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The Living Environment
The study of organisms and their
interactions with the environment.
Topics
• Unit 1:
• Unit 2:
• Unit 3:
• Unit 4:
• Unit 5:
Ecology
The Cell
Genetics
History of Biological Diversity
The Human Body
GENETICS
The science of heredity and the
study of how traits are passed on
from generation to generation.
Mendelian Genetics:
How Genetics Began
• Commonly referred to as the
“father of modern genetics”
Gregor Mendel, born in 1822
in what is now the Czech
Republic, published the first
known findings of heredity in
1866.
• His primary findings were
based on the study of pea
plants during his 14 year
tenure as an Austrian monk
in charge of the monastery
garden.
Mendelian Genetics
• While tending his plants,
Mendel was intrigued by the
pea plants because he
noticed that some were tall
while others were short;
some had white flowers and
some had purple flowers;
some had green peas and
others had yellow peas.
• Mendel was determined to
try to figure out what
determined these different
traits as well as others and
began experimenting.
Plant Sexual Reproduction
• Pollen, produced by the
anther, is transferred to
the stigma, travels down
the style into the ovary,
and fertilizes the ovule
producing a seed.
• Self-pollination occurs
when pollen is
transferred to the stigma
of the same plant.
• Cross-pollination occurs
when pollen is
transferred to the stigma
of another plant.
Mendelian Genetics
• Mendel began cross
pollinating plants with
similar traits and plants
with varying traits and
recording the outcomes of
these crosses in a journal.
• From these various
crosses performed over
many years, Mendel
concluded that traits are
passed on from one
generation to the next and
wrote three laws regarding
his findings.
Mendelian Genetics
• The Law of Dominance states
that certain traits exhibit
dominance over others which
are said to be recessive.
• In other words, if two different
alleles of the same trait are
combined to form offspring, all
of the offspring will exhibit the
dominant allele.
• The only way for the offspring
to express the recessive allele
would be for both inherited
alleles to be the recessive
form of the trait.
Mendelian Genetics
• The Law of Segregation, later
proven by the discovery of the
process of meiosis, states that
each gamete, produced by
each parent, receives only
one allele of each trait; thus
the alleles of each trait are
segregated amongst the
gametes.
• In other words, each sperm
and egg produced only carries
one allele for each trait
resulting in offspring who
receive one allele of each trait
from each parent.
Review of Meiosis
• Recall that meiosis results
in four daughter cells each
containing half the number
of chromosomes as the
original cell and half the
alleles of each gene.
• These daughter cells are
also genetically different
from the parent cell and
from each other due to
cross-over that occurs
during prophase of
meiosis I.
Mendelian Genetics
• The Law of Independent
Assortment states that traits
are inherited independently
of each other.
• For example, with Mendel’s
pea plants, the trait for plant
height is inherited
separately from the trait for
pea color or flower color.
• This law does not apply to
all traits in all organisms as
some traits are genetically
linked and are inherited
together.
Probability and Punnett Squares
• A genotype is a pair of
letters representing a
particular genetic makeup,
or type of genes. These
letters are chosen based
on the dominant allele.
• A phenotype is the
physical characteristic
exhibited by the organism
as a result of its genotype.
• An organism’s phenotype
is dependant on its
genotype.
Probability and Punnett Squares
• A homozygous pair of alleles is
represented by any two of the
same letters, either both capital
or both lowercase. This is
known as a purebred trait,
where both alleles are identical.
• It is possible for a homozygous
trait to be dominant or
recessive.
• A heterozygous pair of alleles is
represented by two different
letters, one capital and one
lowercase. This is known as a
hybrid trait and will always
exhibit the dominant phenotype.
Probability and Punnett Squares
• In the early 1900’s Dr.
Reginald Punnett
developed the Punnett
Square to predict the
possible offspring of a
cross between two
known genotypes.
• Mendel’s journals show
that even he was able
to produce the ratios of
offspring that we can
now easily calculate
using Punnett Squares.
Probability and Punnett Squares
• A monohybrid cross is a
cross involving hybrids of
a single trait.
• A monohybrid cross of the
F1 generation will always
result in 75% of the
offspring exhibiting the
dominant trait.
• A monohybrid cross
results in a genotypic ratio
of 1:2:1 and a phenotypic
ratio of 3:1.
Probability and Punnett Squares
• A dihybrid cross is a cross involving hybrids of two
different traits at the same time using a single Punnett
Square.
• A dihybrid cross results in a genotype and phenotypic
ratio of 9:3:3:1.
• Dihybrid crosses can be used to prove Mendel’s Law
of Independent Assortment.
Incomplete Dominance
• Cases in which one
allele is not completely
dominant over another
are called incomplete
dominance.
• These traits are
sometimes referred to
as “blending” traits.
• Examples include pink
carnations and
palomino horses.
Examples of Incomplete Dominance
+
=
Codominance
• Codominance occurs
when both alleles (from
each parent) contribute
to the phenotype of the
offspring because
neither is dominant.
• Codominance results in
a heterozygous (hybrid)
organism such as a
roan cow which has
both red and white
hairs.
Polygenic Traits
• Traits controlled by two or more genes are
called polygenic traits.
• Polygenic traits often result in a wide range of
phenotypes such as the range of eye colors or
the range of skin tones in humans.
The Discovery of DNA
• Although Mendel’s journals were
discovered around the turn of
the 20th century, scientists
lacked the technology to perform
genetic research in any greater
detail than Mendel himself until
about 1940.
• In 1944, Oswald Avery and his
team determined that genes
were composed of biochemical
molecules called
DeoxyriboNucleicAcid (DNA).
DNA as a Double Helix
• In 1951, Linus Pauling and
Robert Corey determined that
proteins like those found in the
DNA molecule were a helical
type of structure.
• In 1952, Rosalind Franklin using
a technique called X-Ray
diffraction took a “picture” of the
DNA molecule.
• In 1953, James Watson and
Francis Crick developed the
double-helix model of the
structure of DNA.
DNA – The Double-Helix
• DNA, sometimes referred
to as a twisted ladder or
spiral staircase, is a very
long chain molecule,
consisting of sub-units
called nucleotides.
• Each nucleotide is made
up of three basic
structures:
 A sugar called
deoxyribose
 A phosphate group
 A nitrogenous base
DNA Structure
• The backbone of the DNA
structure, or side rails,
are formed by the sugarphosphate groups of
each nucleotide.
• Connecting the two rails
of the DNA structure are
four types of nitrogenous
bases:
 Thymine (T)
 Adenine (A)
 Cytosine (C)
 Guanine (G)
DNA Structure
• The side rails of the twisted
ladder are attached by the
pairing of the nitrogenous
bases extending from each
side of the DNA molecule,
creating the rungs of the
ladder.
• Adenine always pairs with
Thymine, while Guanine
always pairs with Cytosine,
thus creating the base
pairs:
A – T
G – C
DNA Structure
Chromosome Structure
• Chromosomes consist of
tightly packed coils of
DNA called chromatin.
• Chromatin consists of a
DNA molecule tightly
wound around proteins
called histones.
• DNA consists of
nucleotides which code
for individual genes.
• Chromosome
Chromatin
Largest
• Chromosome
Chromatin
DNA
DNA
Gene
Smallest
Nucleotide
DNA Replication
• During DNA replication, the DNA molecule separates
into two strands, then produces two new
complimentary strands following the rules of base
pairing.
• Each strand of the double-helix serves as a template
for the new strand.
DNA Replication
• DNA replication is carried out by a series of enzymes.
• These enzymes “unzip” the DNA
molecule by breaking the bonds of
the base pairs, then synthesize a
complimentary strand of DNA for
each of the original strands.
DNA Replication
The Structure of RNA
• RNA, like DNA, consists
of a long chain of
nucleotides, each made
up of a sugar, phosphate
group, and a nitrogenous
base.
• RNA differs from DNA in
three main ways:
 The sugar is ribose.
 RNA is single stranded.
 RNA contains Uracil (U)
in place of Thymine.
Function of RNA in Cells
• The primary function of RNA in cells is protein
synthesis.
• The assembly of amino acids into proteins is
controlled by RNA.
• The three main types of RNA are:
 mRNA (messenger)
 rRNA (ribosomal)
 tRNA (transfer)
Protein Synthesis
• RNA is produced within a
cell from a strand of DNA
through a process called
transcription.
• mRNA is transcribed in
the nucleus, enters the
cytoplasm, and attaches
to a ribosome.
• Next, translation of the
mRNA strand occurs with
assistance from tRNA
within the ribosome,
synthesizing proteins
from amino acids.
Protein Synthesis
• Proteins are made by
joining amino acids into
long chains called
polypeptides.
• Each polypeptide
consists of a combination
of any or all of the 20
different amino acids.
• The properties of these
proteins are determined
by the order in which the
amino acids are joined to
form the polypeptides.
The Genetic Code
• The “language” of mRNA
instructions is called the
genetic code.
• This code is written in a
language that has only
four letters, AUCG.
• The code is read three
letters at a time so that
each word of the coded
message is three bases
long.
• Each three letter word is
known as a codon.
The Genetic Code
• A codon consists of
three consecutive
nucleotides that specify
a single amino acid
that is to be added to
the polypeptide.
• There are 64 possible
three-base codons.
• Some amino acids can
be specified by more
than one codon.
Amino Acids
The Roles of RNA and DNA
• DNA acts as the “master
plan” and is stored safely
within the nucleus of the
cells of an organism.
• DNA controls every
action of a cell and
essentially every
characteristic of an
organism by producing
“blueprints” in the form of
RNA which will translate
into proteins that control
cellular functions and
characteristics.
Genetic Mutations
• Mutations are changes in
the DNA sequence that
affect genetic information.
• Gene mutations result
from changes in a single
gene.
• Chromosomal mutations
involve changes in whole
chromosomes.
• Mutations can be
beneficial to an organism,
deleterious to an
organism, or have no
effect at all.
Gene Mutations
• Mutations that affect one nucleotide are called point
mutations.
• Some point mutations substitute one nucleotide for
another, resulting in a change in the translated amino
acid in a protein.
Gene Mutations
• If a nucleotide is inserted
or deleted, a frameshift
mutation can occur.
• Frameshift mutations
typically result in big
changes in the translated
amino acids of the protein,
often altering the protein
so it is unable to perform
its normal functions.
Chromosomal Mutations
• Chromosomal mutations
involve changes in the
number or structure of
chromosomes.
• These mutations can
result in the deletion of
genes from
chromosomes, the
inversion of genetic code,
translocation, and
duplication of genes on
chromosomes.
Human Traits
• A pedigree is a diagram used to show how a
particular genetic trait is passed down from generation
to generation – a genetic family tree.
• Squares represent males and circles represent
females. A horizontal line connecting a square and
circle illustrates a parental generation. Siblings are
always drawn with the oldest to the left, youngest to
the right.
Pedigrees
• Pedigrees can illustrate carriers of a genetic trait, as
well as those exhibiting the effects of the trait.
• Fully shaded squares/circles represent individuals
who exhibit the trait. (Homozygous dom./rec.)
• Half shaded squares/circles represent individuals who
carry the trait but who do not exhibit the effects of the
trait. (Heterozygous)
Pedigree of the Royal Family
Human Heredity
• A karyotype is a micrograph
of the pairs of homologous
chromosomes, taken during
mitosis.
• Human cells each contain
22 pairs of autosomes and
one pair of sex
chromosomes equaling a
total of 23 pairs (or 46) total
chromosomes.
• Females have identical sex
chromosomes (XX) while
males have two different sex
chromosomes (XY).
Autosomal Recessive Disorders
Autosomal Dominant Disorders
Sex-linked Genes
• Many genes are found on the X and Y chromosomes
and are therefore referred to as sex-linked genes.
• More than 100 sex-linked disorders have been
mapped on the X chromosome.
• Sex-linked disorders include:
 Colorblindness
 Hemophilia
 Duchenne Muscular
Dystrophy
Colorblind Test
Sex-linked Disorders
Chromosomal Disorders
• A typical chromosomal disorder results from an error
during meiosis called non-disjunction; when
chromosomes do not separate evenly resulting in
trisomy, or three copies of a particular chromosome
instead of the usual two copies.
• Non-disjunction
typically leaves
some gametes
containing only one
copy of a
chromosome,
known as
monosomy.
Chromosomal Disorders
• Alterations of
chromosome number
are serious, often fatal
disorders.
• Down Syndrome, or
trisomy 21, occurs due
to non-disjunction
resulting in offspring
with 47 chromosomes;
an extra chromosome #
21.
Chromosomal Disorders
• Non-disjunction in sex
chromosomes can lead
to disorders such as
Turners Syndrome (X)
and Kleinfelter’s
Syndrome (XXY).
• Individuals with either of
these disorders are
sterile and therefore
cannot reproduce and
pass on their genetic
disorder.
Extra Genetic Material Disorders
Chromosomal Disorders
• Cri-du-chat is a genetic
deletion disorder
whereby a part of the
#5 chromosome was
deleted during DNA
replication.
• Typical effects of this
disorder include mental
retardation, pinched
facial characteristics,
and a cat-like cry.
Genetic Deletion Disorders
Multifactorial Chromosome Abnormalities
DNA Analysis
• Gel electrophoresis is a
technique used to
separate DNA
fragments.
• Separating DNA
fragments is useful in
mapping a DNA
fingerprint in order to
solve criminal
investigations and to
perform genomic
evaluations.
Gel Electrophoresis
• DNA is extracted from a
cell(s), then cut into
segments using a
restriction enzyme.
• The DNA segments are
then separated using gel
electrophoresis.
• The segments are injected
into wells at one end of an
agarose gel.
• Once electricity is applied
across the gel, the
segments of DNA will
spread across the gel.
Gel Electrophoresis
Gel Electrophoresis
• These segments can be viewed under UV light.
• A special camera is then used to photograph the gel
for comparison purposes or for use in court.
DNA Fingerprinting
• Short segments will
travel further down the
gel while long segments
will stay closer to the
wells.
• DNA fingerprinting can
be used to identify a
suspect in a criminal
investigation or
determine the father of
a child.
Human Genome Project
• The Human Genome Project began
in 1990, headed up in the US by
James Watson, and was completed
in June 2000, after a collaborative
effort by geneticists around the
globe.
• The goal was to determine the sequence of base
pairs for the entire human genome and map all
30,000 genes in a human DNA strand.
Key Findings of the Project…
• 1. There are approx. 30,000 genes in human beings, the
same range as in mice and twice that of roundworms.
Understanding how these genes express themselves will
provide clues to how diseases are caused.
• 2. All human races are 99.99 % alike, so racial differences
are genetically insignificant. This could mean we all
descended from the original mother who was from Africa.
• 3. Most genetic mutation occur in the male of the species.
So men are agents of change. They are also more likely to
be responsible for genetic disorders.
• 4. Genomics has led to advances in genetic archaeology
and has improved our understanding of how we evolved as
humans and diverged from apes 25 million years ago. It
also tells how our body works, including the mystery behind
how the sense of taste works.
Genetic Engineering
• Genetic engineering is the purposeful altering or
selection of certain traits in an organism.
• Selective breeding is an indirect method of genetic
engineering.
• Selective breeding is the purposeful mating of
organisms with particular traits in order to produce
offspring that exhibit the desired trait(s).
Genetic Engineering
• Hybridization is a method
of selective breeding
whereby two parents, each
exhibiting different desired
traits are crossed to
produce a more desirable
product.
• Inbreeding is the continued
breeding of individuals with
the desired characteristics,
typically between members
of the same “family” or
same group of offspring.
Genetic Engineering: Manipulating DNA
• DNA can be cut and
pasted to form a “new”
strand of DNA called
recombinant DNA.
• Enzymes are used to cut
and paste the strands of
DNA.
• PCR is a technique used
to build recombinant
DNA.
• The recombinant DNA
can then be inserted into
an organism, thus altering
their genetic code.
Genetic Engineering: Cell Transformation
• During transformation,
a cell takes in DNA
from outside the cell.
• This external piece of
DNA becomes part of
the cell’s DNA.
• Plasmids are small,
circular DNA molecules
commonly found in
bacteria.
• Once reinserted into
bacterial cells, those
cells can be used to
transform other cells.
Genetic Engineering: Cell Transformation
• Bacteria cells containing the recombinant DNA
plasmid can be used to alter the DNA in plant or
animal cells in order to alter that organism’s genetic
code.
• This procedure might be performed to genetically
engineer a plant to have better resistance to insects
or a cow to produce more milk.
Genetic Engineering: Cell Transformation
Genetic Engineering: Transgenic Organisms
• Transgenic organisms
are genetically
engineered organisms,
created by inserting a
gene(s) from one
organism into another.
• Genetically modified
organisms are created to
study various traits in
different organisms as
well as to produce more
useful organisms such as
livestock that produce
more growth hormone.
Genetic Cloning
• Genetic cloning involves
the artificial
reproduction of an
organism that will be
genetically identical to
its parent organism.
• The first organism
reported as being
successfully cloned was
a sheep named ‘Dolly’,
reportedly cloned in
Scotland in 1996.
Genetic Cloning
• Dolly was cloned by inserting the DNA from a somatic
cell of one sheep into the egg cell, whose nucleus had
been removed, of another sheep; then electrically
stimulating the egg and implanting the embryo into the
uterus of the surrogate mother.
Genetic Cloning
• It has long been theorized that extinct organisms
might be resurrected if we could collect the
organisms’ DNA from fossilized remains.
• The recently discovered baby mammoth will soon
undergo a cloning-like process in an attempt to
resurrect this long extinct creature.
• However, an ethical question must first be
answered…should it be done if we can manage to do
it?
• Mammoth Resurrection