1. Start Cats
Warren

2. Human Traits – DISCRETE DEFINED OUTCOMES (one or the other)
Controlled by a SINGLE GENE
Dominant or recessive

3. Human Traits – DISCRETE (one or the other)
Tongue Roll
ROLL = DOMINANT
NON ROLL = recessive

4. Human Traits – DISCRETE (one or the other)
Eye Pigment
**NOT COLOUR SPECIFIC**
PIGMENT = DOMINANT
(green, brown, black)
NO PIGMENT= recessive
(blue, grey)

5. Human Traits – DISCRETE (one or the other)
Ear lobe attachment
FREE = DOMINANT
ATTACHED= recessive

6. Human Traits – DISCRETE (one or the other)
Mid-digital hair
HAIR = DOMINANT
NO HAIR= recessive

7. IS Height
DiScrete??

8. Polygenic Traits
Occurs when more than one gene controls the expression of the trait
The expression of one gene may depend on the expression of another
ie. interaction between many genes
EXAMPLES in HUMANS
Height, skin colour, eye colour, intelligence

10. ALL OF THIS INCREASES VARIATION ALONG THE CONTINUUM
Polygenic traits
Are NON – DISCRETE (expressed along a continuum)
Genes can have multiple alleles, be co-dominant, incompletely dominant and/or affected by environment
ALL OF THIS INCREASES VARIATION ALONG THE CONTINUUM

11. Epistatic Genes
Some genes mask the expression of other genes, similar to dominant and recessive alleles (dominant masks effect of recessive)
The gene that masks the effect of another gene is an epistatic gene
Sometimes they create a new phenotype
Does NOT produce the “normal” phenotypic ratios

12. Epistatic Genes
Coat colour in dogs provides an example of epistatic genes. As shown in the Punnett square, the allele B produces black coat-colour, while the recessive allele b produces brown coat-colour.
However, a second gene also affects coat-colour. The allele W of this second gene prevents the formation of pigment, thereby preventing colour. The recessive allele w does not prevent colour.
The genotype wwBb would be black, but the genotype
WwBb would appear white. The W allele masks the effect of the B colour gene.
In humans, the gene responsible for albinism is epistatic. This gene interferes with the expression of genes that determine pigment formation in the skin, hair, and eyes

13. Environment and Phenotype
Certain environmental factors can control the expression of certain traits
Every CELL in the body has identical DNA, but the EXPRESSION of that DNA differs depending on environmental conditions!!

14. Environment and Phenotype Examples
Himalayan Rabbits and Siamese Cats
Pigment is expressed ONLY in cells BELOW a certain temperature
GARY

15. Environment and Phenotype Examples
Freckles
Sunshine causes freckle phenotype to develop

16. 15 min work time

17. Sex – Linked Traits Genes located on sex xsomes are called sex-linked
On X or Y xsome
Ex. Gene for hairy ears – on Y xsome!!
Many are located on the X xsome
Male – XY
Female – XX
X – linked show up MORE in MALES – why??

18. Sex linked Traits Dominant = R Recessive = r Notation FEMALE MALE
XR XR
XR Xr
MALE
XRY
XrY

19. Inheritance Males can only pass on Y-linked traits to their SONS
Females can be carriers of a recessive allele – MALES CANNOT

20. Example

21. Barr Bodies Every FEMALE body cell has only ONE functioning X xsome
The INACTIVE X xsome is condensed into a BARR BODY (totally random)
Why do you think this happens?
HINT – think about AMOUNT of DNA in males vs females

22. Example – Calico or Tortoiseshell Cats Alleles for Black and Orange fur
Visible effects can be seen in HETEROZYGOUS females

23. Inheritance Patterns – important in pedigree analysis
Autosomal Dominant
Disease or disorder is carried on the DOMINANT ALLELE (only need ONE dominant allele to exhibit)
Autosomal Recessive
Disease or disorder is carried on the RECESSIVE ALLELE (must be homozygous recessive to exhibit)
Sex-linked
Dominant or recessive**
NOTATION X X and X Y

24. HELPFUL HINTS READ QUESTIONS CAREFULLY!!! WRITE DOWN YOUR VARIABLES!!!
Type of inheritance guides notation
ONLY use XX, XY notation when SEX LINKED!!!! Don’t just assume because it says a man and woman have a child that it is sex linked
INHERITANCE:
Dominant/recessive
Multiple Alleles (blood types, hierarchy)
Codominance and Incomplete dominance
Polygenic traits
Epistatic genes
Sex-linked
3 types of inheritance PATTERNS (show up in PEDIGREE)
AUTOSOMAL (dominant and recessive)
SEX-LINKED
READ QUESTIONS CAREFULLY!!!
WRITE DOWN YOUR VARIABLES!!!
PRACTICE PRACTICE PRACTICE!!!

25. YAY – we’re done!!! (types of inheritance…)