MONOHYBRID CROSSES.
1. Among dogs wire hair is a dominant over smooth. If
a heterozygous wire haired male is crossed with a
homozygous smooth haired female, what would be
the genotypes of their puppies?
2. ln rabbits short ears are dominant over long ears.
What would the phenotypes be if two heterozygous
short eared rabbits were mated?
3. Among guinea pigs black hair is dominant over white.
What would be the phenotype of the guinea pigs if a
homozygous white male was mated with a
homozygous white female?
4. In humans brown eyes are dominant over blue
eyes. If a heterozygous brown eyed male marries a
heterozygous brown eyed female, what would be the
phenotypes of the children?
5. Among tulips yellow color is dominant over blue. If
a heterozygous yellow tulip is crossed with a
homozygous blue, what would be the phenotypes and
genotypes of the tulips?
6. Among squash smooth seeds are dominant over
wrinkled seeds. If two heterozygous smooth squash
plants are crossed, what would be the phenotypes and
genotypes of the seeds?
PATTERNS OF
INHERITANCE
AND HUMAN
GENETICS
SIMPLE RECESSIVE
INHERITANCE
►
1.
2.
CYSTIC FIBROSIS:CF
Common in white Americans 1:2000
Caused by defective protein in plasma
membrane.
CYSTIC FIBROSIS:CF
3. Controlled by physical therapy, diet, drug
therapy
4. Life expectancy improving annually
5. Person must have 2 recessive alleles to
suffer from CF. 1 allele carrier but shows
no symptoms
PHENYLKETOURIA (PKU)
►Phenylketouria:
1. Caused by the absence of an
enzyme that converts the amino
acid phenylalanine to tyrosine.
2. Accumulation of phenylalanine leads to
mental retardation and CNS damage
PHENYLKETOURIA (PKU)
3. Newborns are given a blood test to check
for the absence of the enzyme
4. Milk products are high in phenylalanine
5. Disorder is treatable by controlling diet
from birth
►
►
OTHER RECESSIVE
TRAITS
TAY-SACHS
ATTACHED EAR LOBES
SIMPLE DOMINANT
TRAITS
►
1.
HUNTINGTON’S DISEASE:
Lethal disorder, no treatment
2.
Certain areas of the brain breakdown
3.
Symptoms; neurological and muscular show at
the age of 30+
4.
Genetic testing is available before symptoms
show
HUNTINGTON’S DISEASE:
5. Ethical issues
6. Every child of an affected person has a
50/50 chance of inheriting the disease
7. Only 1 defective allelle required for person
to show disease
OTHER DOMINANT TRAITS
1.
2.
3.
4.
5.
6.
7.
8.
Unattached ear lobes
Tongue rolling
Hapsburg lip
Hitchhiker’s thumb
Hairy fingers
Almond shaped eyes
Thick lips
Widow’s peak
INCOMPLETE DOMINANCE
INCOMPLETE DOMINANCE
► Heterozygous
phenotype is intermediate
between those of the two homozygotes
► Red flower x white flower
► Intermediate phenotype is pink
F1
R
R
R’
R’R
R’R
R’
R’R
R’R
F2
R
R
RR
R’
R’R
R’
R’R
R’R’
CODOMINANCE
►
CODOMINANT ALLELES CAUSE THE PHENOTYPE OF
BOTH HOMOZYGOTES TO BE PRODUCED IN THE
HETEROZYGOTE INDIVIDUALS. BOTH ALLELES ARE
EXPRESSED EQUALLY
B
W
B = black feathers in chickens
W = white feathers in chickens
B
BB
BW
BB = black chicken
BW = checkered chicken
WW = white chicken
W
BW
WW
CODOMINANT TRAITS
►
SICKLE-CELL ANEMIA:
1.
Common among African
Americans 1:12
2.
Homozygous people for trait
differ by 1 amino acid coding
for hemoglobin compared to
normal people
SICKLE-CELL ANEMIA:
3. Abnormal hemoglobin is sickle celled
4. Sickle shaped cells block blood vessels
reducing the amount of oxygen reaching the
tissues
5. Shortened life span
HETEROZYGOUS ADVANTAGE
► People
who are heterozygote for the trait
produce both normal and abnormal
hemoglobin
► Show no symptoms of sickle- cell anemia
► Less likely to suffer from malaria
► This explains why African’s suffer more from
sickle-cell anemia
MULTIPLE PHENOTYPES FROM
MULTIPLE ALLELES
► Traits
controlled by more than two alleles
have multiple alleles
POLYGENTIC
INHERITANCE
►A
trait is controlled by two or more
genes.
► Inheritance of eye color, height, stem
length, skin color.
► ABO
BLOOD GROUPS
blood group
► Single gene (represented as “I”) has 3
different alleles
► Blood type A
genotype IA IA
IA i
► Blood type B
genotype IB IB
IB i
► Blood type AB
genotype IA IB (codominant)
► Blood type O
genotype ii (recessive)
► Important in blood transfusions and
paternity suits
SEX DETERMINATION
►Autosomes
22 pairs of
homologous chromosomes
►23rd pair of chromosomes are
sex chromosomes X and Y
►Female XX chromosomes
►Male XY chromosomes
►Gametes
carry either an X or Y
chromosome
►Fertilization results in offspring having
either XX or XY chromosomes
►There is a 50:50 chance of producing
a male or female each time an
offspring is produced.
SEX-LINKED INHERITANCE
► Experiments
conducted by Morgan
► Observed males had white eyes more
often than females
► Suggested gene for eye color was carried
on the X chromosome and Y chromosome
has no corresponding gene for eye color
INHERITANCE OF EYE COLOR IN
DROSOPHILA
COLOR BLINDNESS
► X-linked
disorder
► Inability to differentiate between two colors
such as red and green
► Males are more susceptible because they
have to inherit 1 defective X
chromosome to suffer from the disorder;
females needed to inherit 2 defective
chromosomes.
► Most serious problem is the inability to
detect traffic light colors
HEMOPHILIA
► X-linked
disorder
► Caused
by a lack of factor VIII a blood
clotting enzyme
► Inability
to clot the blood
► Males
are more susceptible because they
have to inherit 1 defective X chromosome to
suffer from the disorder; females needed
to inherit 2 defective chromosomes.
► Treated
by blood transfusions and
injections of factor VIII.
► Treatments are expensive and some people
have contracted AIDS.
► WHO
IS RYAN WHITE???
CHANGES IN CHROMOSOME
NUMBERS
► Nondisjunction:
paired chromosomes fail to
separate properly during meiosis
► TRISOMY:
► Down’s
person has 47 chromosomes total
syndrome: chromosome 21 3 copies
inside of 2. Mental retardation etc, higher
incidence in women over 40.
► Klinfelter’s
chromosome.
syndrome: males, extra X or Y
► MONOSOMY:
45 chromosomes
► Turner’s syndrome: females, missing X
chromosome, mental retardation, sterile.
KARYOTYPE
► Chart
of chromosome pairs used to
evaluate unusual chromosome numbers in
cells.
► Amniocentesis is the procedure by which
the cell are collected for analysis and
production of the karyotype.
Pedigrees
►A
way for scientist to determine whether the
trait is dominant or recessive over several
generations
► Individuals are represented by symbols
I.
II.
III.