CHNOPS- Simulating Protein Synthesis



CHNOPS- Simulating Gene Expression

Objectives:

Before doing this assignment you should be able to:

• define gene

• state where in the cell transcription and translation take place

• describe the structure and function of DNA and RNA in inheritance

After doing this assignment you should be able to:

• distinguish between transcription and translation

• describe the role of mRNA and tRNA in gene expression

• model gene expression from transcription to the level of phenotype (trait)

• relate genes and alleles to genotypes and phenotypes

Background:

Genes are the units that determine inherited characteristics, such as hair color and blood type. Genes are the lengths of DNA molecules that determine the structure of polypeptides (the building blocks of proteins) that our cells make. The sequence of nucleotides in DNA determines the sequence of amino acids in polypeptides, and thus the structure of proteins.

In a process called transcription, which takes place in the NUCLEUS of the cell, RNA Polymerase reads and copies the DNA’s nucleotide sequences in the form of a complementary RNA molecule. Then the mRNA carries this information to the RIBOSOMES, where translation takes place. The code, in DNA or mRNA, specifies the order in which the amino acids are joined together to form a polypeptide. 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 tRNAs arrive in turn and give up the amino acids they carry to the growing polypeptide chain. The process by which the information from DNA is transferred into the language of proteins is known as translation. Transcription and translation together comprise the process called protein synthesis or gene expression. The actual different gene sequences for the traits are the different forms of the gene or alleles. The genotype is by definition what is encoded in the genes. It is the differences between the forms of the genes that result in the differences between proteins, OR the absence of certain functional proteins, that leads to different phenotypes.

Gene (allele1) = DNA sequence ( mRNA sequence ( amino acid sequence ( protein ( phenotype

***mutation***

Gene (allele2) = different DNA sequence ( different mRNA sequence ( different amino acid sequence ( different or nonfunctional protein ( different phenotype

As scientists begin to sequence the genes of organisms found on Earth (and would attempt to do with any extraterrestrial life discovered), they are learning more and more about the genome of each species. This lab begins with a simulation involving the genome of a fictitious organism called a CHNOPS for which scientists have sequenced 6 genes, arbitrarily identified as genes A, B, C, D, E, and F.

What questions do you have after reading? Write them below, then complete the assignment. If you have not answered your own questions, please either look in your notes or text for the answers, or ask your teacher.

Name: _______________________ Per. _______ Date _______

1. Complete Figure 3 using information from Figures 1 & 2.

Figure 1. CHNOPS Codon Table

|tRNA Triplet |Amino Acid Number |

|CCC |1 |

|CGA |2 |

|CGC |3 |

|AAC |4 |

|GGG |5 |

|AUC |6 |

|AGG |7 |

|AAA |8 |

|UUU |9 |

|CUA |10 |

|GGA |11 |

|GGU |12 |

|UAU |13 |

|AGC |14 |

|ACC |15 |

Figure 2. Alleles for Genes A-H in CHNOPS

|Amino Acid Sequence |Trait |Phenotype |

|15-11-13 |Hair |Hairless |

|15-12-13 | |Purple Hair |

|6-6-10 |Body form |Plump |

|6-6-4 | |Skinny |

|14-2 |Leg number |4-Legged |

|(not identified) | |No legs |

|12-7-8 |Nose length |Long nose |

|5-7-8 | |Short nose |

|9-8 |Freckled |No freckles |

|9-4 | |Freckles |

|11-3-2 |Skin pigment |Purple skin |

|11-3-3 | |Orange skin |

Figure 3. Traits for Genes A-F in a Specimen of CHNOPS

|Gene A |Gene B |Gene C |

|DNA: ACC GGT TAT |DNA: |DNA: |

| | | |

|mRNA: UGG CCA AUA |mRNA: |mRNA: |

| | | |

|tRNA: ACC GGU UAU |tRNA: AGC CGA |tRNA: |

| | | |

|AA sequence: 15-12-13 |AA sequence: |AA sequence: |

| | | |

|Phenotype – Purple Hair |Phenotype – |Phenotype – no freckles |

|Gene D |Gene E |Gene F |

|DNA: |DNA: GGT AGG AAA |DNA: |

| | | |

|mRNA: |mRNA: |mRNA: UAG UAG UUG |

| | | |

|tRNA: |tRNA: |tRNA: |

| | | |

|AA sequence: 11-3-3 |AA sequence: |AA sequence: |

| | | |

|Phenotype – |Phenotype - |Phenotype - |

Draw your CHNOPS in the box below illustrating all of its genetic characteristics.

ANALYSIS & CONCLUSIONS

1. Where do you think the name CHNOPS comes from?

2. Distinguish between translation & transcription.

3. What are the specific sites for transcription & translation in the cell?

4. How many tRNA nucleotides form an anticodon that will attach to the mRNA codon?

5. What role does mRNA play in gene expression? tRNA?

6. Suppose you knew the makeup of specific proteins in a cell. How would you determine the particular DNA code that coded for them? (Hint: Given the trait, how would you find the DNA)

7. How could one change in a DNA nucleotide alter the formation of the translated protein? (An example would be the difference between normal and sickle-cell hemoglobin)

8. Describe the three different types of mutations.

9. What does sense and nonsense mutations mean?

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