Genetics and Evolution

Genetic Code of an Organism

Genetic code of an organism is stored in its deoxyribonucleic acid (DNA)

• Organisms will always display a dominant trait, but sometimes carry a gene for a recessive trait

• If an organism has a gene for a dominant trait, and a gene for a recessive trait, it shows the one that’s dominant

e.g. eye color, brown eyes in dominant blue eyes is recessive

Punnett Square Question on Exam

What’s the probability that two parents, both of whom have brown eyes, but who are carriers of a recessive gene for blue eyes, what’s the probability that they’ll have a blue-eyed child?

• B → Brown

• b→ Blue

Use a Punnett square

BB: The child has brown eyes

Bb: The child still has brown eyes

bb: The child has blue eyes

You don’t know if person has 2 dominant genes or a dominant and a recessive gene.

Gregor Mendel

Scientist and Monk

Pioneer in Dominant and Recessive Gene Study

Crossbred pea plants, wrinkly and smooth peas

1st time he bred them

• all the resulting peas were smooth because they were all carrying a recessive gene for being wrinkly, but smooth trait dominated

2nd time he bred them

• a quarter of the offspring were wrinkly. This is how we discovered idea of

  • Successive Generations: the passing of traits over time

However, a recessive trait can be passed down through generations without showing up until two carriers (who each have one copy of the recessive gene) have a child who inherits both recessive copies. This can happen even if the parents show the dominant trait.

Successive Trait

the passing of traits over time

Darwin’s Theory of Evolution

Asserts that organisms have changed overtime to adapt to the unique and varied demands of their changing environments

• organisms have diff traits that may be slightly diff than their parents and we call this variants

Darwin’s Theory of Evolution: VARIANTS

Organisms have diff traits that may be slightly diff than their parents

• Variation on the parents

  e.g. Giraffe w/ longer neck than parents that’s a random variation. That occurred because the way the DNA got combined when they reproduced

Advantageous or Disadvantageous

Depends on the Environment in which an organism exists Giraffe Explain

That trait is not necessarily advantageous or disadvantageous; it depends on the environment in which the giraffe exists

e.g.

If there are high trees where there’s fruit other giraffes can’t reach because they have shorter necks, he enjoys that food exclusively, he’ll

• feed,

• be healthy,

• reproduce,

• and pass on the trait eventually propagate.

However, if trees are short, extra neck length may slow giraffes down, more susceptible to predators

Overall Idea of Organisms Adapting

The traits that they’re advantageous get propagated, and organisms, who have disadvantageous traits end up dying off overtime,

That’s how we get evolution of different types of organisms

Supporting Evidence for Evolution 2 Ways

1. Fossil Records

2. Comparative Anatomy

Supporting Evidence for Evolution Fossil Records

Look at fossil records of diff organisms over time

and

see how minor variations have occurred, and one organism led to the next.

Supporting Evidence for Evolution Comparative Anatomy

• Look certain type of animals, whales, they have little feet buried under their blubber.

• Useless to them, but vestigial remain from when they were a land based animal

• DNA sequences (between hippos and whales) see they’re very similar even though they look like different creatures

Adaptation vs. Accomodation

Pair of terms we gotta know how to differentiate

Accommodations (Non-Genetic Changes)

Non-genetic changes, allow individual organisms to respond to TEMPORARY CHANGES in the environment

e.g.

When cold out, the blood vessels in your body contract, conserving heat.

When it gets warmer, they’ll expand again increasing blood flow.

Not a genetic change.

Ability to contract blood vessels- evolutionary

Action itself- that’s accomodation

Adaptations (Genetic Change)

CHANGES AT THE GENETIC LEVEL ALLOWING A POPULATION TO RESPOND TO LONG TERM CHANGE in the environment

e.g.

effects population, not just me as an individual

e.g. trees getting taller and taller, giraffes in that region evolve a longer neck to be able to reach fruit on those trees

This has to occur over generations

Also, the dilation of the human eye changes temporarily as a temporary change in the environment's amount of light