exam 4 Flashcards
(37 cards)
How many pairs of chromosomes do we have
23; 22 are autosomes and 1 are sex chromosomes
incomplete dominance
A form of inheritance in which heterozygotes have a phenotype that is intermediate between homozygous dominant and homozygous recessive- mixture- example purple flower
co-dominance
Both maternal and paternal alleles contribute equally and separately to the phenotype. Ex cow spots or red and blue flower
Poly-genic trait
Trait that is controlled by multiple genes. Ex: height or skin color
Multi-factorial trait
trait that is controlled by multiple genes and environmental factors. Ex: height again, stress and mental development
MRSA
-Methicillin-resistant Staphylococcus aureus
-Infectious bacterium
* Difficult to treat with antibiotics
* Kills 19,000 people in the United States each year
-Developed resistance to antibiotic drugs*
- Adversely affects people with weakened immune system
antibiotics
chemicals that either kill bacteria or affect their growth.* Interfere with function of essential bacterial cell structures, e.g. beta-lactams that degrade cell wall
antibiotic resistance
-Some bacteria can survive antibiotics
* Acquire random mutations when DNA replicates during asexual reproduction
-Random genetic changes ultimately altered bacterial proteins in ways that helped staph dodge antibiotic drugs.
* Altered or acquired genes code for proteins that can:
* disable antibiotics, or
* code for membrane proteins with altered shapes to which antibiotics can no longer bind.
binary fission
One single parental cell into two daughter cells-mutation replicated and passed down
evolution
change in allele frequencies over time
how populations evolve
-Fitness: organisms’ ability to survive and reproduce in a particular environment
-Interplay between phenotype and environment determine frequency of traits in a population
* If traits improve fitness, traits become more common in population
* Population evolves by natural selection
4 conditions needed for a population to evolve
- The trait is heritable.
- Genetic variation in the trait within the population.
- Variation in fitness within the population.
- Individual fitness varies depending on the trait.
natural selection
differential survival and reproduction of individuals within a population in response to environmental pressure
-Advantageous traits become more common and population becomes better suited, or adapted, to environment
direction selection
Favor only one extreme: Ex; lizards go from short tails to long tails bc they look like snakes
Stabilizing selection
favors the medium from one extreme to another. Ex; Tigers get medium sized tails
disruptive selection
Does not favor the medium at all. Ex: Light- and dark-colored oysters could also have a camouflage advantage as opposed to their medium-colored relatives.
Sextual selection
variation, heritability, variation in reproductive success, trait confers altered reproductive success
individuals with different phenotypes
will have differing abilities to survive and reproduce in a population; that is, they will differ in fitness.
scientific theory
statement providing the current best explanation of how the universe works
–Supported by many lines of evidence
–Withstands repeated experimental tests
microevolution
changes that occur within a biological population.
mosquitoes evolving resistance to DDT.
gene flow
interbreeding between population- less diversity-non adaptive
genetic drift
Random occurrence that causes changes within a population- went from a lot of diversity to less
where did modern humans originate
africa
founder effect
type of genetic drift
a subset moves on to a different area forming a new population
Over time, the resulting new subpopulation will have genotypes and physical traits resembling the initial small, separated group, and these may be very different from the original larger population.
