Karyotypes

A summary of karyotypes:

Here is a human karyotype showing all 46 chromosomes:

Note that the autosomes are all against a purple background and the two sex chromosomesare in the lower right hand corner and are labeled "X" and "Y"

XX = female
XY = male

This example is a male, because there is one X and one Y chromosome (XY).

The autosomes are arranged as 22 homologous pairs...one from each parent. Note that males do not have a homologous pair to the X sex chromosome or the Y sex chromosome.

Females have two X chromosomes, so they DO have homologous pairs for all of their chromosomes.

The chromosomes in that first picture are shown unduplicated. There are no sister chromosomes present, just the homologous pairs.

If there were sisters, each homologous pair would look like two Xs (not to be confused with the X chromosome...) like this picture:

So, in this picture, each "X" shape is a pair of attached sister chromatids and each numbered pair of "Xs" is a duplicated homologous pair.

Sister chromatids are identical copies (a result of DNA synthesis or replication) and are attached to their "sister" at the centromere.

Humans have a total of 46 chromosomes. This is called the diploid number because there are two of each kind of chromosome.

Gametes would have only one of each homologous pair, and would be called haploid.

**Note: haploid and diploid refer to the genome in its unduplicated state.

I don't have a picture of a gamete karyotype. Can you imagine what it would look like?

Some practice questions for the following karyotype (answers at the bottom):
Is this individual male or female?
How many chromosomes are there?
Is this normal for a human?
Are there sister chromatids in this picture?
Are there homologous pairs in this picture? If so, how many pairs?
Is this haploid or diploid?
Is there anything genetically wrong with this individual?
.
.
.
.
.
.


(Answers: male; 46; yes; no (there are no "Xs"); yes...22 pairs; diploid (haploid would be 23 chromosomes...a gamete); yes--trisomy 21 or Down's Syndrome)

DNA Synthesis and Protein Synthesis Animations

Here's a web page another student recommended. It has a nice animation on DNA synthesis AND protein synthesis:

STUMBLE LINK

More DNA animations:

LINK 1 (realistic)

LINK 2 (cartoon)

Here's a nice animation of the replication fork (click the bottom link that says "DNA Replication Fork" on THIS PAGE)

Protein Synthesis Animations:
There are some good ones at this link: Animations
Here's another one from a classmate: LINK

Here are the two more little animations...I think they summarize transcription and translation nicely and might be a helpful review:

Muscle Cells

Here's a little animation:
Sarcomere
There's a lot of great review and summary in this clip, especially at the beginning!

Here's a slide of real muscle cells. If you peer closely, you can actually see the "striations" or stripes of the sarcomeres!

Stem Cells

There are two kinds of stem cell: embryonic and adult. Both kinds can either divide to produce another stem cell like themselves...or produce a more specialized cell.

Embryonic stem cells (from embryos) are truly pluripotent, meaning that they have the potential to develop into any kind of cell.
Adults tissues have stem cells as well. These cells tend to be less plastic, meaning that they can't differentiate into the variety of cells that embryonic stem cells can. They serve the purpose of replenishing lost cells (like skin or blood) .

Bone marrow might come to mind when you think of stem cells, and this is because bone marrow contains stem cells for the creation of new blood cells and is used in the post-chemotherapy treatment of leukemia.

Some adult stem cells, like those found in the umbilical cord, are pluripotent, and this is why you might have heard about "cord blood donations." These cells can differentiate into any kind of cell just like embryonic stem cells.

What can you use stem cells for? Well, think of them the same way you would think of a transplant. You can transplant new cells for a tissue that has lost cells. Wouldn't it be cool to use stem cells and regenerate heart cells that were lost to scarring from a myocardial infarction? Re-growing nerve cells in spinal injuries would also be an exciting new therapy in medicine.

Stem cells could also be used to grow groups of a specific kind of tissue for drug testing.

Want to know more?
LINK: NIH
LINK: How Stuff Works
LINK: Stem Cells in the News

The Endosymbiotic Theory

This is to supplement the Week 3 notes.

There is a very cool theory called the Endosymbiotic Theory that was proposed in the early 1970's by cell biologist Lynn Margulis to explain the origin of two types of organelle: the mitochondrion and the chloroplast.

Dr. Margulis was studying the evolution of eukaryotic cells (the more complex cells with nuclei and membrane-bound organelles...like the cells in our bodies). Her idea was that mitochondria (the ATP producing organelles) and chloroplasts (the photosynthesizing organelles) were originally free-living prokaryotic organisms (like bacteria) that were engulfed by (taken in by) other prokaryotic organisms.

Dr. Margulis wondered if, rather than being digested by their engulfers, these precursors to mitochondria and chloroplasts might have set up a long-term symbiotic relationship with their hosts.

Symbiosis: a prolonged close relationship between two organisms that often (but not always) benefits both organisms

Dr. Margulis was widely criticized for this idea when it first came out, but since then, a large and well-accepted body of evidence has been discovered to support her idea.

Remember from Lab 1... a theory in science is not a guess! An hypothesis is a guess, a theory is supported by a vast body of evidence.

The evidence for this theory includes:

---Mitochondria and chloroplasts have their own separate DNA...and the DNA is circular, like bacterial DNA.

---Mitochondria and chloroplasts divide independently from the rest of the cell

---Mitochondria and chloroplasts have their own ribosomes, and these ribosomes resemble bacterial ribosomes

---Mitochondria and chloroplasts have two membranes with slightly different structures (the inner membrane is more similar to bacterial membranes)

---The few differences in the DNA code or "DNA language" found in living things are found in mitochondria and chloroplasts (this will make more sense later in the course).

---Mitochondria and chloroplasts are around the same size as bacteria.

Mitochondria most closely resemble modern day Rickettsia bacteria...like those that cause Rocky Mountain Spotted Fever and typhus.

Below is an image of Rickettsia invading a human cell. Interestingly, these modern bacteriahave to be engulfed by a host cell in order to survive...

Chloroplasts resemble modern day cyanobacteria...which are photosynthetic bacteria.

Below is a picture of colonies of cyanobacteria:

Atomic Bonding Animations

I found a few animations that might help you review the ideas from lecture:

Really Short Covalent Bond Video

Really Short Ionic Bond Video

Longer Video (about polarity in molecules and the special properties of water)

Covalent and Ionic Bonding

Also, for fun:

A LINK to a video on the elements...check it out!

Welcome to the Biology 100 Blog!

Monday, Wednesday and Friday lecture, 11:00-11:50 in CLC 107
Friday lab, 9:00-10:50 in HILD 102

Requirements for Passing This Section of the Course:

--Attendance at lectures

--Attendance at all laboratories (this is 10% of the final grade)

--Using the online Blackboard resource for notes, announcements and important class information

--Reading assigned pages and chapters in Krough, A Guide to the Natural World.

--Reading and learning the material in the class notes on Blackboard.

--Satisfactory completion (passing grade) of four in-class tests

--Satisfactory completion of all laboratory reports

--Satisfactory completion of a 4-part lab project

--Satisfactory completion of weekly quizzes

--Fair and honest work. Cheating is grounds for expulsion

*******Important!*******

Using Blackboard is a course requirement. I will assume that you are checking Blackboard frequently. If you are unable do this, please let me know immediately.

How can you reach me?

I will be available after all lectures and labs and can set up appointments during other times.

→Please, please never hesitate to come to me with concerns or problems of any kind. I am more than happy to do whatever I can to help make this class work for you! You can always email me at: epershing@smccme.edu or emily.pershing@gmail.com

My best advice for this class..?

--Come to class and be active (ask questions, take notes).
--Don't fall behind...there's a ton of information and it builds on itself.

--Take your own notes during lecture if that helps you learn, but absolutely download or read the notes on Blackboard!!
--Read through the notes after each lecture and come with questions if there are things that don't make sense.

--Read the book to solidify your knowledge and research things we don't go over in lecture

Other recommended reading:

Alcamo, I. Edward. Biology Coloring Workbook. New York: The Princeton Review, 1998.

This book's title is a silly, but it is a wonderful resource for biology basics. It has many of the concepts we will discuss condensed to a one-page summary...and there are pictures to color! If you are a visual learner, this would be a great $18 investment.