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Chapter 13 Study Guide
1. Describe fully the 3 ways RNA is different from DNA.
1 – single-strand
2 – ribose sugar
3 – contains uracil instead of thymine as its 4th nitrogen base
2. What does RNA stand for? ribonucleic acid
3. Draw a RNA nucleotide.
phosphate
group
ribose sugar
4. Describe fully how and where the process of transcription occurs.
IN THE NUCLEUS:
1 - RNA polymerase attaches to a promoter then opens the DNA strand
2 - RNA polymerase then adds in nucleotides to makes a copy of one
strand only, using the base pair rule – substituting U for T so the cell
knows it is just a copy
3 – pre-mRNA is then edited by cutting out the introns then stitching
back together the exons
4 – functional mRNA then leaves through the nuclear pores into the
cytoplasm
5. Describe fully how and where the process of translation occurs.
IN THE CYTOPLASM:
1 – mRNA attaches to a ribosome
2 – ribosome “reads” the code on the mRNA one codon (group of 3
bases) at a time
3 – tRNA molecule brings in the correct amino acid based upon the
codon being read
4 – tRNA attaches to the mRNA codon at its anticodon end (group of 3
complementary bases)
5 – each amino acid is added to the growing polypeptide chain and the
tRNA molecule leaves the ribosome
6 – when the ribosome reads a stop codon, the finished protein is
released from the ribosome
6. List the 3 types of RNA and what role they each have in protein synthesis.
messenger RNA (mRNA) – copies the code (message) from the DNA and
takes it to the ribosome where it is read for making the protein
ribosomal RNA (rRNA) – makes up the structure of the ribosome along
with additional protein
transfer RNA (tRNA) – brings in (transfers) the amino acids from the
cytoplasm to the ribosome where they are linked together into the
polypeptide chain (protein!)
7. When looking at a strand of nucleotides, which base tells us you are looking at
RNA?
uracil
8. Once the DNA template has been copied into a strand of pre-mRNA, what editing
process must occur before the final mRNA strand can leave the nucleus?
introns (junk DNA) must be cut out then the exons (actual coding
sequence) are stitched back together into the true mRNA strand which
can then leave the nucleus
9. What is the base-pair rule for RNA?
cytocine – guanine; uracil - adenine
10. How are amino acids “read” in a strand of mRNA?
In groups of 3 nucleotides called codons
11. What type of cell has introns and exons? eukaryotic
Use the codon chart that was given to you in class to help with the following questions.
12. If the codon is CCC, what is the amino acid? proline
13. Is the codon AUC for alanine? no - isoleucine
14. What is the start codon? AUG
15. If the mRNA sequence reads: C U G A A G C G C U U G , what is the amino
acid sequence created from that mRNA?
leucine – lysine – arginine – leucine
Define the following terms:
16. ribose: sugar found in RNA
17. uracil: 4th nitrogen base in RNA (along with adenine, cytocine, & guanine)
18. RNA polymerase: enzyme used in protein synthesis; unzips the DNA then puts
the nucleotide bases into the mRNA strand according to the base pair rule
19. promoter: the spot on the DNA strand that the RNA polymerase attaches then
unzips the DNA
20. introns: portion of DNA that doesn’t code for anything (junk); gets cut out of
pre-mRNA prior to leaving the nucleus
21. exon: portion of DNA that codes for the actual protein; gets stitched back
together into the functional mRNA strand that will leave the nucleus and go to
a ribosome
22. codon: group of 3 nucleotides on the mRNA strand that code for a specific
amino acid
23. anticodon: group of 3 nucleotides on one end of a tRNA molecule that is
complementary to an mRNA codon
24. amino acid: basic unit of a protein
25. protein synthesis: process of making proteins; occurs in two basic steps –
transcription and translation
26. polypeptide: chain of amino acids that will become a finished protein
27. Identify the types of RNA seen in the diagram.
A = ribosomal RNA (rRNA)
B = transfer RNA (tRNA)
C = messenger RNA (mRNA)