1. Chapter 10 Student 2015

2. DNA REPLICATION “It has not escaped our notice that the specific pairing we have postulated immediately suggested a possible copying mechanism for the genetic material” – Watson and Crick April 1953 the journal Nature © 2012 Pearson Education, Inc.

3. 10.4 DNA replication depends on specific base pairing  In their description of the structure of DNA, Watson and Crick noted that the structure of DNA suggests a possible copying mechanism.  DNA replication follows a semiconservative model.  Each new daughter DNA will have one old and one new strand © 2012 Pearson Education, Inc.

4. Figure 10.4A_s3 A parental molecule of DNA A C G C A T T A The parental strands separate and serve as templates Free nucleotides T A T T A A T A G G G C C A T C G C Two identical daughter molecules of DNA are formed A T T A C G G C

5. Figure 10.4B Parental DNA molecule Daughter strand Parental strand Daughter DNA molecules A T G C A T T A T C G A T G C T C G T A C G C A T G C A T G A A

6.  DNA replication begins at the origins of replication where DNA unwinds (helicase) at the origin to produce a “bubble,” replication proceeds in both directions from the origin, and replication ends when products from the bubbles merge with each other. 10.5 DNA replication proceeds in two directions at many sites simultaneously © 2012 Pearson Education, Inc.

7. Figure 10.5A Parental DNA molecule Origin of replication “Bubble” Parental strand Daughter strand Two daughter DNA molecules

8.  DNA polymerases add nucleotides to growing chain and proof reads  DNA replication is continuous in the 5 to 3 direction, (on the 3’ to 5’ template) – Leading strand Replication is discontinuous in the 3’ to 5’direction (on the 5’ to 3’ template) and forms short segments. Lagging strand – Okazaki fragments DNA ligase links the pieces of DNA together 10.5 DNA replication proceeds in two directions at many sites simultaneously © 2012 Pearson Education, Inc.

9. Figure 10.5C Overall direction of replication DNA ligase Replication fork Parental DNA DNA polymerase molecule This daughter strand is synthesized continuously This daughter strand is synthesized in pieces 3 5 3 5 3 5 3 5

10.  DNA replication ensures that all the somatic cells in a multicellular organism carry the same genetic information. 10.5 DNA replication proceeds in two directions at many sites simultaneously © 2012 Pearson Education, Inc.

11. THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN © 2012 Pearson Education, Inc.

12. 10.6 The DNA genotype is expressed as proteins, which provide the molecular basis for phenotypic traits  DNA specifies traits by dictating protein synthesis.  The Central Dogma  The molecular chain of command is from DNA in the nucleus to RNA and RNA in the cytoplasm to protein.  Transcription is the synthesis of mRNA under the direction of DNA.  Translation is the synthesis of proteins under the direction of RNA. © 2012 Pearson Education, Inc.

13. 10.10 Eukaryotic RNA is processed before leaving the nucleus as mRNA  Eukaryotic mRNA undergoes processing before leaving the nucleus. Eukaryotic mRNA has – introns, interrupting sequences that separate – exons, the coding regions. RNA splicing A cap and tail of extra nucleotides are added © 2012 Pearson Education, Inc.

14. Figure 10.6A_s3 DNA NUCLEUS CYTOPLASM RNA Transcription Translation Protein

15. 10.6 The DNA genotype is expressed as proteins, which provide the molecular basis for phenotypic traits  The connections between genes and proteins  Genes (genotypes) dictate traits (phenotypes) through proteins.  Alkaptonuria  Defect in the enzyme homogentisate 1,2-dioxygenase  Accumulation of alkapton in the blood  urine  Causes “black urine”  Abnormal gene  abnormal enzyme  abnormal phenotype  One gene  one polypeptide © 2012 Pearson Education, Inc.

16. 10.9 Transcription produces genetic messages in the form of Messenger RNA  Transcription is the synthesis of mRNA from a DNA template. In eukaryotic cells, transcription occurs in the nucleus and the mRNA must travel from the nucleus to the cytoplasm One strand of DNA is used A single strand of RNA is made – mRNA: encodes the amino acid sequence – rRNA: part of the ribosome – tRNA: carries the amino acid © 2012 Pearson Education, Inc.

17. Transcription produces genetic messages in the form of Messenger RNA  Overview of transcription The RNA molecule is transcribed from a DNA template by a process that resembles DNA replication. RNA nucleotides are linked by the transcription enzyme RNA polymerase. The “start transcribing” signal is a nucleotide sequence called a promoter.

18. 10.9 Transcription produces genetic messages in the form of RNA Transcription begins with initiation, RNA polymerase attaches to the promoter. elongation, the RNA grows longer. (5’  3’ direction) As the RNA peels away, the DNA strands rejoin. termination, the RNA polymerase reaches a sequence of bases in the DNA template called a terminator, which signals the end of the gene. The polymerase molecule now detaches © 2012 Pearson Education, Inc.

19. Figure 10.9B RNA polymerase DNA of gene Promoter DNA Initiation 1 2 Terminator DNA 3 Elongation Area shown in Figure 10.9A Termination Growing RNA RNA polymerase Completed RNA

20. Figure 10.9A RNA polymerase Free RNA nucleotides Template strand of DNA Newly made RNA Direction of transcription T G A G G A A U C CA C T T A A C C G G U T U T A ACC T A T C

21. 10.10 Eukaryotic RNA is processed before leaving the nucleus as mRNA  Eukaryotic mRNA undergoes processing before leaving the nucleus. Eukaryotic mRNA has – introns, interrupting sequences that separate – exons, the coding regions. RNA splicing A cap and tail of extra nucleotides are added © 2012 Pearson Education, Inc.

22. Figure 10.10 DNA Cap Exon IntronExon RNA transcript with cap and tail ExonIntron Transcription Addition of cap and tail Introns removed Tail Exons spliced together Coding sequence NUCLEUS CYTOPLASM mRNA

23. Explain why most eukaryotic genes are longer than the mRNA that leaves the nucleus.

24. 10.7 Genetic information written in codons is translated into amino acid sequences The flow of information from gene to protein is based on a triplet code: nonoverlapping three-base “words” called codons. Translation involves switching from the nucleotide “language” to the amino acid “language.” © 2012 Pearson Education, Inc.

25. Figure 10.7_1 A Transcription RNA Translation Codon Polypeptide Amino acid AAC C GG C AAAA U U GGCCG U U U U DNA U

26. Figure 10.8A Second base Third base First base

27. 10.8 The genetic code dictates how codons are translated into amino acids  Characteristics of the genetic code Three nucleotides specify one amino acid. – 61 codons correspond to amino acids. – AUG codes for methionine and signals the start of transcription. – 3 “stop” codons signal the end of translation. © 2012 Pearson Education, Inc.

28. 10.8 The genetic code dictates how codons are translated into amino acids  The genetic code is redundant unambiguous nearly universal without punctuation © 2012 Pearson Education, Inc.

29. Figure 10.11A Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon A simplified schematic of a tRNA A tRNA molecule, showing its polynucleotide strand and hydrogen bonding

30. Figure 10.12B tRNA binding sites mRNA binding site Large subunit Small subunit P site A site

31. 10.12 Ribosomes build polypeptides  Translation occurs on the surface of the ribosome. Ribosomes coordinate the functioning of mRNA and tRNA and, ultimately, the synthesis of polypeptides. © 2012 Pearson Education, Inc.

32. Figure 10.12C mRNA Codons tRNA Growing polypeptide The next amino acid to be added to the polypeptide

33. 10.13 An initiation codon marks the start of an mRNA message  Translation can be divided into the same three phases as transcription: 1.initiation, 2.elongation 3.termination. © 2012 Pearson Education, Inc.

34. 10.13 An initiation codon marks the start of an mRNA message Initiation brings together mRNA, a tRNA bearing the first amino acid, and the two subunits of a ribosome. – P site, which will hold the growing peptide chain. – A site is available to receive the next tRNA.

35. Figure 10.13A Start of genetic message Cap End Tail

36. Figure 10.13B Initiator tRNA mRNA Start codon Small ribosomal subunit Large ribosomal subunit P site A site Met AUG U A C 2 AUG U A C 1

37.  Each cycle of elongation has three steps. 1.Codon recognition 2.Peptide bond formation 3.Translocation 10.14 Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation © 2012 Pearson Education, Inc.

38. Figure 10.14_s4 Polypeptide mRNA Codon recognition Anticodon Amino acid Codons P site A site 1 Peptide bond 2 formation Translocation 3 New peptide bond Stop codon mRNA movement

39.  Elongation continues until the termination stage of translation, when the ribosome reaches a stop codon, the completed polypeptide is freed the ribosome splits back into its separate subunits. 10.14 Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation © 2012 Pearson Education, Inc.