Genetics
Heredity passing down of traits or
characteristics from _____________________
Genetics  study of _________________
Gregor Mendel (1822-1884)
Worked with ___________________. 2 major
traits for each plant
Plants were either _________________________
Plants were either _________________________
Mendel’s Experiment
Male and Female sex organs in pea plants are
on the _________________ (___________have
pollen and ______________ contains the egg)
Pure Traits  Traits established through
_______________________
Stamen
Stigma
Genetics
•Pure white individuals x pure purple individuals
•F1 ____________________________
•F1 x F1  ______ ratio of purple to white pea plants
•Out of 1000 plants ______________ were purple and
_______________ were white
•Results of the Parental cross showed that one trait
_______________________ the other trait
X
=
Genetics Vocabulary
Dominant Trait  Trait that _______________
the recessive trait
Recessive Trait  Trait that is
___________________ up
In this cross PURPLE color was dominant
Mendel’s Hypothesis
Gene  sequence of ___________ on a chromosome
Each pea plant trait is a combination of _________genes, one
from __________ and one from ____________
Each alternative gene is called an ______________
Dominant Gene  shown by a capital letter (P)
Recessive Gene  shown by a lower case letter (p)
Pure Purple plants  ________
Pure white plants _______
PP x pp  all _________
Pp x Pp ____________________________
Mendel’s Terms
Homozygous  2 of the same allele
(PP or pp)
Heterozygous  2 different alleles
(Pp)
Punnett Square  Results of a
cross can be predicted
Incomplete Dominance
Some traits do not have dominant alleles
Heterozygotes appear as a mix between 2 parents
1 trait = ___ phenotypes
4 O’clock Flowers
Rr x Rr
Ratio of Offspring
1 _______
2 _______
1 _______
Codominance
Neither allele is dominant
Presence of heterozygote means both alleles are
_________________________
____________________is an example
Sex Determination
Thomas Morgan discovered that chromosomes differed in males and
females
Females- ______
Males- ________
Called _______ Chromosomes
All other chromosomes are called __________
Sex-linked Inheritance
Morgan crossed _________ male with
_______________ female
F1Ratio: _________________
F2 Ratio: 3:1 ratio, but ______ any white
females
Reasoned that there are genes on
__________chromosomes
Allele for eye color is on ______chromosome
No gene for eye color on ______ chromosome
Presence of homozygous recessive, or ONLY a
_______________, yields recessive trait
Morgan’s Crosses
Sex Influenced Traits (Not on test!)
• Sex-influenced traits are autosomal traits
that are influenced by sex. If a male has
one recessive allele, he will show that trait,
but it will take two recessive for the female
to show that same trait. One such gene is
baldness.
• BB normal male & female
• Bb  bald male; normal female
• bb  bald male; bald female
Dihybrid Crosses
Dihybrid Cross: Cross: Cross of 2 individuals for 2 different traits
Example:
In Pea Plants
Tall(T) is dominant to short
Purple(P) is dominant to white
Crossing homozygous tall, purple plant with a homozygous short, white
plant
_______________
Crossing heterozygous tall, purple plant with a heterozygous tall, purple
plant
TtPp x TtPp
Pedigrees & Genetic Diseases
Autosomal dominant disease  Presence of dominant allele means
that _________________________________________
Autosomal recessive disease  Disease only present when
______________recessive alleles are present
Sex-linked Dominant  Disease present when dominant allele is
present on ______________________________
Sex-linked Recessive  Disease present when recessive allele is
________________________________
Common Genetic Diseases
Huntington’s Disease ___________________________;
____________________; degeneration of muscle tissue; onset in early 30’s.
Folk Singer Woody Guthrie had the disease
Cystic Fibrosis _______________________________; Defective Protein is
made that creates excess mucus; clogs lungs.
Color Blindness _________________________________
Inablity to distinguish colors (_______________of male population)
Some Genetics Diseases
Hemophilia Sex-linked recessive
__________________________
Nicholas, Czar of Russia (Mid 1800’s) child was
_________________________
Muscular Dystrophy _______________________
Tay-Sach’s Disease  _______________________
Degeneration of _____________________; infant mortality
Changes in Chromosome Number
Nondisjunction – occurs when:
In meiosis I, homologous pair both go into the same
daughter cell or
In meiosis II, the sister chromatids both go into the
same gamete.
The result:
___________ (3 copies of a single chromosome) or
___________ (1 copy of a single chromosome)
Nondisjunction in meiosis I
Changes in Chromosome Structure
• Mutation - a permanent ____________________.
• Chromosome mutation - a change in
_____________________structure
• Radiation, organic chemicals, or even viruses may
cause chromosomes to break, leading to mutations.
• Types of chromosomal mutations: inversion,
translocation, deletion, and duplication.
Deletions
Deletions occur when a single break causes a
___________, or two breaks result in a loss in the
interior.
An individual inherits a normal chromosome from one
parent and a chromosome with ______________from
the other parent
No longer has a pair of ______________________
A syndrome can result – type depends on
chromosome(s) affected.
Williams Syndrome
• Chromosome ________________________
• Children have a pixie look (turned-up noses, wide
mouth, small chin, large ears)
• Poor academic skills, good verbal and musical
abilities
• Skin ages prematurely from lack of the gene that
controls the production of elastin (also affects
cardiovascular health).
Duplication
Duplication results in a chromosome segment being
__________________________________
Produces extra alleles for a trait.
Ex: An inverted duplication in chromosome 15 causes
inv dup 15 syndrome
Poor muscle tone, mental retardation, seizures,
curved spine, and autistic characteristics
Duplication
Translocation
Translocation is _________________________________
between two, non-homologous chromosomes.
Ex: Alagille syndrome results from a deletion of
chromosome 20 or a translocation that disrupts an
allele on chromosome 20.
Distinctive face, abnormalities of eyes & internal
organs, and severe itching.
Translocation
Inversion
• Inversion involves a segment of a chromosome
being ____________________________
• The reverse sequence of alleles can alter gene
activity.
• Crossing-over between inverted and normal
chromosomes can cause duplications and
deletions in resulting chromosomes.
Inversion