What is the significance of the first and last codons of an mRNA

26 Jun What is the significance of the first and last codons of an mRNA

Question
Assignment Type:Individual Project Deliverable Length:Three parts – submitted in the Graphic Organizer,
Points Possible:125 Due Date:1/25/2013 11:59:59 PM CT

Complete all three parts and answer all questions.

DownloadGraphic Organizerfor answering all questions and genetics exercises in this assignment.

Part I: Genetics – From Genes to Proteins, Mutations

Background:DNA represents the architectural blueprint for all living systems, encoding specific instructions in the sequence of its four nitrogen-containing base pairs that are necessary for building the organism.

During the process of transcription, the information in the DNA codons of a gene is transcribed into RNA.

A change in the DNA sequence, for example as a result of a “mistake” during DNA replication, is defined as a mutation. Mutations may result in a change in the “blueprint,” which may then change the resulting protein product.

Assignment details for part one:

Transcribe and translate EACH of the three following DNA gene sequences.Turn these in using the graphic organizer. The letters represent the DNA N-base sequences of the genes.

The first is the original gene. The next two are mutations of the original. Note that the changes (mutations) are shown in red.

Original Gene sequence 3′-T A C C C T T T A G T A G C C A C T-5

Mutated gene sequence 1 3’-T A CG C T T T A G T A G C C ATT-5′

Mutated gene sequence 2 3’-T AAC C T T T ACT A GG C A C T-5’

Also, answer the following questions:

· What is the significance of the first and last codons of an mRNA transcript?

· What meaning do these mRNA codons have for protein synthesis?

· Did the mutations result in a change in the final proteins? If so, describe the change.

· In general, why might a change in amino acid sequence affect protein function?

Part II: Inheritance of Traits or Genetic Disorders

Background: Cystic fibrosis is an inherited disease that affects the respiratory, digestive, or reproductive systems of the body, with symptoms ranging from mild to severe. Bob and Sally are recently married. Upon deciding to plan a family, both Sally and Bob find out that they are both heterozygousfor cystic fibrosis, but neither of them has symptoms of the disorder.

Assignment details:Complete a Punnett Square for cystic fibrosisfor this couple using the following alleles: C = normal allele; and c = allele for cystic fibrosis.

Complete the Punnett Square in the graphic organizer.

Student Name

Date

Questions

Student Response

Part I

Original DNA Strand:

3’-T A C C C T T T A G T A G C C A C T-5’

Transcription (base sequence of RNA):

Translation (amino acid sequence):

Mutated gene sequence one:

3’-T A C GC T T T A G T A G C C A TT-5′

Transcription (base sequence of RNA):

Translation (amino acid sequence):

Mutated gene sequence two:

3’-T A AC C T T T A CT A G GC A C T-5’

Transcription (base sequence of RNA):

Translation (amino acid sequence):

What is the significance of the first and last codons of an mRNA transcript?

Explanation:

What meaning do these mRNA codons have for protein synthesis?

Explanation:

Did the two mutations result in a change in the final proteins? If so, describe the change.

Response/ explanation:

In general, why might a change in amino acid sequence affect protein function?

Explanation:

Also answer the following questions:
Based on the Punnett square, calculate chances (percentages) for the following:

· for having a healthy child (not a carrier)

· a child that is a carrier for the cystic fibrosis trait

· a child with cystic fibrosis

Be sure to submit these percentages as part of your assignment in the Graphic Organizer.

Part III: Cell division, sexual reproduction and genetic variability

Background: Eukaryotic cells can divide by mitosis or meiosis. In humans, mitosis produces new cells for growth and repair; meiosis produces sex cells (gametes) called spermand eggs.

Although mutations are the ultimate source of genetic variability, both meiosis and sexual reproduction also can contribute to new genetic combinations in offspring.

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

You will submit your Graphic Organizer with all answers in your Submit Assignment area.

Provide references in APA format. This includes a reference list and in-text citations for references used throughout the assignment. Note that there is a Reference page for listing sources included on the Graphic Organizer.

You will submit your Graphic Organizer with all answers.

instructor Comments:

Please use the graphic organizer with the DNA sequences, Punnett Square and questions all laid out for you. Just fill in each of the three parts and answer the questions. For help with this project, please come to chat on Monday or review the archive.

Part 1: Transcription and Translation

Converting DNA to RNA and converting RNA to a peptide sequence are really just like matching games or Morse Code. You find the “matching” letters, and place them in the order dictated by the DNA for transcription, and then by the three base “codons” of the RNA for translation. I have added an explanation in the Instructor Files. It includes pictures and tables, so please use it to learn how to transcribe and translate a DNA sequence. I know it is confusing at first, but it can be fun like a puzzle! Please come to chat or access the archives for a narrated, animated presentation on how to transcribe and translate a gene.