Name: Date: Period:

DIRECTIONS: Use the following passage to answer questions 1-10.

The Belgian Blue Mound of Beef

The Belgian Blue Mound of Beef is an extremely muscular breed

of cattle. At two years of age, males can weigh over 1700

pounds, and females over 1100 pounds! This breed originated

in the 1850’s in Belgium as a result of breeding two different

types of cattle. One question biologists have asked is, what

causes these cattle to develop such large muscles? Is it their

diet, their exercise, or their DNA? We are going to look at some evidence today that suggests that the

secret lies in their DNA.

Myostatin

Myostatin (which is also called growth and differentiation

factor-8) is a protein (a chain of amino acids!) found in the skeletal muscle of

mammals. It is a growth factor - a molecule that plays a part in controlling cell

division, cell growth, and cell development. Experimenters at Johns Hopkins

University first discovered the function of the gene in mice. Mice were

engineered so they had the myostatin gene “knocked out” (which means it didn’t

work). The resulting mice WITHOUT the myostatin gene developed two to three

times more muscle than mice with a normal version of the gene! The mice

were described as looking “like Schwarzenegger mice” by the

experimenters. Analysis of the muscle tissue of the mice showed that the number of muscle cells

and size of muscle cells was two to three times greater in the muscle tissue of the knockout mice

than in normal mice.

1. Based on the appearance of the organisms that have a mutated version of the myostatin gene, what does the function of myostatin seem to be in mammals? (In other words, what does myostatin do when it IS there?)

2. Does this mutation have a positive, negative, or neutral affect on the cattle? Explain your answer.

I wouldn’t want to meet you in a dark alley!

I’ll be back!myostatin knockout

normal mouse

3. Using the DNA sequence below, determine the amino acid sequence for normal myostatin. **NOTE** This is only a small portion of the protein (amino acids 273 – 280 out of 376 total).

                                            

NORMAL MYOSTATIN: 273 280

DNA

mRNA

Amino Acid

4. Using the DNA sequence for below, determine the amino acid sequence for Belgian Blue myostatin. BELGIAN BLUE MYOSTATIN:

273 280

DNA

mRNA

Amino Acid

5. Draw an arrow to point to the mutation in the DNA sequence for Belgian Blue myostatin.

6. Which type of mutation (insertion, deletion, substitution) occurred in the gene for myostatin?

7. How many codons (thus, amino acids) changed as a result of this mutation?

8. Based on the appearance of the organisms that have a mutated version of the myostatin gene, what does the function of myostatin seem to be in mammals? (In other words, what does myostatin do when it IS there?)

9. Does this mutation have a positive, negative, or neutral affect on the cattle? Explain your answer.

10. Remember from our unit on macromolecules that proteins have 4 levels of structure (primary, secondary, tertiary, quaternary). What level of structure of the Belgian Blue myostatin protein was most directly affected by this mutation? Explain your answer.

TGT GAT GAA CAC TCC ACA GAA TCT

TGT GAG AAC ACT CCA CAG AAT CTA