Genetics
and Society
Section 17.3
Breeding Plants
Maize (Corn)
• Humans selected and breed the
plants that produce the largest
grains and most clusters of grain.
Canola (Rapeseed)
• Two chemicals found in rapeseed
are toxic
• Banned from human consumption
• 1970’s – selective breeding resulted
in a variety with very low levels of
the toxins
• New variety is called Canola
Breeding Animals
•
•
•
http://www.farmsanctuary.org/learn/factory-farming/turkeys-used-for-meat/
Selection for cattle that will
produce offspring that produce:
➢ Leaner meat
➢ Higher milk yield
Some turkeys have been selectively
bred to the point where they can
no longer reproduce naturally
Human desire for larger turkey
breasts means the males cannot
mount the females to breed
Human Genetics
To study human genetics, we use a pedigree instead of crossing certain males and females
Pedigree ➔ A flowchart using symbols to show the patterns of relationships and traits in
a family over many generations
Analyzing a Human Pedigree
Pedigrees can be used to determine the pattern of inheritance of traits
Autosomal
Dominant
Inheritance
Autosomal Inheritance
Traits (dominant and recessive) that are coded for by genes
on autosomes
Example: Polydactyly
Autosomal dominant condition
Results in the occurrence of extra fingers and toes
Polydactyly
What do you notice about both parents in
the first generation?
What about their children?
Polydactyly
Whenever a recessive phenotype occurs in a child of
parents who exhibit the dominant trait, the parents must
be heterozygous for that trait.
How do you know that individual II 2 is heterozygous?
Autosomal
Dominant
Inheritance
Huntington’s Disease
• Brain deteriorates over a period of 15 years
• Fatal
• Symptoms usually appear after age 35
• Irritability and memory loss
• Involuntary muscle movements
• Eventually leads to dementia and loss of
muscle control
Autosomal Dominant
Inheritance
Marfan Syndrome
• Connective tissue disorder
• Unusually long bones ➔
Abnormal curvature of the
spine
• Glaucoma and increased risk
of retinal detachment
• Heart and respiratory
problems
• Becomes worse over time
Autosomal
Recessive
Inheritance
Phenylketonuria (PKU)
• Affects development of the
nervous system
• Enzyme that converts
Phenylalanine ➔ Tyrosine
is defective or absent
• Phenylalanine ➔
Phenylpyruvic acid (toxic)
• Newborns with PKU
appear healthy at birth but
can be affected within a
few months
What do you notice about the parents?
Phenylketonuria
How do you know that individual III 1
is heterozygous?
Autosomal
Recessive
Inheritance
Cystic Fibrosis
• Build up of thick mucus in lungs and
digestive system
• Increased risk of pneumonia and
respiratory failure, difficulty
digesting food
• 1 in 2500 Canadian children are born
with cystic fibrosis
Sex-Linked
Traits
Hemophilia
• Affects the body’s ability to produce proteins
involved in blood clotting
• Simple cut can lead to severe blood loss
• Which gender is more affected in the Royal family?
• X-linked recessive trait
Other examples?
X-Linked
Recessive
Traits
Duchene muscular dystrophy
• Can not manufacture the muscle
protein dystrophin
• Muscle tissues weaken and degenerate
• Life expectancy of only 20 years
Assignment
and
Readings
•
•
•
•
Read pages 610 to 616 in textbook
Section 17.3 Review page 617
Pedigree Worksheet
Multiple Alleles Worksheet