Biology 12 DNA and Protein Synthesis – Chapter 10

What are you expected to know?

B4.14 list the major functions of nucleic acids (RNA and DNA)B4.15 name the four nitrogenous bases in ribonucleic acid (RNA) and describe the

structure of RNA using the following terms: – nucleotide (ribose, phosphate, nitrogenous base, adenine, uracil,

cytosine, guanine)– linear, single stranded– sugar-phosphate backbone

B4.16 name the four nitrogenous bases in DNA and describe the structure of DNA using the following terms:

– nucleotide (deoxyribose, phosphate, nitrogenous base, adenine, thymine, cytosine, guanine)

– complementary base pairing– double helix– hydrogen bonding– sugar-phosphate backbone

B4.17 compare the general structural composition of DNA and RNA

Cell Biology - DNA Replication (Estimated Time: 4–5 hours)Vocabulary

complementary base pairing, DNA helicase, DNA polymerase, nucleotides, recombinant DNA, replication, semi-conservative replication

It is expected that students will: B5 Describe DNA replication

B5.1 describe the three steps in the semi–conservative replication of DNA: – “unzipping” (DNA helicase)– complementary base pairing (DNA polymerase)– joining of adjacent nucleotides (DNA polymerase)

B5.2 describe the purpose of DNA replication B5.3 identify the site of DNA replication within the cell

B6 Describe recombinant DNA B6.1 define recombinant DNAB6.2 describe a minimum of three uses for recombinant DNA

Cell Biology - Protein Synthesis It is expected that students will: B7 Demonstrate an understanding of the process of protein synthesis

B7.1 identify the roles of DNA, messenger RNA (mRNA), transfer RNA (tRNA), and ribosomes in the processes of transcription and translation, including initiation, elongation, and termination

B7.2 determine the sequence of amino acids coded for by a specific DNA sequence (genetic code), given a table of mRNA codons

B7.3 identify the complementary nature of the mRNA codon and the tRNA anti-codon

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B8 Explain how mutations in DNA affect protein synthesis

B8.1 give examples of two environmental mutagens that can cause mutations in humans

B8.2 use examples to explain how mutations in DNA change the sequence of amino acids in a polypeptide chain, and as a result may lead to genetic disorders

Vocabularyamino acid, anti-codon, codon, DNA sequence (genetic code), elongation, environmental mutagen, genetic disorder, initiation, messenger RNA (mRNA), mutation, polypeptide chain, ribosomes, termination, transcription, transfer RNA (tRNA), translation

ACTIVITY: DNA & RNA Structure

ACTIVITY: DNA Double Helix

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B5.2 D escribe the purpose of DNA replication

What is DNA replication? _______________________________________________________

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Why must DNA replicate? ________________________________________________________

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Watch video on DNA replication: https://www.youtube.com/watch?v=27TxKoFU2Nw

B5.3 identify the site of DNA replication within the cell

Where does DNA replicate? ______________________________________________________

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Read page 188 and 189 (10.4 and 10.5)

B5.1 describe the three steps in the semi–conservative replication of DNA:

– “unzipping” (DNA helicase)– complementary base pairing (DNA polymerase)– joining of adjacent nucleotides (DNA polymerase)

BIOFLIX: DNA Replication

Why do we describe DNA replication as ‘semi-conservative? __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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Read about DNA Replication on page 189, and create an illustrated note of

A) Multiple Replication Bubbles

Include: Origin of replication, parent strand, daughter strand, replication bubble

B) How Daughter DNA Strands Are Synthesized.

Include: Parent strand, daughter strand, DNA polymerase, DNA ligase, 5’ and 3’, direction of replication, replication fork

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B6 Describe recombinant DNA Page 232-233, 12.1

B6.1 define recombinant DNAhttps://www.youtube.com/watch?v=HZmZ161njr8 See Activity 12G for some interesting uses of recombinant DNA

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B6.2 describe a minimum of three uses for recombinant DNA (page 239). You will need to do some research of your own! These ideas will be shared in class!

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See Cystic Fibrosis and the Promise of Gene Therapy video clip (in chapter 12).

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Protein Synthesis (From gene to protein)

B7.1 identify the roles of DNA, messenger RNA (mRNA), transfer RNA (tRNA), and ribosomes in the processes of transcription and translation, including initiation, elongation, and termination

Activity: OVERVIEW OF PROTEIN SYNTHESIS

http://www.johnkyrk.com/er.html

Activity: TRANSCRIPTION

http://www.johnkyrk.com/DNAtranscription.html

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These two diagrams illustrate the flow of information during the process of protein synthesis: from the DNA to the mRNA to the polypeptide.

1. What is transcription?

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Where in the cell does transcription take place? _________________________________

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Activity: TRANSLATION

2. What is translation?

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Where in the cell does translation take place? __________________________________

3. What is the role of the DNA in protein synthesis?

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4. What is the role of the mRNA in translation?

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5. In translation, what is the role of the tRNA? ________________________________________________________________________

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5. What is the role of the ribosomes in translation?

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Before going any further, you need to know about the genetic code. In other words, how is a sequence of bases in a DNA molecule used to determine the sequence of amino acids in a protein? What is the code?1. The sequence of bases on one side of the DNA molecule (the template strand) is a code

for the sequence of amino acids in a polypeptide (protein).

2. There are 20 different amino acids, so the code needs at least 20 different “code words”.

3. If the code is read in “ones”, there will be only 4 “code words” - A, T, C, and G, so we could only specify four different amino acids.

4. If the code is read in “twos”, there will be 16 “code words”:

A T G C

A

T

G

C

5. There are still not enough, because we need 20 “code words” to specify the 20 different amino acids.

6. If the code is read in “threes”, there will be 64 different “code words” - MORE than enough!

A T G C

AA

AT

AG

AC

TA

TT

TG

TC

GA

GT

GG

GC

CA

CT

CG

CC

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B7.2 determine the sequence of amino acids coded for by a specific DNA sequence (genetic code), given a table of mRNA codons

1. If the DNA code on the template strand is TACGTTAGCGATCTGATC, what will be the sequence of bases on the transcribed mRNA molecule?

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2. What will be the sequence of amino acids in the resulting polypeptide?.

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What is tRNA used for again? _____________________________________________________

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Here is a diagram of a tRNA molecule:

Your textbook simplifies it to look like this:

Here is a close-up diagram of a ribosome in the process of making a polypeptide. How many

subunits make up a working ribosome? ____________________

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Here is a simplified diagram of a ribosome, showing where everything attaches:

Do you remember this?

This diagram shows the ribosome in the process of translation:

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The mRNA has a ‘start’ and a ‘stop’ position. The ribosome attaches near the start position to begin translation:

This diagram summarizes the first stage of translation, known as initiation.

This diagram summarizes the next stage of translation, known as elongation. Elongation continues until the whole polypeptide has been constructed:

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When the polypeptide has been completed, the final stage of translation, known as termination, released the completed polypeptide from the ribosome:

Fill in the following concept map on protein synthesis:

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What is a polyribosome? (Note: we discussed this with the cell structure unit, but are just reminding you now that you can understand it a bit more clearly.)

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B8 Explain how mutations in DNA affect protein synthesis

B8.2 use examples to explain how mutations in DNA change the sequence of amino acids in a polypeptide chain, and as a result may lead to genetic disorders

A good example to illustrate this point is the mutation that leads to sickle-cell anemia. Sickle-cell anemia is an inherited genetic disorder. Study the following diagram.

How does the DNA mutate (change) to

cause this disease? _________________

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How does the mRNA change as a result

of the DNA mutation?

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How does the resulting hemoglobin molecule change?

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This diagram illustrates the many health problems that a person experiences if they inherited the gene for sickle-cell hemoglobin from both parents:

Here are two general types of DNA mutations and their effects. Why are these types of mutations

in the DNA called ‘point mutations’?

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Which type of point mutation seems to cause more problems overall, substitution or deletion?

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Why? _____________________________________

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What do we mean by a spontaneous mutation?

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B8.1 give examples of two environmental mutagens that can cause mutations in humans

What is a mutagen?

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Finally, what are some examples of environmental mutagens?

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