3/24/10 Happy Wednesday! DNA fun facts!!! It takes about 8 hours for 1 of your cells to completely copy its DNA!It takes about 8 hours for 1 of your cells to completely copy its DNA! If one person’s DNA was laid in a straight line, it would stretch to the sun and back over 600 times (it's 93 million miles from here to the sun)! WOW!!!If one person’s DNA was laid in a straight line, it would stretch to the sun and back over 600 times (it's 93 million miles from here to the sun)! WOW!!! You could fit one million threads of DNA across the period at the end of this sentence.You could fit one million threads of DNA across the period at the end of this sentence.

Remember DNA = genetic information DNA replication = unzipping of double helix and creating a new strand of DNA!

Picture this..... You are a cell!! You want to make a protein, what do you do??? You have to get DNA  RNA  protein DNA  RNA  protein Protein synthesis!!

RNA carries DNA’s instructions. Central dogma = info. flows in 1 direction, from DNA to RNA to protein!Central dogma = info. flows in 1 direction, from DNA to RNA to protein! 8.4 KEY CONCEPT Transcription converts a gene into a single- stranded RNA molecule.

It includes 3 processes: – Replication – Transcription – Translation RNA =RNA = Ribonucleic acid RNA = link btwRNA = link btw DNA & proteins! DNA & proteins! replication transcription translation

Oh Man!!! DNA can’t leave the nucleus!!! Which organelle makes proteins????Which organelle makes proteins???? RIBOSOMES!RIBOSOMES! DNA’s code must be carried from the nucleus to the cytoplasm!!!DNA’s code must be carried from the nucleus to the cytoplasm!!! RNA does the job!RNA does the job!

Let’s compare DNA & RNA!! Deoxyribose sugar A, C, T, G Double stranded Ribose sugar A, C, Uracil, G Single stranded

Transcription Process by which a portion of DNA (a “gene”) is copied into a complementary strand of RNA.Process by which a portion of DNA (a “gene”) is copied into a complementary strand of RNA. –The DNA code is transferred out of the nucleus  ribosomes

Let’s see this in action... urces/htmls/animated_biology/unit3/bio_ch08_0 237_ab_dnarep.htmlhttp:// urces/htmls/animated_biology/unit3/bio_ch08_0 237_ab_dnarep.html

RNA polymerase recognizes start site of gene & UNWINDS DNA!! RNA pol. reads template & makes complimentary strand!! RNA strand hangs free & detaches once transcribed!!! DNA molecule Nucleotides New RNA strand RNA polymerase

Transcription is catalyzed (started) by RNA polymerase. –RNA polymerase and other proteins form a transcription complex. –The transcription complex recognizes the start of a gene and unwinds a segment of it. start site nucleotides transcription complex

–RNA polymerase bonds nucleotides together. –DNA helix winds again as the gene is transcribed. – Nucleotides pair with one strand of the DNA. DNA RNA polymerase moves along the DNA

– The RNA strand detaches from the DNA once the gene is transcribed. RNA

Transcription makes 3 types of RNA: –carries the message that will be translated to form a protein. –forms part of ribosomes (where proteins are made) –takes amino acids from the cytoplasm to a ribosome. Ribosomal RNA (rRNA) Transfer RNA (tRNA)

The transcription process is similar to replication....HOW?? Transcription & replication both involveTranscription & replication both involve –complex enzymes & –complementary base pairing. BUT...have different end results:BUT...have different end results: –Replication copies all the DNA; transcription copies a gene. –Replication makes one copy; transcription can make many copies. growing RNA strands DNA onegene

REVIEW!! What’s the “central dogma” for molecular biology?What’s the “central dogma” for molecular biology? Does transcription take place in the nucleus or cytoplasm?Does transcription take place in the nucleus or cytoplasm? What about DNA replication?What about DNA replication? Transcription is...Transcription is... What does RNA polymerase do?What does RNA polymerase do? How are DNA and RNA different?How are DNA and RNA different? What are the 3 types of RNA & their functions?What are the 3 types of RNA & their functions? Why might a cell make lots of rRNA but only one copy of DNA?Why might a cell make lots of rRNA but only one copy of DNA? Let’s Practice!!Let’s Practice!!

Practice! DNADNA RNARNA

DNA Puzzle DNA ReplicationDNA Replication TranscriptionTranscription