Metabolism and Environment  (A.S. 91159 (Bio 2.7 Ext ) Gene Expression )

You are the you, you are, as a result of the interactions between the instructions the DNA - Genotype your body has and the effects that the environment has through interactions with your physical you - your Phenotype. 

We know that the environment can affect you in more than just physically ...... however we will only be looking at some particular environmental conditions that can rearrange the metabolic pathways that are how our bodily systems operate.

Step 1 : We have all ready met how our genotype can change - both micro and macro evolution. 

But we'll be focusing here on the "instant" changes that mutations can bring. In particular the changes at the gene level - that cause changes to the amino acid sequence of the polypeptide chains that create proteins. 

Mutations always sound like bad news .... but they are actually a normal everyday thing and without them we wouldn't have the variation that allows us to survive so well. They can happen spontaneously = just happen - mostly "hiccups" during DNA replication that our body's "spell Check" misses. Or the can be induced by things we call mutagens - stuff that accelerate the natural rate of mutation.

We'll begin with a reminder of mutations and then have a closer look at mutagens - accelerating is when things get out of control. When cells get out of control - particularly division - we call it cancer. (Learn)

Mission 1 : Now that you remember mutations - spontaneous, induced, silent/neutral, harmful, beneficial ..... see how you get on with the questions on mutations in your workbooks. (Learn)

Done that? = Share with your teacher.

Yes = now its time for your next Step/Video clip/Challenge/Mission.

No = go back and complete the Step/Video clip/Challenge/Mission please.

Step 2 : One of the most common Silent or Neutral gene mutations is a base substitution = one base is changed for another. Due to the redundancy in the DNA Code caused by degeneracy a lot of base changes have no effect. 

A base change that doesn't change the amino acid sequence is a "same-sense" (AKA silent) mutation. A base change that changes an amino acid this can either have no effect on the finished proteins, or result in a change in shape = a change in function these are "missense" mutations. But a base change that results in a major effect on the finished protein (a stop codon in wrong place) is a "nonsense" mutation. 

I've included explanations of the sense changes, sickle cell anemia and a bonus of how sickle cell can help with malaria (also often an exam question) (Learn)

Mission 2 : See if you can make "Sense" of all of this - both base substitution and sickle cell anemia. If you have trouble remembering about somatic vs gametic cells = go back to Step 8 of Genetic Change. (Learn) 

Done that? = Share with your teacher.

Yes = now its time for your next Step/Video clip/Challenge/Mission.

No = go back and complete the Step/Video clip/Challenge/Mission please.

Step 3 : A gene mutation that always causes a change is when a base is either inserted or deleted. As the code is read in triplets - adding or removing a base changes this sequence of 3's = shifts the "reading frame". Often these are called "frameshift" mutations. Usually these are Harmful mutations, and are commonly lethal. 

See what happens with a single base change - in or out. (Learn)

Mission 3 : Your turn to practice shifting the reading frame and recalculating the results - see how a 1 base change has a major flow on effect. You'll need to use the genetic code table found in the Protein and Protein Synthesis part of your workbooks. (Learn)

Done that? = Share with your teacher.

Yes = now its time for your next Step/Video clip/Challenge/Mission.

No = go back and complete the Step/Video clip/Challenge/Mission please.

Step 4 : The sum of all the chemical reactions going on in all of your cells is your metabolism. 

In any one of these reaction or metabolic pathways a starting chemical = the substrate gets acted on by an enzyme  (a name ending in -ase is often an enzyme) and becomes a product. Some pathways are simple = substrate + enzyme = product. Others are longer involving multiple enzymes and steps - where the product of one reaction becomes the substrate of the next step. Pathways can be loops too. 

Pathways can also be turned off and on by feedback from the absence or presence of substrates and/or products.

If an error occurs in the making of one the enzymes in a pathway = the pathway stops at that point - we get a build up of the last product made. This can become toxic and cause health issues. Or as the pathway fails to make key final products other health issues can arise. This can lead to phenotype changes in the organism.

Here is a video explaining all of that plus two key examples (phenylketonuria (PKU) and albinism) found in your workbook ..... I have, in the past, taught students with these conditions. (Learn)

Mission 4(a) : After watching the video read and complete the work on metabolic pathways and more metabolic pathways. (Learn)

Mission 4(b) : Rewind the clip if needed and complete the questions on phenylalanine.  This next clip may help also. (Learn)

Mission 4 c) : As its part of the same metabolic pathway - metabolising phenylalanine carry on with the work on guinea pig coat colour and albinism. 

You could also look at this clip too .....  PKU results from build up of Tyrosine ..... albinism is a result of tyrosine not being converted into melanin. (Learn) 

Done that? = Share with your teacher.

Yes = now its time for your next Step/Video clip/Challenge/Mission.

No = go back and complete the Step/Video clip/Challenge/Mission please.

Step 5 : At the start of this topic I said ..... You are the you, you are, as a result of the interactions between the instructions the DNA - Genotype your body has and the effects that the environment has through interactions with your physical you - your Phenotype. 

We've seen how mutations can change your phenotype - but what about just the environment that you are in. 

Lets have a closer look at that. (Learn)

Mission 5(a) : Using what you've learned from the videos and these images complete the phenotype and environment questions. (Learn)

Mission 5(b) : Once again using what you've  seen in the clips and can read in your workbooks answer the questions on cats and cold. (Learn)

Done that? = Share with your teacher.

Yes = now its time for your next Step/Video clip/Challenge/Mission.

No = go back and complete the Step/Video clip/Challenge/Mission please.

Mission 6 : At the end of this section of your workbook you'll find (maybe) a puzzle page or two, a review planning page then a practice copy of the end of topic test. Complete these pages plus don't forget the definition page found at the start of the topic = you'll be ready for the test. (Learn) 

Here are some summary power points that go over the key points covered in this topic, plus quite a bit of extra that will stretch your thinking too. (Learn)

Metabolism and the effect of the environment review questions - you should have completed these by now = we'll go over the answers together. This should give you an idea of where you are at with your understanding of Metabolism and the effect of the environment = let you know what you need to do the get ready for the practice exam at the end of the whole section on Genet Expression. 

Final Mission : At the end of this topic there is also a practice exam that puts problems from the 2 topics (Protein and Protein Syntehesis and Metabolism and the Effect of the Environment) together in the form of the type of exam you'll be sitting at the end of the year. (we'll use for a trial run later in the year for the school practice exams) Do a bit more revision and give it a go. (Learn) (Share) 

Something to ponder = Epigenetics ..... Have a look - what do YOU think??