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Genetics
The science of genes, heredity, and variation of inherited characteristics
Chromosomes
Found within cells made of many molecules of DNA. One unique string of DNA
DNA (Deoxyribonucleic Acid)
A molecule that carries genetic information
Gene
A portion of “Subunit” of DNA that codes a particular trait / characteristic (One gene = One protein)
Locus (Pl. Loci)
Where a particular gene is located on a chromosome
Asexual Reproduction
New individual produced by a single parent through cell division
Genetically identical offspring
No need to seek a mate
Sexual Reproduction
Individual produced through fusion of 2 sex cells
Genetic Variability = adaptability
Costly
Mitosis
A single cell making two cells by an equal split of nucleus content
The goal of mitosis is to create 2 new genetically identical diploid (2n) daughter cells from one parent cell
Cytokinesis
The equal split of cytoplasm and organelles contained within it
Parent Cell - Daughter / Sister cells
The Og cell that is going to divide
The 2 cells that result from the division
Somatic Cells
All cells except reproductive Cells
Growth, Tissue Repair, Cell Replacement
Interphase
Growth(1) : duplication of everything except chr.
S : single stranded chr. → double stranded chr. (Two identical copies of
each (sister chromatids) are attached at the centromere)
Growth(2) : check and fix errors of S
Prophase 1
“Prep” phase
Nuclear membrane dissolving
DNA wound around Nucleosomes
2 Copies of each Chr.
Spindle fibers form
Centrioles moving towards poles of the cell
Synapsis occurs – homologous pairs line up side by side, chromatids will cross over to exchange
genetic information (crossing over produces variability)
Metaphase 1
“Middle” phase
Homologous pairs (tetrads) align along the equator of the cell
Spindle fibres attach to the pair of sister chromatids
Anaphase 1
“Apart” phase
Homologs separate and move to opposite poles.
Sister chromatids remain attached at their centromeres.
Telaphase 1
“The END”
Nuclear membrane reforms
Pairs of sister chromatids are found in each haploid daughter cell
Simultaneous with Cytokinesis
Diploid Chr. Count
Humans : 2n=46
2 of each 23 pairs
23 sex cells
Meiosis
Sexual reproduction (Germ Cell - Parent Cell)
The goal of meiosis is to create 4 gametes (haploid (1n) sex cells e.g. sperms, egg) from one parent cell
Each gamete cells contain different genetic information
2 divisions: (starts with 46 double stranded chromosomes (2n)
after 1st division - 23 double stranded chromosomes (n)
after 2nd division - 23 single stranded chromosomes (n)
Allele
Different versions of the same gene
Homologous Chr.
Pair of chromosomes containing the same gene sequence (each from one parent)
Same genes not always same alleles
Spermatogenesis
Diploid spermatogonia → primary spermatocytes → 4 spermatids
Oogenesis
Oogenesis → primary oocytes → 1 egg + 3 polar bodies (non-functioning reproductive cells, die over time)
Recombination
Crossing over between homologous chr.
Occurs in prophase of Meiosis 1
Changes the Allele combination
Independent Assortment
The homolog of one chromosome can be inherited with either hololog of the other chromosome
Karyotypes
A photographic inventory of an individuals chrs.
22 pairs of Autosomes and 1 pair of sex chr.
Nondisjunction
A failure in chr separation
Homologous chr fail to separate during Meiosis 1
Sister chromatids don’t separate during Meiosis 2
Abnormal # of sex chr.
Extra or missing sex chr. due to nondisjunction
Does not upset the genetic balance as much as an unusual # autosomes
Offspring usually viable
Cytoplasmic Inheritence
Sperm does not contribute mitochondria or chloroplasts to the zygote so the DNA in each of those are Maternal Inheritance
Mit / chlor not separating evanly = genetic variation
Sperm has much less cytoplasm then an egg meaning it contribute less
Nucleotide
1.Pentose sugar (5 carbon ring)
2.Phosphate group with negative charge
3.Nitrogenous base (4 types, A=T, G=C)
Phosphate-sugar = backbone
Bases = pair up in the middle
Law of Segregation
Members of a pair of alleles for a given trait are segregated (seperated) when gametes are formed
One allele could express itself (dominant) while the other allele is not expressed (recessive) if both
alleles are found together.
Incomplete Dominance
One allele is not completely dominant, traits blend
Big letter (Not x) ^Subscript uppercase letter
Codominance
Both genes in a heterozygous organism are expressed
Don’t blend but are both present
Big letter (Not x) ^Subscript uppercase letter
Multiple Allelism
When their is more then 2 alleles for a given trait
Allows for a large number of genotypic and phenotypic possibilities
Sex Linked Inheritance
Female XX = have two copies of X
Male Xy = have one copy of X
Pedigree Chart
Traces the inheritance of traits among family members
Law of Independent Assortment
when two or more characteristics are considered at one time, each pair shows dominance and segregation independently of the other
Evolution
the relative change in the characteristics of populations that occur over successive generations
Genetic Variation
There are different versions of genes, known as alleles, in a population which is the basis of biodiversity
Gene Pool = total of all genes in a population
Theory of Evolution - 1
Random mutation can occur and change the DNA of an organism in a way that affects its offspring (creates new genes)
Theory of Evolution - 2
Mutation is either beneficial, harmful, or neutral
If harmful, then offspring survival decreases, reproduction rates decrease ; mutation dies out and does not get passed on to the next gen
If beneficial, then the opposite happens
Theory of Evolution - 3
Through reproduction, the beneficial mutation spreads. The process of eliminating bad mutations and spreading good mutations is called natural selection
Biodiversity
the observes geographic patterns of distribution of species
Based on both living and fossilized species
Darwin found “unusual” animals on Galapagos which resembled those on the nearest land mass
Homologous Structures
Similar structures in species that share a common ancestor
Structures that originally function one way in ancestral species become modified as they take on new functions
Suggest common evolutionary origins
E.g. All mammals have 28 skull bones, 7 neck bones!
Analogous Structures
Evolved independently to have the same function
Suggests distant evolutionary relationship
i.e. Eyes/wings of insect vs. eyes/wings of bird
Vestigial Structures
Type of homologous structure
Remnants of structures that may have had important functions in the ancestral species but has no clear function in modern descendants
Fossils
Fossilized ancestors of animals living in the same area
Natural Selection - Directional
selection favours individual with a more extreme variation and eliminates the rest
Natural Selection - Stabilizing
selection acts to eliminate the both extremes from the population; the average phenotype is
favoured
Natural Selection - Disruptive
selection eliminates intermediate types, environment can favour more then one phenotype (could end up with two species)
Natural Selection - Sexual
the preference by one sex for certain characteristics of individuals of the other sex
Evolutionary Change w/out Selection - Genetic Drift
change in populations allele frequency due to chance
smaller population, more influence
Loss of Diversity
Evolutionary Change w/out Selection - Bottleneck Effect
hugh reduction in population size due to chance event
loss in genetic diversity
Rare alleles eliminated
Evolutionary Change w/out Selection - Founders Effect
when a small, random sample of a population colonizes an area and is culturally isolated (reduces genetic variation in original population, may often lead to unique species)
Biological Species Concept
A species is a population or group of populations whose members can breed under Natural Conditions and produce fertile offspring
Hybridization = crossbreeding between species, rare in nature
Reproductive Isolation
inability of two organisms to reproduce due to some kind of physical or behavioral barrier
Prezygotic Isolation
Prevention of mating or fertilization
Ecological ; different habitats
Habitat ; different habitat in the same location
Temporal ; different breeding seasons
Behavioural ; different signals or rituals for mating
Mechanical ; physically incompatible
Gamete ; sperm and egg are unable to recognize each other by their molecular markers
Postzygotic Isolation
zygote forms but mature, reproducing offspring not produced
Zygote maturity ; zygotes do not develop to maturity
Hybrid inviability ; dies early in development
Hybrid infertility
Allopatric Speciation
when 2 populations become geographically separate, mutations occur until the populations are reproductively isolated
Sympatric Speciation
Populations in same geographical location split into separate gene pools due to genetic polymorphism ( 2 or more different phenotypes)
Often due to disruptive selection
Adaptive Radiation
A common ancestral species evolves into multiple new species (distinct but closely related)
Divergent Evolution
is the accumulation of differences between groups which can lead to the formation of new species
Convergent Evolution
geographically isolated species evolve similar phenotypes due to similar selection pressures
Coevolution
the process which one species evolves in response to the evolutionary changes in another species
Mutualistic Relationship
symbiotic relationship in which both organisms benefit
Antagonistic Relationship
symbiotic relationship in which one organism benefit and the other is harmed
Evolutionary Arms - Race : struggle between competing co-evolving genes that develop adaptations and counter - adaptations
Commensalism
symbiotic relationship in which one organism benefits and the other is not affected
Mimicry : one species, the mimic, resembles another species, the model
Phylogeny
the study of evolutionary relationships between species
Illustrated with a phylogenetic tree based on many different things
Phylogenies are based on evidence from a combination of morphological, developmental structures, biochemical, and gene sequence.
Charecteristics of life
Growth, Reproduction, Adaptation, Movement, Metabolism, Irritability, Cells
Components of biodiversity
Diversity of genes - the total number of genetic characteristics that makeup a species; individuals in the same species have different genes
Diversity of species - diversity in the different number of species (species richness)
Diversity of ecosystems - the diversity of ecosystems present in the biosphere
Diversity of habitats - the range of sizes, shapes, and distribution of individuals
Diversity of Interactions - the interdependent of species creates stability
Biodiveristy Definition
The variety and number of life forms on earth
Taxonomy
The science of naming and classifying organisms based on similarities in structure and function
Helps identify and understand organisms
Domains
Eukarya (Plantae, Animalia, Protista, Fungi)
Eukaryotes, may be unicellular or multicellular
Bacteria (Eubacteria)
“Ture bacteria”
Prokaryotes, unicellular
Very diverse (over 4 million), only 4000 have been classified
Archaea(Archaebacteria)
“Ancient bacteria”
Prokaryotes, unicellular
Lives in extreme environments (volcanoes, low oxygen, high acidity)
Lytic Cycle
Attachment of receptor site - proteins in capsid specifically fits structure of the cell wall/membrane = specific virus-hort infection
Penetration - virus injects genetic material
Multiplication - Produces copies of viral genetic material and protein capsids. Transcription (duplication) of host cell DNA stops
Assembly - new viruses are assembled
Lysis - release of nes viruses that infect neighbouring cells
Lysogenic cycle
Viral DNA is combined with host DNA and forms a provirus (does not interfere with normal function)
Viral DNA can replicate along with the host cells DNA for many generations
Virus is reactivated by a stimulus (stress, UV light)
Re-entry into the lytic cycle
Ex. cold sores, chicken pox/shingles
Characteristics of Viruses
Viruses are not alive
Do not have their own cellular organization or metabolism
Do not grow larger and divide, they cause the host cell to make new viruses
Typically much smaller than cells
All are infectious
Classifications of Viruses
Based of size, shape, genetic material, and their host
RNA and DNA surrounded by a capsid (protein coat)
Some have a “membrane” but this comes from the host cell - attaches as it leave the cell
Viroids
Just RNA (no capsid), plant pathogens
Prions
Abnormal proteins cause abnormalities in hosts protein structure (i.e. mad cow disease)
Archaea
Single celled organism (unicellular)
Prokaryotes
Cell walls lack peptidoglycan
Genetically different than Eubacteria
Can live in extreme environment
Methanogens : lives in low oxygen environments, produces methane gas
Halophiles - salty environment
Thermophiles - hot environment (70 - 95)
Psychrophiles - cold environment (-10 - 20
Eubacteria
Small 1-10 uM (bigger than Archaea)
Single celled organisms
Flagella (movement)
Pili (attachment to other cells or surfaces)
The bacteria DNA is made of a single chromosome
Cell wall contains peptidoglycan (provides structure and support)
Reproductions of Prokaryotes
Asexual - Binary Fission
Can divide every 15-20 minutes under favourable conditions
Exact replication is made
Individual bacterial mutations are low, but because of high reproduction rate, overall mutations for bacteria are high
Sexual - Conjugation
Two bacterial cells come together via protein bridges where the plasmid of one cell is transferred to the other cell
The cell that receiver the plasmid has a different genetic material than before
This may cause the bacterial to develop traits that will davout changing conditions
Origin of eukaryotic cells (endosymbiosis)
Internal mitochondria and chloroplasts are thought to have originated from prokaryotes that were engulfed by another cell
Evidence
They have 2 membranes
Inner membrane is similar the prokaryote
Have this own chromosomes (circular)
Now “live” within another cell (mutualistic)
Characteristics of Protists
The first Eukaryotes
Single celled organisms OR multicellular with cells that are all the same (seaweed)
Sexual and Asexual reproduction
Extremely diverse in cell structure, nutrition, metabolism, reproduction and habitats (difficult to classify)
Key role in aquatic ecosystems
Many are parasitic
Alterations of Generations
Multicellular Diploid (Sporophyte) produces haploid reproductive cells (spores) through Meiosis. A spore will undergo cell division / Mitosis to grow into a multicellular organism (Gametophyte). The Multicellular Haploid will produce gametes (sperm and eggs) which fuse to produce a diploid zygote. Which then grows into a Multicellular organism
Characteristics of Fungi
Most multicellular, all heterotrophic, eukaryotes (lack chlorophyll)
Saprobes
Absorb nutrients from their environment by secreting enzymes to break down dead organic matter (decomposers)
Sexual and Asexual Reproduction
Most fungi contain hyphae (thread like filament; when hyphae continues to branch out (asexual) leads to the development of Mycelium)
Mycelium - used to absorb nutrients
Cell wall made of chitin (unlike cellulose in plants)
Reproduction of Fungi
All fungi can reproduce Asexually
Budding of binary fission
Fragmentation
Some reproduce sexually through spores - Alternation of Generations
General Characteristics of Plants
Multicellular eukaryotes with cell walls containing cellulose
Autotrophs : contain chloroplasts
Reproduce sexually and Asexually
Mostly terrestrial, variety of living conditions
Adapted for Land
Cuticle – waxy coating to prevent water loss
Stomata – open for gas exchange, close to prevent water loss
Phylum Characteristics of Plants
Bryophytes (mosses)
No real tissues - roots, stems, leaves
Produces spores
Lycophytes and Pterophytes (ferns)
Contains conducting tissues - xylem and phloem to transport water + nutrients = taller plants
Gymnosperms (conifers)
Specialized reproductive structure called cones : sexual reproduction
Male cones (pollen cones) produce pollen grains and the female cones (egg cones) produce ovules
Angiosperm (flowers)
Flowering plants
Reproduce sexually by pollenations
Can self pollinate or cross pollinate by way of bird, bees, insects, wind, and water
Characteristics of Animals
Multicellular, Eukaryotes (no cell wall), Heterotrophic
Cells can be organized into tissues (nervous and muscular tissue)
Most reproduce sexually- diploid in life cycle
Mostly mobile
Uses oxygen for aerobic respiration
No nerves ?
Porifera
No mesoderm ?
Porifera ; No nerves
Cnidaria ; Nerves
Protostome ?
Platyhelminthes ; reproduce by fission
Nematoda ; Parasitic
Annelida ; Segmented
Rotifera ; Small, aquatic
Mollusca ; Radula - tongue-like organ with many rows of teeth
Arthropoda ; Exoskeleton
Deuterostome ?
Echinodermata ; No head
Chordata ; Have a notochord or supporting rod
Common shapes and Living Arrangements for Prokaryotes (Classification)
Coccus (pl. Cocci) - round
Bacillus (pl. Bacilli) - rod shaped
Spirillum (pl. Spirilla) - Spiral
Diplo - two (Diplococcus)
Strepto - chain (Streptococcus)
Staphylo - clump (Staphylococcus)
Plasmid
Bacteria contain small rings of DNA other than the DNA chromosomes
Plasmids are located in the cell but are not necessary for the function of bacteria
Metabolism - Nutrition of Prokaryotes (Bacteria)
Most eubacteria are Heterotrophs
Parasites: absorb nutrient from living organisms
Saprobes: Decompose dead organic matter
Some eubacteria are autotrophs
Photoautotrophs : obtains energy from sunlight
Chemoautotrophs : obtain energy from chemical reactions
Metabolic Rate
Rate for converting stored energy into working energy
Depends on
Size : larger needs more energy
Activity Level : Muscles burn more than fat
Sex : males larger (typically more muscles)
Age : metabolism decreases with age
Heredity : genetics
Carbohydrates
Main source of energy
C,H, and O (Hydrocarbons)
3 main kinds:
Monosaccharide = one “base” unit (single sugar)
Disaccharide = two “base” units (double sugar)
Polysaccharides = more than two! (100s...)
Proteins
Control Chemical reactions
Movement (muscle fibers)
Hormones - chemical messengers
Enzymes - speed up/control chemical reactions
Polymers of AAs
20 different AAs used to build proteins
12 - non essential (we make from other AAs)
8 - essential (need to eat, cannot rearrange)
Lipids
Concentrated energy
Vitamin absorption
Cell membranes (vital)
Insulation
Hormones (ex. estrogen)
A lipid molecule usually consists of three fatty acids (Carbon/Hydrogen chains) bonded to a
“backbone” of glycerol.
Fats and Oils