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Genetics
Genetics
Genetics
– the study of heredity
• heredity?
– passing of traits from parents to offspring
• Traits
– Distinguishing characteristics that are inherited, ie
eye color, leaf shape, tail length
Father of genetics
Gregor Mendel
• born in Austria, 1822
• monk, lived in monastery
• worked with pea plant
• work published in
1900’s,after his death
Genetics
Father of genetics
• Why was the pea plant so good?
– grow easily
– available
– self pollinating
– display traits easy
to see
– produce a large
number of offspring
Genetics
Father of genetics
• 7 main traits
Genetics
Genetics
Generations
• Mendel would cross pollinate the pea plants
with different traits and observe the offspring
produced.
• cross between parents with different traits is
called a hybrid
• P = parental generation
• F means filial
– F1 generation = offspring from the parent
– F2 generation = offspring from offspring
from parents.
Generations
Genetics
Genetics
Mendel’s Laws
• Cross between smooth x wrinkled seeds
– F1 = all smooth
Genetics
Mendel’s Laws
• Mendel concluded that alleles segregate from
each other during the formation of gametes
• Law of Segregation
– Organisms inherit two copies of each gene,
one from each parent.
– Organisms donate only one copy of each
gene in their gametes, thus 2 copies of each
gene segregate, or separate, during
gamete formation.
Genetics
Mendel’s Laws
• Law of Segregation
– Ex GG plant will send an G allele while a gg
plane will send a g allele
– What alleles can a Gg plant give?
– G or g
The same gene can have many
versions!
• Allele- any of the alternative forms of a
gene that may occur at a specific locus.
• They may be HOMOZYGOUS-two of the
same alleles at a specific (could both be
white flowers)
• Or they may be HETEROZYGOUS-two
different alleles at a specific locus. (one for
white, one for purple!)
Genes influence the development
of traits
• Genome-ALL of an organism’s genetic
material
• Genotype-refers to the genetic makeup of a
specific set of genes
• Phenotype-physical characteristics, or
traits, of an individual
– Hidden genes don’t matter in the phenotype
Genetics
Mendel’s Laws
• Law of Dominance
– some alleles are dominate (CAPITAL letter)
and some are recessive (lower case letter)
– ex the allele for tall
(T) pea plants is
dominant to the
allele for short (t)
pea plants
- An allele is dominant simply b/c it in a
heterozygote it is expressed and the other
allel is not.
Genetics
Punnett square
– A grid system for predicting all possible
genotypes resulting from a cross.
• The axes represent the possible gamete genotypes of
each parent
• Grid boxes show possible genotype of offspring from
those two parents.
– find genotypes
of parents
– purple Pp
– purple Pp
• segregate alleles
– P p; P
p
Genetics
Punnett square
Looking at results
• How many of each genotype are possible
– 1 PP, 2 Pp, 1pp
• know the phenotype of each genotype
Genetics
Punnett square
Looking at results
• How many of each genotype did you made
– 1 PP, 2 Pp, 1pp
• know the phenotype of each genotype
• 1PP homozygous dominant
• 2Pp heterozygous
• 1pp homozygous recessive
Punnett square
Looking at results
• know the genotype ratio
– 1 PP: 2 Pp: 1pp
– 1:2:1
– A hybrid cross will
always give you a
1:2:1 ratio
Genetics
Punnett square
Looking at results
• know the phenotype ratio
– 3 purple:1 white
– 3:1
Genetics
Mendel’s Laws
• Cross between
smooth x wrinkled
seeds
– F1 = all smooth
– F1 x F1
– F2 = 3 smooth,
1 wrinkled
• Monohybrid cross
– Examine the inheritance
of only 1 specific trait.
Genetics
Genetics
Mendel’s Laws
• Cross between smooth x wrinkled seeds
– F1 = all smooth
– F1 x F1
– F2 = 3 smooth, 1 wrinkled
• Where did the recessive trait in the F2 come
from?
– some how they were carried but not
expressed in the plant
Mendel’s Laws
• Looking at two different
traits at the same time,
Mendel found they were not
always paired together.
– ex yellow & round
do not always
show up together
in offspring
Dihybrid crosses-examine
the inheritance of two
different traits
Genetics
Genetics
Mendel’s Laws
• Law of Independent Assortment
– alleles for different traits segregate
independently of one another
• ex yellow seed color is independent of smooth
seed texture
– getting one trait does not
guarantee you another
trait
Mendel’s Laws
• Law of Independent Assortment
– made possible because of?
– Meiosis
Genetics
NON-MENDELIAN GENETICS
Genetics
Patterns of Inheritance
incomplete dominance
• neither allele is dominant to the other
• both are expressed equally, often a blending
of the two traits occurs
Patterns of Inheritance
incomplete dominance
• CR is not
dominant to CW
Genetics
Genetics
Patterns of Inheritance
codominance
• two or more alleles are expressed at the same
time
• both are expressed in patches on the
organism
Patterns of Inheritance
codominance
• CS and CD
are both
expressed
in patches
Genetics
Genetics
Patterns of Inheritance
codominance
• human blood types
– blood types code for protein on surface of
red blood cells
– A, B, O, AB
Patterns of Inheritance
codominance
• human blood types
Genetics
Patterns of Inheritance
codominance
• human blood types
Genetics
Genetics
Patterns of Inheritance
codominance
• human blood types
– cross a father with AB blood with mother O
blood
Genetics
Patterns of Inheritance
• human blood types also demonstrate multiple
alleles
• multiple alleles refer to a trait (one gene)
which is coded for by more than two alleles
– What alleles are present in human blood?
– IA, IB, i
Genetics
Patterns of Inheritance
Determining sex of offspring
• punnett square can help predict the sex of
offspring
• female is
– XX
• male
– XY
Genetics
Patterns of Inheritance
sex-linked traits
– traits found on sex chromosomes, X or Y
chromosome
(all non-sex chromosomes are autosomes)
• X chromosome is larger = more traits
• female is XX, male XY
– traits on the X chromosome are more likely
to be expressed in males
– ex hemophilia, colorblindness
Patterns of Inheritance
sex-linked traits
• sex-linked
dominant
Genetics
Patterns of Inheritance
sex-linked traits
• sex-linked
recessive
Genetics
Genetics
Tracking inheritance
• pedigree
– traits can be tracked over several
generations
– affected individuals
Genetics
Tracking inheritance
• karyotyping
– tool used to look at chromosomes of
individuals to look for mutations
Genetics
Tracking inheritance
• nondisjunction
• failure of chromosomes to separate during cell
division
Tracking inheritance
• nondisjunction
Genetics
Frontiers of Biotechnology!
I. DNA manipulation
A. During recent years, scientists have
developed a technique to manipulate DNA,
enabling them to study DNA and genes.
B. A DNA molecule is too small for a
scientist to cut themselves, so it is cut by
special restriction enzymes.
II. Restriction Enzymes
A. Used by bacteria to cut up DNA of
viruses.
B. Many different types that cut DNA at
different sequences.
III. Copying DNA
A. Often, DNA samples are very small.
B. In order to get enough DNA to study,a
polymerase chain reaction (PCR) is used to
copy the same segment over and over.
IV. Separating DNA
A. Gel
electrophoresis
separates the cut
DNA by length,
using an electrical
current.
V. How is the DNA used?
A. Genetic engineering- new genes can be
added to an organisms DNA.
B. Mutations and genetic diseases can be
shown through different DNA fragments.
C. A DNA fingerprint can identify a
criminal, body, or missing person.
D. DNA from different species can be
compared to determine their relationship.
I. Genetic Engineering
A. When humans make a
change in an organism’s
DNA code.
B. In recombinant DNA ,
genes from one species can
be inserted into another.
C. Is frequently used in many
of the foods we eat.
II. GM foods
A. These are crops that have been genetically engineered
(modified).They are also called transgenic, because
they have genes from another species.
B. GM crops make up 52% of the soybeans and 25% of
the corn we eat.
III. How is it done?
A. In bacteria:
1.A restriction enzyme is used to cut a
gene.
2. The gene is added to a bacterial plasmid
using sticky ends.
3. The plasmid is added to a bacteria,
which makes many copies of the plasmid.
B. In plants:
1. The bacteria is
modified (see A)
2. The modified bacteria
can be allowed to
infect a plant
C. In animals:
1. A fertilized egg cell must be used.
2. The foreign DNA is inserted into the
nucleus using restriction enzymes and
sticky ends.
3. The egg is implanted in a female.
4. The female gives birth to the transgenic
organism.