Name: _______________________________________ Date: __________________________ Block: ________

Evolution:Extensions on Mendelian GeneticsINHERITANCE PATTERNS ARE OFTEN MORE COMPLEX THAN PREDICTED BY SIMPLE MENDELIAN GENETICS

The relationship between genotype and phenotype is rarely as simple as in the pea plant characters

Mendel studied

o Many heritable characters are not determined by ________________________________.

o However, the basic principles of _____________________ and

_______________________________ apply even to more complex patterns of inheritance

EXTENDING MENDELIAN GENETICS FOR A SINGLE GENE

Inheritance of characters by a single gene may _________________ from simple Mendelian patterns

in the following situations:

DEGREES OF DOMINANCE:

1. ________________________________________ occurs when

phenotypes of the heterozygote and dominant homozygote are

______________________.

2. In ______________________________________ , the phenotype

of F1 hybrids is somewhere _____________________ the

phenotypes of the two parental varieties

3. In __________________________, two dominant alleles affect

the phenotype in separate, distinguishable ways

Biology 11 Enriched Mr. Lau

Name: _______________________________________ Date: __________________________ Block: ________

FREQUENCY OF DOMINANT ALLELES:

Dominant alleles are not necessarily more common in

populations than recessive alleles

o For example, one baby out of 400 in the United States is

born with

________________________________________

The allele for this unusual trait is __________________ to the allele for the more

common trait of five digits per appendage

In this example, the recessive allele is far more ______________________ than the

population’s dominant allele

MULTIPLE ALLELES

Most genes exist in populations in more than 2 allelic forms

For example, blood types

The 4 blood types are:

The 4 phenotypes of the ABO blood group in humans

are determined by 3 alleles for the enzyme (I) that

attaches A or B carbohydrates to red blood cells: IA,

IB, and i.

o A alleles =

o B alleles =

o i alleles =

Blood types is also an example of

__________________________.

Biology 11 Enriched Mr. Lau

Name: _______________________________________ Date: __________________________ Block: ________

PLEIOTROPY

Most genes have _____________ phenotypic effects a property called pleiotropy

o For example, pleiotropic alleles are responsible for the multiple symptoms of certain

hereditary diseases, such as _____________________ and ________________ disease

EXTENDING MENDELIAN GENETICS FOR TWO OR MORE GENES

Some traits may be determined by two or more genes

EPISTASIS

In epistasis, a gene at one ___________ alters the _______________________________________

of a gene at a ___________________

o For example, in mice and many other mammals,

______________________ depends on two

genes

One gene determines the

______________________________

(BB/Bb = black & bb = brown)

The other gene determines whether the

pigment will be

______________________ in the hair.

(CC/Cc = color & cc = no color)

Biology 11 Enriched Mr. Lau

Name: _______________________________________ Date: __________________________ Block: ________

POLYGENIC INHERITANCE

Quantitative characters are those that vary in the population along

a _________________________________________

o Quantitative variation usually indicates polygenic

inheritance, an additive effect of two or more genes on a

single phenotype

_____________________ in humans is an

example of polygenic inheritance

NATURE AND NURTURE: THE ENVIRONMENTAL IMPACT ON PHENOTYPE

Another departure from Mendelian genetics arises when the

phenotype for a character depends on ________________________

AND genotype

o The norm of reaction is the phenotypic range of a genotype

influenced by the environment

Biology 11 Enriched Mr. Lau

Name: _______________________________________ Date: __________________________ Block: ________

For example, _________________________________ of the _________________________ range

from blue-violet to pink, depending on soil acidity

An organism’s phenotype includes its:

An organism’s phenotype reflects its overall _____________________ and unique

________________________________________

GENE LINKAGE

Some genes do not _________________________________________

They are often _________________________________________ because they are on the same

chromosome.

New allele combinations can be produced if chromosomes ________________________ during

_________________

o _________________________ chromosomes and gametes are produced

SEX LINKAGE

Females: __________ Males: ___________

Some genes are found only on the X chromosome.

Biology 11 Enriched Mr. Lau

Name: _______________________________________ Date: __________________________ Block: ________

o Because males are _______________________________ (X and Y) and

___________________________ (only 1 X), whatever genes are on the X chromosome will

be expressed

Example: Color Blindness

The gene for seeing color has 2 alleles: B and b. The locus for this gene is on the X chromosome.

Genotype

(female)

Phenotype

MENDELIAN GENETICS AND HUMANS

Humans are not good subjects for genetic research

However, basic Mendelian genetics endures as the foundation of human genetics

PEDIGREE ANALYSIS

A pedigree is a family tree that describes the interrelationships of parents and children across

generations

Pedigree analysis allows us to figure out whether an allele controlling a particular phenotype is

__________________________ or ____________________________.

Dominant Trait: Recessive Trait:

Biology 11 Enriched Mr. Lau

Genotype (male) Phenotype

Name: _______________________________________ Date: __________________________ Block: ________

Pedigrees can also be used to make predictions about ___________________________________.

We can use the multiplication and addition rules to predict the probability of specific phenotypes

Biology 11 Enriched Mr. Lau