ap biology discussion notes wednesday 4/29/2015. goals for the day understand how we influence the...

AP Biology Discussion Notes

Wednesday 4/29/2015

Goals for the Day

• Understand how we influence the environment & organisms around us

• Be able to tie together multiple disciplines in biology

Question of the Day 4/29

• Is it possible that things that are advantageous in one environment are “maladaptive” or disadvantageous in others? Give an example to explain your answer.

Food Selection – The Research Part III

Saito et al, 2005

Th

e D

ES

IGN


Saito et al, 2005

Th

e E

XP

ER

IME

NT

TRICHROMATICVISION

DICHROMATICVISION

Photo: KENPEI, J Smith


Saito et al, 2005

Th

e T

RA

ININ

G

Photo: KENPEI


Saito et al, 2005

Th

e T

ES

T

Photo: KENPEI


Saito et al, 2005

Th

e D

ES

IGN


Saito et al, 2005

Th

e E

XP

ER

IME

NT

TRICHROMATICVISION

DICHROMATICVISION

Photo: KENPEI, J Smith


Saito et al, 2005

TRICHROMATICVISION

DICHROMATICVISION


Saito et al, 2005

Th

e R

ES

ULT

S

Food Selection – Summary

Research suggests that trichromatic

vision is more likely to be

selected for when food is distinguished

from non-food by color.

Research suggests that dichromatic vision is more likely to be selected for when food is distinguished from non-food by shape.

So why not trichromacy in the “New world”

The Battle of the Paramecia!Competitive Exclusion!

Alone, both species do just fine. The increase in population until the reach the limit of their surroundings and level off. When they try to hang out TOGETHER, things change—for ONE of the species, anyway. Which one? Who wins? Any ideas why that might be?

The Cell Biology ofColor Vision in Monkeys

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

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.

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 ProteinGenes code for…. Proteins which lead to function!.

Chromatic Vision: Cone CellsCone 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 Cone cell

The Brain

Color

Light Waves

• 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.

• When 11-cis-retinal absorbs a photon (a basic unit of light), it changes from 11-cis-retinal to All-trans-retinal.

• 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.

• 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.

• When 11-cis-retinal absorbs a photon (a basic unit of light), it changes from 11-cis-retinal to All-trans-retinal.

• 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.

Ops

in Im

age

mod

ified

from

Sci

entifi

c Am

eric

an, A

pril

09

All-trans-retinal11-cis-retinal

Opsin

The Cell Biology ofColor 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.

The Role of OpsinsThere 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.


- 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

3D Visualization

What is the building block ( ________mer) of an opsin protein?

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

The LWS opsin differs from the MWS opsin in three significant places in the amino acid sequence:

Position 180: alanine to serinePosition 277: phenylalanine to tyrosine

Position 285: alanine to threonine

MWS opsin

LWSopsin

Opsin StructureThe LWS opsin differs from the MWS opsin in three significant places in the amino acid sequence:

Position 180: alanine to serinePosition 277: phenylalanine to tyrosine

Position 285: alanine to threonine

MWS opsin

LWSopsin

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 ofColor Vision in Monkeys

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.

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


Gene Duplication

Unequal Crossing Over(Meiosis, Prophase 1)

Origin of the LWS Opsin Gene


The MWS Opsin Gene

The MWS Opsin Gene

1092 Nucleotides

The MWS Opsin Gene

1092 Nucleotides

GTCGTTAGATAG

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


Fact or Fiction? A monkey researcher in South America

discovered that some monkey females are trichromatic.

1. Definitely Fact2. Possibly Fact3. Possibly Fiction4. Definitely Fiction

The Case of Trichromatic Females

Genes code for opsin proteins; the opsin proteins facilitate color vision.

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.

The Phylogenetics ofColor Vision in Monkeys

Biogeography of Global Monkeys

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

Monkeys of the World

Phylogenetics – Exploring Relationships Among Species

Geology: Plate Tectonics and Drift

Hum

an

Chim

panz

ee

Gor

illa

Ora

ngut

an

Gib

bon

Rhes

us

Man

gabe

y

Babo

on

Mon

a

Colo

bus

Lang

ur

Woo

ly M

onke

y

Mar

mos

et

Saki

s

Ow

l Mon

key

Squi

rrel

Mon

key

Capu

chin

Spid

er M

onke

y

Continents Split50 Million Years Ago

Color Vision Evolves!Gene Duplication and Mutation

Rise of Primates75 Million Years Ago

Primates In New/Old World55 Million Years Ago

Old

World New

World

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)

Hum

an

Chim

panz

ee

Gor

illa

Ora

ngut

an

Gib

bon

Rhes

us

Man

gabe

y

Babo

on

Mon

a

Colo

bus

Lang

ur

Woo

ly M

onke

y

Mar

mos

et

Saki

s

Ow

l Mon

key

Squi

rrel

Mon

key

Capu

chin

Spid

er M

onke

y

Continents Split50 Million Years Ago

Color Vision Evolves!Gene Duplication and Mutation

Rise of Primates75 Million Years Ago

Primates In New/Old World55 Million Years Ago

Old

World New

World

Day 3 Questions

Can you find the bird?

Here’s a hint…

It’s an American Bittern!

Now that you know what you’re looking for, can you find him in this picture?.........

American Bittern

ap biology discussion notes wednesday 4/29/2015. goals for the day understand how we influence the...

Documents