Genetics, Evolution, and Ecology: A Comprehensive Guide
Gregor Mendel
-His principles of genetics and inheritance had four specific rules, 1. Organisms that reproduce sexually, genes are passed from parents to offspring, 2. In the case of two genes for the same trait one must be recessive and the other dominant, 3. Offspring have 2 or more copies of a gene one from each parent, they segrate when gametes are formed, 4. The alleles for different genes usually segrate independently of one another.
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mendel named dominant and recessive through his pea pod experiments. Dominant ration 3:1
law of segregation
-members of a pair of homologous chromosomes separate during the formation of gametes and are distributed to different gametes so that every gamete receives only one member of the pair. Come back together during fertilization.
gentoype
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allele combinations
phenotype
-what an organism looks like as a consequence of its genotype
diploid
-means has two sets of genetic makeup (father & mother). Diploid cells can’t have more than two alleles per gene.
homozygous
-having identical alleles at corresponding chromosomal loci. If a plant is homozygous then all the offspring will have the dominant phenotype.
heterozygous
-having dissimilar alleles at corresponding chromosomal loci. Offspring will be half dominant half recessive.
Punett Square
-A chart that shows all the possible combinations of alleles that can result from a genetic cross
Law of independent assortment (or segregation)
-Mendel’s second law, stating that each allele pair segregates independently during gamete formation; applies when genes for two characteristics are located on different pairs of homologous chromosomes.
trihybrid crosses
-A cross between individuals of the same genotype that are heterozygous for 3 pairs of alleles at 3 different loci ( e.G. Ss Yy Cc x Ss Yy Cc)
allele
-an alternate form that a gene may have for a single trait; can be dominant or recessive
incomplete dominance
-creates a blended phenotype; one allele is not completely dominant over the other
polygenic inheritance
-process by which several genes interact to produce a certain trait; responsible for most important traits
pleitropy
-the control of more than one phenotypic characteristic by a single gene
linked genes
-any pair of genes that tend to be transmitted together. They are not separated during independent assortment.
tetrads
-the paired chromosomes consisting of four chromatids
crossing over
-process in which homologous chromosomes exchange portions of their chromatids during meiosis
cytoplasmic inheritance (maternal)
-inheritance of characteristics encoded by genes in the cytoplasm like that from mitochondria or chloroplasts
epistasis
-the suppression of a gene by the effect of an unrelated gene
zygote
-the cell resulting from the union of an ovum and a spermatozoon (including the organism that develops from that cell)
totipotent
-Having the ability to become anything; a zygote is totipotent.
ATP
-adenosine triphosphate, an organic molecule that acts as the main energy source for cell processes; composed of a nitrogenous base, a sugar, and three phosphate groups
Translation
-(genetics) the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm (central dogma of molecular biology)
central dogma of molecular biology
-The idea that genetic information flows from the DNA sequence, to the RNA sequence to the protein sequence.
DNA Polymerase
enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule
DNA
(biochemistry) a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix
RNA
(biochemistry) a long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of a cell where it is associated with microsomes
enzymes
Molecules, usually proteins or nucleic acids, that act as catalysts in biochemical reactions.
amino acids
Simple forms of protein normally used to build tissues or, under some conditions, burned for energy
nucleotides
Basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases
Beadle Tatum Hypothesis
One gene, one-polypeptide. Genes encode polypeptides (they also encode RNA)
codons
A three-
nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
messenger RNA (mRNA)
RNA molecule that carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell
Transcription
(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA
promoter
A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA. (synthesizes RNA by using the DNA template)
amatoxins
poison that blocks Transcription by preventing the movement of RNA polymerase along DNA. (in mushrooms, i.E. Mushroom poisoning)
terminator
A special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene. The RNA must then be moved out of the nucleus before it can be translated
exons
expressed sequence of DNA; in RNA it is the region that is coded for protein
introns
a non-coding, intervening sequence within a eukaryotic gene
spliceosome
A complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons.
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one of the final events in processing RNA is that guanosine triphophate (GTP) is added to one end of the RNA. This is called a cap. (GTP is similar to ATP)
Poly(a) tail
A sequence of 50 to 250 adenine nucleotides added onto the 3′ end of a pre-mRNA molecule. Supports the transport of RNA from the nucleus to the cytoplasm
FINALLY
only when RNA has entered the cytoplasm is it called messenger RNA (mRNA) and then it can be translated
Ribosomal RNA (rRNA)
RNA that makes up the ribosomes; clamps onto mRNA and uses its information to assemble amino acids in the correct order
Transfer RNA (tRNA)
An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
Anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
Translation Initiation
tRNA: starts from AUG (methionine), “start” codon, tRNA carries amino acid and pairs with complimentary codon on mRNA
Translation Elongation
Ribosome “reads” the mRNA instructions three letters at a time, matching tRNA brings the appropriate amino acid, the ribosome moves down the mRNA, continuously matching the tRNA and mRNA, bonding the amino acids together as it goes using dehydration synthesis
signal peptide
A stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell.
Translation Termination
end of the process of translation when the ribosome reaches a stop codon; tRNA does not add an anticodon to the stop codon on mRNA, but a protein called a release factor does, and the protein is released
Point Mutation (SNPs)
mutation that affects a single nucleotide, usually by substituting one nucleotide for another. This may cause coding for a different amino acid. Physiology of organism may be altered as a result. This is less likely since it usually takes multiple nucleotides to code for something.
neutral mutation
a mutation that has little or no effect on the function of the encoded protein
frameshift mutations
mutation that shifts the “reading” frame of the genetic message by inserting or deleting a nucleotide. Types of mutations that result from insertion or deletion of a single nucleotide into the normal DNA sequence.
Chromosomal Mutations
changes in a DNA sequence that affect an entire chromosome or multiple chromosomes.
aneuploidy
A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number.
nondisjunction
error in meiosis in which homologous chromosomes don’t separate; gametes end up with wrong number of chromosomes
polyploidy
A chromosomal alteration in which the organism possesses more than two complete chromosome sets.
Evolution
generation-to-generation change in the proportion of different inherited genes in a population that account for all of the changes that have transformed life over an immense time
Gene Flow (Evolution)
movement of alleles into or out of a population due to the migration of individuals to or from the population
Genetic Drift (Evolution)
A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects of genetic drift are most pronounced in small populations.
Mutation (Evolution)
a change in a cell’s genetic material. Once the genetic material has changed, the change is inherited by the offspring of that cell
Natural Selection
process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest
Sexual Selection
A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
Geographical Isolation (Speciation)
a form of reproductive isolation in which two populations are separated physically by geographical barriers such as rivers, mountains, or stretches of water
Reproductive Isolation
separation of species or populations so that they cannot interbreed and produce fertile offspring.
PCR
polymerase chain reaction- DNA is copied multiple times to produce many copies of the original molecules helpful when there’s only a small DNA sample
DNA Fingerprints
The number and sizes of DNA fragments, or DNA fingerprints, produced by restriction enzymes are used to determine genetic similarities
Transgenic Organisms
any living creature that has received a foreign gene and phenotype by means of genetic engineering; new phenotypes are the result of manipulations of DNA in the laboratory (‘microsurgery’); the changes must be heritable to the offspring
GMO
genetically modified organism; organism whose genetic material has been altered using genetic engineering techniques
Pros of GMO
Enhanced taste and quality
Reduced maturation time
Increased nutrients, yields, and stress tolerance
Improved resistance to disease, pests, and herbicides
New products and growing techniques
Cons of GMO
Potential human health impacts, including allergens, transfer of antibiotic resistance markers, unknown effects
Potential environmental impacts, including: unintended transfer of transgenes through cross-pollination, unknown effects on other organisms (e.G., soil microbes), and loss of flora and fauna biodiversity
Domination of world food production by a few companies
Increasing dependence on industrialized nations by developing countries
Biopiracy, or foreign exploitation of natural resources
Violation of natural organisms’ intrinsic values
Tampering with nature by mixing genes among species
Objections to consuming animal genes in plants and vice versa
Stress for animal
Abiotic Factors
non-living factors including temperature, water, sunlight, wind, rocks and soil that effect an ecosystem. Also, fore flood and tornados ( or disturbances). Latitude also effects growth and devlopment (day length, temperature etc) subtropical highs El nino, La Nina.
Biomes
Ambient Temperature
most plants have- Temperature of the surrounding environment. Some plants can alter their temperature with physical structures like leaf hairs, but most are ambient.
Timberline
line marking the upper limit of tree growth in mountains or northern latitudes. Contingent on factors like water and temperature as well as rock and soil.
biogeographic realms
A geographic region where a group of plant and animal species evolved. Transition boundaries known as ecotones, vast expanses where they could expect to find communities of certain types of plants and animals
Tropical Forests
emergent layer, canopy, understory, forest floor.
Savannas
a region of grassland with scattered trees lying between the equatorial forest and the hot deserts in either hemisphere.
Grasslands
A biome dominated by grasses and associated herbaceous plants, occur where there is enough rain to support abundant grass but not enough for forests.
deserts
a type of biome characterized by low moisture levels and infrequent and unpredictable precipitation. Daily and seasonal temperatures fluctuate widely.
Chapparal
a scrubland biome of dense, spiny evergreen shrubs found at midlatitudes along coasts where cold ocean currents circulate offshore; characterized by mild, rainy winters and long, hot, dry summers
Temperate Deciduous Forests
biome, occupy regions that have warm summers, cold winters, and moderate precipitation, shed leaves in winter, found near Riparian communities-of or relating to or located on the banks of a river or stream
Coniferous Forests
evergreens such as spruce, fir, pine, and aspen are the most common. This region has, deer, moose, black bears, and many fur-bearing animals, as well as hawks, eagles, and various types of wild ducks. Soils aren’t very fertile. Taiga, largest biome on earth (northern america) 11% of earth surface
Tundra
Treeless arctic or alpine biome characterized by cold, harsh winters, a short growing season, and potential for frost any month of the year; vegetation includes low-growing perennial plants, mosses and lichens
Biotic Factors
the biological influences on organisms within an ecosystem
Population
a group of organisms of the same species populating a given area
Plant Distribution
Determined by seed distribution, weather patterns, populations of animals. Survivor ship curves show plant versatility and life longevity
Carrying Capacity
largest number of individuals of a population that a environment can support can limit/encourage plant growth.
R-Selection
The concept that in certain (r-selected) populations, a high reproductive rate is the chief determinant of life history.
K-Selection
Selection for life history traits that are sensitive to population density; also called density-dependent selection.
Commensalism
the relation between two different kinds of organisms when one receives benefits from the other without damaging it
Mutualism
the relation between two different species of organisms that are interdependent
Predation
interaction in which one organism captures and feeds on another organism (killed)
Herbivory
An interaction in which an organism eats parts of a plant or alga. (not necessarily fatal)
Parasitism
the relation between two different kinds of organisms in which one receives benefits from the other by causing damage to it (usually not fatal damage)
Intraspecific Competition
in a community competition for resources among members of the same species (self-thinning)
Interspecific Competition
in a community competition for resources between members of different species (elimination or co-existance)
Dominant Species
Those species in a community that have the highest abundance or highest biomass. These species exert a powerful control over the occurrence and distribution of other species.
Keystone Species
a species whose impact on its community or ecosystem are much larger and more influential than would be expected from mere abundance
Horizontal Distribution
horizontally differential distribution of species in a community; regular, random, and clustered distribution
Primary Succession
an ecological succession that begins in a an area where no biotic community previously existed. Begins with lichens and mosses on rocks
Secondary Succession
the process by which one community replaces another community that has been partially or totally destroyed
Climax Community
a relatively stable long-lasting community reached in a successional series; usually determined by climax and soil type
Biological Magnification
increasing concentration of a harmful substance in organisms at higher trophic levels in a food chain or food web (Mercury and DDT)
Nitrogen Cycle
the continuous sequence of events by which atmospheric nitrogen and nitrogenous compounds in the soil are converted, as by nitrification and nitrogen fixation (nitrogen to ammonium), ammonification- ammonium by decomposers, nitrification-ammonium to nitrate/nitrite, assimilation-uptake of ammonium & nitrate by plants, denitrification- conversion of nitrate to nitrogen gas.
Ecosystem Fragmentation
-Deforestation & agriculture. Affects population size, density & species diversity
Chlorofluorocarbons
group of chemical compounds used in refrigerators, air conditioners, foam packaging, and aerosol sprays that may enter the atmosphere and destroy ozone
Global Biodiversity
Global issues the whole world must work together to deal with. Biodiversity threat: growing extinction of animal and plant species b/c of habitat destruction