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Replication DnA Dna

Replication DnA Dna. We lose from 30,000-40,000 cells/day……these need to get replaced Before a cell duplicates, it makes an exact copy of its DNA for new cell Double helix “unzips” through an enzyme ( helicase ) that breaks H bonds

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Replication DnA Dna

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  1. ReplicationDnADna

  2. We lose from 30,000-40,000 cells/day……these need to get replaced • Before a cell duplicates, it makes an exact copy of its DNA for new cell • Double helix “unzips” through an enzyme (helicase) that breaks H bonds • DNA polymerase attaches nucleotides to DNA strand to form complementary strands Replication


  4. DNA never leaves the nucleus, is protected • RNA is a copy of DNA that goes out of nucleus to give cell instructions to make proteins • 3 Main Differences between RNA to DNA • Single stranded, smaller • Contains ribose sugar • Contains uracilin place of thymine RNA: ribonucleic acid Adenine: A Uracil: U Guanine: G Cytosine: C Ribose Sugar

  5. DNA unzips at site of desired gene at promoters (specific base sequence signal for start) RNA polymerase creates a complimentary strand of gene with RNA nucleotides mRNA leaves nucleus to ribosome for protein synthesis transcription

  6. Sometimes in the RNA copy, there are some portions that don’t code for the protein (introns) Introns get discarded and remaining portions (exons) of RNA get spliced back together. RNA Editing

  7. DNA mRNA mRNA Cytoplasm of cell Nucleus Once in the cytoplasm, the mRNA is used to make a protein Transcription happens in the nucleus. An RNA copy of a gene is made. Then the mRNA that has been made moves out of the nucleus into the cytoplasm

  8. Messenger RNA (mRNA)- carry info on polypeptide synthesis from nucleus to ribosomes Ribosomal RNA (rRNA)- make up subunits that make ribosomes Transfer RNA (tRNA)- bring amino acids to the ribosome and matches them to coded mRNA message 3 main types of rna

  9. Table 14.2 Types of RNA Type of RNA Functions in Function Messenger RNA (mRNA) Nucleus, migrates to ribosomes in cytoplasm Carries DNA sequence information to ribosomes Transfer RNA (tRNA) Cytoplasm Provides linkage between mRNA and amino acids; transfers amino acids to ribosomes Cytoplasm Ribosomal RNA (rRNA) Structural component of ribosomes


  11. TRANSLATION • *Ribosome binds to mRNA in cytoplasm • Genetic code is read in words that are 3 letters long called CODONS • Each codon codes for an AMINO ACID

  12. Virtually all organisms share the same genetic code “unity of life” Second Base U C A G UUU UCU UAU UGU U tyr phe cys UUC UCC UAC UGC C ser U UUA UCA UAA stop UGA stop A leu UUG UCG UAG stop UGG trp G CUU CCU CAU CGU U his CUC CCC CAC CGC C pro arg leu C CUA CCA CAA CGA A gln CUG CCG CAG CGG G First Base Third Base AUU ACU AAU AGU U ser asn AUC ACC AAC AGC C ile thr A AUA ACA A AAA AGA lys arg AGG AUG ACG AAG G met (start) GUU GCU GAU GGU U asp GUC GCC GAC GGC C val G ala gly GUA GCA GAA GGA A glu GUG GCG GAG GGG G mRNA AMINO ACID CHART

  13. As each codon passes through ribosome, tRNA brings the proper amino acids to ribosome to build a polypeptide TRANSLATION Anticodon is used to base pair with mRNA codons

  14. The polypeptide chain continues to grow until it reaches a “stop” codon on mRNA Ribosome releases new polypeptide and mRNA, completing translation

  15. Transcribed strand TRANSLATION DNA Transcription RNA CODONS Startcodon Stopcodon Translation Polypeptide Figure 10.8B

  16. Normal hemoglobin DNA Mutant hemoglobin DNA mRNA mRNA Normal hemoglobin Sickle-cell hemoglobin Glu Val Figure 10.16A

  17. Mutations can change the meaning of genes • Mutations are changes in the DNA base sequence • caused by errors in DNA replication or by mutagens (chemical/physical agents) • Point mutation involves change in one or a few nucleotides

  18. NORMAL GENE • Types of mutations mRNA Protein Met Lys Phe Gly Ala BASE SUBSTITUTION Met Lys Phe Ser Ala Missing BASE DELETION or INSERTION *Frameshift Mutation (more serious) Met Lys Leu Ala His Figure 10.16B

  19. POINT Mutation- can produce defective protein FRAMESHIFT: Shifts entire sequence over, can result in defective protein

  20. TAC GCC TGG AAA AUG CGG ACC UUU MET ARG THR PHE Silent mutation (substitution) because there is more than one codon for each AA

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