1. 11.3 Other Patterns of Inheritance
Genes can act in various ways
Dominant vs. Recessive – one allele completely covers another allele.
Incomplete Dominance
Definition : one allele is not completely dominant over another
Ex: flowers – white x red flowers = pink flowers

2. Beyond Dominant and Recessive
3. Codominance
Definition: both alleles contribute to the phenotype of the organism
Ex: chicken feather – black and white alleles = black and white feathers
Colors don’t blend like incomplete dominance

3. blood-type donors and recipients
Multiple Alleles
Definition: more than two alleles
(more than 2 alleles exist in a population not an individual)
Ex: rabbit’s coat color
Ex: human’s blood type
blood-type donors and recipients

4. Polygenic Traits
Definition: traits that are controlled by 2 or more genes
Ex: fruit fly red eyes - 3 genes involved in making pigment
Diff. combo of genes produce different eye colors
Ex: Human skin color – more than 4 different genes

5. Genetics and the Environment
Does the environment have a role in how genes determine traits? - YES
1. Phenotype is only partly determined by genotype
2. Environmental conditions affect gene expression and influence genetic traits
Ex. Butterfly color is temperature dependent
Hydrangea flowers blue or pink depending on soil pH.

6. 11.5 Gene Linkage
Thomas Hunt Morgan noticed in fruit flies that genes for certain traits seemed to be inherited together
The reason: these genes are on the same chromosome (linked)
It is the chromosomes that assort independently, not the genes.

8. 14.1 Human Chromosomes
Karyotype –photograph of chromosomes taken during mitosis, then arranged in decreasing size
Where did these chromosomes come from?
23 from mom
23 from dad
5,000

9. 14.1 Human Chromosomes Chromosome pairs 1 - 22 = autosomes
Chromosome pair 23 = sex chromosomes (XX or XY)
Females are written as 46XX; males are written as 46XY.

10. Sex Chromosomes Males and females born in 50:50 ratio
X chromosome carries about 1,200 genes. Y carries only about 140.

11. Sex-Linked Genes Sex-linked Genes – genes located on the X chromosome
More than 100 sex-linked genetic disorders have been linked to the X chromosome
Y chromosome is much smaller and contains only a few genes
Males have only 1 X chromosome
All alleles on the X chromosome are expressed in males, even if they are recessive

12. X Chromosome Disorder Colorblindness
3 genes associated with colorblindness are found on the X chromosome
1/10 males are colorblind
1/100 females are colorblind
Why is colorblindness more common in males?
Males need only one allele to be colorblind. Females need two alleles to be colorblind.

13. Chromosomal Disorders
Nondisjunction – homologous chromosomes fail to separate during meiosis
Abnormal number of chromosomes find their way into gametes

14. Chromosomal Disorder Trisomy – having three copies of a chromosome
Trisomy in chromosome 21 – Down Syndrome
1/800 births, causes mild to severe mental retardation

15. Chromosomal Disorder Turner Syndrome
Females are born with only one X chromosome
Females are sterile because sex organs do not develop at puberty.
Klinefelter’s Syndrome
Males born with an extra X chromosome
Male is sterile

16. Human Traits
How does one trace an inherited trait through generations? How does one predict who in the next generation will show that trait?
The Pedigree Chart – show the relationships within a family

17. Human Traits Circle represent female Square represents male
Horizontal line represents marriage
Vertical line represents children

18. Human Traits
Unshaded circle or square indicates that the person does not express the trait
Half shaded circle or square indicates the person is a carrier for the trait.
Completely shaded circle or square indicates that the person expresses the trait.
How many generations are shown? 3