1 / 71

Understanding DNA: Structure, Function, and Significance

Explore the composition and importance of DNA, the molecule of heredity, its components, and how it determines organism traits through proteins. Discover the discoveries and structure of DNA, leading to Watson and Crick's groundbreaking findings.

adelia
Download Presentation

Understanding DNA: Structure, Function, and Significance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bellwork: Write the 2 questions and answer them in your notes. Then, draw and label the parts of the nucleotide below. 1. What are the 3 components of this DNA nucleotide?2. What is the function of DNA in the cell?

  2. Unit Overview – pages 250-251 Genetics DNA and Genes DNA: The Molecule of Heredity

  3. Contributors to DNA Discovery • 1943 Oswald Avery: DNA carries genetic information • 1952 Franklin took the first picture of DNA using X-RAY

  4. Contributors to DNA Discovery 1953 - Watson & Crick proposed the structure of DNA 1962 - Nobel Prize to Watson and Crick • “FATHERS OF DNA”

  5. Contributors to DNA Discovery • What event occurred allowing Watson and Crick to discover the DNA structure?

  6. Section 11.1 Summary – pages 281 - 287 What is DNA? • Deoxyribonucleic Acid • determines an organism’s traits • ultimately determines the structure of proteins. • body is made up of proteins • body’s functions depend on proteins called enzymes.

  7. Section 11.1 Summary – pages 281 - 287 The Structure of DNA • DNA is a polymer made of nucleotides. • Nucleotides have three parts: • simple sugar • phosphate group • nitrogenous base.

  8. Nucleotide Structure: Section 11.1 Summary – pages 281 - 287 • composed of one atom of phosphorus surrounded by four oxygen atoms. carbon ring structure that contains one or more atoms of nitrogen. Nitrogenous base Phosphate group Sugar (deoxyribose) • Deoxyribose is the simple sugar in DNA

  9. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • In DNA, there are four possible nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). *always pair * always pair Cytosine (C) Thymine (T) Guanine (G) Adenine (A)

  10. The structure of nucleotides • Thus, in DNA there are four possible nucleotides, each containing one of these four bases. • Nucleotides join together to form long chains. • Formed by covalent bonds • These chains are known as the Double Helix

  11. Section 11.1 Summary – pages 281 - 287

  12. Section 11.1 Summary – pages 281 - 287 The importance of nucleotide sequences The sequence of nucleotides in each gene contains information for assembling the string of amino acids Chromosome

  13. Genes and Proteins • DNA ultimately determines structure of proteins • Proteins make up the structure of an organism AND control all of the organism’s chemical reactions to keep it alive

  14. Section 1 Check Question 1 Which of the following is NOT a component of DNA? A. simple sugars B. phosphate groups C. nitrogenous bases D. proteins The answer is D.

  15. Section 1 Check Question 2 Which of the following correctly comprises a complimentary base pair? A. adenine – thymine B. thymine – guanine C. guanine – adenine D. cytosine – thymine The answer is A.

  16. DNA and Cell Division

  17. DNA to Proteins • Remember…DNA ultimately determines structure of proteins. • These proteins are what makes “us” and enables “us” to function….. • So how do we get these specific proteins?

  18. Section 11.1 Summary – pages 281 - 287 Replication of DNA • Before a cell can divide by mitosis or meiosis, it must first make a copy of its chromosomes.( Interphase) • The DNA in the chromosomes is copied in a process called DNA replication. • Without DNA replication, new cells would have only half the DNA of their parents.

  19. Section 11.2 Summary – pages 288 - 295 Cells Start Here: Transcription • Transcription results in the formation of one single-stranded RNA molecule. • takes place in the nucleus • mRNA, which is seen in here, takes the instructions from the nucleus to the cytoplasm.

  20. Section 11.2 Summary – pages 288 - 295 What is RNA? • RNA is single stranded • The sugar is ribose • Rather than thymine, RNA contains a similar base called uracil (U). Uracil Adenine Hydrogen bonds

  21. Why RNA? • DNA provides workers with the instructions for making the proteins, and workers build the proteins. • The workers for protein synthesis are RNA molecules.

  22. Back to Copying DNA…. • Once mRNA is in the cytoplasm… Ribosomal RNA(rRNA) binds to the mRNA and uses the instructions to assemble the amino acids in the correct order. • This starts Translation

  23. Section 11.2 Summary – pages 288 - 295 Translation: From mRNA to Protein • Translation is the process of converting the information in a sequence of nitrogenous bases in mRNA into a sequence of amino acids in protein. • Translation takes place at the ribosomes in the cytoplasm.

  24. 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. • An anticodon is a sequence of three bases found on tRNA. Chain of RNA nucleotides Transfer RNA molecule Anticondon

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

  26. 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. • Then the ribosome slides along the mRNA to the next codon.

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

  28. 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

  29. 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

  30. 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

  31. 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)

  32. DNAi • Triplet code • Translation http://www.pbs.org/wgbh/nova/body/rnai.html

  33. Section 2 Check Question 1 What are the three chemical differences between RNA and DNA? Answer RNA consists of a single strand of nucleotides whereas DNA is a double strand. RNA contains ribose as its sugar and DNA contains deoxyribose as its sugar. Uracil in RNA replaces thymine in DNA as the nitrogenous base.

  34. Section 2 Check Question 2 What is the role of rRNA in protein synthesis? Answer Ribosomal RNA binds to messenger RNA and assembles the amino acids in the order needed for the protein to be synthesized.

  35. Section 2 Check Question 3 Which regions of the mRNA travel to the ribosome; introns, exons, or both? Answer Only exons, which contain coding information, travel to the ribosome. Introns, noncoding nucleotide sequences, do not travel to the ribosome.

  36. Section 2 Check Question 4 What is an anticodon, and what does it represent? Answer An anticodon is a sequence of three nucleotides on the tRNA molecule that binds to a codon of the mRNA strand.

  37. Section 2 Check Question 4 What is the product of replication; of transcription; of translation? Answer Two DNA molecules; one mRNA molecule; a protein

  38. 11.3 Section Objectives – page 296 1. Why is this exact base sequence important? 2. What may be the result of “wrong” base sequencing?

  39. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations • Organisms have evolved many ways to protect their DNA from changes. • In spite of these mechanisms, however, changes in the DNA occasionally do occur. • A mutation is any change in a DNA sequence. • Mutations can be caused by errors in replication, transcription, cell division, or by external agents.

  40. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations in reproductive cells • Mutations can occur in the reproductive cells. • This then becomes part of the genetic makeup of the offspring. • If the change makes a protein nonfunctional, the embryo may not survive.

  41. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations in body cells • What happens if powerful radiation, such as gamma radiation, hits the DNA of a nonreproductive cell, a cell of the body such as in skin, muscle, or bone? • If the body cell’s DNA is changed, this mutation would not be passed on to offspring. • The mutation may cause problems for the individual.

  42. 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.

  43. 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

  44. 11.3 Section Summary 6.3 – pages 296 - 301 Frameshift mutations • A frameshift mutationis a mutation in which a single base is added or deleted from DNA. • A frameshift mutation shifts the reading of codons by one base. • This mutation would cause nearly every amino acid in the protein after the deletion to be changed.

  45. 11.3 Section Summary 6.3 – pages 296 - 301 Frameshift mutations Deletion of U mRNA Frameshift mutation Protein

  46. 11.3 Section Summary 6.3 – pages 296 - 301 Chromosomal Alterations • Chromosomal mutationsare structural changes in chromosomes. • When a part of a chromosome is left out, a deletion occurs ABCDEFGH A B C E F G H Deletion

  47. 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

More Related