Molecules of Life Part 2

Learning Objectives Learn how genes code for proteins. Learn about the base-pairs within a DNA molecule. Understand how proteins are made.

Success Criteria I can explain the link between genes and proteins. I understand that different genes result in different proteins. I can explain how mRNA is involved in protein synthesis.

Starter Think about your favourite meal. Write a recipe/instructions for making this meal in no more than 8 steps. Now think of a small animal such as a cat. How many ‘instructions’ do you think it takes to make the animal? Answer: Millions of genes!

From DNA to Organism! Today’s lesson is about the link between DNA and a complete organism. You probably know that DNA acts as a set of instructions to make a whole organism. But how?

Genetic Code The genes found in your DNA make up your genetic code. This controls the activities of your cells. It also controls your features. The DNA in your genes is a code for making proteins, which give you the features shown above. <- hair colour skin colour height ->

Task Answer the questions 11 – 13 (in full sentences) on page 12 of the new student textbook. Answers: 11. DNA or chromosomes (accept genes). 12. For growth/ For repairing damage/ Features such as eye and skin colour are due to proteins. 13. DNA.

Modelling DNA A model of DNA can be built with either pasta or sweets. Your task!: You are going to attempt to make a model using the equipment provided. Follow the instructions carefully! After completing, evaluate your model by working through worksheet 2. If you want to make the pasta model as described in the new course material, there are instructions in the file named “practical”. Alternatively, you can stick to the model we usually make out of sweets (midget gems etc), and provide your own instructions.

DNA and Proteins The actual information in DNA is a sequence of bases. They can be thought of as the ‘rungs’ of the double-helix ladder. It’s the sequence of the bases that codes for a particular protein. Every protein in your body has it’s own base code. The bases: Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Copy these steps into your book, under the subtitle, protein synthesis (3) The mRNA is then used by ribosomes to make a protein! (1) The DNA can’t leave the nucleus, but it’s code is needed outside the nucleus! Protein!  (2) A special copy called mRNA is made which can leave the nucleus. Copy these steps into your book, under the subtitle, protein synthesis

Task For each of the four bases (A, T, C, G), think of a specific shape (eg. square, circle, star). Draw the chain of shapes for the following base sequences: G T A T G A C G C T C G A G A C G C T A C T G T A T G A A C G G G C A G What do the shapes represent, if the chains of shapes are proteins?

higher

DNA and Proteins Look at the double helix on the right. Notice how the yellow sections only pair up with the blue sections. Similarly, the red sections only pair up with the green sections. This is known as the base-pairing rule: A’s only pair with T’s C’s only pair with G’s This is important when mRNA is made just before proteins are made (next slide). In order to fit the DNA modelling and the higher content into one lesson, you may want to cover this next lesson.

nucleus cytoplasm G A C U C C T G A G G A C C U mRNA! DNA Tell students that the letter ‘U’ replaces T in mRNA. G G A C C U DNA

Protein Synthesis On a strand of mRNA, each three bases codes for one amino acid. A U C C G U A C G U A C A U C C G These two sets of three bases would therefore code for 2 amino acids. READ PAGE 13 & STUDY FIGURE 10 CAREFULLY!! Then answer questions 16 – 19. This stuff is tricky, so ask if you need help or are stuck!!

plenary

What would happen to the resulting protein? Think about what would happen if the base sequence in a gene was incorrect. What would happen to the resulting protein? Does anyone know what a mutation is? These things will be discussed next lesson!

Learning Objectives Learn how genes code for proteins. Learn about the base-pairs within a DNA molecule. Understand how proteins are made.