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DNA Replication

DNA Replication . DNA Replication. DNA must be copied (before a cell divides) The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing: A-T, G-C. Each strand of the original DNA serves as a template for the new strand. DNA Template.

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DNA Replication

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  1. DNA Replication

  2. DNA Replication • DNA must be copied (before a cell divides) • The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing: A-T, G-C • Each strand of the original DNA serves as a template for the new strand

  3. DNA Template Parental DNA New DNA DNA Replication • Semiconservative Model: 1.Watson and Crick showed: the two strands of the parental moleculeseparate, and each functions as a template for synthesis of a new complementary strand. .

  4. How can entire chromosomes be replicated during S phase? • The hydrogen bonds between base pairs are broken • DNA replication begins at many specific sites • The main enzyme responsible is DNA Polymerase Parental strand Origin of replication Daughter strand Bubble Two daughter DNA molecules Figure 10.5A

  5. DNA Transcription • DNA can “unzip” itself and RNA nucleotides match up to the DNA strand. • Both DNA & RNA are formed from NUCLEOTIDES and are called NUCLEIC acids.

  6. Transcription produces genetic messages in the form of mRNA RNA nucleotide RNApolymerase Direction oftranscription Templatestrand of DNA

  7. RNA polymerase DNA of gene Promoter DNA Terminator DNA Initiation • In transcription, DNA helix unzips • RNA polymerase binds to DNA and separates strands • RNA nucleotides line up along one strand of DNA, following the base-pairing rules • single-stranded messenger RNA peels away and DNA strands rejoin Elongation Area shownin Figure 10.9A Termination GrowingRNA Completed RNA RNApolymerase

  8. Eukaryotic RNA is processed before leaving the nucleus Exon Intron Exon Intron Exon DNA • Noncoding segments, introns, are spliced out • A cap and a tail are added to the ends TranscriptionAddition of cap and tail Cap RNAtranscriptwith capand tail Introns removed Tail Exons spliced together mRNA Coding sequence NUCLEUS CYTOPLASM Figure 10.10

  9. Replication Quiz A---? G---? C---? T---? A---? G---? A---? G---? C---? A---? G---? T---? 1. Why is replication necessary? 2. When does replication occur? 3. Describe how replication works. • Use the complementary rule to create the complementary strand:

  10. Replication Quiz A---T G---C C---G T---A A---T G---C A---T G---C C---G A---T G---C T---A 1. Why is replication necessary? So both new cells will have the correct DNA 2. When does replication occur? During interphase (S phase). 3. Describe how replication works. Enzymes unzip DNA and complementary nucleotides join each original strand. 4. Use the complementary rule to create the complementary strand:

  11. The information constituting an organism’s genotype is carried in its sequence of bases • The DNA is transcribed into RNA, which is translated into the polypeptide DNA TRANSCRIPTION RNA TRANSLATION Protein Figure 10.6A

  12. (1961) Watson & Crick proposed… • …DNA controlled cell function by serving as a template for PROTEIN structure. • 3 Nucleotides = a triplet or CODON (which code for a specific AMINO ACID) • AMINO ACIDS are the building blocks of proteins.

  13. AMAZING DNA FACTS… • DNA from a single human cell extends in a single thread for almost 2 meters long!!! • It contains information equal to some 600,000 printed pages of 500 words each!!! (a library of about 1,000 books)

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