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Chapter 12

Chapter 12. DNA & RNA. Interest Grabber. Section 12-1. Order! Order!

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Chapter 12

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  1. Chapter 12 DNA & RNA

  2. Interest Grabber Section 12-1 • Order! Order! • Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three of these units form a code. The order, or sequence, of a code and the type of code determine the meaning of the message. 1. On a sheet of paper, write the word cats. List the letters or units that make up the word cats. 2. Try rearranging the units to form other words. Remember that eachnew word can have only three units. Write each word on your paper, and then add a definition for each word. 3. Did any of the codes you formed have the same meaning? 4. How do you think changing the order of the nucleotides in the DNA codon changes the codon’s message?

  3. Interest Grabber Section 12-2 • A Perfect Copy • When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.

  4. I Section 12-2 1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2. Hold the papers side by side, and compare the lines. Do they look the same? 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4. How could you use the original paper to draw exact copies of the line without tracing it? 5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?

  5. II. Chromosomes & DNA Replication • A-DNA & Chromosomes • In cytoplasm in prokaryotes • In _______________________found in cell nucleus in the form of a number of chromosomes(46 humans,8 Drosophilia and 22 Sequoia trees) eukaryotes

  6. 1--DNA length • 1.6 mm in E.coli(has 4,639,221 base pairs)---obviously it must be tightly folded

  7. 2-Chromosome Structure • Eukaryotic cells have about 1000 times as many base pairs of DNA than a bacterium • Humans cells have ~ 1 m DNA • Eukaryotic chromosomes contain DNA and a protein ,which together make _____________________-consisting of DNA tightly packed around proteins called histones chromatin

  8. DNA and histone together make beadlike_____________________________ • Nucleosomes pack together to make thick fibers,drawn together during mitosis…also separating • Role of nucleosomes-fold great lengths of DNA into tiny spaces nucleosomes

  9. Prokaryotic Chromosome Structure Section 12-2 Chromosome E.coli bacterium Bases on the chromosome

  10. Figure 12-10 Chromosome Structure of Eukaryotes Section 12-2 Nucleosome Chromosome DNA double helix Coils Supercoils Histones

  11. B. DNA Replication • Each strand of DNA double helix has all the info to___________________________by base pairing • Strands are complementary • In prokaryotes,this begins @single point and proceeds-often in 2 directions • In Eukaryotes,DNA replication begins @ 100’s of places,going both directions until complete • __________________________is where replication occurs Reconstruct the other half Replication fork

  12. 1-Duplicating DNA • __________________________or duplication of DNA happens before cell division---ensuring each cell has a complete set of DNA molecules • Each strand of a double helix serves as a _____________________or model for new strand • A pairs w/ T and C w/ G template replication

  13. 2-How Replication Occurs • Carried out by a series of enzymes that unzip a molecule • ____________________________________ joins individual nucleotides to make a DNA molecule….also proof reads the new strands DNA polymerase

  14. Figure 12–11 DNA Replication Section 12-2 Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand

  15. III. RNA & Protein Synthesis • The double helix structure explains how DNA is copied,but not how a gene works-_______________are coded DNA instructions that control the production of protein in the cell. • A) The structure of RNA • Long chain of nucleotides • 3 main differences between DNA & RNA: • 1--Sugar is _________________ • 2---Generally single-stranded • 3---RNA contains ________________(U) in place of thymine (T) ribose uracil genes

  16. Protein synthesis B. Types of RNA • Main job=_________________-ie the assembly of amino acids into proteins • 3 Types: • ____________________(mRNA)-carry copies for instructions from DNA to rest of cell • ____________________(rRNA)-type of RNA that helps make up ribosomes,where proteins assembled • ________________(tRNA)transfers each amino acid to the ribosome as it is coded for on mRNA. messenger ribosomal Transfer

  17. Messenger RNA Ribosomal RNA Transfer RNA Bringamino acids toribosome Combine with proteins tRNA mRNA Carry instructions rRNA DNA Ribosome Ribosomes Concept Map Section 12-3 RNA can be which functions to also called also called which functions to also called which functions to from to to make up

  18. C. Transcription-produces RNA molecules by copying part of nucleotide sequence of DNA into a complementary sequence in RNA • Requires enzyme known as _______________________________________-binds to DNA and separates DNA strands.Then uses one strand as template to make RNA • The enzyme only binds to areas known as promoters-signals that indicate where to make RNA.Similar signals tell where to stop RNA-polymerase

  19. Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA

  20. D. RNA editing • ________________________ in eukaryotic genes ,sequences of nucleotides that ARE NOT involved in coding for proteins • _______________________-DNA sequence that does code for protein exons introns

  21. E. Genetic Code polypeptide • ______________________-chain of amino acids=proteins • _________________-3 consecutive nucleotides that specify a specific amino acid • Example –UCGCACGGU reads UCG_CAC_GGU and codes for Serine-Histidine-Glycine codon

  22.  The Genetic Code Section 12-3

  23. Universal code • 64 possible 3 base codons • AUG can specify methionine or start codon • 3 stop codons that do not code for an amino acid

  24. F. Translation ribosome • ______________________reads the instructions for the order in which amino acids should be joined by reading mRNA • ____________________________is the decoding of an mRNA message into a polypeptide(protein) • Before translation occurs,mRNA is transcribed from DNA and released into __________________________. • Translation begins when mRNA molecule in cytoplasm attaches to a _____________________. translation cytoplasm ribosome

  25. tRNA • As each codon of the mRNA moves through the moves through the ribosome,_____________brings in the proper,indicated amino acid and transferred to polypeptide chain • Each tRNA carries one kind of amino acid • __________________ is a group of 3 bases on a tRNA that are complementary to a mRNA codon • Ribosome forms a _________________bond between amino acids and breaks tRNA bond releasing it • Protein keeps growing until ribosome reaches stop codon on mRNA peptide anticodon

  26. Figure 12–18 Translation Section 12-3

  27. Figure 12–18 Translation (continued) Section 12-3

  28. IV.Mutations=________________________ Changes in genetic material Gene mutation • A.---Kinds of Mutations • 1) • ________________________________-changes in a single gene • _____________________________________-changes in 1 or a few nucleotides-@ a single point in DNA-includes substitutions,insertions and deletions • Substitutions usually affect no more than 1 amino acid • ____________________________________-insertions or deletions where the reading frame of the codon message is changed-can VERY much alter or even stop the function of a protein Point mutation Frameshift mutation

  29. 2)Chromosomal Mutations-change in the # or structure of chromosomes-can change the location of genes on chromosomes and /or number of copies of some genes. • 4types-1)Deletions-loss of all or part of a chromosome • 2)__________________-extra copies of a part of a chromosome • 3)________________reverse directions of parts of chromosomes • 4)____________-part of one chromosome breaks off and attaches to another translocations duplication inversions

  30. Gene Mutations: Substitution, Insertion, and Deletion Section 12-4 Deletion Substitution Insertion

  31. Figure 12–20 Chromosomal Mutations Section 12-4 Deletion Duplication Inversion Translocation

  32. B. Significance of Mutations • Many have no effect • Harmful effects include genetic disorders and cancer • ________________________-contains extra set of chromosomes-bad in most cases but often helpful in PLANTS. polyploidy

  33. V. Gene Regulation operon • Only a fraction of a gene expressed at one time • ___________________-group of genes that operate together • ________________-where repressor binds operon (when it)is turned off • Operons not usually found in eukaryotes-these genes are usually controlled individually and regulation more complex---mainly because of cell specialization • Hox genes-control differentiation of cells and tissues in the embryo operator

  34. Typical Gene Structure Section 12-5 Promoter(RNA polymerase binding site) Regulatory sites DNA strand Start transcription Stop transcription

  35. Karyotypes

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