Ch. 12 Patterns of Heredity and Human genetics
12.1 Mendelian Inheritance of Human Traits
I
A. Making a ____________________ – a graphic
II
representation of genetic inheritance
III
B. Simple Recessive Heredity – most disorders
are caused by recessive alleles.
1. ____________
____________ (CF) – 1
in 20 white Americans carries the recessive allele that
causes a defective protein in the plasma membrane
that causes ________________________ to build up
in the lungs and GI tract. Fatal disorder, although life
expectancy is rising.
2. _________ ________ _____________ –
recessive disorder of the central nervous system.
_________________________ to break down a lipid
produced in the central nervous system.
3. Phenylketonuria (__________) – a recessive disorder that
________________________________ to break down the amino
acid phenylalanine (found in milk). Mental __________________
occurs in children whose brains are developing. Now, all infants are
tested and special diets can prevent the expression of trait.
C. Simple Dominant Heredity
1. __________ ____________________ traits: tongue
rolling, free earlobes, widow’s peak, hitchhiker’s thumb…
2. ____________________ disease – a lethal disorder
caused by a dominant allele. Break down of the nervous system
12.2 When Heredity Follows Different Rules
A. Complex Patterns of Inheritance
1. ____________________ – causes the both alleles to be
expressed equally. EX: Blood type AB
2. Multiple phenotypes from multiple alleles
a). ________________ _______________ – traits controlled by more than two
alleles. Ex: hair color
3. Sex determination
a). _______________ – the 22 pairs of matching
homologous chromosomes
b). ______ _______ ________ – In humans: XX in
females, XY in males
4. Sex-linked inheritance
a). _____ - ______________________–
traits controlled by genes located on sex
chromosomes
Ex: Thomas Hunt Morgan (1910) – discovered traits linked to sex
chromosomes in white-eyed fruit fly males, and red-eyed females
5. Polygenic inheritance – controlled by two or more genes
Ex: skin color, height
B. Environmental Influences
1. Influence of external environment – temperature, light, nutrition, chemicals… can express
traits differently. Ex______________
2. Influence of internal environment – some traits are expressed differently in males then in
females.
Ex: ______________is dominant in males , recessive in females
Ex: Milk production in females, beard growth – results
from hormone levels
12.3 Complex Inheritance of Human Traits
A. Codominance in Humans
1. ________ - ______ ______________– caused by an
abnormal hemoglobin in RBC’s. Causes cells to “sickle”, can lead to
stroke
B. Sex – Linked Traits in Humans
1. Red-Green Color blindness
2. Hemophilia
C. Polygenic Inheritance in Humans. Ex: skin color
D. Changes in Chromosome Numbers – Normal humans have 46 chromosomes in body cells
1. Down’s Syndrome – caused by ______________of the 21st pair of chromosomes
2. ______________________ Syndrome – caused by extra Y chromosomes (XYY)
3. ______________________Syndrome – caused by one X in females
E. Genetic testing: ___________________ (mapping of chromosomes), amniocentesis, PKU