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Cumulative review dna rna-protein synthesis-mutations


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Cumulative review dna rna-protein synthesis-mutations

  1. 1. <ul><li>What You’ll Learn </li></ul><ul><li>You will relate the structure of DNA to its function. </li></ul><ul><li>You will explain the role of DNA in protein production. </li></ul><ul><li>You will distinguish among different types of mutations. </li></ul>
  2. 2. <ul><li>Analyze the structure of DNA </li></ul><ul><li>Determine how the structure of DNA enables it to reproduce itself accurately. </li></ul>Section Objectives
  3. 3. What is DNA? <ul><li>Although the environment influences how an organism develops, the genetic information that is held in the molecules of DNA ultimately determines an organism’s traits. </li></ul><ul><li>DNA achieves its control by determining the structure of proteins. </li></ul><ul><li>Within the structure of DNA is the information for life— the complete instructions for manufacturing all the proteins for an organism. </li></ul>
  4. 4. DNA as the genetic material <ul><li>Hershey and Chase labeled the virus DNA with a radioactive isotope and the virus protein with a different isotope. </li></ul><ul><li>By following the infection of bacterial cells by the labeled viruses, they demonstrated that DNA, rather than protein, entered the cells and caused the bacteria to produce new viruses. </li></ul>
  5. 5. The structure of nucleotides <ul><li>DNA is a polymer made of repeating subunits called nucleotides . </li></ul><ul><li>Nucleotides have three parts: a simple sugar, a phosphate group, and a nitrogenous base. </li></ul>Sugar (deoxyribose ) Nitrogenous base Phosphate group
  6. 6. The structure of nucleotides <ul><li>The simple sugar in DNA, called deoxyribose (dee ahk sih RI bos) , gives DNA its name—deoxyribonucleic acid. </li></ul><ul><li>The phosphate group is composed of one atom of phosphorus surrounded by four oxygen atoms. </li></ul><ul><li>A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen. </li></ul><ul><li>In DNA, there are four possible nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). </li></ul>Thymine (T) Cytosine (C) Adenine (A) Guanine (G)
  7. 7. The structure of nucleotides <ul><li>in DNA there are four possible nucleotides, each containing one of these four bases. </li></ul><ul><li>The phosphate groups and deoxyribose molecules form the backbone of the chain, and the nitrogenous bases stick out like the teeth of a zipper. </li></ul>Nucleotide Sugar-phosphate backbone Phosphate group Sugar (deoxyribose) DNA nucleotide Nitrogenous base (A, G, C, or T) Thymine (T)
  8. 8. The structure of nucleotides <ul><li>Base pairing rule: </li></ul><ul><li>A always pairs with T </li></ul><ul><li>G always pairs with C </li></ul><ul><li>A-T </li></ul><ul><li>G-C </li></ul>
  9. 9. The structure of DNA <ul><li>James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin </li></ul><ul><li>(1953) </li></ul>
  10. 10. The structure of DNA <ul><li>Watson and Crick also proposed that DNA is shaped like a long zipper that is twisted into a coil like a spring. </li></ul><ul><li>Because DNA is composed of two strands twisted together, its shape is called double helix . </li></ul>
  11. 11. The importance of nucleotide sequences <ul><li>The sequence of nucleotides forms the unique genetic information of an organism. The closer the relationship is between two organisms, the more similar their DNA nucleotide sequences will be. </li></ul><ul><li>Scientists use nucleotide sequences to determine evolutionary relationships among organisms, to determine whether two people are related, and to identify bodies of crime victims. </li></ul>Chromosome
  12. 12. Replication of DNA <ul><li>Before a cell can divide by mitosis or meiosis, it must first make a copy of its chromosomes. </li></ul><ul><li>The DNA in the chromosomes is copied in a process called DNA replication . </li></ul><ul><li>Without DNA replication, new cells would have only half the DNA of their parents. </li></ul><ul><li>DNA is copied during interphase prior to mitosis and meiosis. </li></ul><ul><li>It is important that the new copies are exactly like the original molecules. </li></ul>
  13. 13. Replication of DNA <ul><li>DNA replication depends on specific base pairing </li></ul><ul><li>In DNA replication, the strands separate </li></ul><ul><ul><li>Enzymes use each strand as a template to assemble the new strands </li></ul></ul>Parental molecule of DNA Nucleotides Both parental strands serve as templates Two identical daughter molecules of DNA
  14. 14. Replication of DNA <ul><li>Untwisting and replication of DNA </li></ul>
  15. 15. <ul><li>Section Objectives </li></ul><ul><li>Relate the concept of the gene to the sequence of nucleotides in DNA. </li></ul><ul><li>Sequence the steps involved in protein synthesis. </li></ul>
  16. 16. Genes and Proteins <ul><li>The sequence of nucleotides in DNA contain information. </li></ul><ul><li>This information is put to work through the production of proteins. </li></ul><ul><li>Proteins fold into complex, three- dimensional shapes to become key cell structures and regulators of cell functions. </li></ul><ul><li>Thus, by encoding the instructions for making proteins, DNA controls cells. </li></ul>
  17. 17. Genes and Proteins <ul><li>You learned earlier that proteins are polymers of amino acids. </li></ul><ul><li>The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein. </li></ul>
  18. 18. RNA <ul><li>RNA like DNA, is a nucleic acid </li></ul><ul><li>RNA structure differs from DNA structure in three ways. </li></ul><ul><ul><li>1. Has ribose sugar instead of deoxyribose (DNA) </li></ul></ul><ul><ul><li>2. Replaces thymine (T) with uracil (U) </li></ul></ul><ul><ul><li>3. Single stranded as opposed to double stranded DNA </li></ul></ul>Sugar (ribose) Phosphate group Uracil (U) Nitrogenous base (A, G, C, or U)
  19. 19. RNA <ul><li>RNA has a different function than DNA </li></ul><ul><li>Whereas DNA provides the instructions for protein synthesis, RNA does the actual work of protein synthesis. </li></ul><ul><li>They take from DNA the instructions on how the protein should be assembled, then—amino acid by amino acid—they assemble the protein. </li></ul>
  20. 20. RNA <ul><li>3 types of RNA </li></ul><ul><ul><li>1. Messenger RNA (mRNA), single, uncoiled strand which brings instructions from DNA in the nucleus to the site of protein synthesis. </li></ul></ul><ul><ul><li>2. Ribosomal RNA (rRNA), globular form, makes up the ribosome –the construction site of proteins binds ( site of protein synthesis); binds to the mRNA and uses the instructions to assemble the amino acids in the correct order. </li></ul></ul><ul><ul><li>3. Transfer RNA (tRNA) single, folded strand that delivers the proper amino acid to the site at the right time </li></ul></ul>
  21. 21. Protein Synthesis: 2 step process 1. Transcription 2. translation <ul><li>Transcription: DNA -> mRNA </li></ul><ul><li>In the nucleus, enzymes make an RNA copy of a portion of a DNA strand in a process called transcription . </li></ul><ul><li>The main difference between transcription and DNA replication is that transcription results in the formation of one single-stranded RNA molecule rather than a double-stranded DNA molecule. </li></ul>
  22. 22. RNA Processing <ul><li>Not all the nucleotides in the DNA of eukaryotic cells carry instructions — or code — for making proteins. </li></ul><ul><li>Genes usually contain many long noncoding nucleotide sequences, called introns , that are scattered among the coding sequences. </li></ul><ul><li>Regions that contain information are called exons because they are ex pressed. </li></ul><ul><li>When mRNA is transcribed from DNA, both introns and exons are copied. </li></ul><ul><li>The introns must be removed from the mRNA before it can function to make a protein. </li></ul><ul><li>Enzymes in the nucleus cut out the intron segments and paste the mRNA back together. </li></ul><ul><li>The mRNA then leaves the nucleus and travels to the ribosome. </li></ul>
  23. 23. RNA Processing:simplified <ul><li>Noncoding segments called introns are spliced out ( coding segment = exons ) </li></ul>
  24. 24. Genetic information written in codons is translated into amino acid sequences <ul><li>Transfer of DNA to mRNA uses “language” of nucleotides </li></ul><ul><ul><li>Letters : nitrogen bases of nucleotides (A,T,G,C) </li></ul></ul><ul><ul><li>Words : codons ~ triplets of bases </li></ul></ul><ul><ul><li>( ex. AGC) </li></ul></ul><ul><ul><li>Sentences : polypeptide chain </li></ul></ul><ul><ul><li>The codons in a gene specify the amino acid sequence of a polypeptide </li></ul></ul>
  25. 25. The Genetic Code <ul><li>The nucleotide sequence transcribed from DNA to a strand of messenger RNA acts as a genetic message, the complete information for the building of a protein. . </li></ul><ul><li>Virtually all organisms share the same genetic code </li></ul>
  26. 26. Translation: From mRNA to Protein <ul><li>process of converting the information in a sequence of nitrogenous bases in mRNA into a sequence of amino acids in protein is known as translation . </li></ul><ul><li>takes place at the ribosomes in the cytoplasm. </li></ul><ul><ul><li>Involves 3 types of RNA </li></ul></ul><ul><ul><li>1. Messenger RNA (mRNA ) =carries </li></ul></ul><ul><ul><li>the blueprint for construction of a protein </li></ul></ul><ul><ul><li>2. Ribosomal RNA (rRNA) = </li></ul></ul><ul><ul><li>the construction site where the protein is made </li></ul></ul><ul><ul><li>3. Transfer RNA (tRNA) = </li></ul></ul><ul><ul><li>the truck delivering the proper amino acid to the site at the right time </li></ul></ul>
  27. 27. Transfer RNA molecules serve as interpreters during translation <ul><li>In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a polypeptide </li></ul><ul><li>The process is aided by transfer RNAs </li></ul><ul><li>Each tRNA molecule has a triplet anticodon on one end and an amino acid attachment site on the other </li></ul><ul><li>Anticodon base pairs with codon of mRNA </li></ul>
  28. 28. <ul><li>Section Objectives: </li></ul><ul><li>Categorize the different kinds of mutations that can occur in DNA. </li></ul><ul><li>Compare the effects of different kinds of mutations on cells and organisms. </li></ul>
  29. 29. Mutations <ul><li>Any change in DNA sequence is called a mutation . </li></ul><ul><li>can be caused by errors in replication, transcription, cell division, or by external agents. </li></ul><ul><li>If mutation occurs in gametes it will be passed on to offspring </li></ul><ul><li>may produce a new trait or it may result in a protein that does not work correctly. </li></ul><ul><ul><li>the mutation results in a protein that is nonfunctional, and the embryo may not survive </li></ul></ul><ul><ul><li>In some rare cases a gene mutation may have positive effects. </li></ul></ul>
  30. 30. Mutations <ul><li>If mutation takes place in a body cell, it is not passed on to offspring </li></ul><ul><ul><li>Damage to a gene may impair the function of the cell </li></ul></ul><ul><ul><li>When that cell divides, the new cells also will have the same mutation </li></ul></ul><ul><ul><li>Some mutations of DNA in body cells affect genes that control cell division. </li></ul></ul><ul><ul><li>This can result in the cells growing and dividing rapidly, producing cancer. </li></ul></ul>
  31. 31. Types of Mutations <ul><li>A point mutation is a change in a single base pair in DNA. </li></ul><ul><ul><li>A change in a single nitrogenous base can change the entire structure of a protein </li></ul></ul><ul><ul><li>Normal </li></ul></ul>Point mutation Replace G with A mRNA mRNA Protein Protein
  32. 32. Frameshift mutations <ul><li>A mutation in which a single base is added or deleted from DNA is called a frameshift mutation because it shifts the reading of codons by one base. </li></ul><ul><li>This mutation would cause nearly every amino acid in the protein after the deletion to be changed. </li></ul>Deletion of U mRNA Protein
  33. 33. Chromosomal Mutations <ul><li>Chromosome breakage can lead to rearrangements that can produce genetic disorders or cancer </li></ul><ul><ul><li>Four types of rearrangement are deletion, duplication, inversion, and translocation </li></ul></ul>
  34. 34. Causes of Mutations <ul><li>sometimes a mistake in base pairing during DNA replication. </li></ul><ul><li>many mutations are caused by factors in the environment </li></ul><ul><li>Any agent that can cause a change in DNA is called a mutagen . </li></ul><ul><ul><li>Mutagens include radiation, chemicals, and even high temperatures </li></ul></ul>
  35. 35. Repairing DNA <ul><li>Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides. </li></ul><ul><li>These repair mechanisms work extremely well, but they are not perfect. </li></ul>