Sunday, December 18, 2011

Oh, the news and finals question 16 (thinking about multicellularity)

 Why Almost All Multicellular Organisms Begin Life as a Single Cell

As soon as one turns around, there is a newsy item that directly relates to a Biofundamentals exam question.  Question 16:   In the context of social slime molds consider i) a cell in your brain to one of your eggs or sperm and ii) a sterile worker mole rate to a queen mole rat.  How is this possible, evolutionarily.  

Saturday, December 10, 2011

Tuesday, December 06, 2011

A little perspective.....

Turns out, the largest black hole ever (or rather, so far) has been identified.  Here it is described "a black hole with nearly ten billion times the mass of our Sun, an event horizon that would stretch five times further than the orbit of Pluto if we had the misfortune to have it drop in, and a gravitational sphere of 4,000 light-years."

Lynette Cook's impression of a black hole larger than our solar system in the middle of the galaxy (NGC 3842) composed of trillions of stars (perhaps as many stars as there are cells in one person's brain!!!!!!)

Monday, December 05, 2011

Being eusocial....

Based on today's discussion, it was clear to me that I needed to know more about i) sexual determination in the naked mole rat; ii) something about the organism's genome (link here), and iii) the (perhaps weird and perhaps not) fact that mole rats are extremely resistant to cancer (link here).   So here it is.

Turns out naked mole rats, both males and females are diploid.  In a colony there is one female breeder, and their presence appears to inhibit breeding by other females.
  "Female nonbreeders have small uteri as well as small ovaries without corpora lutea, indicative of complete failure to ovulate. Thus, despite achieving adult body size, the non-reproductive females remain in a pre-pubertal state throughout life." from Holmes et al, 2009.  

If, however, such a non-breeding female is removed from the company of the breeding female, and placed with a male, it can become fertile and breed successfully.  This is how laboratory colonies are started (apparently).

Also, please note that I made a mistake about sex determination in bees. All females are diploid, males are haploid.  Whether a female becomes a female worker or a fertile queen is determined by what it is fed during development.  Female workers can lay eggs, but these are unfertilized and develop into males (drones).  The Wikipedia article on this is good.