TOPIC – TRANSCRIPTION: THE MAKING OF RNA

DNA Replication Bell Ringer The sequence below represents the bases of a single strand of a DNA molecule. Complete the complementary strand of DNA. A T T A C G A T C T G C A C A A G A T C C T

REVIEW:  Where in the cell is DNA stored?  Where are proteins built in the cell?  What are some functions of proteins?  If DNA cannot exit the nucleus, how can cells make proteins?

BenchmarkObjectives Compare and contrast RNA and DNA. Describe the process of transcription. What are we learning today? SC.912.L.16.5 – SC.912.L.16.5 – Explain the basic processes of transcription and translation, and how they result in the expression of genes.

What is the essential question? Suppose you start with two DNA strands: ACCGTCAC and TCGCACGT. Use the “rules” of base paring to list the bases on mRNA strands transcribed from those DNA strands.

What is the essential vocabulary? RNA polymerase – enzyme that binds to DNA and separates the DNA strands during transcription. (Makes RNA from DNA) Transcription – Process during which RNA molecules are produced by copying part of the nucleotide sequence of DNA. Intron – sequence of DNA that is not involved in coding for a protein. Exon – sequence of DNA that is involved in coding for a protein.

How is DNA like or not like RNA? nucleic acids  RNA and DNA are nucleic acids. consist of a long chain of nucleotides  RNA, like DNA consist of a long chain of nucleotides. differences  There are three main differences between RNA and DNA: sugar is ribose, sugar is deoxyribose. 1. The sugar in RNA is ribose, the sugar in DNA is deoxyribose. single stranded double stranded 2. RNA is single stranded, DNA is double stranded. contains uracil (U) contains thymine (T). 3. RNA contains uracil (U) DNA contains thymine (T).

What are the three types of RNA?

How does transcription work? Right-click slide Select “Play”

How does transcription work? transcription  RNA molecules are produced by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA during a process called transcription. RNA polymerase  Transcription requires an enzyme known as RNA polymerase. promoters  RNA polymerase only binds to regions in DNA known as promoters with specific base sequences.  Promoters are signals in DNA that indicate to the enzyme where to bind to make RNA.

How does transcription work? 1. RNA polymerase binds to DNA and separates the DNA strands. 2. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA. RNA polymerase add to the 3’ end only 3. When RNA polymerase reaches a termination signal in the DNA, the DNA and new RNA are released.

How does transcription work? A certain gene has the following sequence of nucleotides. From left to right, write the sequence of the mRNA molecule transcribed from this gene. DNA 3’ GACAAGTCCACAATC 5’ mRNA

How does transcription works? DNA template strand TRANSCRIPTION mRNA TRANSLATION Protein Amino acid Codon Trp Phe Gly 5 5 Ser UUUUU G G GGCC T C A A AAAAA TTT T T G GGG CCC GG DNA molecule Gene 1 Gene 2 Gene 3 C C

Click the Picture Below for Transcription in action

What is RNA editing? introns  The DNA of eukaryotic genes contain sequences of nucleotides, called introns, that are not involved in coding proteins. exons  The DNA sequences of nucleotides that code for proteins are called exons.  When the RNA molecules are formed, both the introns and exons are copied from the DNA and is called pre-mRNA.  However, introns are cut out of RNA molecules while they are still in the nucleus.  The remaining exons are then spliced back together to form the final mRNA.

What is the essential question? Suppose you start with two DNA strands: ACCGTCAC and TCGCACGT. Use the “rules” of base paring to list the bases on messenger RNA strands transcribed from those DNA strands.