Transcript Mendel`s Experiments

Mendel’s Experiments
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1.
2 Types of Fertilization:
Self-pollination: pollen fertilizes the egg
cells in the very same flower.
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They inherit all the characteristics of the
single parent that bore them.
This is called true-breeding.
Mendel used true breeding plants.
Mendel’s Experiments
2.
Cross-pollination
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Male cells in the pollen of one flower
fertilize the egg cells of another plant.
Mendel controlled this by cutting off the
male anthers of one plant and dusting
that flower with the pollen from another
plant.
Terms
 Phenotype: physical characteristics
 Genotype: set of alleles, genetic makeup, RR,
Rr, rr
 Homozygous: 2 identical alleles for a certain
gene. Example: RR or rr
 Heterozygous: 2 different alleles for a gene.
Example: Rr (a hybrid)
Your numbers
should always
add up to 16!
Codominance
 Codominance: both alleles show up in the
phenotype of the organism
 Roan Cows
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Coat has both red and white
 Speckled chickens
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Feathers are black and white
Multiple Alleles
 Multiple Alleles: genes with more than two
alleles
 Four alleles in rabbits can produce four
possible combinations of coat color. (Fig. 1112 on pg. 273)
 Human blood type is also determined by
multiple alleles –A, B, and O
Polygenic Traits
 Polygenic traits: traits produced by a
combination of several genes.
 Examples
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Human eye color, this is why there are so many
different shades
Human skin color
Height and weight
2 Kinds of Reproduction
 Asexual Reproduction
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Only one parent is needed
Somatic (body) cells are copied by Mitosis
 Sexual Reproduction
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2 parent cells produce a new individual
Production of sex (germ) cells occurs through
Meiosis
Chromosome Number
 Diploid (“two sets”) cells have both sets of
homologous chromosomes (the set from the male
and the set from the female)
 Diploid is represented 2N
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for fruit flies 2N = 8
for humans 2N = 46
Chromosome Number
 Haploid (“one set”) cells have only a single set of
chromosomes, so a single set of genes.
 Haploid is represented N
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for fruit flies N = 4; for humans N = 23
 Sex cells (gametes) are haploid cells
 Somatic (body) cells are diploid cells
Meiosis
 The result:
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Four new haploid daughter cells
Each of the four cells is different because
of crossing-over.
Ch. 12 DNA
Structure of DNA
 3 parts of a nucleotide:
1.
2.
3.
5-carbon sugar called deoxyribose
A phosphate group
A nitrogenous base
DNA
Replication
Structure of RNA
RNA
 Ribose sugar
 Single-stranded
 Uracil replaces
thymine to pair with
adenine
DNA
 Deoxyribose sugar
 Double-stranded
 Thymine pairs with
adenine
3 Types of RNA
 Messenger RNA (mRNA)—carries copies
of instructions for assembling amino acids
into proteins.
 Ribosomal RNA (rRNA)—contained in the
ribosome where proteins are made.
 Transfer RNA (tRNA)—transfers amino
acids to the ribosome; anticodon
Codons
 Codons are three-letter “words” in mRNA
 Three consecutive nucleotides code for
an amino acid
 There are 64 possible three-base
codons for mRNA (4x4x4=64)
Recap
 Transcription happens in the nucleus
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DNA to mRNA
 Translation happens in the cytoplasm
(ribosome)
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mRNA to polypeptide
 mRNA has the codons, tRNA has the
anticodons and the amino acids
Reading a DNA Fingerprint
Gene Mutations
 Point mutations: affect only one nucleotide
1. Substitutions
THEFATCAT
THEFTTCAT
Ex.-Sickle cell anemia
ATCCGGACT
ATCGGGACT
Gene Mutations
 Frame shift mutations: change in one nucleotide
affects all following nucleotides
2. Insertion
THEFATCAT
THEFAATCAT
ATCCGGACT
ATCCGGGACT
3. Deletion
THEFATCAT
THEFTCAT
ATCCGGACT
ATCGGACT
Chromosomal Mutations
 Change in the number or structure of
chromosomes.
1. Deletion: loss of all or part of a chromosome
2. Duplication: segment of chromosome is repeated
3. Inversion: segments are reversed
Chromosomal Mutations
4. Translocation: part breaks off and
attaches to a non-homologous
chromosome
5. Insertion: gain part of or a whole extra
chromosome.
Human Chromosomes
 Humans have 46 chromosomes (23 pairs)
 1 pair (#23) are sex chromosomes
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XX for female
XY for male
 The other 22 pairs are called autosomes.
Karyotyping
 Karyotypes make it easy to see any chromosomal
abnormalities in an individual.
Normal male
karyotype
www.wikipedia.org
p.342
Human Blood Groups
 Human blood is divided into 2 groups: ABO and
Rh.
 Rh blood group is determined by a positive or
negative allele of a single gene.
 Rh stands for “rhesus monkey” because it was
discovered in this animal.
 The second group, ABO, is determined by three
alleles for the gene (multiple alleles).
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A, B, and O.
Also written IA, IB, and i.
 A and B are codominant, neither is stronger or
dominant over the other.
 Type O is recessive.
 It is important to know blood types for
transfusions.
 Type O- is the universal donor.
 AB+ is the universal acceptor.
 - can only receive from –
 + can receive from + or – since + is dominant.
 + can only donate to +
 - can donate to + or -
Chromosome 21
 Similar to 22
 Associated with ALS or Lou Gehrig’s
Disease
 Loss of muscle control due
to destruction of nerves
Sex-Linked Genes
 Genes on X are called sex-linked
 More than 100 sex-linked disorders on X
 Y only has a few genes because it’s
small
 We will study 3 sex-linked disorders:
colorblindness, hemophilia, duchenne
muscular dystrophy
1. Colorblindness
 In males, if the X chromosome is affected, he will
be colorblind
 Defective version of genes produces
colorblindness in males.
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Red-green colorblindness: 1 in 8 males in US
 Colorblindness is very rare in females. Why?
Other Sex-linked Disorders
2. Hemophilia
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Missing a protein required for blood clotting
A recessive allele in 1 of 2 genes causes it
Can bleed to death
Royal family in England
Occurs in 1 out of 10,000 males
Chromosomal Disorders
 Nondisjunction: (“not coming apart”) homologous
chromosomes fail to separate during meiosis.
 May cause extra chromosomes.
 Trisomy- three copies of a chromosome
Down’s Syndrome
 Down’s Syndrome: Trisomy 21, three
copies of #21.
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Mild to severe mental retardation
Birth defects
More susceptible to diseases
Sex Chromosome Disorders
 Turner’s syndrome: a female with only
one X chromosome (XO)
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Cannot have children
Usually short
May have cognitive limitations
1 in 2500 females
Webbed neck
Hands and feet swollen
Sex Chromosome Disorders
 Klinefelter’s Syndrome: males with an
extra X chromosome (XXY) or (XXXY)
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Cannot have children
Breast enlargement
1 in 500-1000 males
Lack of facial hair, overweight
Why aren’t they females?
Human Genome Project
 Attempt to sequence all human DNA
 Began in 1990
 Essentially complete in June 2000
 Still in progress
 Estimated 30,000 genes
Gene Therapy
 Replaces a missing or faulty gene with a
normal gene
 Enables protein production
 First attempt in 1990
Key Words
 Biotic: living factors that shape an ecosystem,
ex.- birds, trees, animals, etc.
 Abiotic: non-living factors that shape an
ecosystem, ex.- climate, wind, soil, etc.
 Autotrophs: producers, make own food,
ex.- plants
 Photosynthesis: using light energy to produce
sugar or starch
 Chemosynthesis: using chemical energy to
produce carbohydrates. Ex.-bacteria in hot
springs in Yellowstone Park.
 Heterotrophs: consumers, eat other organisms for food
and energy
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Herbivores- eat plants.
Ex.-cows, deer, rabbits
Omnivores- eat plants or animals.
Ex.-humans, bears
Carnivores- eat animals.
Ex.- snakes, lions
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Detritivores- feed on plant and animal remains
ex.- snails, crabs, earthworms
Decomposers- break down
food from dead organisms
ex.- bacteria & fungi
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Food Chain
 Energy flows in one direction:
Producers
Primary
Consumers
Secondary
Consumers
Tertiary
Consumers
Food Web
 Links all food chains
in an ecosystem.
 Each step is called
a trophic level
(determines the
source of energy)
Ecological Pyramids
Secondary
carnivores
4th level
 Trophic levels are
diagramed on
ecological
pyramids
 P. 72
Primary
carnivores
Herbivores
Producers
3rd level
2nd
level
1st
level
www.eelsinc.org/id64.html
Energy Pyramids
 Only 10% of energy is transferred as you
go up the pyramid.
 90% of energy is lost from one trophic
level to the next.
 More levels between consumer and
producer = less energy gained.
Key words/ideas
 Niche: the role an organism plays in its
environment. It’s “occupation”
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the conditions in which an organism lives
and the way it uses them
 Habitat-area where an organism lives. It’s
“address”
-Includes biotic and abiotic factors.
 No 2 species can
occupy the same
niche in the same habitat.
 Resources-necessities
of life-water, food, light,
space
Community
1. Competition: two organisms try to use
the same resource in the same place at
the same time
 Competitive Exclusion Principle: If 2
species are competing, the one that
uses the resources more efficiently will
eliminate the others.
Community
2. Predation: one organism (predator)
feeds on another (prey). This will
decrease competition.
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Can be active or passive
Community
3. Symbiosis- “living together”
a. Mutualism: both species benefit, ex-flowers depend
on insects for pollination, insects get food; lichens
(algae and fungus)  
Symbiosis
b. Commensalism: one member benefits, the other is
not helped or harmed, ex-barnacles on a whale
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c. Parasitism: one member benefits, the other is
harmed, ex-tapeworms, fleas, ticks
 
Ecological Successionchanges over time
 Primary—on land where nothing has grown
before.
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Pioneer species: first inhabitants, lichens, volcanic
eruptions
 Secondary—occurs where there has been
previous growth
- abandoned farmland,
fires see p. 94
Definitions
 Biome: a large land region with certain plants
and animals.
 Ecosystem: the living and nonliving things in an
area interacting with each other
 Climate: the average temperature and
precipitation pattern of a region
 Microclimate: small area that differs from the
climate around it. Ex.- California has redwood
forest & a few miles away is the desert.
Population Growth
 3 factors affecting population size:
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Number of births
Number of deaths
Number of individuals entering (immigration) or
leaving (emigration)
 Growth = birthrate > than death rate
 Shrinking = birthrate < than death rate
Exponential Growth
 Reproduction at a constant rate.
 J shaped curve.
 With ideal conditions and unlimited resources
this happens.
Logistic Growth
 Growth slows or stops. S shaped curve.
 Less resources available.
 Birthrate <, death rate >.
History
 Carolus Linnaeus was a Swedish physician who
founded taxonomy
 Taxonomy: identifying, classifying,
and naming living things.
 He tried to classify organisms with similar
structures.
 He founded the binomial nomenclature system =
2 names
 Scientific names have two parts
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Genus (written with a capital letter)
Species (not capitalized)
 Scientific name is written in italics in Latin
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Grizzly bear = Ursus arctos
Polar bear = Ursus maritimus
cation
Species
Genus
Family
Order
Class
Phylum
Kingdom
Kingdoms and Domains
 3 Domains: 6 Kingdoms
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Bacteria: Eubacteria
Archaea: Archaebacteria
Eukarya: Protista, Fungi, Plantae, Animalia
Kingdom Archaebacteria
 Live where other organisms can’t survive
 Hot springs
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Water is 194°F
 Absorb food
 Extremophiles:
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halophiles,
thermophiles, acidophiles
Kingdom Eubacteria
 Live in soil, water, and human body
 Some are helpful and some are harmful.
 Absorb food
 E. coli
Kingdom Protista
 Single-celled or simple multicellular
 Eukaryotes (have a nucleus)
 May have evolved from ancient bacteria
 Most diverse kingdom
Kingdom Fungi
 Complex multicellular organisms
 Absorb nutrients from decomposing
organisms
 Mushrooms, molds, yeast
Kingdom Plantae
 Plants are multicellular eukaryotes
 Make sugar for food by
photosynthesis
 Many different sizes and forms
 Giant sequoia, ferns, flowers, etc.
Kingdom Animalia
 Complex multicellular organisms
 Consumers: feed on other plants
or animals
 Most move from place to place
and have nervous systems
 Many different types of animals
Body Parts
 Segmented body, exoskeleton, and jointed
appendages
 Specific to insects—
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Head
Thorax
Abdomen
3 pairs of legs (attached to thorax)
Darwin’s Data
 He paid special attention to:
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Land tortoises
Marine iguanas
Finches
Darwin’s Work
 Natural variation: all organisms display
differences within the species
 Artificial selection: nature provides variation,
humans choose varieties that are most
beneficial.
 Natural Selection: only certain individuals of a
population successfully reproduce.
Animal Adaptation
 An adaptation is a change to adjust to
environmental conditions.
 Adaptation is change that increases the chance
of survival.
 This change takes place over several
generations.
http://home.honolulu.hawaii.edu/~pine/book1qts/embryo-compare.html
Analogous Structures
 They perform the same or similar
function by a similar mechanism but
evolved separately
 Ex.- the wings on butterflies,
bats, and birds.
The wings of pterosaurs (1), bats (2) and birds (3)
Relative Dating
 Estimate fossils’ age
compared to other fossils
 Layers of rock are studied
and age is estimated
 Top layers are most
recent, and bottom layers
are the oldest
Radioactive Dating
 Isotopes break down at a constant rate
 Half-life is length of time required for half
the radioactive atoms to decay
 Carbon-14 has half-life of 5730 years
 Carbon-12 is not radioactive; does not
decay
time
 Divided into eras and
periods
Cenozoic
Mesozoic
 Represents evolutionary
Paleozoic
Geologic Time
Scale (p. 421)
Era
Precam
brian
Period
Time(mya)
Quaternary
1.8-present
Tertiary
65-1.8
Cretaceous
145-65
Jurassic
208-145
Triassic
245-108
Permian
290-245
Carboniferous
363-290
Devonian
410-363
Silurian
440-410
Ordovician
505-440
Cambrian
544-505
Vendian
650-544