genetics - wca life science - home
TRANSCRIPT
genetics the study of the inheritance of traits
inheritance the passing of traits from parents to offspring
• male gamete: sperm
• female gamete: egg
Gametes
Gametes sperm egg
haploid a cell that has one of each kind of chromosome that is normally found in the organism
Tall plants Short plants
Axial flowers Terminal flowers
Inflated pods Constricted pods
Mendel’s
Experiments • tall plants and short plants
• axial flowers and terminal flowers
• inflated pods and constricted pods
• yellow pods and green pods
• yellow peas and green peas
• round peas and wrinkled peas
• green seed coats and white seed coats
Mendel’s
Experiments
purebred an organism that has had the same traits for many generations
1. Pollen-containing structures are removed from short-plant flowers. 2. Tall-plant pollen
is collected using a brush.
3. Tall-plant pollen is placed onto stigmas of short-plant flowers.
cross mating purebred plants of opposite traits to test how they inherit traits
Mendel’s
Experiments
short tall + tall ??? =
Mendel’s
Experiments
F1—1st Filial Generation
Mendel’s
Experiments
F2 Generation
Mendel’s
Experiments
tall tall + tall =
short tall + tall =
Mendel’s
Experiments
hybrid an offspring of two genetically unrelated individuals
• Each offspring had two factors for each trait, one from each parent.
Mendel’s
Experiments
• Each factor in the set of two factors for a trait was either dominant or recessive.
Mendel’s
Experiments
Mendel’s
Experiments
F2 Generation
x
tt TT x Tt (F1)
Tt x TT Tt Tt Tt tt
Terms • phenotype
• genotype
— tall
— TT, Tt
What was the phenotype of the peas in Mendel’s F1 generation?
What Do You Think?
tall
List the genotypes of the peas in the F1 generation.
Tt
What Do You Think?
What phenotypes did Mendel see in the F2 generation?
tall and short
What Do You Think?
What genotypes did Mendel find in the F2 generation?
TT, Tt, tt
What Do You Think?
chromosome
number the number of chromosomes in the nucleus
Punnett square a diagram used to visualize genetic crosses
parent characteristic
pare
nt ch
ara
cte
ristic
offspring offspring
offspring offspring
parent characteristic
pare
nt ch
ara
cte
ristic
Hybrid Tall Parent
Purebred Short Parent
Tt x tt T t
t
t
Hybrid Tall
Parent
T t
T
t
Hybrid Tall Parent Tt x Tt
Purebred Short Parent tt x tt t t
t
t
Purebred Short Parent
Purebred Tall Parent TT x tt T T
t
t
Tt Tt
Tt Tt
Purebred Short Parent
Tt x Tt T t
T
t
TT Tt
Tt tt
Hybrid Tall Parent
Hybrid Tall
Parent
tt Tt Tt TT TT
25%
Tt 25%
Tt 25%
tt 25%
incomplete
dominance a type of inheritance in which the genes expressing a particular characteristic are neither dominant nor recessive;
both genes influence the characteristic of an organism
Hybrid
Hybrid
CwCr x CwCr Cw Cr
Cw
Cr
CwCw CwCr
CwCr CrCr
codominance a type of inheritance pattern where two traits are equally expressed
Chestnut
White
HBHB x HWHW
HB
HBHW HBHW
HBHW HBHW
HB
HW
HW
multiple gene
inheritance two or more gene pairs are responsible for producing a single trait
X chromosome the female sex chromosome
Y chromosome the male sex chromosome
XX x XY
X
XX XX
XY XY
X
X
Y
sex-linked trait a characteristic that has a gene on the X-chromosome but no gene on the Y-chromosome
XgY x XGXG
Xg Y
XG
XG
carrier an individual who possesses a gene for a specific trait but does not exhibit that trait
Xg
XGXg XGY
XGXg XGY
Y
XG
XG
XgY x XGXG
XGY x XGXg
XG
XGXG XGY
XGXg XgY
Y
XG
Xg