Natural Selection
What does it mean for a trait to "vary"?
There is more than one version of the trait.
e.g. rock pocket mice can be light brown, dark brown, black, or albino.
T or F
Alleles are proteins
False
A or a
M+ or M0
are examples of...
When DNA polymerase makes an exact copy of all the DNA in a cell*
*Mutations may occur
In meiosis, there is __ round(s) of DNA replication and ____ round(s) of cell division
In meiosis, there is 1 round(s) of DNA replication and 2 round(s) of cell division
True or false: all variation in traits is genetic
FALSE! You must prove "it's not a flamingo"--provide evidence that a trait is inherited
T or F
A person can evolve in their lifetime
False populations evolve
A Punnet square has the genotypes of the ________ on the outside and the ____________ on the inside
parents
possible offspring
What are the two gametes in humans?
Egg and Sperm
1 round of meiosis creates how many daughter cells? Are the daughter cells genetically identical or genetically unique?
1 round of meiosis creates 4 genetically unique daughter cells (gametes)
Which of the following is the BEST EVIDENCE that a trait is genetic?
a. members of a population in the same environment share similar traits
b. a trait is caused by one or more proteins
c. one or more genes is known to code for a trait
d. offspring share similar traits to their parents
THE BEST evidence is c. However, lacking direct information about which gene(s) code for traits, the other types of evidence may be used.
T or F
Selection pressures are traits
False
Selection pressures are environmental conditions that cause a certain version of a trait to be advantageous
Parents: AA x aa
Draw a punnet square.
% chance of getting Aa?
50% chance
What is an allele AND what is it made of?
An allele is a version of a gene. Alleles are made of DNA.
What is independent assortment?
Independent assortment states that each gamete receives 1 RANDOM copy of each homologous chromosome.
True or False: If all members of a population have the same version of a trait, that means no DNA mutation is happening in that population
FALSE! DNA mutation is always happening. If all members of a group share a version of a trait, there may be strong selection pressure for that version.
T or F
Mutations are usually caused by an organism's environment
False: Mutations happen randomly. Environmental pressures determine which mutations help organisms survive and reproduce.
For the O skin color gene:
Parents: O+3 O+1 x O+2 O+0
% chance getting a child darker than the darkest parent?
25% chance
Gametes have 1 copy of each chromosome; body cells have 2
What is crossing over?
Crossing over is when both replicated homologous chromosomes swap small sections of DNA with each other.
Give an example of a trait that could be helpful in some environments and unhelpful in others. Explain HOW it could be helpful or unhelpful
e.g. light skin is helpful in areas with low UV radiation because it allows people to absorb enough UVB radiation to synthesize vitamin D. This allows people to absorb enough calcium from their diet to develop healthy bones and a strong immune system. However, light skin is unhelpful in areas with high UV radiation because it does not provide enough protection from UV radiation to protect folate. If UV degrades the folate in someone's blood, that person cannot produce healthy offspring--they either cannot make healthy sperm cells, or their offspring will likely be born with severe birth defects.
T or F
Luck has nothing to do with evolution
False
For skin color- S gene
Parents: S+2 S+1 x S+1 S+0
% chance of getting an offspring between the two parents' skin tone (medium)
50%
What are homologous chromosomes?
Homologous chromosomes contain the same genes, but may contain different alleles for those genes. We inherit 1 copy of each homologous chromosome from each parent.
HOW are new alleles made? (250)
WHEN are new alleles made? (250)
New alleles are made through mutations during DNA replication. It must happen in cells that will become gametes.