DNA, RNA, and Protein Synthesis

Study Guide Answers

1. Results from Griffith’s experiment.

• Griffith worked with 2 strains of bacteria: R strain (harmless) and S strain (which caused pneumonia).

• Mice injected with R strain were fine.• Mice injected with S strain developed pneumonia within days

and died.• He killed the S strain bacteria with heat, injected it into mice

and they lived.• Then he mixed the heat-killed S strain bacteria with R strain

bacteria and injected them. They died!

• Conclusion: the genetic material in the S bacteria was passed on, making the R bacteria deadly as well Transformation!

2. Results of Avery’s experiment. Idea he is credited with discovering?

• Avery wanted to know if the “transforming agent” that Griffith saw in his experiment was DNA, RNA, or protein.

• His experiment concluded that the genetic material (“transforming agent”) was DNA.

3. Hershey and Chase experiment and results?

• They studied the virus that infects bacteria cells and makes them produce more viruses.

• Looking to see what type of genetic material is passed from the virus to the bacteria.

• They concluded that DNA is the molecule that holds the genetic information and is passed along.

4. Watson and Crick are credited with discovering the shape of DNA!!!!

5. DNA is located in the

nucleus!!!

6. Structure of the DNA molecule.

• Double helix shape (like a spiral staircase)• Made up of nucleotides (next slide)• Backbone is made up of alternating sugar and

phosphates• Middle of molecule is made up of A, T, C, G

and held together by hydrogen bonds• DNA is a very large molecule!• Sugar in DNA is deoxyribose!

7. A nucleotide…

8. Deoxyribose is the sugar in DNA!

9. Chargaff made the observation that every DNA molecule always had the same amount of adenine as it had of thymine and the same amount of guanine as it had of cytosine.

10. What is DNA replication? Where does it take place?

• It is the process by which new DNA molecules are made.

• It occurs in the nucleus.

11. What is the semi-conservative model of DNA replication?

• It says that new DNA strands are synthesized using the old strands as a template.

• So, each new molecule of DNA that is produced has one of the parent strands and one new one.

12. The enzymes which unwinds the double helix and breaks the hydrogen

bonds?

Helicase

13. The enzyme that adds nucleotides in order to create DNA?

DNA polymerase

14. The enzyme that synthesizes RNA primer?

primase

15. Difference between leading and lagging strands?

• Leading: synthesized continuously, toward the opening of the rep. fork

• Lagging: synthesized discontinuously, in the opposite direction (away from the fork.)

16. The enzyme that links Okazaki fragments?

Ligase

17. Make the complementary strand of DNA.

G T T C A A C C G A T

C A A G T T G G C T A

18. Explain what occurs in DNA replication.

• DNA molecule is split by helicase, forming a replication fork.

• RNA primer is synthesized.• DNA polymerase attaches and begins adding

nucleotides to exposed bases.• End product: 2 DNA molecules, each with 1

parental strand and 1 new strand

19. 3 similarities and 3 differences between DNA and RNA?

• Similarities: both are nucleic acids, both are made up of nucleotides, both created in nucleus, both contain sugar, phosphate, adenine, cytosine, guanine, etc.

• Differences: sugar, DNA is double stranded and RNA is single stranded, DNA has thymine and RNA has uracil, DNA must stay in nucleus and RNA can leave, etc.

20. Explain what occurs in transcription.

• DNA molecule is split by helicase.

• RNA polymerase moves along ONE strand of DNA and adds nucleotides to exposed bases.

• When the stop sequence is reached, mRNA detaches and is free to go.

• Start: DNA, End: mRNA

21. 3 Types of RNA and their functions.

• mRNA: carries instructions from nucleus to cytoplasm/ribosomes

• tRNA: carries and attaches amino acids to make a protein

• rRNA: makes up the ribosomes

22. A codon is a 3 letter segment of mRNA that codes for a specific

amino acid.

23. Type of RNA that carries amino acids?

tRNA

24. Explain what occurs during translation.

• Small subunit of ribosome binds to mRNA upstream of the start sequence.

• Moves downstream until it reaches the start sequence, then large subunit attaches.

• tRNA anticodons match up with mRNA codons and attach their amino acids to create a polypeptide chain.

• Stop sequence is reached, mRNA and protein are released.

25. Genes contain instructions for assembling proteins!

26. Role of RNA polymerase?

• Creates mRNA molecule by adding nucleotides to exposed bases on a strand of DNA.

27. During transcription, mRNA is produced!

28. The enzyme at work during transcription? How does it work?

• RNA polymerase• It moves along ONE strand of DNA, adding

nucleotides to the exposed bases to create a strand of mRNA.

29. The codons below code for:

AUG-GCC-AUC-GGU-CUA-GUU-UAG

(start)Methionine-alanine-phenylalanine-glycine-leucine-

valine-stop

30. Complementary DNA sequence?

mRNA: AUG GCC AUC GGU CUA GUU UAG

DNA: TAC CGG TAG CCA GAT CAA ATC

31. The function of tRNA is to carry amino acids.