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BIOL 107: EXAM 2
Sex Chromosomes |
Chromosomes that determine sex
Humans: Male = XY Female= XX
|
Autosome |
All chromosomes that aren't sex chromosomes (humans 22 pairs)
|
Polyploidy |
more than 2 sets of chromosomes
common in flowering plants but rare in animals |
Karyotype |
display of an individual's chromosomes
photograph of homologous pairs
|
Fertilization |
union of 2 gametes to form zygote
|
Mitosis |
cell duplication division that produces identical cells
|
Meiosis |
cell reduction division that produces haploid cells
|
Haploid |
1 set of chromosomes (humans 1n=23) |
Homologous Chromosomes |
Pair of chromosomes that have the same size, genetic loci, centromere position, and staining pattern.
One homologous is inherited from each parent |
Animal Life Cycle |
Gametes (1n) --> zygote (2n) --> development |
What is different between 1st Meiosis and 2nd Meiosis? (as far as division names go) |
1st Meiosis is reduction division
2nd Meiosis is duplication division |
Phases of Meiosis |
Meiosis I
Interphase (chromosomes replicated)
Prophase I (crossing over to exchange genes)
Metaphase I (chromosomes line up independently)
Anaphase I (homologous chromosomes separate)
Telophase I / cytokinesis
Meiosis II (cells now haploid and have undergone recombination)
Prophase II
Metaphase II
Anaphase II
Telophase II (4 cells) |
Independent assortment of chromosomes |
random distribution of material and paternal homologous to gametes |
2^n |
# of different combinations, gametes |
N |
haploid # of chromosomes
|
Crossing over |
exchange of genetic material between non-sister chromatids of homologous chromosomes
|
Random fertilization |
egg cell (8 million) + sperm cell (8 million) = zygote (64 trillion)
|
Genetic variation |
raw material for evolution
|
Spermatogenesis |
sperm produced in seminiferous tubules in testes
|
Oogenesis |
eggs produced in follicles of ovary
|
Aneuploidy |
Monosomy 2n-1
Trisomy 2n+1
|
Nondisjunction |
failure of chromosomes to separate during meiosis
primary- Meiosis I
secondary- Meiosis II
|
Barr Body |
inactivated X chromosomes form inactive heterochromatin
genes on barr body are not expressed |
Chromosomes mutations |
Deletion: Cri- du - chate - mainly due to deletion on the sperm- chromosome 5
Duplication: Pallister Killian Syndrome- short arms on chromosome 12
Inversion: chromosomes 6 & 9 are involved
Translocation: Chronic Myelogenous Leukemia- from chromosome 22 to chromosome 9 |
Genetics |
the study of transmission of traits from on generation to the next and how these traits are expressed
|
Blending Theory |
mixing traits (paint) would forever change the traits |
Particulate Theory |
discrete inheritable units, "genes" (marbles) explains how traits can skip generations |
Allele |
alternative or variant form of a gene |
Dominant Allele |
can mask expression
|
Recessive Allele |
masked by another allele |
Gene Locus |
location of a gene on a chromosome |
Mendel's law of segregation |
the 2 gene factors split during meiosis and random fusion of gametes occurs at fertilization
|
Mendel's law of independent assortment |
alleles of a gene for 1 trait segregate independently of alleles of another trait |
Multiple alleles
|
more than 2 allelic forms for a gene in a population (ex. ABO blood types)
|
Rh factor |
gene that has 2 alleles and is inherited in dominant/ recessive fashion
Rh+ = dominant
Rh- = recessive |
Codominance |
heterozygote expresses phenotypes of both homozygotes (ex. blood type AB = A antigen and B antigen) |
Incomplete dominance |
interaction of 2 alleles, neither allele is completely dominant
|
Incomplete penetrance |
dominant alleles that are partially expressed or not expressed
|
Pleiotropy |
a single mutant gene affects 2 or more unrelated traits
marfan syndrome is due to a mutant gene that codes for the protein fibrin (elastic fibers in connective tissues)
|
Polygenic inheritance |
single trait controlled by more than 1 gene
traits vary along a continuum
quantitative (ex. height, skin color) |
Environmental effects on gene expression |
nature vs. nurture
phenotype = genotypes + environment |
Natural Theology |
Believed earth was only a few thousand years old and a "fixed species" |
Linnaeus |
father of taxonomy
hierarchy of classification (order in diversity) |
Cuvier |
French scientist
Explained succession of life forms as catastrophism
After each catastrophe (or extinction) a region was repopulated by a new species
|
Erasmus Darwin |
Life evolved from a common ancestor forming "one living filament"
|
LaMarck |
In 1802, proposed one of the first theories stating a mechanism for evolutionary change
Inheritance of acquired characteristics (use or lose)
False, but theory recognized that evolution involved interaction of organisms with their environment
|
Two facets of Darwinian View of Life |
a) common decent
b) natural selection |
Alfred Wallace |
Developed theory of natural selection independent of Darwin
|
Homologous structures |
inherited from a common ancestor
different in function
|
Analogous structures |
similar in function; different in origin |
Vestigial structure |
structures retained in organisms even though they may not be functional |
Types of natural selection |
1. Directional- favors extreme
2. Disruptive- favors 2 extreme phenotypes over the average phenotype
3. Stabilizing- favors intermediate variants
|
Sexual Selection |
leads to an increased ability to secure a mate
1. Female choice (intersexual)
2. Male competition (intrasexual)
|
Maintenance of diversity |
a) Natural selection
b) Heterozygote advantage
|
Speciation |
splitting of one species into two or more |
Temporal isolation |
frogs occupy the same habitat but breed at separate times |
Behavioral isolation |
Blue footed boobies present elaborate courtship displays |
Habitat isolation |
crickets occupy different habitats in same geographic zone |
Mechanical isolation |
male dragonfly claspers only work to hold the female of their own species |
Gamete isolation |
gamete of 2 sea urchin species are not compatible
|
Prezygotic isolation |
prevent reproductive attempts or successful fertilization
|
Postzygotic isolation |
prevent successful development
|
Hybrid inviability |
hybrids form but don't complete development |
Hybrid sterility |
female horse and male donkey = sterile mule |
F2 fitness |
hybrid offspring are sterile |
Allopatric speciation |
2 populations are geographically isolated from one another and 2 different species result
|
Sympatric speciation |
new species arise in the midst of parent population without a geographical barrier
|
Adaptive radiation |
emergence of numerous species from a single ancestral species that spreads to new environments |
Convergent evolution |
similar trait evolves in 2 unrelated species due to similar environmental pressure |
Principles of macroevolution |
1. Rates of evolution
2. Development genes
3. Evolution is not goal oriented
|
Rates of evolution |
1. Gradualistic model
"slow gradual changes" in isolated populations
2. Punctuated equilibrium model
"spurts of relatively rapid change" followed by long periods of stasis
THESE 2 THEORIES ARE NOT MUTUALLY EXCLUSIVE |
Development genes |
Regulatory genes that control genes for animal body shapes, patterns, and organs.
Similar to "switches" to turn genes on and off
1. Pax 6 gene- responsible for eye formation in all animals
2. Hox gene- control # and appearance of repeated structures along main body axis of vertebrates |