Types of Inheritance:

1. Types of Inheritance: AutosomalDominance (A.D.): If the genotype contains a dominant allele, the phenotype will show the dominant trait. If it does not contain a dominant allele, it will show the recessive trait. A.D. occurs on your autosomes, which are the 44 chromosomes that are not your sex chromosomes. This is the rule that Mendel came up with after studying pea plants!

2. Examples of Autosomal Dominance • Earlobe attachment • Hitchhiker’s thumb • Widow’s peak • Eye dominance • Mid-digital hair

3. Side note • Genetic conditions may be referred to as “autosomal dominant” or “autosomal recessive”. • AD – the trait is dominant • AR – the trait is recessive • Autosomal means it is not on a sex chromosome (X or Y) • These are always “either or” traits!

4. There are exceptions to this rule! • Some traits are not “one way or the other” or they do not have just one dominant form. • We know several exceptions to this rule!

5. Co-Dominance: A heterozygous genotype shows BOTH phenotypes. Both of the alleles present will show up separately, they are equally dominant Examples: Red horse and white horse  roan coat (both red and white hair) Human blood types

6. Roan Coat Horses

7. Blood Types (Co-Dominance) • Humans have different types of blood. You can have A, B, AB, or O. • Types of blood indicate what antigens are present (or absent) on your red blood cells • You have 2 alleles (one from each parent) for blood type, making your genotype one of the following: AO, AA, BO, BB, AB, or OO. • A and B are both dominant, O means you do not have any antigens!

8. Side note: You also have a + or - • The positive and negative symbols represent the presence or absence of the Rh factor (a protein found in your blood). • + means you have it • – means you do not + can only donate to + - can donate to – and +

9. Incomplete Dominance: A heterozygous genotype displays a mix of the 2 traits in its phenotype. The dominant does not fully cover up the recessive – the recessive shows through Examples: Red roses and white roses  pink roses Brown hair with red color tints Black fur and white fur  gray fur

10. Polygenic: Means “many genes” The trait is controlled by more than one gene. Examples: Skin color Eye color Wheat kernel color Hair color

11. Epistasis: “Epi” means… top! One gene suppresses or masks the effects of another gene. (1 phenotype controlled by 2 genes) Examples: Square chin – masked if the person does not have a prominent chin Deafness – deafness gene can be masked with a healthy gene

12. Sex-Linked (or X-Linked) • An X-linked gene means the gene is carried on the sex chromosome (the X chromosome) • You have 2 sex chromosomes (XX = girl or XY = boy) in addition to your 44 autosomes • You get the X from your mom and either an X or a Y from your dad • Usually, these show up in men but they get it from their mom! • Examples: • Color blindness • Hemophilia

13. How sex-linked (or X-linked) disorders are passed to offspring: • X from mom, X or Y from dad = XX is a girl and XY is a boy • Sex linked disorders are found on genes that are carried on the X chromosome • They are usually recessive • Men usually have these but they get them from their mother because she contributes the X chromosome that it is carried on…

14. Color Blindness The picture shown above is the Creamer Colorblindness test.  A colorblind individual can see the circle, but not the star. About Color Blindness

15. Example: This is a different way of looking at it, but this is a Punnett Square! This red band is the color blindness recessive gene

16. Trisomy/Trisomies(Extra chromosomes) • Trisomy 21 – Down Syndrome • 3 chromosomes on the 21st pair of autosomes • Associated with older men and women (over 35) becoming parents… • At age 30 a woman has less than a 1 in 1,000 chance of conceiving a child with DS. Those odds increase to 1 in 400 by age 35. By 42, it jumps to about 1 in 60. • Symptoms: flat facial profile, low set small ears, upward slant to the eyes, hyper-flexibility, cognitive and physical delays, mental retardation… the extent of these symptoms can vary from child to child.

17. Other Trisomy Disorders… • Trisomy 18: Edward’s Syndrome • 90% die within the first year • Trisomy 13: Patau’s Syndrome • 82% die within the first year • Trisomy 16: • The most common trisomy in humans, occurring in more than 1% of pregnancies. This condition results in spontaneous miscarriage in the first trimester. • Trisomy involving sex chromosomes in humans includes: • XXX (Triple X syndrome) • XXY (Klinefelter's syndrome) • XYY (XYY syndrome)

18. Missing Chromosomes/Mosaics • Turner’s Syndrome – Missing one of the 2 X chrom. in a female (X instead of XX) • Cri du chat – Missing part of chrom. #5 • Many others… but not common • Mosaics: The abnormality is only found in some (not all) cells in the body.

19. Other abnormalities(Other ways chromosomes can “mess up” during meiosis and fertilization) • Deletion - loss of part of a chromosome • Duplication - extra copies of a part of a chromosome • Inversion - reverse the direction of a part of a chromosome • Translocation - part of a chromosome breaks off and attaches to another chromosome