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Chapter Intro-page 280

Chapter Intro-page 280. What You’ll Learn. You will relate the structure of DNA to its function. You will explain the role of DNA in protein production. You will distinguish among different types of mutations. 1 of 42. Section 11.1 Summary – pages 281 - 287. What is DNA?.

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Chapter Intro-page 280

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  1. Chapter Intro-page 280 What You’ll Learn You will relate the structure of DNA to its function. You will explain the role of DNA in protein production. You will distinguish among different types of mutations. 1 of 42

  2. Section 11.1 Summary – pages 281 - 287 What is DNA? • The genetic information that is held in the molecules of DNA ultimately determines an organism’s traits. • DNA achieves its control by determining the structure of proteins.

  3. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • DNA is a polymer made of repeating subunits called nucleotides. Nitrogenous base Phosphate group Sugar (deoxyribose) • Nucleotides have three parts: a simple sugar, a phosphate group, and a nitrogenous base.

  4. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • The simple sugar in DNA, called deoxyribose (dee ahk sih RI bos), gives DNA its name—deoxyribonucleic acid.

  5. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen. • In DNA, there are four possible nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Cytosine (C) Guanine (G) Thymine (T) Adenine (A)

  6. Section 11.1 Summary – pages 281 - 287 The structure of DNA • In 1953, Watson and Crick proposed that DNA is made of two chains of nucleotides held together by nitrogenous bases. • Watson and Crick also proposed that DNA is shaped like a long zipper that is twisted into a coil like a spring. • Because DNA is composed of two strands twisted together, its shape is called double helix.

  7. Section 11.1 Summary – pages 281 - 287 The importance of nucleotide sequences The sequence of nucleotides forms the unique genetic information of an organism. Chromosome

  8. Section 11.1 Summary – pages 281 - 287 Replication of DNA • The DNA in the chromosomes is copied in a process called DNA replication.

  9. Section 11.1 Summary – pages 281 - 287 DNA Replication Replication of DNA Replication

  10. Section 11.1 Summary – pages 281 - 287 Copying DNA New DNA molecule Original DNA Strand Free Nucleotides New DNA molecule New DNA Strand Original DNA Strand Original DNA

  11. Section 11.2 Summary – pages 288 - 295 RNA • RNA like DNA, is a nucleic acid. RNA structure differs from DNA structure in three ways. • First, RNA is single stranded—it looks like one-half of a zipper—whereas DNA is double stranded.

  12. Section 11.2 Summary – pages 288 - 295 RNA Ribose • The sugar in RNA is ribose; DNA’s sugar is deoxyribose.

  13. Section 11.2 Summary – pages 288 - 295 RNA • Both DNA and RNA contain four nitrogenous bases, but rather than thymine, RNA contains a similar base called uracil (U). • Uracil forms a base pair with adenine in RNA, just as thymine does in DNA. Uracil Hydrogen bonds Adenine

  14. Section 11.2 Summary – pages 288 - 295 RNA • DNA provides workers with the instructions for making the proteins, and workers build the proteins. • The workers for protein synthesis are RNA molecules.

  15. Section 11.2 Summary – pages 288 - 295 RNA • There are three types of RNA that help build proteins. • Messenger RNA (mRNA), brings instructions from DNA in the nucleus to the cell’s ribosome. • The ribosome, made of ribosomal RNA (rRNA), binds to the mRNA and uses the instructions to assemble the amino acids in the correct order.

  16. Section 11.2 Summary – pages 288 - 295 • Transfer RNA (tRNA) is the supplier. Transfer RNA delivers amino acids to the ribosome to be assembled into a protein.

  17. Section 11.2 Summary – pages 288 - 295 Transcription • In the nucleus, enzymes make an RNA copy of a portion of a DNA strand in a process called transcription.

  18. Section 11.2 Summary – pages 288 - 295 Transcription A DNA strand RNA strand RNA strand C B DNA strand

  19. Section 11.2 Summary – pages 288 - 295 RNA Processing • Regions that contain information are called exons because they are expressed. • When mRNA is transcribed from DNA, both introns and exons are copied. • The introns must be removed from the mRNA before it can function to make a protein.

  20. Section 11.2 Summary – pages 288 - 295 RNA Processing • Enzymes in the nucleus cut out the intron segments and paste the mRNA back together. • The mRNA then leaves the nucleus and travels to the ribosome.

  21. The Genetic Code • Biochemists discovered that a group of three nitrogenous bases in mRNA code for one amino acid. Each group is known as a codon.

  22. Section 11.2 Summary – pages 288 - 295 The Genetic Code • Sixty-four combinations are possible when a sequence of three bases is used; thus, 64 different mRNA codons are in the genetic code.

  23. Section 11.2 Summary – pages 288 - 295 The Genetic Code The Messenger RNA Genetic Code First Letter Third Letter Second Letter U A G C U U Phenylalanine (UUU) Serine (UCU) Tyrosine (UAU) Cysteine (UGU) C Cysteine (UGC) Phenylalanine (UUC) Serine (UCC) Tyrosine (UAC) A Stop (UGA) Serine (UCA) Stop (UAA) Leucine (UUA) G Leucine (UUG) Serine (UCG) Stop (UAG) Tryptophan (UGG) C U Arginine (CGU) Leucine (CUU) Proline (CCU) Histadine (CAU) Arginine (CGC) Proline (CCC) C Leucine (CUC) Histadine (CAC) A Proline (CCA) Arginine (CGA) Leucine (CUA) Glutamine (CAA) Arginine (CGG) G Glutamine (CAG) Proline (CCG) Leucine (CUG) A U Isoleucine (AUU) Threonine (ACU) Asparagine (AAU) Serine (AGU) C Serine (AGC) Asparagine (AAC) Isoleucine (AUC) Threonine (ACC) A Arginine (AGA) Isoleucine (AUA) Threonine (ACA) Lysine (AAA) G Arginine (AGG) Methionine;Start (AUG) Threonine (ACG) Lysine (AAG) G Glycine (GGU) U Valine (GUU) Alanine (GCU) Aspartate (GAU) Valine (GUC) Aspartate (GAC) Glycine (GGC) Glycine (GGC) C Alanine (GCC) A Glycine (GGA) Alanine (GCA) Glutamate (GAA) Valine (GUA) Glutamate (GAG) Glycine (GGG) Alanine (GCG) G Valine (GUG)

  24. Section 11.2 Summary – pages 288 - 295 Translation: From mRNA to Protein • The 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. • Translation takes place at the ribosomes in the cytoplasm.

  25. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • For proteins to be built, the 20 different amino acids dissolved in the cytoplasm must be brought to the ribosomes. • This is the role of transfer RNA.

  26. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA Amino acid • Each tRNA molecule attaches to only one type of amino acid. Chain of RNA nucleotides Transfer RNA molecule Anticondon

  27. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA Ribosome mRNA codon

  28. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • The first codon on mRNA is AUG, which codes for the amino acid methionine. • AUG signals the start of protein synthesis. • When this signal is given, the ribosome slides along the mRNA to the next codon.

  29. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA Methionine tRNA anticodon

  30. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • A new tRNA molecule carrying an amino acid pairs with the second mRNA codon. Alanine

  31. Section 11.2 Summary – pages 288- 295 The role of transfer RNA • The amino acids are joined when a peptide bond is formed between them. Methionine Alanine Peptide bond

  32. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • A chain of amino acids is formed until the stop codon is reached on the mRNA strand. Stop codon

  33. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations • Any change in DNA sequence is called a mutation. • Mutations can be caused by errors in replication, transcription, cell division, or by external agents.

  34. 11.3 Section Summary 6.3 – pages 296 - 301 The effects of point mutations • A point mutation is a change in a single base pair in DNA. • A change in a single nitrogenous base can change the entire structure of a protein because a change in a single amino acid can affect the shape of the protein.

  35. 11.3 Section Summary 6.3 – pages 296 - 301 The effects of point mutations mRNA Normal Protein Stop Replace G with A Point mutation mRNA Protein Stop

  36. 11.3 Section Summary 6.3 – pages 296 - 301 Frameshift mutations • 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. • Structural changes in chromosomes are called chromosomal mutations.

  37. 11.3 Section Summary 6.3 – pages 296 - 301 Causes of Mutations • Any agent that can cause a change in DNA is called a mutagen. • Mutagens include radiation, chemicals, and even high temperatures. • Forms of radiation, such as X rays, cosmic rays, ultraviolet light, and nuclear radiation, are dangerous mutagens because the energy they contain can damage or break apart DNA.

  38. 11.3 Section Summary 6.3 – pages 296 - 301 Chromosomal Alterations • When a part of a chromosome is left out, a deletion occurs. ABCDEFGH A B C E F G H Deletion

  39. 11.3 Section Summary 6.3 – pages 296 - 301 Chromosomal Alterations • When part of a chromatid breaks off and attaches to its sister chromatid, an insertion occurs. • The result is a duplication of genes on the same chromosome. A B C B C D E F G H A B C D E F G H Insertion

  40. 11.3 Section Summary 6.3 – pages 296 - 301 Chromosomal Alterations • When part of a chromosome breaks off and reattaches backwards, an inversion occurs. A D C B E F G H A B C D E F G H Inversion

  41. 11.3 Section Summary 6.3 – pages 296 - 301 Chromosomal Alterations • When part of one chromosome breaks off and is added to a different chromosome, a translocation occurs. F G H E B C D F G A W X B C D E H A X Y Z Y Z W Translocation

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