1. OTHER PATTERNS OF INHERITANCE

2. Law of Independent Assortment
Mendelian Genetics
4/27/2017
Law of Independent Assortment
Alleles for different traits are distributed to sex cells (& offspring) independently of one another.

3. Trait determined by a gene on a sex chromosome (usually X).
Sex-Linked Traits
Trait determined by a gene on a sex chromosome (usually X).
Examples:
Colorblindness
Hemophilia
Muscular Dystrophy

4. Females with only 1 affected X are carriers.
Sex-Linked Traits:
*Females must receive 2 affected X’s in order to
express the trait.
Females with only 1 affected X are carriers.
Males that receive one X from mother expresses the trait.

5. Sex-Linked Punnett Square Practice
Cross a colorblind mother with a father who has normal vision: Give the genotypic and phenotypic ratios.
Key: XcXc = colorblind mother XY = normal vision father
Cross: XcXc (x) XY
Genotypic Ratio:
Phenotypic Ratio: Xc X Y
Answer on next slide…

6. Sex-Linked Genotypic Ratio: 2:4 XcX 2:4 XcY Phenotypic Ratio:
Mendelian Genetics
4/27/2017
Sex-Linked
Key: XX = female XY = male
Cross: XcXc (x) XY X Y Xc Xc
Genotypic Ratio:
2:4 XcX
2:4 XcY
Phenotypic Ratio:
2:4 Carrier Female
2:4 Colorblind Male
XcX
XcY

7. Polygenic Traits
“Many genes” ; Many traits are controlled by more than one gene; have a variety of choices for expression.
Ex: _hair color, eye color, skin tone___

8. Multiple Alleles Genes that have more than 2 alleles Ex: blood group.
There are 3 possible alleles for this gene. i ii

9. Blood Type Punnett Square Practice
Cross a female who is Type AA with a male who is Type O (ii): Give the genotypic and phenotypic ratios.
Key: AA = mother ii = father
Cross: AA x ii A
Genotypic Ratio:
Phenotypic Ratio: i
Answer on next slide…

10. Blood Type Genotypic Ratio: 4:4 Ai Phenotypic Ratio: 4:4 Type A Blood
Mendelian Genetics
4/27/2017
Blood Type
Key: AA = female ii = male
Cross: XcXc (x) XY i A A
Genotypic Ratio:
4:4 Ai
Phenotypic Ratio:
4:4 Type A Blood Ai

11. Mendelian Genetics
4/27/2017
Incomplete Dominance
Neither allele has “complete” dominance over the other; heterozygous phenotype is a blend of the 2 homozygous phenotypes
Ex: snapdragons
R = red
W = white
RW = pink

12. Incomplete Dominance
Cross a red (RR) snapdragon with a White (WW) snapdragon. Give the genotypic and phenotypic ratios.
Key: R = red flower W = white flower
Cross: RR x WW
Genotypic Ratio:
Phenotypic Ratio: W R
Answer on next slide…

13. Incomplete Dominance Genotypic Ratio: 0RR: 4RW: 0WW Phenotypic Ratio:
Mendelian Genetics
4/27/2017
Incomplete Dominance
Key: R = red W = white
Cross: RR x WW R W W
Genotypic Ratio:
0RR: 4RW: 0WW
Phenotypic Ratio:
0 Red: 4 Pink: 0 White RW

14. Mendelian Genetics
4/27/2017
Incomplete Dominance
Practice: Cross a pink snapdragon with a red snapdragon. Give the expected phenotypic and genotypic ratios.
Key: __________________
Cross: _________________
Genotypic Ratio: ________________________
Phenotypic Ratio: ________________________

15. Incomplete Dominance R R R RR RR W RW RW
Mendelian Genetics
4/27/2017
Incomplete Dominance
Practice: Cross a pink snapdragon with a red snapdragon. Give the expected phenotypic and genotypic ratios. R R
Key: R = red W = white RW = pink
Cross: _RW x RR__
Genotypic Ratio: __2RR: 2RW: 0WW__
Phenotypic Ratio: __2 red: 2 pink: 0 white_ R RR RR W RW RW

16. Mendelian Genetics
4/27/2017
Codominance
Codominance – Both alleles share dominance and are always expressed if present.
Ex: In chickens
B = black feathers
W = white feathers
BW = black AND white
feathers X

17. CODominance Cross a black (B) rooster with a white (W) chicken.
Give the genotypic and phenotypic ratios.
Key: B = black feathers W = white feathers
Cross: BB x WW
Genotypic Ratio:
Phenotypic Ratio: W B
Answer on next slide…

18. CODominance Key: B = black W = white Cross: BB x WW B W W BW
Mendelian Genetics
4/27/2017
CODominance
Key: B = black W = white
Cross: BB x WW B W W
Genotypic Ratio:
0BB: 4BW: 0WW
Phenotypic Ratio:
0 black:
4 black and white:
0 white BW

19. Mendelian Genetics
4/27/2017
CODominance
Practice: Cross two black and white feathered chickens. Give the expected phenotypic and genotypic ratios of the offspring.
Key: __________________
Cross: _________________
Genotypic Ratio: ________________________
Phenotypic Ratio: ________________________

20. CODominance B W B BB BW W BW WW
Mendelian Genetics
4/27/2017
CODominance
Practice: Cross two black and white feathered chickens. Give the expected phenotypic and genotypic ratios of the offspring. B W
Key: B = black W = white
BW = black and white
Cross: _BW x BW__
Genotypic Ratio: __1BB: 2BW: 1WW_
Phenotypic Ratio: _1 black: 2 black and white: 1 white_ B BB BW W BW WW