BUT THE DOCTORS TOLD MY PARENTS I WOULD BE, LIKE, 6 FEET TALL!!! WHAT’S UP WITH THAT?
The Teacher Said… Yes, Yes, Yes… The teachers ALWAYS say that GENOTYPE determines PHENOTYPE And you KNOW that teachers ARE ALWAYS RIGHT!!!!
GENOTYPE vs ENVIRONMENT Your GENOTYPE determines how tall you MIGHT be able to grow to… BUT environmental factors determine how tall you actually become. Environmental factors such as: eating habits health exercise, etc. will determine the height you will actually be in life.
Foot binding
Nutrition & Health Their genotype might code for a 6’7” line-backer body… Poor nutrition and health stand in the way
What Traits are Affected??? Expression of many phenotypes can be affected by the environment. For example, our Hair and Skin color are influenced by the amount of sun exposure: - Hair tends to lighten with a lot of sunlight - Skin tends to darken with a lot of sunlight
Go Ahead… Ask Me Why… Human skin is affected by the amount of ultraviolet radiation to which people are exposed (i.e, how much time you spend in the sun) Your skin contains a pigment called melanin Remember? Albinos? No Melanin! Melanin acts as a UV filter UV light is a mutagenic agent - Mutagens cause mutations (such as skin cancer!)
to protect the nuclear DNA from mutations caused by the sun’s rays Melanosomes which make the protein melanin pile up on top of a cell’s nucleus to protect the nuclear DNA from mutations caused by the sun’s rays The more a cell is exposed to the sun, the more melanin is produced to protect the nucleus! - Why??? DNA!!! Pile On!
The more melanin, the darker your skin… The more exposure you (and your ancestors) have had to the sun, the more melanin you will have in your epidermis (skin) The more melanin in your epidermis, the darker your skin appears…
Himalayan Rabbits Himalayan rabbits are native to the Himalayan Mountains, where it is COLD!!!! These rabbits have WHITE FUR over most of their bodies, with BLACK FUR on their ears, noses, feet and tails. This color pattern is the result of an environmental factor! Temperature differences in different parts of the rabbits’ bodies change the color of their fur Areas where the body temperature is below 33°C the fur grows in black.
How do we know? A scientist shaved an area of fur on the backs of “regular” Himalayan rabbits. Ice packs were kept on the shaved areas long enough for the rabbits’ fur to begin growing back. When the ice packs were removed, the fur growing beneath them was black.
The Same Rabbit Before Ice Packs After Ice Packs
Answer this……. Suppose you wanted a Himalayan rabbit with white feet Which of these procedures would you follow? A. place ice packs on the rabbit’s feet B. place the rabbit outside on a sunny day C. place the rabbit outside when it is snowing D. place the rabbit in a cage with a heated floor
Siamese Cats Cat kept Indoors Cat kept outdoors
Answer this……. The Siamese cat has a gene that controls for fur color. The cat in the first photo is kept indoors. The cat in the second photo was kept outdoors. Which statement best explains the differences in fur color between these two cats? The cat kept indoors is older than the cat kept indoors The environment influenced the production of proteins when the cats were kittens The environment influences the expression of fur color genes The cat kept outdoors has a gene mutation that prevents it from producing light-colored fur
WHY do we need to know this? We need to understand the relationship between genes and the environment As the environment changes, the genotype that is best able to adapt will survive We cannot judge which is more valuable: the genotype or the phenotype
The Relationship The relationship between genotype and phenotype is summarized this way: genotype + environment → phenotype
But… How does it happen? Genotype is the genetic code which gives instructions to make a specific protein Genes are made up of sequences of DNA The DNA is copied (by RNA, remember?) and the RNA finds a Ribosome to build the protein This is Protein Synthesis! genotype + environment → phenotype