.
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The P site holds the tRNA attached to the growing polypeptide. The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain.
Discharged tRNA leaves via the E site. In a prokaryotic cell, the mRNA binding site the initiation complex. Proteins called initiation on this subunit recognizes a specific nucleotide factors not shown are required to bring all the sequence on the mRNA just upstream of the start translation components together.
GTP provides codon.Simply, a series consisting of four bases A,G,C,T is transcribed and translated into a series of 20 amino acids. This shift from one chemical language to another is accomplished through the genetic code, a set of precise rules that govern how every possible sequence of three RNA nucleotides a codon corresponds to a specific amino acid.
The genetic code can be read as a table, whereby each three-letter codon is broken into its first, second and third RNA bases. These bases converge on a single amino acid, and this amino acid is the actual translated product of the original DNA nucleotides. The initiation codon also codes for the amino acid Methionine. Methionine with Tryptophan is one of only two amino acids that correspond to a single codon.
In other words, the genetic code can be very redundant.
5.8 Using the genetic code
Rather, it seems that much of your DNA is regulatory, and controls how much, or what kind, of a protein is synthesized. Some DNA is part of a gene that was active in our ancestors, but is no longer functional; for example, humans have several vestigial olfactory genes, suggesting that modern humans are not as dependent on our sense of smell as were our hominid ancestors.
And some DNA was adopted from viruses that attacked human ancestors; these endogenous retroviruses say a lot about our evolutionary past with pathogens, but are not functioning genes. It is also probable that many DNA sequences have functions yet to be identified. Regardless of the exact percentages, it is clear that while much of our DNA does not directly code for protein, the human genome is far from being packed with junk.
The genetic code consists of all the RNA codons and their associated amino acids. What else does DNA do? Previous: 5. Next: 5.The nucleus at top right is now in prophase of mitosis; the nucleus at bottom right is now in prophase I of meiosis. Drag the labels to their appropriate targets to correctly identify the various chromosome structures. Labels can be used more than once. In the life cycle of an organism, meiosis is paired with the process of fertilization. Understanding the life cycle of an organism is the key to understanding how sexual reproduction ensures the inheritance of traits from both parents and also introduces genetic variation.
Complete the diagram to show the life cycle of a typical animal. Follow these steps: First, drag blue labels onto blue targets only to identify each stage of the life cycle. Next, drag pink labels onto pink targets only to identify the process by which each stage occurs. Then, drag white labels onto white targets only to identify the ploidy level at each stage. Labels can be used once, more than once, or not at all. Can you recognize the eight stages of meiosis based on the location and behavior of the chromosomes?
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Drag the diagrams of the stages of meiosis onto the targets so that the four stages of meiosis I and the four stages of meiosis II are in the proper sequence from left to right.
Note that only one of the two daughter cells is shown for meiosis II. Crossing over plays a critical role in increasing the genetic variation among offspring of sexual reproduction. It is important to understand how crossing over occurs and its consequences in meiosis.
Assume that the red chromosomes are of maternal origin and the blue chromosomes are of paternal origin. Drag the labels to fill in the targets beneath each diagram of a cell.
Note that the diagrams are in no particular order. Drag the blue labels to the blue targets to identify the stage of meiosis depicted in each diagram.
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Drag the pink labels to the pink targets to identify whether the configuration of the chromosomes related to crossing over is possible or not. The parent cell that enters meiosis is diploid, whereas the four daughter cells that result are haploid.
Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II?View larger. Preview this title online. Request a copy. Download instructor resources. Additional order info. Buy this product. Buy an eText. Now completely up-to-date with the latest research advances, the Seventh Edition of James D.
Twenty-two concise chapters, co-authored by six highly distinguished biologists, provide current, authoritative coverage of an exciting, fast-changing discipline. Unbound Saleable. Access Code Card. James D. Watson is Chancellor Emeritus at Cold Spring Harbor Laboratory, where he was previously its Director from toPresident from toand Chancellor from to He spent his undergraduate years at the University of Chicago and received his Ph.
Between andhe did postdoctoral research in Copenhagen and Cambridge, England. While at Cambridge, he began the collaboration that resulted in the elucidation of the double-helical structure of DNA in Later inhe went to the California Institute of Technology. He moved to Harvard inwhere he taught and did research on RNA synthesis and protein synthesis until Watson was sole author of the first, second, and third editions of Molecular Biology of the Geneand a co-author of the fourth, fifth and sixth editions.
These were published in,andrespectively. He is also a co-author of two other textbooks: Molecular Biology of the Cell and Recombinant DNAas well as author of the celebrated memoir, The Double Helix, which in was listed by the Library Of Congress as one of the 88 books that shaped America. She received a B. Her graduate research was carried out in the laboratory of Professor Arthur Kornberg and focused on mechanisms of initiation of DNA replication. She did postdoctoral research in the laboratory of Dr.
Her current research explores mechanisms and regulation of genetic recombination, enzyme-catalyzed protein unfolding, and ATP-dependent protein degradation.
He received B. His graduate research was carried out in the laboratory of Dr. Robert Tjian and focused on eukaryotic transcription. He did postdoctoral research in the laboratory of Dr. His current research focuses on the mechanisms controlling the duplication of eukaryotic chromosomes. He received his B. Sc in microbiology from University College London and a Ph.
His graduate research was carried out in the laboratory of Noreen Murray and focused on DNA recognition by restriction enzymes. He did postdoctoral research in the laboratory of Mark Ptashne at Harvard, working on transcriptional regulation, and that of Jeremy Brockes at the Ludwig Institute of Cancer Research at University College London, where he worked on newt limb regeneration. He was a Lecturer at Lancaster University, U.Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic. Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains. A virus with a double helix made up of one strand of DNA complementary to a strand of RNA surrounded by viral protein.
Radioactive nitrogen has a half-life ofyears, and the material would be too dangerous for too long. Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive. Amino acids and thus proteins also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many. The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. ATP is found only in human cells; the nucleoside triphosphates are found in all animal and plant cells.
The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction. The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end. The leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together.
A nucleoside triphosphate is added to the 5' end of the DNA, releasing a molecule of pyrophosphate. A nucleoside triphosphate is added to the 3' end of the DNA, releasing a molecule of pyrophosphate. The correct letters used to replace errors in a document after they have been deleted in a word processor. Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes. Many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA.
Certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors. Metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies. A single gene codes for a single polypeptide chain, and many enzymes are made up of more than one polypeptide chain. RNA acts as an expendable copy of the genetic material, allowing the DNA to serve as a permanent, pristine repository of the genetic material.
Many mRNA molecules can be transcribed from a single gene, increasing the potential rate of gene expression. RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase. RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript. RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript.
Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA. Their presence allows exons to be moved around more easily, creating proteins with new combinations of functional domains.View larger. Preview this title online. Request a copy.
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