Biology Gr.11

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

1. Homologous chr fail to separate during Meiosis 1

2. 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

1. Diversity of genes - the total number of genetic characteristics that makeup a species; individuals in the same species have different genes

2. Diversity of species - diversity in the different number of species (species richness)

3. Diversity of ecosystems - the diversity of ecosystems present in the biosphere

4. Diversity of habitats - the range of sizes, shapes, and distribution of individuals 

5. 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

1. Attachment of receptor site - proteins in capsid specifically fits structure of the cell wall/membrane = specific virus-hort infection 

2. Penetration - virus injects genetic material

3. Multiplication - Produces copies of viral genetic material and protein capsids. Transcription (duplication) of host cell DNA stops 

4. Assembly - new viruses are assembled

5. 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

1. 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

2. 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

1. Bryophytes (mosses)

• No real tissues - roots, stems, leaves

• Produces spores

2. Lycophytes and Pterophytes (ferns)

• Contains conducting tissues - xylem and phloem to transport water + nutrients = taller plants 

3. Gymnosperms (conifers)

• Specialized reproductive structure called cones : sexual reproduction

• Male cones (pollen cones) produce pollen grains and the female cones (egg cones) produce ovules 

4. 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