Ap Biology Discussion Notes Monday 5/2

Goals for the Day Be able to tie together multiple disciplines in biology Be prepared for the AP test

Question of the Day 5/2 Is it possible that things that are advantageous in one environment are “maladaptive” or disadvantageous in others? Give an example to explain your answer. Emphasize not just structure but FUNCTION that is tied to what is going on in our cells! All cells have same DNA, but do different things based on gene expression.

Dichromatic Vision

Trichromatic Vision

Day 3

The Cell Biology of Color Vision in Monkeys ** Notes for this section: The following slides are included as an overview of the cell biology of the Monkey Opsins case. For more information visit: http://www.evo-ed.com A retinal chromophore opsin molecule is activated by a photon of light. This in turn stimulates the opsin protein that tells the cone cell to send a signal to the brain.

How Does Color Vision Work? Cell Biology The retina has two types of cells: rod cells and cone cells. There are more rod cells than cone cells. Cone cells are responsible for color vision.

How Does Color Vision Work? Cell Biology The retina has two types of cells: rod cells and cone cells. There are more rod cells than cone cells. Cone cells are responsible for color vision.

How Does Color Vision Work? There are three types of cone cells. More accurately, any given cone cell may be using only one of three types of transmembrane opsin proteins. On the left – photo of cone and rod cells. On the right – cartoon representation.

How Does Color Vision Work? There are three types of cone cells. More accurately, any given cone cell may be using only one of three types of transmembrane opsin proteins. There are three types of cone cells. More accurately, any given cone cell may be using only one of three types of transmembrane opsin proteins. On the left – photo of cone and rod cells. On the right – cartoon representation.

Three types of Cone Cell Different kinds of opsin proteins embedded in the membrane of cone cells make each kind able to receive different information from the others. Central Dogma of Molecular Biology: DNA  RNA  Protein Genes code for…. Proteins which lead to function!.

Chromatic Vision: Cone Cells Cone cells in the retina of the eye allow light of different wavelengths to be interpreted as color in the brain. The following slides describe how this pathway works. The Brain Light Waves Color The Cone cell

(i) Non-animated version of slide opsin-chromophore-brain slide To produce the signal for color vision, retinal must stimulate the opsin protein but this cannot occur while the retinal molecule is in its cis- conformation.

(ii) Non-animated version of slide opsin-chromophore-brain slide When 11-cis-retinal absorbs a photon (a basic unit of light), it changes from 11-cis-retinal to All-trans-retinal.

(iii) Non-animated version of slide opsin-chromophore-brain slide All-trans-retinal stimulates the opsin in the membrane of the cone cell.

The cone cell sends a signal to the brain, resulting in vision. (iv) Non-animated version of slide opsin-chromophore-brain slide The cone cell sends a signal to the brain, resulting in vision.

The cone cell sends a signal to the brain, resulting in vision. Opsin Image modified from Scientific American, April 09 All-trans-retinal ATTENTION! ANIMATION SLIDE! This slide contains an animation and is meant to be played in slide show format. The following four slides contain a non-animated version of this slide. If you do not wish to show this slide, right click it in the slide layout (to the left) and select “Hide” in this slide and in the ones that follow would be specific to only ONE type of opsin molecule. 11-cis-retinal Opsin To produce the signal for color vision, retinal must stimulate the opsin protein but this cannot occur while the retinal molecule is in its cis- conformation. The cone cell sends a signal to the brain, resulting in vision. All-trans-retinal stimulates the opsin in the membrane of the cone cell. When 11-cis-retinal absorbs a photon (a basic unit of light), it changes from 11-cis-retinal to All-trans-retinal.

The Cell Biology of Color Vision in Monkeys A retinal chromophore opsin molecule is activated by a photon of light. This in turn stimulates the opsin protein that tells the cone cell to send a signal to the brain. ** Notes for this section: The following slides are included as an overview of the cell biology of the Monkey Opsins case. For more information visit: http://www.evo-ed.com A retinal chromophore opsin molecule is activated by a photon of light. This in turn stimulates the opsin protein that tells the cone cell to send a signal to the brain.

The Role of Opsins There are three types of opsins: Short Wave Sensitive (SWS) Medium Wave Sensitive (MWS) Long Wave Sensitive (LWS) An individual possessing only SWS and MWS opsins will have dichromatic vision. An individual possessing SWS, MWS and LWS opsins will have trichromatic vision.

How Does Color Vision Work? When cone cells with the MWS opsin protein are stimulated, green color is perceived by the brain. When cone cells with the LWS opsin protein are stimulated, red color is perceived by the brain. When cone cells with the SWS opsin protein are stimulated, blue color is perceived by the brain. When cone cells with the MWS opsin protein are stimulated AND cone cells with the LWS opsin are stimulated, yellow color is perceived by the brain. When cone cells with the MWS opsin protein are stimulated AND cone cells with the SWS opsin are stimulated, violet color is perceived by the brain. When cone cells with the SWS opsin protein are stimulated AND cone cells with the LWS opsin are stimulated, cyan color is perceived by the brain. When all cone cells are stimulated in equal proportions, white light is perceived by the brain. We perceive different shades of light when our different types of cone cells are stimulated in different proportions.

How Does Color Vision Work? When cone cells with the MWS opsin protein are stimulated, green color is perceived by the brain. When cone cells with the LWS opsin protein are stimulated, red color is perceived by the brain. When cone cells with the SWS opsin protein are stimulated, blue color is perceived by the brain. When cone cells with the MWS opsin protein are stimulated AND cone cells with the LWS opsin are stimulated, yellow color is perceived by the brain. When cone cells with the MWS opsin protein are stimulated, green color is perceived by the brain. When cone cells with the LWS opsin protein are stimulated, red color is perceived by the brain. When cone cells with the SWS opsin protein are stimulated, blue color is perceived by the brain. When cone cells with the MWS opsin protein are stimulated AND cone cells with the LWS opsin are stimulated, yellow color is perceived by the brain. When cone cells with the MWS opsin protein are stimulated AND cone cells with the SWS opsin are stimulated, violet color is perceived by the brain. When cone cells with the SWS opsin protein are stimulated AND cone cells with the LWS opsin are stimulated, cyan color is perceived by the brain. When all cone cells are stimulated in equal proportions, white light is perceived by the brain. We perceive different shades of light when our different types of cone cells are stimulated in different proportions.

How Does Color Vision Work? When cone cells with the MWS opsin protein are stimulated AND cone cells with the SWS opsin are stimulated, violet color is perceived by the brain. When cone cells with the SWS opsin protein are stimulated AND cone cells with the LWS opsin are stimulated, cyan color is perceived by the brain. When all cone cells are stimulated in equal proportions, white light is perceived by the brain. We perceive different shades of light when our different types of cone cells are stimulated in different proportions. When cone cells with the MWS opsin protein are stimulated, green color is perceived by the brain. When cone cells with the LWS opsin protein are stimulated, red color is perceived by the brain. When cone cells with the SWS opsin protein are stimulated, blue color is perceived by the brain. When cone cells with the MWS opsin protein are stimulated AND cone cells with the LWS opsin are stimulated, yellow color is perceived by the brain. When cone cells with the MWS opsin protein are stimulated AND cone cells with the SWS opsin are stimulated, violet color is perceived by the brain. When cone cells with the SWS opsin protein are stimulated AND cone cells with the LWS opsin are stimulated, cyan color is perceived by the brain. When all cone cells are stimulated in equal proportions, white light is perceived by the brain. We perceive different shades of light when our different types of cone cells are stimulated in different proportions.

Chromatic Vision: Opsins What is the building block ( ________mer) of an opsin protein? 3D Visualization

Chromatic Vision: Opsins 3D Visualization 2D Visualization The opsin protein is composed of a string of amino acids. Each green dot in the 2D visualization represents one amino acid.

Opsin Structure MWS opsin LWS opsin The LWS opsin differs from the MWS opsin in three significant places in the amino acid sequence: Position 180: alanine to serine Position 277: phenylalanine to tyrosine Position 285: alanine to threonine

Opsin Structure The LWS opsin differs from the MWS opsin in three significant places in the amino acid sequence: Position 180: alanine to serine Position 277: phenylalanine to tyrosine Position 285: alanine to threonine MWS opsin LWS

Opsin Response to Light The responses to light of each opsin protein (S, M and L) in trichromats are shown to the right. Note how similar the curves look for M and L. The L curve is shifted by about 30 nm response maximum to the right (longer wavelength).

Opsin Response to Light A third opsin provides another channel for sending color signals to the brain. Three opsin proteins allow the eye to detect a richer variety of light wavelengths resulting in the ability to distinguish more colors.

The Genetics of Color Vision in Monkeys ** Notes for this section: The following slides are included as an overview of the genetics of the Monkey Opsins case. Trichromatic vision arises from gene duplication and gene mutation of the MWS opsin protein, resulting in the creation of the LWS opsin protein. For more information visit: http://www.evo-ed.com

The Genetics of Color Vision The section of DNA on a chromosome that codes for an opsin protein is called an opsin gene.

Location of Opsin Genes The gene coding for the SWS opsin protein is located on chromosome #7. The gene coding for the MWS and LWS opsins are located on the X-chromosome. OPTIONAL ACTIVITY! See activity notes.

Evolution of LWS Opsin Gene The LWS gene arose through gene duplication and gene mutation of the MWS gene on the X-chromosome.

Origin of the LWS Opsin Gene The LWS gene arose through gene duplication and gene mutation of the MWS gene on the X-chromosome.

Gene Duplication Gene duplication happens during meiosis in prophase I where unequal crossing over can occur.

Unequal Crossing Over (Meiosis, Prophase 1) For more information see: http://http://en.wikipedia.org/wiki/Unequal_crossing_over

Origin of the LWS Opsin Gene The LWS gene arose through gene duplication and gene mutation of the MWS gene on the X-chromosome.

Origin of the LWS Opsin Gene The LWS gene arose through gene duplication and gene mutation of the MWS gene on the X-chromosome.

This slide may be useful in an ecology/organismal course where a brief refresher of DNA and nucleotides may be helpful.

The MWS Opsin Gene This slide may be useful in an ecology/organismal course where a brief refresher of DNA and nucleotides may be helpful.

The MWS Opsin Gene 1092 Nucleotides This slide may be useful in an ecology/organismal course where a brief refresher of DNA and nucleotides may be helpful. When we write out the DNA sequence of a gene, we just write out the sequence of the coding strand since nucleotides are complimentary. 1092 Nucleotides

The MWS Opsin Gene  GTCGTTAGATAG  1092 Nucleotides This stretch of the DNA strand would be written out as a series of letters, as shown. 1092 Nucleotides

MWS Opsin Gene vs. LWS Opsin Gene Each opsin gene is exactly the same length (1092 nucleotides) MWS Opsin Protein vs. LWS Opsin Protein These 1092 nucleotides undergo transcription and translation and result in a protein that is 364 amino acids in length.

MWS Opsin Gene vs. LWS Opsin Gene (mutations at the nucleotide level that result in protein functional changes) G  T T  A G  A Three simple substitution mutations change the properties of the opsin protein. Now, rather than being maximally stimulated at ~534nm, the resulting opsin protein is maximally stimulated at ~564nm.

What difference does this make at the protein level?

Evolution of LWS Opsin Gene The LWS gene arose through gene duplication and gene mutation of the MWS gene on the X-chromosome. Summary/recap slide.

Fact or Fiction? A monkey researcher in South America discovered that some monkey females are trichromatic. Definitely Fact Possibly Fact Possibly Fiction Definitely Fiction

The Case of Trichromatic Females

Genes code for opsin proteins; the opsin proteins facilitate color vision. Some new world monkey species have two different MWS alleles. If a female is heterozygous for these alleles she can produce three different types of opsin protein. This means that SOME females in SOME new world species are trichromatic. Females that are homozygous for the MWS gene on the x-chromosome are dichromatic.

Genes code for opsin proteins; the opsin proteins facilitate color vision. Some new world monkey species have two different MWS alleles. If a female is heterozygous for these alleles she can produce three different types of opsin protein. This means that SOME females in SOME new world species are trichromatic. Females that are homozygous for the MWS gene on the x-chromosome are dichromatic. Some new world monkey species have two different MWS alleles. If a female is heterozygous for these alleles she can produce three different types of opsin protein. This means that SOME females in SOME new world species are trichromatic. Females that are homozygous for the MWS gene on the x-chromosome are dichromatic.

The Phylogenetics of Color Vision in Monkeys ** Notes for this section: The following slides are included as an overview of the phylogenetics and biogeography of the Monkey Opsins case. For more information visit: http://www.evo-ed.com

Biogeography of Global Monkeys Photo: Frans de Waal, M Arunprasaad, D Wright, P Gonnet, L DeVoldor, W Endo

Monkeys of the World Old world monkeys have two different opsin genes on their X chromosomes whereas new world monkeys only have one.

Phylogenetics – Exploring Relationships Among Species This tree is a representative sample of new world and old world monkeys. It is not meant to encapsulate all species. From a genetic perspective, Old World Primates are more closely related to one another than they are to New World Primates (and vice versa). Evidence suggests that they share a common ancestor in whom the gene duplication and mutation events occurred.

Geology: Plate Tectonics and Drift When did color vision evolve? The next few slides bring in aspects of geology and paleontology to help answer this question.

Primates In New/Old World Squirrel Monkey Owl Monkey Spider Monkey Wooly Monkey Chimpanzee Human Gorilla Orangutan Gibbon Rhesus Baboon Mangabey Mona Langur Colobus Capuchin Marmoset Sakis Continents Split 50 Million Years Ago ATTENTION!!! ANIMATED SLIDE! A non-animated version of this slide follows. These events can now be mapped onto the phylogenetic tree to give a fuller picture. Research suggests that color vision evolved around 40 million years ago: http://www.sciencedirect.com/science/article/pii/S0169534703000120 Old World New World Color Vision Evolves! Gene Duplication and Mutation Primates In New/Old World 55 Million Years Ago Rise of Primates 75 Million Years Ago

Ancestral Characteristic An Ancestral Characteristic is a characteristic shared through common ancestry. A characteristic that is thought to have also been present in the common ancestor. In primates for example DICHROMATIC vision would be considered an “ancestral characteristic” while trichromatic vision would be considered a derived characteristic (one not present in the common ancestor of 2 groups)

Primates In New/Old World Squirrel Monkey Owl Monkey Spider Monkey Wooly Monkey Chimpanzee Human Gorilla Orangutan Gibbon Rhesus Baboon Mangabey Mona Langur Colobus Capuchin Marmoset Sakis Continents Split 50 Million Years Ago ATTENTION!!! ANIMATED SLIDE! A non-animated version of this slide follows. These events can now be mapped onto the phylogenetic tree to give a fuller picture. Research suggests that color vision evolved around 40 million years ago: http://www.sciencedirect.com/science/article/pii/S0169534703000120 Old World New World Color Vision Evolves! Gene Duplication and Mutation Primates In New/Old World 55 Million Years Ago Rise of Primates 75 Million Years Ago

Day 3 Questions