Sunday, November 5, 2017

Red Cedar Mist

Fall has come to Michigan. The crabapple blossoms I featured in my last post have borne fruit. 
A heavy mist floated above the Red Cedar River this morning. 

Tuesday, May 9, 2017

Crabapple Blossoms

My favorite time of year is when the crabapple trees are pink and white at the same time. 

Thursday, May 4, 2017

How to Make a DNA Model

Figure 1
One of the students I tutor had to build a DNA model for an assignment for 9th grade biology. We built our model, photographed it and posted it on Facebook. Some friends saw the picture and asked me to post instructions, so they could build similar models with their kids.

Let’s start with the basics.
DNA consists of several units:
  • Phosphates and ribose molecules comprise the backbone. The phosphates and riboses alternate.
  • The two strands of the phosphate-ribose backbone are antiparallel. That means the two strands go in opposite directions.
  • The cross-links are the nucleotide base pairs.
  • The nucleotides are: Adenine (A), Guanine (G), Cytosine (C) and Thymidine (T).
  • Adenine and Guanine are purines. Cytosine and Thymidine are pyrimidines.
  • Correct base pairing is A with T and G with C. (Figure 1)
  • A-T base pairs are connected by two hydrogen bonds.  G-C base pairs are connected with three hydrogen bonds. (Figure 1)
  • DNA forms a right-handed helix. In other words, when you look down from the end, the twist is counterclockwise.
  • One twist occurs about every ten base pairs.
The assignment stated that the model must be made with household items, not a molecular model kit. We chose wire and beads. The assignment also had several criteria to make the finished model as realistic as possible. The criteria were:
  • The phosphate-ribose backbones must be antiparallel. This means that if you start with a ribose on one strand, start with a phosphate on the opposite strand. In our model, the ribose molecules were five-pointed stars, so we were able to emphasize the directionality with the star beads. (Figure 1)
  • The ribose molecules must be larger than the phosphate molecules.
  • The ribose and phosphate molecules must be different shapes or different colors.
  • Base pairing must be correct. (A with T and G with C)
  • Purines (A and G) must be larger than pyrimidines (C and T).
  • Base pairs must be attached to the ribose molecules only.
  • The hydrogen bonds must be smaller than the nucleotides.
  • The model must include at least 15 base pairs.
  • The model must include at least two twists.
Materials:
  • 18-gauge plastic-coated steel wire for the phosphate-ribose backbone. (This wire is sturdy enough to support the structure, yet malleable enough to bend and twist.)
  • 22-gauge dark annealed steel wire for the cross-links. (This wire was bendable and worked for the project. However, the dark coating rubbed off on our hands. Another type of thin malleable wire might work better.)
  • Pony beads for the phosphate molecules – at least 60.
  • Star-shaped crafting beads for the ribose molecules – at least 60. (The ones I bought were plastic with a metallic-sheen coating.) Make sure the hole in the bead is big enough to allow both the 18 gauge and 22 gauge wires to go through at the same time.
  • Wooden beads of assorted shapes and colors for the nucleotides. You’ll need four types of beads and approximately 15 beads of each. The A and G beads must be larger than the C and T beads. The A beads should be a different color than the T beads. The G beads should be a different color than the C beads. Make sure the 22 gauge wire will go through the hole in the beads.
  • Drinking straws in two colors
  • A sharpie marker
  • Scissors
  • Wire cutters
  • Needle-nosed pliers
  • A platform (We used a piece of Styrofoam. Clay would also work. Alternately, the model can hang from a string.)
Methods:

Create the phosphate-ribose backbone.
  • Cut two 2.5-foot lengths of the 18-gauge wire.
  • Bend a small loop in one end of each wire so the beads don’t slide off.
  • Start one strand with a phosphate (pony bead). Alternate riboses (stars) and phosphates (pony beads) until you have 30 beads on the wire.
  • The second strand must be antiparallel. That means you need to start with a ribose (star) and follow with a phosphate (pony bead). Make sure the stars point in opposite directions on the two strands. String 30 beads on the wire.
  • Bend a small loop in the far end of the wire so no beads slide off.
Create the nucleotide cross-links.
  • Remember the nucleotides must be connected to the ribose molecules. (The nucleotides are supposed to be connected only to the ribose molecules, but we twisted the 22-gauge wire around the 18-gauge wire for stability. This slight structural convenience is hidden by the beads.)
  • Use the sharpie to label the wooden beads with A, G, C or T. Make sure the As and Gs are larger than the Cs and Ts.
  • Flatten two drinking straws. Make two vertical lines on both sides on one straw with the marker. Make three vertical lines on both sides of the other straw.
  • Cut straws into short pieces (smaller than the nucleotide beads). The pieces of straw are hydrogen bonds.
  • Cut 30 seven-inch pieces of 22-gauge wire.
  • Loop the 22-gauge wire once or twice around the 18-gauge wire between the phosphate and the ribose beads.
  • Twist the 22-gauge wire around the arms of the ribose star. Do not use all of the seven inches.
  • String a nucleotide bead on the 22-gauge wire.
  • String the appropriate hydrogen bond (straw pieces) next. Remember A-T base pairs have 2 hydrogen bonds and C-G base pairs have 3 hydrogen bonds.
  • String the appropriate nucleotide bead to pair with the first on the cross-bridge. (If the first was a C, string a G. If the first was a T, string an A, etc.)
  • Twist the end of the 22-gauge wire around the star on the opposite strand to secure.
  • Repeat until all of the ribose molecules (stars) on the two strands have cross-bridges. 
Create the double helix.
  • You may have extra 18-gauge wire at the top of the phosphate ribose backbones that needs to be trimmed.
  • We made one-inch loops at the top to insert into the Styrofoam platform. Other types of platforms may require different wire accommodations.
  • When you figure out how much wire you’ll need to attach the DNA to the platform, trim the 18-gauge wire and make loops in the ends.
  • Look at the DNA molecule end-on so the loops in the wire are facing you.
  • Twist the structure counterclockwise to create a right-handed helix.
  • Try to get about ten base pairs per turn.
  • Attach the structure to the platform or hang it with string.

Wednesday, April 19, 2017

Mouse

A friend is sketching mice for her newest project. While I realize that excellent photos of mice are available on the internet, I wanted to give her a couple of mine. Here is one of the six mice that decided to live in our kitchen last winter. My husband trapped them in a live trap. We released them in the woods several miles from here. The woods are on the other side of the Red Cedar River and a highly-trafficked four-lane road. We don't think our mice will come home again. 

Mice are difficult to photograph. They don't pose. Once this one was clear of the trap, he or she dashed for cover.



Monday, February 20, 2017

London II

If you go to London with a musician, especially a guitarist, don't miss Denmark St. Lots of 1960s and 1970s rock and roll was recorded there. A couple recording studios are still in operation. Nearly every other storefront sells guitars. Jeremy tried out a vintage Les Paul electric guitar with a maple fretboard. We did not spend over £3000 on it, although one of us wanted to. 


I didn't take many pictures inside the Tower of London, but the Tower is well worth a visit. Built by William the Conqueror as a home and fortress, the original walls are fifteen feet thick at the base and eleven feet thick at the top. Great Britain has a bloody history and the Tower has many reminders of that. Yes, the object on the green is a trebuchet. 


The Tower Bridge can be seen from the Tower of London. (This is not the London Bridge.)


Skyline showing the Shard and the Tower of London.


I took this picture of the Buckingham Palace gates in the afternoon after the crowds who came to see the Changing of the Guard had left. 


Are you watching Victoria on PBS? This statue decorates the fountain across from the palace. 


The changing of the guard happens daily in the summer and every other day in the winter. We arrived an hour early, and already the crowds had all the prime viewing locations. Jeremy took these pictures because he's tall enough to hold the camera over the heads of other onlookers. The changing of the guard often includes musical accompaniment. Surprisingly, we heard several pop numbers including Latin-Jazz fusion. 

I heard a few wrong notes, then Jeremy said, "Don't lock your knees! That's band camp 101." Apparently one of the trombonists became disorientated and started to sway. His companions grabbed his arms and eased him down before he or his trombone hit the pavement. 


Finally, a use for selfie-sticks. The only way I could see the changing guard was to look at the screens of cell phones on sticks. 


This guy plays a flaming tuba outside the Tate Modern. In my view, that museum is not worth the time and effort to get there.


We didn't have an opportunity to go inside St. Paul's Cathedral. It's supposed to be lovely, and if you get there in the evening, you can hear evensong. 

I hope my friends who are visiting London soon enjoyed these two posts. 
Again, click on the pictures to enlarge them. 

Saturday, February 18, 2017

London I

I recently had an opportunity to go to London with my husband and my younger son, Jeremy. Our older son couldn't go with us as he is in graduate school. I'm planning to divide my pictures and discussions over two or three posts. 

Several of my friends are planning to visit London soon, so I through I'd turn these posts into a travel guide. Get Rick Steves' book, LONDON. He describes where to stay (Victoria Station Neighborhood or South Kensington Neighborhood), how to get around (The Underground) and where to eat (everything from pubs to tea shops). His descriptions of sights, museums and landmarks are detailed so you can choose what interests you. 

We started with Rick's "Westminster Walk." I included the picture of Big Ben to prove that the sky was blue once while we were in London. 


If you've read any British historical fiction, you've heard of Horse Guards.


Westminster Abbey is a wonderful place. Read up on the people and features before you go. The audio tour was excellent. (You can't take pictures inside.)


This is the London Eye (Ferris Wheel) and a view of the Thames. The Thames river boat cruises are supposed to be great. Unfortunately, the weather was mostly cold and rainy while we were there, so we opted not to spend time on the river. 


Trafalgar Square is fun on its own, but it's near the National Gallery and the National Portrait Gallery. The National Gallery has an impressive collection of paintings. We were particularly taken with the Impressionist wing. I've never before seen a Monet in person. The collection also includes several paintings by Van Gogh, including The Sunflowers. See the National Portrait Gallery after you've seen Westminster Abbey and learned about some of the historical figures of Britain. 


The Sherlock Holmes Museum is fun. It's located, of course, at 221b Baker St. Some of the rooms are made up to look like the descriptions of Watson and Holmes' home in the books. They also have mannequins dressed up to depict scenes from favorite stories. 


Of course, I had to take a picture of Holmes' chemistry set.


Abbey Rd is near Baker St. Here's my favorite rock star.


The Abbey Rd. recording studio is still in operation. Jeremy says it has the best compressor in the world. Also nearby are the Beatles Store which is okay, but doesn't have anything out of the ordinary, and the Rock and Roll store which carries Rainbow Rising T-shirts, if you're in desperate need of a couple. 

As I said, there's more coming - after I crop and resize another set of photographs. 

Click on the pictures to enlarge. 

Monday, January 30, 2017

Sea Lions and Pelicans

We were in San Diego last weekend. When we went for a walk along the ocean, I forgot to bring my camera. (I know!) These pictures were taken with my phone. People sell fresh fish on the pier, and one stand cleans the fresh fish. The extra bits are thrown into the water where a couple of  sea lions beg like dogs at the table, and the pelicans squabble over scraps. 



Click on the pictures to enlarge them. 

Sunday, January 1, 2017

In the Bleak Midwinter



As the water level falls, some ice is suspended above the river. 

leaf patterns
more leaf patterns