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CHAPTER 26: INHERITANCE OF TRAITS 

Genetics:

Chromosomes:

2 Main Jobs of the Nucleus:

Genes:

Examples of traits: Eye color, hair color, shape of body parts (ears), chemical processes (some diseases)

Dominant & Recessives Genes

Dominant Genes:

Recessive Genes:

Pure Dominant:

Pure Recessive:

Heterozygous:

Phenotype –

Genotype –

Predicting Phenotypes of Offspring (Punnett Squares)

The likely percentage of offspring that will display certain phenotypes can be estimated using a tool called a Punnett Square. 

Example:   Attached earlobes are Dominant to Free  Earlobes (Recessive)

 A mother that is Pure Dominant (AA) for attached earlobes marries a man that is Pure Recessive for free earlobes (aa).  What percentage of their offspring will be likely to have attached earlobes?

Now…consider that BOTH parents are Heterozygous, with attached earlobes (Aa) and (Aa). Predict the offspring below:

Expected Results – The results you EXPECT to see from a Punnett Square cross.

 Using a Punnett Square, predict the probability of offspring phenotypes based on the parents’ genotypes.

 Cleft Chin is Dominant (Ii) (II)
Smooth Chin is Recessive (ii)

 Mother is Heterozygous (Ii), Father is Pure Recessive (ii):

Observed Results – The ACTUAL results you observe from a real cross.

 ·        DO NOT always match expected results.

·        The ______________ the sample size (more results) observed, the more _______________________________________________________________

_______________________________________________________________

Example: Flipping a coin:

EXPECT:
50% chance of heads, 50% chance of tails.

OBSERVE:
·         Flip a few times –

·        Flip many (100) times –

Gregor Mendel –

Mendel’s Work:

• Used mathematics (quantitative data) to explain basic laws of genetics (Mendel’s Law)

• Explained Dominant & Recessive traits

• Showed that traits were passed from parents to offspring

Complete Dominance - The dominant gene completely hides the recessive gene.

 Example trait: Height

Incomplete Dominance – “Blending” of traits.

Example Trait: Flower Color of Pea Plant.