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BIOS 1300 SI
SI WORKSHEET 8 (Chapter 3 Cont.)
SI Leader: Merrin Jeffries (email:)
February 5, 2015
DNA Base Pairing
There are base pairing rules for writing complimentary DNA strands for a given strand.
A pairs with T
C pairs with G
In RNA, A pairs with U, instead of T.
1. Write the complimentary DNA strand for each given strand of DNA.
a. CGTAAGCGCTAATTA
b. TCTTAAATGATCGATC
c. AATGAATAGCTAGCTT
d. GGCATTCGCGATCATG
e. CGTTAGCATGCTTCAT
f. ACTAACGGTAGCTAGC
2.Now write the mRNA strand for the given DNA strand.
a. ATGTCGCTGATACTGT
b. GAAGCGATCAGTTACG
c. AATGAATAGCTAGCTT
d. GGCATTCGCGATCATG
e. CGTTAGCATGCTTCAT
f. ACTAACGGTAGCTAGC
3. Write the tRNA sequence for the given strand of mRNA
- AGGUCAUGCAUGGGCAUGCAU
b. AGAGAUUCAGCUAGCACGAUA
c. GUCAUCGAUCGAUCGGAUGCC
d. UUUCAGUCAGCUAGCGAUCGU
4. Now you will translate the amino acid sequence for the given tRNA strand. Remember that codons are 3 base pairs long.
- AUG CAC UGU CCU UUC GCU GAC
b. GAG AUC UGG UUG GAA UCG
c. AGC GUA UUA ACG UAU CAU
d. AGU CGA UCG AUG CGG AUG AUA
e. GUC GUC GAU AGC UAU CAU GCA
5. Transcribe the following DNA strand. Then translate the tRNA strand you wrote.
a. TGAGTCGACTGGCTGACCGTAGAC
b. CTTGGCTTATGGTGGTTCGCTCGC
6. The following are pieces of mRNA. Give the DNA strand from which it was transcribed.
a. GAGAUCUGGUUGGAAUCG
b. AGCGUAUUAACGUAUCAU
7. Complete the table below showing the sequences of DNA, mRNA codons, tRNA anticodons and the amino acids. Remember the genetic code is based on mRNA codons.
DNA / GATmRNA codon /
/ UAU
tRNA anticodon / UUC
Amino Acid / Tryptophan
8. Using the following piece of DNA, give the mRNA molecule and the amino acid sequence for which it codes.
DNA- A T A T A A A C G A G G A A A T T C C G G G C G
mRNA:
tRNA:
Amino acids:
9. Use the mRNA sequence to find the DNA sequence and the amino acid sequence.
DNA
mRNA- A U G C C U A C A U G U G G U G U A A C C U U A
tRNA
Amino acids
10. For each codon below, give the tRNA anticodon.
a. UUC ______
b. AUC ______
c. CCG ______
d. CGU ______
Gene expression:The process by which DNA directs the synthesis of proteins
I. Transcription:
1. Initiation
- RNA polymerase attaches to the DNA at the promoter, ______, and separates the 2 DNA strands
- In prokaryotes, RNA polymerase attaches directly to the promoter
-In eukaryotes, RNA polymerase binds to a specific promoter sequence called the ______with the help of ______.
2. Elongation: RNA polymerase adds RNA nucleotides to the ______end of the growing mRNA chain
3. Termination
- In prokaryotes, transcription ends once a ______sequence is transcribed
- In eukaryotes, transcription ends 10-35 nucleotides after a ______is transcribed
II. RNA processing: modifications to an mRNA transcript that occur only in ______.
- Alteration of mRNA ends: the 5’ end receives a ______and the 3’ end receives a ______that have 3 important functions:
1. Facilitate export of mature mRNA from ______.
2. Protect mRNA from degradation by ______.
3. Help ______attach to the 5’ end of the mRNA in the cytoplasm
- RNA splicing: the removal of large portions of non-codingDNA, called ______, from pre-mRNA
- The remaining coding regions are called ______.
- Introns are removed by a spliceosome complex, consisting of many snRNPs (made of ______)
-Alternate RNA splicing allows 1 pre mRNA to code for multiple proteins
III. Translation:
1. Initiation: mRNA, a tRNA corresponding to the ______codon, and 2 ribosomal subunits unite to form a translation initiation complex with the help of ______factors
2. Elongation: Amino acids are added one by one to the growing polypeptide chain by tRNA’s with the help of ______factors
- Involves the recognition of mRNA codons by the ______codons of tRNA
- Translocation:
3. Termination: a ______codon in the mRNA is reached and translation stops with the help of a ______factor
IV. Post-translational modifications:
Folding: A protein’s secondary and tertiary structures form automatically based on ____-group interactions, but folding may be mediated by ______ protein
Modifications:
Targeting: may be targeted for the ER (& ultimately secretion) by a ______.