If someone has had a heart attack or stroke, or is identified as being at high risk of one, in addition to the lifestyle changes and drug treatments, those with severe coronary heart disease (CHD) (who have had a heart attack like Peter) may need surgery. Coronary angioplasty techniques may be used when coronary arteries narrow or become blocked. A catheter is inserted into an artery in the groin and guided by X-ray imaging up to the narrowed coronary artery. A tiny balloon at the tip of the catheter is inflated to stretch or open the constriction and improve the passage for blood flow (Figure 1). Usually there is a short wire-mesh tube, called a stent, around the balloon. The stent expands when the balloon is inflated. The balloon is deflated and the balloon-tipped catheter is removed leaving the stent in place permanently. The procedure is completed under local anaesthetic so the patient remains awake
In Crick’s expressed view, the problem was susceptible to X-ray diffraction methods ‘if anyone knew how to use them, which Rosalind did. But it’s slower than model building, and she wouldn’t build models … It was all there. [Maurice] had as much information as we had. He says now he picked up the point in Chargaff’s article [the 1:1 base paring ratio] … but he didn’t see it, and that’s all there is to it. Meanwhile Rosalind was wasting time with Patterson superposition methods, and that took her off in the wrong direction entirely. I don’t know why she did this. I think Luzzati may have advised it … It was a mistake. But absolutely, she’d have got it out sooner or later.’
1 The method using a 2B pencil works very well. A good, dark print is produced if you touch the pencil-shaded area a couple of times before using the sticky tape. Take care to lift directly off the pencil shading and tape to avoid smudging. This method also means the prints are the view you would see if you looked at your own fingers. The prints of different fingers of the same person are all different from one another, although they may have the same basic patterns, but differ in the detail, for example, the number of ridges present. It is rare for all fingers to have the same pattern. 2 The group results may or may not produce some trends. They may reflect the general frequency
Now think about what happens when both the PG gene and the introduced artificial gene make messenger RNA. (You might like to work out the first 15 bases of these two mRNAs.) What do you notice about these two mRNA sequences? In the tomato cells what happens is that these two sorts of mRNA with their complementary sequences base pair with each other in the cytoplasm. Indeed, they stick together so firmly (as a result of hydrogen bonding) that neither mRNA makes much protein. Measurements show that PG activity in these GM (genetically modified) tomatoes is only about 1% of normal. As a result, the tomatoes stay firmer for longer and the grower saves money. The tomato was patented and trademarked as the Flavr Savr ™ tomato. Tomato paste made with genetically modified
Now carefully pick through your sample. Do not neglect the very small organisms that may be on dead leaves, or stuck to rocks. Try to identify your animals using a key (see Figure 4 for one simple example). If you cannot identify an organism show it to your teacher/lecturer. In the end it matters less what the correct name for each organism is than that the whole class calls it the same thing if you are pooling your data. Once you have an idea of what you have, count the individuals in each taxon and record your results in an appropriate format (see Table 1). This is usually easiest if you select one taxon and count the individuals in it into another small container. (This makes recounts easier.) Having one person acting as a scribe while the other counts will help here. Tallies are a useful way of keeping a running total. Put all of your animals back into the stream when you have finished.
100 young male soccer players aged 10 to 12 years were recruited to the study. Half of the boys played in their soccer club’s best team; these boys formed the elite group. The other half played for the lowest ranked teams; they formed the non-elite group. The mean ages of the groups were 11.9 ± 0.5 (SD) (elite) and 11.6 ± 0.7 years (non-elite). Blood serum testosterone levels were measured three times at half-yearly intervals for all boys. A fourth measurement was taken for a subset of 28 boys (16 from the elite group and 12 from the non-elite group). The results are shown in Figure 1. At the same time, strength measurements were made. These include a board jump taking off and landing with both feet together, and the determination of back and abdomen muscle strength by measuring maximum voluntary contraction using a strain gauge dynamometer. In each case the best of three attempts was recorded as the maximum (Figure 2).
Students compare base sequences for four organisms and work out their evolutionary relationship. The students may draw the tree themselves or may use the template provided. It is worth noting that researchers have identified a number of misconceptions that students have when interpreting phylogenetic trees. Students thought that the horizontal order of species was significant, with age of species linked to the order. They also thought that species on tips close together were more closely related to each other. Some students followed the branching pattern and thought that the number of nodes in a pathway indicated the relationship between species, in that the fewer nodes, the more closely related were the species; thus in Figure 1 below, A and D would be considered more closely related than B and D, which is not the case. It was also found that when trees are drawn with one straight line from the common ancestor with other species appearing to all branch off, students may view the species at the tip of the straight line as the ancestor of all the other species.
In Unit1, your child will play the following games. Addition Top-It See Student Reference Book, page 263. This game provides practice with addition facts. Polygon Pair-Up See Student Reference Book, page 258. This game provides practice identifying properties of polygons.
1 DNA is a very important molecule in living organisms as it carries the genetic code that controls all characteristics. When a cell divides, the DNA molecule replicates so that each resulting daughter cell is genetically identical to the original parent cell. The diagram below shows part of this process of DNA replication.