Genetic Coding, Essay Example

Question 1

If Gene X has the DNA base sequence of 3’-TACCCTTTAGTAGCCACT-5’ the RNA base sequence will be as follows 5’-AUGGGAAAUCAUCGGUGA-3’

Question 2

Using the mRNA that you transcribed above, use the genetic code table to determine the resulting amino acid sequence. Turn this in.

AUG-Methionine (Initiation site)

GGA-Glycine

AAU-Asparagine

CAU-Histidine

CGG-Arginine

UGA-Opal (Stop Sequence)

Sequence- 5’- Met-Gly-Asn-His-Arg-Opal-3’

Question 3

The first and the last codons are the start and stop codons respectively. They initiate the protein synthesis and stop the process at the end as well as play a major role in determining the conformation of the protein.

Question 4.

Then, explain why a change in amino acid sequence might affect protein function. Turn in your answer.
Here is the original sequence, followed by two mutated sequences, 1 and 2:

Original sequence 3′- TACCCTTTAGTAGCCACT-5’

Mutated sequence 1) 3’-TACGCTTTAGTAGCCATT-5′

Mutated sequence 2) 3’-TAACCTTTACTAGGCACT-5’.

Mutated Sequence 1 mRNA                                      Mutated sequence 2 mRNA                             

5’-AUGCGAAAUGAUCGGUAA-3’                                    5’-AUUGGAAAUGAUCCGUGA-3’

Amino Acid Sequence for Mutant 1                          Amino Acid Sequence for mutant 2

Met-Arg-Asn-Asp-Arg-Ochre (stop)                          Ile-Gly-Asn-Asp-Pro-Opal (stop)

Protein function is a function of the amino acids in the sequence, the nature of the protein is determined by the amino acid. The amino acids have varied isoelectric points which determine their conformation hence determining the king of proteins they form.

Question 5-Cystic Fibrosis

Assuming the C-Normal Allele and c is a carrier allele, the recessive gene c needs to be in homozygous recessive form cc to cause the disease while heterozygous Cc is a carrier. Homozygous dominant CC is free of any genetic factors for the disease.

Punnet’s Square

Results

CC-Normal (genotypically and phenotypically (1/4)

Cc/cC- carrier (2/4)

cc- Cystic Fibrosis Positive (1/4).

Probabilities for

Healthy Child -25%

Carrier Child-50%

Child with cystic fibrosis-25%.

Question: How do both meiosis and sexual reproduction (fertilization) produce offspring that differ genetically from the parents? Be sure to talk about steps in meiosis that increase variability as well as the process of fertilization.

The process of genetic variability is determined by the variances in genetic matter between parent and offspring. In meiosis, the genes achieve genetic variability through a process called crossing over. During the stage, the telomere material of the various genes is exchanged between the various chromomatids that are initially in one pair of a chromosome. Once this genetic  material is exchanged, the resulting chromosomes are different from the precursors in that they possess genetic information that was not in the parent hence genetic variability.

In sexual reproduction, the gamete cells normally are haploid in nature. This means that they possess half the number of chromosomes is a somatic cell. Once they mate, the cells fuse each contributing half the number of chromoses to form a diploid (normal cell). This means that the off-springs only get half of characteristics form one parent and the other half from the other hence the genetic variability.

Reference

Lehninger, A., Nelson, D & Cox, M. (1993) “Principles of Biochemistry” 2^nd edition. Worth Publishers, Inc. Washington.