Name _____________________________

Date ______________________________

Worksheet on DNA, RNA, and Protein Synthesis

1. The letters “DNA” stand for _____________________________________.

2. DNA is composed of smaller subunits know as ________________________.

3. The three parts of a nucleotide are _____________________, ________________________, and

________________________.

4. The four nitrogen bases that are found in DNA are ___________________, __________________,

____________________ and ____________________.

5. Two of the nitrogen bases are single ring structures known as ____________________. These two bases

are _______________ and _______________.

6. The other two bases are double ring structures known as ___________________. These two bases are

___________________ and ____________________.

7. _________________ and _________________ are the two scientists that discovered the structure of the

DNA molecule.

8. DNA looks like a ladder twisted into a shape known as a ___________________.

9. The two molecules that make up the sides of the ladder or the side portion of a DNA molecule are

________________ and _________________.

10. The molecules that meet across the middle, forming the steps of the “ladder’” are known as

____________________.

11. Which nitrogen bases always pair with one another?

12. According to Chargaff’s rules, the percentages of ____________________ are equal to those of thymine

and the percentages of _____________________ are equal to those of guanine in th DNA molecule.

13. The nitrogen bases are held together in the center of the molecule by _______________________.

14. True or False? According to the principle of base pairing, hydrogen bonds could form only between

adenine and cytosine.

15. The type of sugar found in DNA is ________________________.

16. If the sequence on the right hand side of the DNA molecule was TAGGCTCA, the complimentary side

would have a sequence of _______________________.

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17. Label the parts of the drawing below. Include all of these terms: nucleotide, phosphate, sugar, nitrogen

base, hydrogen bond, covalent bond, purine, pyrimidine, hydroxyl group, the 5’ end, the 3’ end, adenine,

thymine, cytosine, and guanine.

18. The process in which DNA builds an exact duplicate of itself is known as _______________________.

19. What is the primary function of DNA?

20. Why is it so important that the DNA molecule be able to make copies of itself?

21. During replication, the two nucleotide chains _______________ and each chain serves as a

________________ for a new nucleotide chain. The sites where DNA replication and separation occur are

called _______________________.

22. During replication, enzymes called ____________________ untwist the double helix, separating the two

parental strands. The point at which the two chains separate is known as the _______________________.

23. Enzymes called ____________________________ move along the separated strands assembling the new

chains of DNA.

24. True or False? The replication of DNA begins at one end of the molecule and proceeds to the other end.

25. True or False? DNA replication occurs simultaneously at many sites along the molecule speeding up the

process of replication.

26. When replication is complete, two ________ copies of the DNA molecule have been produced and the cell

is ready to begin __________________________.

27. True or False? Each DNA molecule resulting from replication has one original strand and one new strand.

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28. The process of replication is very accurate. There is about _____ error in every ___________ bases. A

change in the nucleotide sequence is known as a ____________________. These errors may be caused

when enzymes fail to “proofread “ properly, or they may be caused by outside sources such as

___________________________________________________________.

29. The letters “RNA” stand for ______________________________.

30. In RNA, adenine always pairs with the nitrogen base known as __________________.

31. List three ways that DNA is different from RNA:

a)

b)

c)

32. There are three kinds of RNA. ______________________ carries the information from the nucleus to the

ribosomes in the cytoplasm. ____________________ reads the message and binds to the specific

_____________________ to make the protein. ___________________ is the most abundant form of

RNA and makes up ribosomes.

33. The process of making a strand of RNA from a strand of DNA is called ___________________.

34. __________________________ are the primary enzymes that synthesize RNA copies from DNA. These

enzymes bind to specific regions of the DNA molecule called ___________________. This marks the

beginning of the section of the DNA molecule that will be ______________________. In eukaryotic

cells, the section of DNA being transcribed is a _____________. Transcription continues until RNA

polymerase reaches the end of the gene, a sequence of nucleotides known as the

_______________________.

35. Many RNA molecules from eukaryotic genes have sections called _____________ edited out of them

before they become functional. The remaining pieces called __________ are then spliced together.

36. Proteins are made in the cytoplasm by cellular structures called _____________________.

37. Proteins are composed of smaller subunits called ________________ of which there are _______

different kinds. The functionality of the protein depends on its unique __________________________

which is determined by its amino acid sequence.

38. The sequence of nucleotides in mRNA is _________________ into a sequence of _________________.

39. A group of 3 nitrogen bases forms a ______________.

40. Each codon is the code for one particular __________________. There are __________ different

combinations of nitrogen bases when taken in sequences of three at a time.

41. True or False? All amino acids are specified by only one codon.

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42. Below is a chart of characteristics found in either DNA or RNA or both. Use check marks to indicate which are found in DNA and which are found in RNA.

Characteristic Found in DNA Found in RNA

Ribose present

Deoxyribose present

Phosphate present

Adenine present

Thymine present

Uracil present

Guanine present

Cytosine present

Double stranded

Single stranded

Remains in the nucleus

Moves out of the nucleus

43. __________________________ occurs in the ribosomes in the cytoplasm. The DNA in the nucleus tells the

ribosomes which proteins to make and how to make them. In the nucleus, _____ transcribes ______. The

RNA is then sent to the cytoplasm in the form of _________. A combination of three ____________ is used

as a code for each ________________. This group of three bases is called a _________. Each codon calls

for one _______________. It takes many amino acids to form a protein. These amino acids are found

______________________________________ and are transported to the ribosomes by _______________.

The tRNA has a cloverleaf shape. At one end of the tRNA is a sequence of three nucleotides that are

complementary to the mRNA; this is called an __________________. At the opposite end of the tRNA is

the attachment site for the _______________. The amino acids are linked together by _________________.

44. Ribosomes are found in two locations within a cell. They may be floating free in the cytosol or they may be

attached to the endoplasmic reticulum. What types of proteins are made by:

a) free ribosomes

b) bound ribosomes

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45. The assembly of a polypeptide begins when a ribosome attaches to the ___________________ on mRNA.

This codon is always _________ . This codon attaches to the anticodon _______ on a _________ molecule.

The tRNA then brings the amino acid ___________________ to the ribosome to start the synthesis of the

protein. Subsequent amino acids are added one at a time and are bound together by ___________________.

Eventually the ribosome reaches a _________ codon, bringing _______________ to an end.

46. Below is a list of the mRNA codons for each amino acid.

Alanine: GCU Histidine: CAU Serine: UCUArginine: CGU Isoleucine: AUU Threonine: ACUAsparagine: AAU Leucine: UUA Tryptophan: UGGAspartic Acid: GAU Lysine: AAA Tyrosine: UAUCysteine: UGU Methionine: AUG Valine: GUUGlutamic Acid: GAA Phenylalanine: UUU Terminator: UAAGlycine: GGU Proline: CCC

If the sequence on the DNA molecule calls for a protein with the following DNA codons, (1) what would be the sequence on the mRNA, (2) what would be the sequence on the tRNA, and (3) what would be the amino acid sequence of the protein being made?

DNA TAC TTA CAA ACC ATA ATT

mRNA

tRNA

Amino Acids:

47. What would be the effect if one of the bases were deleted in the very first mRNA codon?

48. What would happen if there was a substitution of one base for another in one of the mRNA codons?

49. Mutations that occur at one single nitrogen base are referred to as __________ mutations. A mutation involving the insertion or deletion of a nucleotide is called a ___________________ mutation.

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Worksheet on DNA and RNA - Answers

1. Deoxyribonucleic acid2. Nucleotides3. Sugar, phosphate, and a nitrogen base4. Adenine, cytosine, guanine, and thymine5. Pyrimidines; thymine, cytosine6. Purines; adenine, guanine7. Watson and Crick8. Double helix9. Sugars and phosphates10. Nitrogen bases11. Adenine pairs with thymine; Cytosine pairs with guanine12. Adenine, cytosine13. Hydrogen bonds14. False15. Deoxyribose16. ATCCGAGT17.

18. Replication19. The primary function of DNA is to store information that tells the cells which proteins to make.20. Just prior to cell division, the DNA must replicate so that each new daughter cell receives an exact copy of

the genome for that cell. All cells that divide to form new cells must pass exact copies of their DNA to offspring cells.

21. Separate, template, replication fork22. Helicase, replication fork23. DNA polymerases24. False25. True26. Exact, cell division27. True28. One, 100,000; mutation; Chemicals and ultraviolet radiation from the sun

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29. Ribonucleic acid30. Uracil31. List three ways that DNA is different from RNA:

(1) DNA HAS THE SUGAR DEOXYRIBOSE AND RNA HAS THE SUGAR RIBOSE.(2) DNA IS DOUBLE STRANDED AND RNA IS SINGLE STRANDED.(3) DNA HAS THE NITROGEN BASE THYMINE. RNA HAS N THYMINE, BUT HAS URACIL INSTEAD.

32. Messenger RNA (mRNA); Transfer RNA (tRNA), amino acids; Ribosomal RNA (rRNA)33. Transcription34. RNA polymerases; promoter; transcribed; single gene; termination site.35. Introns; exons36. Ribosomes37. Amino acids, 20; three-dimensional shape38. Translated, amino acids39. Codon40. Amino acid; 6441. False

42. Below is a chart of characteristics found in either DNA or RNA or both. Use check marks to indicate which

are found in DNA and which are found in RNA.

Characteristic Found in DNA Found in RNA

Ribose present X

Deoxyribose present X

Phosphate present X X

Adenine present X X

Thymine present X

Uracil present X

Guanine present X X

Cytosine present X X

Double stranded X

Single stranded X

Remains in the nucleus X

Moves out of the nucleus X

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43. Translation; DNA, RNA; mRNA; nitrogen bases, amino acid; codon; amino acid; floating freely in the cytosol, tRNA

44 a) Free ribosomes produce proteins that will be used within the cell.b) Bound ribosomes produce membrane proteins and proteins that will be exported for use outside the cell.

45. Start codon; AUG; UAC, tRNA; methionine; peptide bonds; stop, translation

46.

DNA TAC TTA CAA ACC ATA ATT

mRNA AUG AAU GUU UGG UAU UAA

tRNA UAC UUA CAA ACC AUA AUU

Amino Acids: INITIATOR, ASPARAGINE, VALINE, TRYPTOPHAN, TYROSINE, TERMINATOR

47. What would be the effect if one of the bases were deleted in the very first mRNA codon? THE DELETION OR ADDITION OF A NUCLEOTIDE WOULD CHANGE THE REST OF THE SEQUENCE. THE WRONG PROTEIN OR A NONFUNCTIONAL PROTEIN WOULD BE MADE.

48. What would happen if there was a substitution of one base for another in one of the mRNA codons? SUBSTITUTIONS WOULD AFFECT JUST THAT ONE AMINO ACID. IF THE SUBSTITUTION IS IN THE THIRD POSITION, IT IS LESS LIKELY TO HAVE AN AFFECT. A SUBSTITUTION IN THE FIRST OR SECOND POSITION WOULD AFFECT THE AMINO ACID BEING CALLED FOR.

49. Point mutations; Frameshift mutation

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