DNA, RNA and Protein Synthesis Review

1. What does DNA stand for?

Deoxyribonucleic Acid

2. What are the repeating subunits called that make up DNA?

Nucleotides

3. Sketch and label the 3 parts of a DNA nucleotide.

Include a phosphate, deoxyribose sugar, and nitrogenous base

4. Name the 4 nitrogen bases on DNA (spelled out – spelling counts on the test).

Adenine (A) Thymine (T) Guanine (G) Cytosine (C)

5. What scientists made the first ever model of DNA as a double helix?

James Watson and Francis Crick

6. What is Chargaff’s rule?

Chargaff found that for a particular species, the concentration of adenine is roughly equal to the concentration of thymine (A=T) and cytosine is roughly equal to guanine (G=C)

This helped found the base pair rule, that A always pairs with T, and C always pairs with G

In the DNA of a particular species, there is 26% adenine

Since A = T, A. Thymine = 26% (roughly) To figure out C and G, subtract from 100%100 – 26 – 26 = 48, then divide equally into C

and G B. Cytosine = 24% C. Guanine = 24%

*Be prepared to do problems without a calculator on the test

7. How did Rosalind Franklin contribute to determining the structure of DNA?

She produced an X-Ray diffraction photo that showed DNA.

8. What makes up the sides of a DNA molecule?

Sugar & Phosphate

9. What makes up the “steps” of a DNA molecule?

The nitrogenous bases (A,T,G,C)

10. What type of bonds hold the DNA bases together? Are they strong or weak bonds?

Weak hydrogen bonds

11. What type of bonds hold the "backbone" of the DNA molecule together?

Covalent bonds join sugar & phosphate

12. Name the complementary base pairs in DNA.

Adenine – Thymine Guanine - Cytosine

13. Why must DNA be able to copy itself?

DNA must be copied in order for a cell to divide

Transmit information for traits to the next generation

14. Define semi-conservative replication. (in DNA coloring packet!)

DNA saves or conserves 1 strand to produce 1 new strand

Produces 2 identical double-stranded DNA molecules, each containing 1 “original” strand, and 1 “new” strand

15. What is the first step that must occur in DNA replication?

Separating of the two strands of DNA by breaking the hydrogen bonds

16. What is a replication fork?

The place where DNA separates in order to be copied.

17. What are the functions of DNA polymerase?

DNA polymerases add nucleotides to new DNA strands

DNA polymerase also proofreads the strands for errors

18. Why aren’t many genes located on the tips, or telomeres, of chromosomes? What does telomerase do to help with this?

Telomeres are susceptible to damage, and thus don’t contain many genes

Telomerase is an enzyme that adds short, repeated nucleotides to the ends so that if damage occurs, the chromosomes are not affected, since the sequences don’t contain genes

19. If the sequence of nucleotides on the original DNA strand was A-G-G-C-T-A, what would be the nucleotide sequence on the complementary strand of DNA?

TCCGAT

20. Does replication of DNA begin at one end and proceed to the other? Explain.

No, it can begin at many places, and proceeds in opposite directions until the entire sequence has been replicated

21. Why does DNA replication take place at many places on the molecule simultaneously?

To replicate (copy) the DNA quicker.

22. Is DNA replicated before or after cell division?

Before cell division (interphase – S phase = DNA synthesis, which is the another way of saying DNA replication)

23. Sketch & label DNA replication.

24. Give 3 differences between prokaryotic and eukaryotic replication:

Prokaryotic replication involves circular DNA (vs. double helix)

Prokaryotic replication takes place in the cytoplasm (vs. nucleus)

Prokaryotic replication has 1 origin (vs. many origins for eukaryotic replication)

25. What sugar is found on RNA, as compared to DNA?

Ribose (vs. deoxyribose)

26. What base is missing on RNA, & what other base replaces it?

Thymine is replaced by Uracil

27. Uracil will pair with what other on DNA?

Adenine – Uracil

28. Is RNA double or single stranded?

Single stranded

29. Name the 3 types of RNA and tell the job of each.

mRNA – carries code from DNA out into cytoplasm; codons on mRNA code for 1 amino acid

tRNA – transfers amino acids to the ribosome based on mRNA codons Anticodon is complementary to codon

rRNA – makes up subunits of the ribosome (which are the protein-makers)

30. In transcription, _______ is converted to ______. This occurs in the ________.

DNA is converted to RNA in the nucleus

31. What happens to the newly made mRNA molecule following transcription in the nucleus?

mRNA travels out the nuclear pores into the cytoplasm and attaches to the ribosome

32. What is RNA polymerase & what is its function?

Enzyme that copies DNA into RNA

33. What bases pair with each other during transcription?

DNA RNA Cytosine guanine Guanine cytosine Adenine uracil Thymine adenine

34. In what part of a cell are proteins made?

Ribosomes, floating in the cytoplasm or attached to the rough endoplasmic reticulum

35. What are the subunits called that make up proteins?

Amino acids

36. How many different kinds of amino acids make up proteins?

There are 20 amino acids and they can be combined in all different combinations to create every protein in your body

Everything in you is made OF or BY at least one protein

37. What is a codon & what does each codon code for?

Group of three bases on mRNA Codes for 1 amino acid

38. How many codons exist?

64

39. What are the START (1) and STOP (3) codons for protein synthesis?

Start codon = AUG Stop codons = UAG, UAA, UGA

40. What is the ‘start’ codon used for? What is the stop codon used for?

Start codons initiate protein synthesis (tell the ribosome to start making the protein)

Stop codons halt protein synthesis (tell the ribosome that the protein is done)

41. Name the amino acid coded for by each of these codons.

A. UUA = Leucine B. AUU = Isoleucine C. UGU = CysteineD. AAA = LysineE. GAG = Glutamic AcidF. CAA = Glutamine

42. Proteins are synthesized (made) at what organelle in the cytoplasm?

Ribosomes

43. Sketch and label a tRNA molecule & tell its function.

Purple ball is the amino acid (top) Attached to the bottom

is the anticodon Function is to carry the

amino acids for proteinsynthesis

44. Describe translation from the beginning, to the final end product:

mRNA attaches to ribosome tRNA carries amino acids to ribosome

and matches them to coded mRNA message (codon)

Amino acids bond together, forming long chain called a polypeptide

Polypeptides are folded depending on their function and begin their job

(See p368-69, esp figures @ bottom)

45. Where are amino acids found in a cell?

Floating in the cytoplasm, attached to tRNA molecules

46. What is an anticodon & where is it found on tRNA?

Complementary to mRNA codon At the bottom

47. What codon on mRNA would bind with these anticodons: (use p367)

A. AAA = UUUB. GGA = CCUC. UAC = AUGD. CGU = GCA

Polypeptide chains

48. What are the long chains of amino acids called?

49. Fill in the chart below with the anticodons/amino acids that would be coded for by the mRNA sequence provided:

UAA CAA GGA CGA UCC (codons) AUU GUU CCU GCU AGG (anticodons) Stop, glutamine, glycine, arginine,

serine Remember, the CODONS code for

amino acids, not anticodons Anticodons help match amino acids

to the codons

2nd question on #49

UGA CCC GAU UUC AGC (codons) ACU GGG CUA AAG UCG (anticodons) Stop, glycine, aspartic acid, lysine,

serine