2. Molecular Biology – 2.7 / 7.1 Part 2 - Protein Synthesis

Name:

Understandings, Applications and Skills (This is what you maybe assessed on)

Statement Guidance & WOORKBOOK2.7.U4 Transcription is the synthesis of mRNA copied from the

DNA base sequences by RNA polymerase.Activity 58 p. 78

2.7.U5 Translation is the synthesis of polypeptides on ribosomes.

2.7.U6 The amino acid sequence of polypeptides is determined by mRNA according to the genetic code.

Activity 59 p. 79

2.7.U7 Codons of three bases on mRNA correspond to one amino acid in a polypeptide.

2.7.U8 Translation depends on complementary base pairing between codons on mRNA and anticodons on tRNA.

2.7.A2 Production of human insulin in bacteria as an example of the universality of the genetic code allowing gene transfer between species.

2.7.S1 Use a table of the genetic code to deduce which codon(s) corresponds to which amino acid.

Activity 59 p. 79

2.7.S3 Use a table of mRNA codons and their corresponding amino acids to deduce the sequence of amino acids coded by a short mRNA strand of known base sequence.

Activity 59 p. 79

2.7.S4 Deducing the DNA base sequence for the mRNA strand. Activity 59 p. 797.1.A3 Tandem repeats are used in DNA profiling. Activity 100-101 p. 133-1357.1.S1 Analysis of results of the Hershey and Chase experiment

providing evidence that DNA is the genetic material.Activity 210 p. 291The Hershey-Chase experiment

7.1.S2 Utilization of molecular visualization software to analyse the association between protein and DNA within a nucleosome.

http://www.rcsb.org/pdb/explore/jmol.do?structureId=1AOI&bionumber=1

7.1.U6 Some regions of DNA do not code for proteins but have other important functions.

Activity 213 p. 295The regions of DNA that do not code for proteins should be limited to regulators of gene expression, introns, telomeres and genes for tRNAs.

Connections to other sections:

2.4 Proteins: Amino acids are linked together by condensation to form polypeptides There are 20 different amino acids in polypeptides synthesized on ribosomes Amino acids can be linked together in any sequence giving a huge range of possible polypeptides The amino acid sequence of polypeptides is coded for by genes A protein may consist of a single polypeptide or more than one polypeptide linked together The amino acid sequence determines the three-dimensional conformation of a protein Living organisms synthesise many different proteins with a wide range of functions

http://www.bioknowledgy.info/ (Chris Paine)

2.4 Amino Acids:

2.6 RNA Structure:

• 3 differences between DNA and RNA:– RNA has ________________________________– RNA is ________________________________________________________________– RNA contains a nitrogen base called ________________________________instead of thymine.

• 3 Types of RNAMessenger RNA (mRNA):

– copies ________________________________and carries the info to the ribosomes (in cytoplasm)Ribosomal RNA (rRNA):

– makes up a ________________________________; reads and decodes mRNATransfer RNA (tRNA):

– carries amino acids to the ribosome where they are ________________________________

2.7 U4 Transcription is the synthesis of mRNA copied from the DNA base sequence by RNA polymerase

Protein synthesis is the assembly of amino acids (by RNA) into proteinsInvolves two steps:

1. _________________________________ – copying DNA code into mRNA

2. ___________________________________ – reading the mRNA code and assembling amino acids into a polypeptide chain (protein)

TRANSCRIPTION: The enzyme ______________________________ binds to a site on the DNA at the start of a gene

o (The sequence of DNA that is transcribed into RNA is called a gene).

RNA polymerase ______________________________ and synthesizes a complementary RNA copy from the ___________________________ DNA strand

It does this by covalently bonding ______________________________that align opposite their exposed complementary partner (using the energy from the cleavage of the additional phosphate groups to join them together)

Once the RNA sequence has been synthesised:- RNA polymerase will ______________________________- ______________________________ from the DNA- the ______________________________reforms

• Transcription occurs ______________________________ (where the DNA is) and, once made, the mRNA moves to the ___________________ (where translation can occur)

GeneThe __________________________________________________________________ into RNA is called a gene

The strand that is transcribed is called the ______________________ strand and is complementary to the RNA sequence 

The strand that is not transcribed is called the ______________________ strand and is identical to the RNA sequence (with T instead of U)

2.7 U5 Translation is the synthesis of polypeptides on ribosomes.

Translation is the process of protein synthesis in which the genetic information encoded in mRNA is translated into a sequence of amino acids in a polypeptide chain

The Ribosome:A ribosome is composed of two halves, ____________________________________________. During translation, ribosomal subunits assemble together like a sandwich on the strand of mRNA:

• Each subunit is composed of ____________________________________________• The small subunit binds to the mRNA• The large subunit has binding sites for tRNAs and also ____________________________________________

between amino acids2.7 U6 The amino acid sequence of polypeptides is determined by mRNA according to the genetic code2.7 U 7 Codons or three bases on mRNA correspond to one amino acid in a polypeptide2.7 U8 Translation depends on complementary base pairing between codons on mRNA and anticondons on tRNATranscription:

• The ______________________ in an mRNA molecule serves as instructions for the order in which amino acids are joined to produce a polypeptide

• Ribosomes decode the instructions by using codons, ______________________ that each code for 1 amino acid

• Each codon is matched to an anticodon, or complementary sequence ______________________to determine the order of the amino acids

2.7 S1 Use a table of the genetic code to deduce which codon(s) corresponds to which amino acid2.7 S3 Use a table of mRNA codons and their corresponding amino acids to deduce the sequence of amino acids coded by a short mRNA strands of known base sequence. 2.7 S4 Deduce the DNA base sequence for the mRNA strand

1. Deduce the codon(s) that translate for Aspartate.

2. If mRNA contains the base sequence CUGACUAGGUCCGGA

a. deduce the amino acid sequence of the polypeptide translated.

b. deduce the base sequence of the DNA antisense strand from which the mRNA was transcribed.

3. If mRNA contains the base sequence ACUAAC deduce the base sequence of the DNA sense strand.

4. Transcribe the DNA into mRNA

5. Now Transcribe it into the amino acid chain

7.1 U6 - Some regions of DNA do not code for proteins but have other important functions._________________, the regions of DNA that code for polypeptides, contain both _________________ and

_________________DNA.

• Introns are __________________________________of messenger RNA (mRNA)

• mRNA is translated by ribosomes into polypeptides

• Therefore _________________for the __________________________________Between genes exist non-coding

regions of DNA. Although such DNA does not code for polypeptides it

__________________________________of mRNA.

_________________ sequences are attachment points for _________________________________adjacent to the gene

Some of these regions act as binding sites for particular proteins, which in turn affect transcription of

the nearby gene:

• _________________ are sequences that _________________ _________________ (when a protein is bound to it)

• _________________ inhibit transcription (when a protein is bound to it)

The end of chromosomes contain highly repetitive DNA sequences. These regions are called

________________________ and they protect the DNA molecule from degradation during replication.

non-coding DNA description

2.7.A2 Production of human insulin in bacteria as an example of the universality of the genetic code allowing gene transfer between species.

• All living things use the same bases and the same genetic code.• Each codon produces the same amino acid in transcription and translation, regardless of the

species. • So the sequence of amino acids in a polypeptide remains unchanged. • Therefore, we can take genes from one species and insert them into the genome of another species.

Explain in your own words and using diagrams how the process of Gene Transfer for the production of insulin works:

7.1.S1 Analysis of results of the Hershey and Chase experiment providing evidence that DNA is the genetic material.

Make sure you watch the video and check out the links to understand the summary given below. Include your annotated notes:

7.1.A3 Tandem repeats are used in DNA profiling

How they are used in profiling: Dyes markers (e.g. attached to

dideoxyribonucleic acids) are attached to the tandem repeats during PCR (DNA Replication).

Restriction enzymes can be used to cut DNA between the tandem repeats.

Electrophoresis enables scientists therefore to calculate the length of the tandem repeat sequence of an individuals.

If different tandem repeats at different loci are used then a unique profile, for an individual can be identified.

Review questions

1. Transcription and translation is also known as protein synthesis, and is the expression of genes. The genetic code determines the amino acid sequence of a polypeptide, and the properties of the amino acids give the final structure and function of the protein. Other than membrane proteins, state four functions of proteins in the cell.

2.7.U4 Transcription is the synthesis of mRNA copied from the DNA base sequences by RNA polymerase.

2. Outline the process of transcription in the nucleus, including the roles of RNA polymerase, ribonucleoside triphosphates and complementary base pairing.

2.7.U5 Translation is the synthesis of polypeptides on ribosomes.

3. Complete the table to compare and contrast the processes of transcription and translation.

Transcription Translation

Begins with… mRNA

Ends with…

Location

Uses… RNA polymerase

4. Ribosomes are the cell components that carry out the process of translation. Outline the structure of the ribosome and explain how it is adapted to carry out translation.

2.7.U6 The amino acid sequence of polypeptides is determined by mRNA according to the genetic code. 2.7.U7 Codons of three bases on mRNA correspond to one amino acid in a polypeptide.

5. Define mRNA in terms of it’s function

6. Suggest why the length of mRNA molecules varies.

7. Describe what is meant by the term ‘genetic code’.

8. Define the term codon.

9. Calculate the number of different codons combinations.

10. State the number of amino acids that can be translated by ribosomes.

11. Explain what is meant by the term degenerate. Refer to the last two questions in your answer.

2.7.U8 Translation depends on complementary base pairing between codons on mRNA and anticodons on tRNA.

12. State the molecule on which anti-codons, which are complementary to codons, can be found.

13. Complete the steps to outline the process of translation.

a. mRNA binds to the ________________ of the ribosome.

b. The mRNA contains a series of ___________________ each of which codes for an amino acid.

c. tRNA molecules contain ____________which are complementary to the ________ on the

_______.

d. tRNA molecules bind to a _____________________ that corresponds to the anticodon

e. The _____________ binds to the small subunit of the ribosome.

f. There are ____ binding sites on the ________________ of the ribosome, but only _____ can

contain tRNA molecules at a time

g. The _____________ moves along the mRNA and presents codons in the first two

________________.

h. ______ with anticodons ________________ to the codons bind (the bases are linked by the

formation of ________________ )

i. A ________________ is formed between the two amino acids (carried by the tRNAs)

j. As the ________________ moves along ______ a tRNA moves to the ______ binding site and

________________.

k. Another ______ carrying an amino acid binds to the ______ site and a second

________________ is formed.

l. The process (i.e. the last two steps) repeats forming a ________________.

Extension: sketch diagrams below to show translation and use the steps above as annotations.

2.7.S1 Use a table of the genetic code to deduce which codon(s) corresponds to which amino acid. 2.7.S3 Use a table of mRNA codons and their corresponding amino acids to deduce the sequence of amino acids coded by a short mRNA strand of known base sequence.2.7.S4 Deducing the DNA base sequence for the mRNA strand.

Use the genetic code table to help answer the questions below.

14. Deduce the codon(s) that translate for Aspartate.

15. If mRNA contains the base sequence CUGACUAGGUCCGGAa. deduce the amino acid sequence of the polypeptide translated.

b. deduce the base sequence of the DNA antisense strand from which the mRNA was transcribed.

c. If mRNA contains the base sequence ACUAAC deduce the base sequence of the DNA sense strand.

The genetic code – how mRNA codons translate to amino acids

http://www.ib.bioninja.com.au/_Media/genetic_code.jpeg

16. Transcribe and translate this DNA sequence.

DNA T A C G G G C C C G T G A C A G C C A C T

mRNA

Amino acid

17. An mRNA strand has 76 codons. How many amino acids will be in the polypeptide?

18. A polypeptide contains 103 amino acids. What is the length of the gene (unit = base pairs)?

19. A gene is 105kbp (kilobase pairs). How many amino acids are in the polypeptide?

2.7.A2 Production of human insulin in bacteria as an example of the universality of the genetic code allowing gene transfer between species.

21. Describe what is meant by the term ‘universality of the genetic code’

7.1.U6 Some regions of DNA do not code for proteins but have other important functions.

22. Distinguish between coding and non-coding regions of DNA.

23. Outline how non-coding regions can be involved in gene expression.

24. Most of the eukaryotic genome is non-coding. There are two types of repetitive sequences: moderately repetitive sequences and highly repetitive sequences otherwise known as satellite DNA. Give an example of a region of DNA that contains highly repetitive sequences and outline the function of that region.

7.1.A2 Use of nucleotides containing dideoxyribonucleic acid to stop DNA replication in preparation of samples for base sequencing.

25. State how dideoxyribonucleic acid affect DNA replication.

26. State what is attached to dideoxyribonucleic acid during base sequencing.

27. Outline how do the answers to the above two questions enable scientists to identify the base sequence of DNA.

7.1.A3 Tandem repeats are used in DNA profiling.

28. State the two different sources of DNA used in paternal and maternal profiling.

29. Suggest a reason why non-coding regions are more useful than coding regions in DNA profiling.

30. Describe what is meant by the term tandem repeat sequence.

31. Describe why tandem repeats are useful in DNA profiling.

32. Explain how tandem repeats are used in DNA profiling.

a. Complete the table to outline the keys steps in the process of gene transfer.

Diagrams Notes

Citations:

Allott, Andrew. Biology: Course Companion. S.l.: Oxford UP, 2014. Print.

Taylor, Stephen. "Essential Biology 03.4 DNA Replication.docx." Web. 1 Oct. 2014. <http://www.slideshare.net/gurustip/essential-biology-34-dna-replication-core>.

Taylor, Stephen. "Essential Biology 03.5 DNA Transcription and Translation.docx." Web. 1 Oct. 2014. <http://www.slideshare.net/gurustip/essential-biology-35-transcription-translation-core>.

Taylor, Stephen. "4.4 Genetic Engineering and Biotechnology.pptx" Web. 1 Oct. 2014. <http://www.slideshare.net/gurustip/genetic-engineering-and-biotechnology-presentation>.