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first generation - dominant
[produced purple flowers in Mendel's experiment]
F2 generation (results)
3:1 ratio of dominant: recessive
Why is F1 dominant, but F2 different?
because F1 is heterozygous dominant so F2 will vary
phenotype v. genotype
phenotype: expression of a trait
genotype: individual's genetic make up
what is complete dominance?
a diploid individual will have 2 chromosomes
each chromosome contains a separate gene that codes for that specific trait
does each gene contribute?
yes, each gene contributes to an allele to genotype-
but only one phenotype is expressed
kinds of chromosomes in complete dominance?
where are the genes located?
located at the same locus
law of segregation
alleles segregate independently of each other when forming gamete
heterozygote exhibits a phenotype that is intermediate between he homozygous counterparts
[same capital letter, different superscript]
heterozygote exhibits both phenotypes
what allele is codominant?
Law of Independent Assortment
genes on different chromosomes assort independently of each other
what kind of genes assort independently? (in other words, what genes are on different chromosomes)
genes that code for different traits:
i.e. pea shape and pea color
phenotypic ratio of a dihybrid cross
II. Humans - which chromosome establishes sex of the individual?
male v. female
male = X and Y
female = X and X
what does sex-linked mean?
when a gene is found on the sex chromosome -
will sort dependently on the sex of the individual
which male chromosome carries the allele for sex-linked traits?
X not Y
if a dominant allele is carried by X chromosome in the male is it expressed? what about if it's recessive?
always expressed: dominant or recessive
III. Evolution - what is a gene pool?
total of all alleles in a population
the course of development (zygote to adult) reflects....
[human fetus has pouches reflecting a gilled ancestor]
Kingdom, Phylum, Class, Order, Family, Genus, Species
what determines a species?
all organisms that can reproduce fertile offspring
whoever produces more offspring
[doesn't matter what you do, all that matters is that the species doesn't go extinct]
survival of the fittest
one species will exploit the environment more efficiently
leads to extinction of the others with the same niche
involves producing large numbers of offspring that mature rapidly
(little or no parental care)
slow maturing of offspring
(strong parental care)
growth curves for r- and k-selection
r-selection = exponential
k-selection = sigmoidal
who has high mortality rate? who can survive in changing environments?
what is polymorphism?
some phenotypes vary gradually within a species [ex: height]
what is symbiosis?
relationship between two species
beneficial for both
beneficial for one, doesn't affect the other
beneficial for one, detrimental for the other
one allele may be permanently lost due to the death of all members having that allele
binomial theory: what does it predict?
genotype frequency of a gene in a population in Hardy-Weinberg equilibrium
what are the equations?
p2 + 2pq + q2
p + q = 1
What are chordates characterized by?
(not all of them have a backbone)
or chordates proteostomes or deuterostomes?
anus develops from or near blastopore
What other features do chordates have?
- paryngeal slits
- dorsal, hollow nerve chord
what is a notochord?
axial support, not the backbone
have notochord replaced by cartilage or bone structure
also have a distinct brain enclosed in skull