Genetics

Vocabulary TermsWorking Problems

Monohybrid Crosses

Heredity Heredity and and

GeneticsGenetics

Heredity- the passing of traits (characteristics) from parents to offspring

Genetics- the branch of biology that focuses on heredity

Gregor Mendel

Father of Genetics

During his early years at the monastery, Mendel began studying and breeding

mice.

During his early years at the monastery, Mendel began studying and breeding

mice.The

bishop was not

pleased.

The bishop was not

pleased.

Brother Gregor settled on bees . . .

Brother Gregor settled on bees . . .

and peas. and peas.

Mendelian Theory of Heredity(the foundation of genetics)

1. For each inherited character, an individual has two copies- one from each parent

2. There are different versions of genes= alleles

For example, the gene for flower color in peas can exist in a “purple” version or a “white” version

When a trait has two forms and one trait is expressed over the other, the trait that shows up is

DOMINANT.

Dominant traits are represented by upper case letters.

B - brown

When a trait has two forms, the trait that is hidden or masked is RECESSIVE.

Recessive traits are represented by the same letters

as dominant traits but lower case. b - blue

An individual having two like genes for a trait, such

as BB or bb, is HOMOZYGOUS.

These individuals can also be called pure.

HOMO = SAME

examples: BB, bb, PP, ww

An individual that has two unlike genes for a trait is

HETEROZYGOUS.

These individuals can also be called hybrid.

HETERO = DIFFERENT

examples: Tt, Ss, Rr, Ww

Modern Terms

Genotype- the genetic makeup of an organism (the set of alleles an individual has)

Phenotype- the physical appearance of an organism

Ex. PP or Pp

Ex. Purple

MONOHYBRID CROSS: shows the possible offspring for one trait

Bb x Bb

B b

B

b

BB Bb

Bb bb

Genotypic Ratio: (BB: Bb: bb) - 1 : 2 : 1

Phenotypic Ratio: (Dom: Rec) 3 brown : 1 white

B: Brownb: white

B B

b

B BB

Bb

BB

Bb

Cross a HOMOZYGOUS dominant individual with a HETEROZYGOUS one using the same trait as the previous problem.

Practice #1!

Offspring Genotype:

_____% homozygous dominant_____% homozygous recessive_____% heterozygous

Offspring Phenotypes:

_____% brown

_____% white

50

0

10050

0

What is the GR? What is the PR?

2 : 2 : 0 4 : 0

Practice #2!Cross a HOMOZYGOUS recessive individual with a HETEROZYGOUS one using the same trait as the problem before.

b b

B

b

Bb Bb

bb bb

What is the GR?

What is the PR?

0 : 2 : 2

2 : 2