1 Chapter 12

2 DNA structure and replication RNATranscription Translation Protein synthesis Amino acids

3 Discovery of the Genetic MaterialAfter the rediscovery of Mendel’s work, scientist began to look for the molecule involved in inheritance. For many years, scientists struggled to determine if DNA or protein was the source of genetic information. Copyright © McGraw-Hill Education

4 Discovery of the Genetic MaterialMiescher 1860’s “nuclein” Griffith First major experiment searching for the genetic material Involved transformation between two forms of S. pneumoni Copyright © McGraw-Hill Education

5 Chromosome Structure To fit into a cell, DNA coils around a group of beadlike proteins Group together into chromatin fibers Supercoil to form a chromosome. Copyright © McGraw-Hill Education DNA: The Genetic Material

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7 Chromosome Structure Eukaryotes DNA in individual chromosomes NucleusProkaryotes DNA in Cytoplasm Copyright © McGraw-Hill Education DNA: The Genetic Material

8 DNA Structure James Watson (L) and Francis Crick (R), and the model they built of the structure of DNA. Copyright © McGraw-Hill Education

9 DNA Structure Double helixX-ray diffraction techniques indicated that DNA was a double helix, or a twisted ladder shape. Formed by two strands of nucleotides twisted around each other. Copyright © McGraw-Hill Education

10 The structure of DNA and RNAGenetic material of living organisms is either DNA or RNA. DNA – Deoxyribonucleic acid RNA – Ribonucleic acid Genes are lengths of DNA that code for particular proteins.

11 DNA and RNA are PolynucleotidesBoth DNA and RNA are polynucleotides. Poly = many They are made up of smaller molecules called nucleotides. DNA is made of two polynucleotide strands: RNA is made of a single polynucleotide strand: Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide

12 DNA Structure NucleotidesNucleotides are the subunits of nucleic acids, and consist of 5-carbon sugar Phosphate group Nitrogenous base

13 DNA Structure Pentose Sugar 5 carbon sugar DNA – deoxyriboseRNA - ribose

14 DNA Structure Phosphate GroupLink the sugar of one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide.

15 AS Biology. Gnetic control of protein structure and functionDNA Structure A Nitrogenous base: In DNA the four bases are: Thymine Adenine Cytosine Guanine In RNA the four bases are: Uracil AS Biology. Gnetic control of protein structure and function

16 Four DNA bases Four kinds of nitrogenous bases: Purine basesPyrimidine bases

17 DNA: Complimentary base pairingAdenine pairs with Thymine A = T Bond Type = double Cytosine pairs with Guanine C = G Triple

18 DNA Structure DNA often is compared to a twisted ladder.Rails of the ladder are represented by the alternating deoxyribose and phosphate. The pairs of bases (cytosine-guanine or thymine- adenine) form the steps.

19 DNA STRUCTURE VIDEO YUMMY GUMMY DNA

20 DNA Replication (in nucleus)Matching bases allows DNA to be easily copied

21 Making new DNA Replication Copying DNADNA starts as a double-stranded molecule matching bases (A:T, C:G) then it unzips…

22 DNA Replication Strands “unzip” at the weak bonds between bases

23 DNA Replication Enzyme DNA polymerase adds new basesDNA bases in nucleus Enzyme DNA polymerase adds new bases DNA polymerase

24 Copying DNA Build daughter DNA stranduse original parent strand as “template” add new matching bases synthesis enzyme = DNA polymerase DNA Polymerase

25 New copies of DNA Get 2 exact copies of DNA to split between new cellspolymerase DNA polymerase

26 Copied & Paired Up Chromosomescentromere

27 Comparing DNA ReplicationEukaryotes and Prokaryotes Eukaryotic DNA unwinds in multiple areas as DNA is replicated. In prokaryotes, the circular DNA strand is opened at one origin of replication. Copyright © McGraw-Hill Education

28 Replication of DNA and ChromosomesSpeed of DNA replication: ,000 nucleotides/min in human ,000 nucleotides/min in E.coli Accuracy of DNA replication: Very precise (1 error/1,000,000,000 nt) AS Biology. Gnetic control of protein structure and function

29 3

30 Base your answer to the following question on the diagram below which represents a portion of a double-stranded DNA molecule and on your knowledge of biology. The base sequence of strand II is most likely: C-A-C-T-G-G G-T-G-U-C-C G-G-T-C-A-C G-T-G-A-C-C 4

31 Practice On your paper, complete the missing DNA strand by adding the complementary bases. A T C G T T G C C A T C T A G C A A C G G T A G

32 DNA, RNA & Protein Chapter 12: Section 3

33 Central Dogma Investigate how DNA served as a genetic code for the synthesis of proteins. Geneticists accept that the basic mechanism for reading and expressing genes is from DNA to RNA to protein. This is referred to as the central dogma of biology: DNA codes for RNA, which guides the synthesis of proteins. Copyright © McGraw-Hill Education

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35 RNA differs from DNA DNA has a sugar deoxyribose1. RNA has a sugar ribose DNA has a sugar deoxyribose 2. RNA contains uracil (U) DNA has thymine (T) 3. RNA molecule is single-stranded DNA is double-stranded

36 Three Types of RNA Central DogmaMessenger RNA (mRNA): long strands of RNA that are formed complementary to one strand of DNA; direct synthesis of a specific protein Ribosomal RNA (rRNA): associates with proteins to form ribosomes in the cytoplasm Transfer RNA (tRNA): smaller segments of RNA that transport amino acids to the ribosome Copyright © McGraw-Hill Education

37 Central Dogma TranscriptionFirst step synthesis of mRNA from DNA in a process called transcription. RNA polymerase moves along the DNA strand in a 3’ to 5’ direction, synthesizing mRNA. Copyright © McGraw-Hill Education

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39 Practice Make the complementary RNA strand for the single strand of DNA below: A A T C A T C A C G T T U U A G U A G U G C A A T A C C C G A G G T A G C C G C G T A T T A U G G G C U C C A U C G G C G C A U A A

40 Reading the genetic codeThe genetic code is responsible for building all the proteins in the body using 20 different amino acids. How many 3 letter words can you make from the letters A,T,G and C? Answer: 64

41 The three-base code in DNA or mRNA is called a codon.The Code Scientists hypothesized that the instructions from protein synthesis were encoded in DNA. Experiments during the 1960s demonstrated that the DNA code was a three-base code. The three-base code in DNA or mRNA is called a codon. Copyright © McGraw-Hill Education DNA, RNA, and Protein

42 Codons A three letter “word” that specifies an amino acid.

43 A. Messenger RNA (mRNA) A U G C aa1 aa2 aa3 aa4 aa5 aa6 peptide bondsstart codon codon 2 codon 3 codon 4 codon 5 codon 6 codon 7 codon 1 methionine glycine serine isoleucine alanine stop codon protein Primary structure of a protein aa1 aa2 aa3 aa4 aa5 aa6 peptide bonds

44 The Code Translation After synthesis, mRNA moves from the nucleus into the cytoplasm, where it connects to a ribosome. The mRNA code is read and translated into a protein through a process called translation. Copyright © McGraw-Hill Education DNA, RNA, and Protein

45 tRNA molecules act as the interpreters of the mRNA codon sequence. The Code Translation tRNA molecules act as the interpreters of the mRNA codon sequence. The tRNA is activated by an enzyme that attaches a specific amino acid to the end. The middle of the folded tRNA contains an anticodon, a complementary sequence to the mRNA codon. Copyright © McGraw-Hill Education DNA, RNA, and Protein

46 The role of the ribosome The Code The role of the ribosome Ribosomes provide a site for protein synthesis. When mRNA leaves the nucleus, the two ribosomal subunits come together to hold the mRNA in place for translation. The ribosome structure has grooves that hold the mRNA and serve as tRNA sites for amino acid attachment. Copyright © McGraw-Hill Education

47 From DNA to Protein

48 found inside the nucleusDIFFERENCES DNA RNA Deoxyribonucleic acid Double strand G, C, A, T deoxyribose sugar Inheritance of traits & enzyme production NUCLEIC ACIDS C, G, A found inside the nucleus Ribonucleic acid Single strand G, C, A, U ribose sugar protein synthesis SIMILARITIES

49 If the cell is a school… The Nucleus is the school officeThe Nucleolus is the principal’s office The DNA is the principal Ribosomes are the cafeteria ladies mRNA is the from the principal to the cafeteria lady

50 Review/Explain: Types of Nucleic AcidsWhat are the two types of nucleic acids? Ribonucleic Acid (RNA) Single Stranded Deoxyribonucleic Acid (DNA) Double Helix (Twisted Ladder)

51 DNA Deoxyribose Sugar Base Pairs A-T G-C Phosphate Most Importantly---Contains the Code for ALL the Proteins in the Body

52 RNA Ribonucleic Acid Sugar + Phosphate backbone Differs from DNASingle Stranded Ribose Sugar Base Pairs A-U, G-C RNA assists DNA in manufacturing needed proteins

53 Questions Name one difference between DNA and RNA.DNA – Double Helix, RNA – Single Stranded DNA --- A-T, RNA ---A-U DNA ---Deoxyribose Sugar, RNA--- Ribose What is a similarity of DNA and RNA? G binds with C in both DNA and RNA Both have sugar and phosphate backbone

54 Gel Electrophoresis use to separate DNA fragments determinerelationships used in forensics

55 Study the diagram on the left side of this slide.Which of the following DNA samples of individuals are most closely related? EXPLAIN. DNA sample 1 & 7

56 Crime Scene #1

57 Crime Scene #2

58 Crime Scene #3

59 Paternity

60 Paternity #1 Dad 2

61 Paternity #2

62 WHO ARE THE PARENTS?

63 WHO ARE THE PARENTS? Child 1 Child 2 Child 3 Child 4Mom and Dad Mom Neither