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