From Atoms to Traits Q & A

1. Mendel conducted a breeding experiment with peas in 1850's and 1860's. The peas had obvious morphological differences and when the breeding of two plants crossed, their offspring resembled one of the two parents. Both traits would reappear in further generations. Mendel's experiments changed the general perception of that time that heritable variants from ephemeral and blendable to discreet entities passed from parents to offspring, present even though they are not always visible. Mendels findings were soon seen in the behavior of chromosomes in the cell nucleus.

2. James D Watson and Francis Crick had proposed a structure for the DNA molecule in 1953, that helped us understand hereditary and variation physically. It helped us sequence various organisms and their offspring, and look for any spontaneous changes in the long chain of DNA letters passed down from generation to generation.

3. Point mutation, insertion, gene copy number, duplication and regulatory changes are all examples of variations that occur to DNA. 

Point mutation: Or single base substation, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA. This also includes insertions or deletions of a single based pair. For example in whipped dogs, a single based pair change makes the difference between a slender silhouette and a hulking animal. The mutation inactivates the gene for a signaling molecule that regulates muscle growth is uncontrolled because there is no "stop" signal. 

Insertion: Is the addition of one or more nucleotide base pairs into a DNA sequence. For example, in pea plants, an 800 base pair sequence inserted into a gene produces wrinkled peas instead of smoothed ones. The intruding DNA element disables a gene necessary for starch synthesis, altering the peas sugar and water content. 

Gene Copy Number: Entire genes can be duplicated by copying errors during cell division, leading to differences between species and variation among the individuals of the same species. For example, the genome of chimpanzees, which have a diet consisting of mostly green plants, normally contains just a single gene for the starch-digesting enzyme salivary amylase, where as humans can carry up to 10 copies of that gene. 

Duplication: Sequences containing the same based pair copied and repeated eight or more times, known as homopolymers, are highly prone to copying errors. For example, in pigs, the gain of two additional C-G pairs in such as sequence inactivates a gene for a signal receptor in pigment cells, producing light colored coats. Copying mistakes in the individual cells can also cause the lose of bases which restores the gene's function and causes dark colored spots in the coats. 

Regulatory Changes: Mutations in the DNA that controls when and where genes are activated can produce profound trait changes by altering the formation of body parts during the development of the organism. For example, the shape difference between the bushy teosinte plant and its descendant the modern cornstalk are different because of the change in the regulatory regions of a single gene that controls patterns of cell division during stem development. 

4. Evo-devo is a subspecialty within evolutionary biology that concentrates on studying the effects of changes in important developmental genes and the role they play in evolution. It adresses the origin and evolution of embryonic development; how modifications of development and developmental processes lead to the production of novel features, such as feathers; the role of developmental plasticity in evolution; how ecology impacts development and evolutionary change; and the developmental basis of homology. 

5. In the case of some dietary adaptations, the changes enabled entire populations to migrate and take up new ways of life, such as herding and agriculture. An example of such as trait, the ability to digest milk into adulthood, is found to have risen independently in groups on different continents, attesting to the great nutritional advantage the variant provides and to the possibility of directly connecting simple DNA sequence changes to human cultural evolution. Lactose intolerant people cannot digest complex milk sugar lactose because of the lack of lactase produced. Its retention in milk dependent societies also illustrates how culture can reinforce the forces of evolution. 

Class 18

      Today we finished the movie "Journey of Man" and our worksheets. We learned about the importance of the Y chromosome as it is the best place to look for a genetic marker because it does not get recorded every time like the X chromosome, instead it gets passed down unchanged through generations. The narrator goes to an isolated village with indigenous people that have not had outside encounters so he could find the genetic marker. We learned that Africa had a drought were animals and resources were scarce so they migrated. The environment of different places changed the human race to either be lighter or darker complected. We learned that the first Americans arrived on the continent 13,000 to 11,000 years ago.  

Class 17

Today in class we watched "The Journey of Man," a documentary film about the evolution of the human species. We were given a worksheet of questions that we would answer while watching the film. I learned that we can trace back in history and find information from the past by examining blood and DNA samples of different people. I learned that 50,000 years ago our ancestors were still living in Africa. The Sanbushmen is the tribe of the first ancestors of mankind. I observed many different races in just one of their faces, from European to African to Asian features. A genetic marker is a mutation that occurs through generations of offspring. The Sanbushmen were very advance thinkers using bone as spears instead of stone and creating a language of their own. We learned about the routes that people took out of Africa such as the route to Austraila.

Test 2

Today in class we took our unit 2 test about evolution and the evidences for evolution. I first wrote an essay on population genetics and comparative anatomy and embryology to support the theory of evolution. I wrote about Darwins theories, his work and contribution to evolution. I explained overpopulation and effects of mutation. I also gave examples of population genetics and adaptive radiation. I compared homologous structures and explained their link to a common ancestor. Then we did 30 multiple choice and a few extra credit questions. We were free to leave once we finished the test.

Does Race Exist

Does Race Exist?

     People differentiate themselves based on their physical characteristics, traits and most importantly, their "race." What makes an individual a member of a particular race differs from region to region. Humans originated in Africa and then migrated over a vast period of time to all parts of the world. They learned to adapt to their different environmental changes and go through "survival of the fittest." These facial features and traits are influenced by natural selection and divide people into "races."Studies have shown that 90 percent of human genetic variation occurs within a population living on a given continent than whereas 10 percent of human variation distinguishes continental populations. Individuals from different populations, on average, are slightly more different from one another than individuals from the same population. Two groups that are genetically similar to each other might be exposed to different selective forces in their environments. Natural selection can define some of the differences between groups, making it easier to see the physical differences and harder to see the genetic similarities. In the "Journey of a Man" video, we were shown the tribe in Africa of the first ancestors of mankind called the Sanbushmen. Each individual face had physical characteristics that are seen in different areas of the world today. They had eyes and rounded foreheads of an Asian or Pacific Islander, lips and noses of an African or African American, and pointed chins and ears of a European. We could already see from the faces of the Sanbushmen that humans originated in Africa, having identical similarities, but through adaptation and mutation, have been modified.
     Genetic analysis can distinguish groups of people according to their geographic origin to a certain extent. Geneticists rely on polymorphisms in human's DNA to determine the degree of relatedness among groups. A study was done examining 100 different Alu polymorphisms in each of the 565 people born in sub-Saharan Africa, Europe and Asia. They sorted the people into groups only based on their genetic information, removing the identifying labels of origin. Once they placed the labels to the person accordingly, they realized that the groups correlated with origin and ethnicity, having one group of Europeans, one group of Asians and one group of Africans. The results of this study indicate that genetic analyses can distinguish groups according to their geographic origin. Populations have adapted to survive in their environment. They have also passed down mutations to their offspring which altered parts of their DNA. These different mutations alter health by preventing some diseases or influencing them. Several polymorphisms that differ in frequency from group to group affect health. Genetic variation plays a major role in individual susceptibility in diseases such as influencing AIDS because of the polymorphisms in CCR5 receptor gene found mostly in northeastern Europeans that increases HIV-1 infection leading to AIDS. Polymorphisms in genes might have an affect on one group and a different affect on another. Scientists can group individuals according to their probable ancestry by looking at their DNA and "genetic marker." Membership in geographically or culturally defined group can be correlated with health related genetic traits.  

class 16

   Today in class we learned about population genetics and evolution, the Hardy-Weinburg law of genetic equilibrium and the relationship between evolution and changes in allele frequency by using the class to represent a sample population. There are five conditions that have to be met in order for the populations allele and genotype frequencies will remain constant from generation to generation. These conditions are:
   1. The breeding population is large
   2. Mating is random
   3. There is no mutation of the alleles

   4. No differential migration occurs
   5. There is no selection

   We then tested allele frequencies for a specific trait within the population (class). We had to put PTC taste test papers in our mouths for 15 seconds and see if we tasted chemical or not. We recorded the number of people who tasted and did not taste and determined the frequencies of the two alleles using the Hardy Weinburg equation. We then did case studies where we are given 4 cards, two dominant and 2 recessive. We would then find a partner and then choose a card from them without looking at the card. We did this 5 times, each with a new person. Then we did Case IV about genetic drift where a river split the population so we had to trade cards 5 times to create 5 offspring babies with different traits. With this information we used the Hardy equation to find the frequencies. Then we took a quiz on Hardy Weinburg equations.

Class 14

 

   Today was parents day!!! We came into class and recorded data for the brine shrimp after 48 hours of being in the solutions. We wrote down our data of which ones survived and which ones died.

   We learned about Natural Selection in humans. We did an activity about femininity and masculinity attributes to a person that makes them more attractive to a male or female. We were shown 2 of the same face that had different features and had to circle the one that was more attractive. We were shown ten female faces and ten male faces, finding out that one of the faces was feminine and the other masculine. Both the parents and students were shocked that men and women find feminine faces much more attractive on both a male and female. My results were that I thought feminine features in girls and guys were more attractive than masculine faces. I learned that i like feminine faces in men because i feel like the man is loving, compassionate, caring and can protect me while I think feminine faces in girls are more attractive and try to compete with her because men like feminine faces. Studies show that the only time that a girl would usually find a feminine face more attractive is when she is ovulating.