Name:________________________________________________________ Period: _________

Simulating Protein Synthesis                             Lab # 4

Introduction:

Genes are the units that determine inherited characteristics, such as hair color and blood type. Genes are lengths of DNA molecules that determine the structure of the proteins that our cells make. The sequence of nucleotides in DNA determines the sequence of amino acid in a polypeptide, and thus the structure of proteins.

In a process called transcription, which takes place in the nucleus of the cell, the DNA’s nucleotide sequence is copied into the form of a complementary mRNA molecule. Then the mRNA carries this information in the form of a code to the ribosome where protein synthesis takes place. The code, in DNA or mRNA, specifies the order in which the amino acids are joined together to form a protein. The code words in mRNA, however, are not directly recognized by the corresponding amino acids. Another type of RNA called transfer RNA (tRNA) is needed to bring the mRNA and amino acids together. As the code carried by mRNA is “read” on a ribosome, the proper tRNA’s arrive in turn and give up the amino acids they carry to the growing protein. mRNA codons are matched with tRNA anticodons. The process by which the information from DNA is transferred into the language of proteins is known as translation.

In this investigation, you will simulate the mechanism of protein synthesis and thereby determine the traits inherited by the fictitious organisms called BILEELEWS. These organisms whose cells contain only one chromosome, are members of the kingdom Animalia. A BILEELEWS chromosome is made up of eight genes (A, B, C, D, E, F, G and H), each of which is responsible for a certain trait.

Procedure:

1.      To determine the trait for Gene A of your BILEELEWS, fill in the information in the box labeled Gene A in the Data Table. Notice the sequence of nucleotides in DNA. On the line provided, write the sequence of nucleotides of the mRNA that are complementary to DNA. This is simulating the process of transcription.

2.      Then, on the line provided, write the sequence of nucleotides of tRNA that are complementary to the mRNA nucleotides you just wrote down. This is simulating the matching of tRNA and mRNA during translation.

3.      In order to determine the sequence of amino acids, look up each mRNA codon and find the specific amino acid in Figure 1. Use a hyphen (-) to separate each amino acid number and record this information in the appropriate place in the Data Table.

4.      Using Figure 2, match the specific amino acid with the correct amino acid number

5.      Using Figure 3, find the trait that matches the amino acid number sequence. Record this information in the appropriate place in the Data Table.

6.      Repeat steps 1-6 for the remaining genes (B through H).

7.      Using all of the inherited traits, sketch your   BILEELEWS in the space provided.

Data Table:

Gene A

DNA          ACC    GGT    TAT

 

mRNA  ______________________________

 

tRNA  _______________________________

 

Amino acid

Sequence_____________________________

 

Amino acid

# sequence ____________________________

 

Trait _________________________________

 

Gene B

DNA          TGC    CGA   

 

mRNA  ______________________________

 

tRNA  _______________________________

 

Amino acid

Sequence _____________________________

 

Amino acid

# sequence ____________________________

 

Trait _________________________________

 

Gene C

DNA          TTT   AAC

 

mRNA  ______________________________

 

tRNA  _______________________________

 

Amino acid

Sequence _____________________________

 

Amino acid

# sequence ___________________________

 

Trait _________________________________

 

Gene D

DNA          CAT    ACG    ACG

 

mRNA  ______________________________

 

tRNA  _______________________________

 

Amino acid

Sequence _____________________________

 

Amino acid

# sequence ____________________________

 

Trait _________________________________

 

Gene E

DNA          GTG    GTT    AAA   CCC

 

mRNA  ______________________________

 

tRNA  _______________________________

 

Amino acid

Sequence _____________________________

 

Amino acid

# sequence ___________________________

 

Trait _________________________________

Gene  F

DNA          ATG    ATG    AAA

 

mRNA  ______________________________

 

tRNA  _______________________________

 

Amino acid

Sequence _____________________________

 

Amino acid

# sequence ____________________________

 

Trait _________________________________

 

 

 

 

Gene G

 

DNA          TAT    CTA    AGC

 

mRNA  ______________________________

 

tRNA  _______________________________

 

Amino acid

Sequence _____________________________

 

Amino acid

# sequence ___________________________

 

Trait _________________________________

 

 

Gene H

 

DNA          GGT    GGT    AAC    ACC

 

mRNA  ______________________________

 

tRNA  _______________________________

 

Amino acid

Sequence _____________________________

 

Amino acid

# sequence ___________________________

 

Trait _________________________________

 

 

Figure 1: mRNA codon chart

 

Figure 2                                                                                  Figure 3

Amino Acid

Amino acid #

 

Amino acid # sequence

Trait

Tryptophan (try)

20

 

20-11-13

Hairless

Serine (ser)

16

 

20-12-13

Hairy

Alanine (ala)

2

 

13-10-16

Fat

Leucine (leu)

4

 

13-8-16

Skinny

Cysteine (cys)

3

 

16-2

Four legs

Histidine (his)

5

 

15-2

Six legs

Glutamine (glu)

7

 

12-7-8-1

Long nose

Phenylalanine (phe)

8

 

5-7-8-1

Short nose

Lysine (lys)

9

 

9-8

No freckles

Proline (pro)

12

 

9-4

Freckles

Isoleucine (iso)

13

 

11-3-2

Blue skin

Glycine (gly)

1

 

11-3-3

Orange skin

Tyrosine (tyr)

6

 

6-6-10

Horns

Aspartic Acid(asp.A.)

10

 

6-6-8

No horns

Valine (val)

11

 

12-12-4-20

One eye

Threonine (thr)

15

 

12-11-4-20

Two eyes

 

 

Sketch your BILEELEWS here:

 

 

 

 

 

 

 

 

 

 

 


 

Questions:

1.      Describe what happens during transcription.

 

 

2.      Where in the cell does transcription occur?

 

3.      Describe what happens during translation.

 

 

 

4.      Where in the cell does translation occur?

 

5.      Suppose you knew the amino acid sequence of a specific protein in a cell. How would you determine the particular DNA code that coded for that protein? In other words: If I gave you 12-12-4-20 as an amino acid # sequence and the three figures found above, what would you do to find out the DNA code for that particular amino acid sequence? (be very specific)

 

 

 

 

 

 

6.      How could one change in a DNA nucleotide alter the formation of the translated protein? In other words: If instead of the DNA being TTT AAA which translates into lysine-phenylalanine which gives the trait of no freckles, the DNA is changed into TTT AAC, what would happen to the mRNA, and then the tRNA and then the translated protein and in turn the trait? (be very specific)