RNA, DNA, and Transcription

Promoter

A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.

Polyadenylation

- 250 consecutive A-ribonucleotides, also known as Poly(A) - Added to end of mRNA transcript -Poly(A) Tail - Stabilizes mRNA and helps it from being degraded - The hydroxyl group (-OH) on the 2nd carbon of the sugar ring likes to react with other molecules, making RNA unstable compared to DNA

5' Cap

- 7-methylguanosine (a nucleotide) - Ribosome recognizes 5' cap - Without it, translation will not happen - Stabilizes mRNA

Elongation

- Addition of amino acids to the polypeptide chain - Continues until it reaches a stop codon

Between which molecules in a DNA strand are hydrogen bonds formed?

- Guanine and Cytosine - Adenine and Thymine

CFTR gene

- Is located on chromosome 7 - Contains 188,703 nucleotides long - Contains 27 exons - Codes for a 1480 amino acid protein - Mutations in CFTR result in cystic fibrosis

What is a nucleic acid composed of?

- Phosphate group - Nitrogen containing base - 5-carbon sugar

Transcription Step 3: Termination

- RNA polymerase reaches the terminator - RNA polymerase molecules detach from RNA strand - mRNA detaches from DNA

Transcription

- RNA synthesizes from 5' to 3' end of RNA - Reads DNA 3' to 5' - Error rate= 1 in 10,000 nucleotides

Alternative splicing

- Removal of different introns leads to different proteins produced from one original transcript - This is necessary to have a large diversity of proteins

Sugars

- Ribose (RNA) - Deoxyribose (DNA)

Complementary base pairing

- The association between specific nitrogenous bases of nucleic acids stabilized by hydrogen bonding. - Adenine pairs with thymine ( in DNA) or Uracil ( in RNA) - Guanine pairs with cytosine - The two strands of a DNA molecule have complementary base pairs - The nucleotide sequence of each strand automatically supplies the information needed to produce its partner.

RNA processing

- The modification of mRNA before it leaves the nucleus that is unique to eukaryotes.

Transcription Step 1: Initiation

- Tools: - RNA polymerase - Transcription factors - Where? - Promoter - Eukaryotes (TATA Box) - Separation of the DNA strand forms a transcription bubble

RNA polymerase

-Enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription - Restores the original DNA strand

A strand of DNA is found to have 30% Cytosine. What % of Guanine does the strand contain?

30% G% must equal C A% must equal T

What would the complementaryRNA transcript message be for 3'-GAG TCT ATT AGC-5'?

5' -CUC AGA UAA UCG -3'

A portion of an exon in the CFTR gene has the sequence:3' GAC TCA CCT CCA GTT CGT 5' What is the correct transcribed mRNA sequence?

5' -CUG AGU GGA GGU CAA GCA -3'

Modification #2

5' Cap

What is the common sequence in the eukaryotic promoter?

5'-TATAAA-3' (TATA box)

If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence ________.

5'TGCAAT3'

Transcription factors

Additional proteins that bind DNA and assist RNA polymerase with transcription

Purines

Adenine and Guanine

Nitrogenous bases

Adenine, guanine, cytosine, thymine, uracail

Ribosomal RNA (rRNA)

Aid in translation, found in ribosomes (a protein)

Ribozyme

Any RNA molecule that can act as a catalyst to increase the rate of a chemical reaction

Where does transcription start?

At the promoter DNA (TATA box)

Transfer RNA (tRNA)

Carry individual amino acids into the protein translation complex so they can be added to a growing polypeptide chain

Where does translation occur?

Cytoplasm

Pyrimidines

Cytosine, thymine, uracil

What is the sugar in DNA?

Deoxyribose

What is meant by antiparallel strands of DNA?

Describes the opposite orientation of nucleic acid strands that are hydrogen bonded to one another, with one strand running in the 5' —> 3' direction and the other in the 3' —> 5' direction

Ribosome

Enzyme responsible for protein synthesis

Slipceosome

Enzyme that removes introns

Where does transcription take place?

Inside the nucleus

Why is RNA less stable than DNA?

It has an extra Hydroxyl Group making it more susceptible to hydrolysis

What happens once RNA has been spliced and modified?

It leaves the nucleus and goes to the cytoplasm for translation

A gene in an anteater cell acquired a mutation in the TATA box such that transcription factors (TFs) cannot bind to it. Will transcription take place?

No, because TFs binding to the TATA box initiate transcription in eukaryotes

Introns

Noncoding regions

How does polymerase know when to stop?

Once RNA polymerase sequences through the Poly(A) sequence, it will eventually fall off of the RNA

Modification #3

Polyadenylation

Why does promoter location matter?

Promoter location determines which strand is transcribed

Exons

Protein coding segments of eukaryotic DNA.

Basal transcription factors

Proteins, present in all eukaryotic cells, that bind to promoters and help initiate transcription.

Regulatory RNA

Regulatory role where they can inhibit translation or destroy a RNA transcript

Splicing

Removal of introns

Transcription Step 2: Elongation

Ribonucleotides are added to the 3' end of the growing mRNA strand

What is the sugar in RNA?

Ribose

Eukaryotic transcription and translation is separated in_________

Space and time

Modification #1

Splicing

Hydrolysis

Splitting one molecule into 2 using water

What happens when nucleotides bond together to form a single stranded DNA?

The 3' carbon of the first nucleotide forms a covalent bond with the phosphate group of the next nucleotide

When nucleotides bond together to form a single stranded DNA, which of the following is correct?

The 3' carbon of the first nucleotide forms a covalent bondwith the phosphate group of the next nucleotide

The CFTR gene contains 188,703 nucleotides; the final CFTR mRNA that codes for protein contains 4440 nucleotides. Which of the following do NOT occur to create the final CFTR mRNA?

The spliceosome binds to the CFTR pre-mRNA transcript in the cytoplasm

What pyrimidine does not exist in RNA?

Thymine

Condensation

Two molecules form a bond to become one and water is a product