1. Extending Mendelian Genetics Chapter 7
Complex Patterns of Inheritance
Day One

2. GENES are more complicated than Mendel thought
ENVIRONMENT influences
____________________________ the ________________________.
= ________________________
Genes ________ the ______ for development, but how plan unfolds also _______ on ______________conditions.
expression of genes
“Nature versus Nurture”
provide plan
depends
environmental

3. GENES are more complicated than MENDEL thought
Traits determined by ____________have
_____“___________”
phenotypes.
more than one gene
many
in-between

4. Sex-linked Traits Traits (genes) located on the sex chromosomes
Mendelian Genetics
9/19/2018
Sex-linked Traits
Traits (genes) located on the sex chromosomes
Sex chromosomes are X and Y
XX genotype for females
XY genotype for males
Many sex-linked traits carried on X chromosome
copyright cmassengale

5. Sex-linked Traits Example: Eye color in fruit flies Sex Chromosomes
Mendelian Genetics
9/19/2018
Sex-linked Traits
Example: Eye color in fruit flies
Sex Chromosomes
XX chromosome - female
XY chromosome - male
fruit fly
eye color
copyright cmassengale

6. Sex-linked Trait Problem
Mendelian Genetics
Sex-linked Trait Problem
9/19/2018
Example: Eye color in fruit flies
(red-eyed male) x (white-eyed female) XRY x XrXr
Remember: the Y chromosome in males does not carry traits.
RR = red eyed
Rr = red eyed
rr = white eyed
XY = male
XX = female XR Xr Y
copyright cmassengale

7. Sex-linked Trait Solution:
Mendelian Genetics
9/19/2018
Sex-linked Trait Solution: XR Xr Y
50% red eyed female
50% white eyed male
XR Xr
Xr Y
copyright cmassengale

8. Sex Linked Traits Most sex-linked traits on X chromosome are recessive
Examples include: hemophilia, red-green colorblindness, and a form of muscular dystrophy

9. Colorblindess Test
A person with red-green color blindness sees a number 2.

10. Colorblindess Test

11. Colorblindness Test

12. Hemophilia
In this pedigree, only males are affected, and sons do not share the phenotypes of their fathers.
Thus, hemophilia is linked to a sex chromosome–the X.
Expression of hemophilia often skips generations.
Thus, it is recessive.
Extensive bruising of the left forearm and hand in a patient with hemophilia.
Hemophilia
Hemophilia is a condition of excessive bleeding caused by missing clotting factors in the blood. Hemophiliacs are prone to bruising, as illustrated in the photo here, and to other, potentially fatal, risk factors. In this pedigree, there is a trend for only males to express the trait strongly suggesting the role of sex chromosomes. However, the sons do not share the phenotypes of their fathers, so the Y chromosome is not a likely candidate. Thus, we can conclude that the gene for hemophilia is on the X chromosome.
Since the trait skips generations, we can assume that an allele for hemophilia is recessive to an allele for normal blood clotting factors. Although rare, a female can be afflicted if she inherits an allele for hemophilia on both X chromosomes.
Reference
Campbell, N. E. & Reece, J. B. (2002). Biology (6th ed.). San Francisco: Benjamin Cummings.
Image Reference
Young, M. (2005). Pedigree chart. Houston, TX: Baylor College of Medicine, Center For Educational Outreach.
Hemophilia A. Retrieved from

13. Genotypes for females XHXH = normal blood clotting, non-carrier
XHXh = normal blood clotting, carrier of gene
XhXh = female with hemophilia
Queen Victoria of the
United Kingdom was a
carrier of hemophilia

14. Genotypes for Males XHY = normal blood clotting
XhY = male with hemophilia
Tsarevich Alexei of Russia
had hemophilia

15. Cross a carrier mother with a normal father.XH Xh Y

16. No daughters with hemophilia, ½ of sons with hemophiliaXH Xh
XHXH
XHXh Y
XHY
XhY

17. Cross a hemophiliac father with a normal (non-carrier) mother.XH Xh Y

18. All daughters are carriers, no sons have hemophilia.XH Xh
XHXh Y
XHY

19. Disorders Caused by Recessive Alleles
Two copies of the allele must be present for a person to have the disorder.
Appear in offspring of parents who are both heterozygotes.
Each parent has one dominant (normal) allele that masks the disease-causing allele.
A person that is homozygous for the recessive allele has the disease.
A person that is heterozygous for the allele will not have the disease, but will be a carrier.
Carrier – does not show disease symptoms but can pass on the disease-causing allele.

20. GENES are more complicated than MENDEL thought
KINDS OF DOMINANCE
____________________
COMPLETE DOMINANCE
INCOMPLETE DOMINANCE
CO-DOMINANCE

21. COMPLETE DOMINANCE __________ allele _______ the ___________ one
Dominant
__________ allele _______ the ___________ one
PATTERN ? ____________ allele ________
in a _____ratio in the ____ generation
masks
recessive
Recessive
returns
3:1 F2

22. INCOMPLETE DOMINANCE __________ expected _____ ratio in F2 generation
DON’T SEE
__________ expected
_____ ratio in F2
generation
_____________ organisms
with one dominant and
one recessive allele show
a _________ in-between
trait
3:1
Heterozygous
BLENDED

23. Incomplete Dominance
An individual displays a trait that is intermediate between the two parents
Example: a red snapdragon
crossed with a white
snapdragon produces
pink offspring

24. Red = RR, White = WW, Pink = RW

25. Make a Punnett square for a red plant crossed with a white plant

26. All offspring are pink, with RW genotype
R R RW W

27. What happens if you cross two pink snapdragons?

28. Offspring are 1 red, 2 pink, and 1 white
R W RR RW WW R W

29. 1 red (RR), 2 pink (RW), 1 white (WW)

30. Incomplete
dominance
in horse
coat color

31. Codominance Two dominant alleles are expressed at the same time
Roan coat color in horses or cows is an example
A roan horse has both red and white hair

32. Codominance red white roan
Defined: When both alleles are dominant and equally expressed
The colors do NOT blend together, but are equally seen
Ex: Cattle Coat
Red cow x White cow =
Roan Cow
Ex: Human Blood types
Type A x Type B = Type AB
red
white
roan

33. Roan 
has red
and white
hairs

34. CO-DOMINANCE BOTH SAME TIME
_______ traits are expressed at ___________ (_____________________) in heterozygote
NO BLENDING
ROAN
A ________HORSE has ______________ hair and __________ hair side by side
BOTH RED
WHITE

35. Parents  
Codominance
in chicken
feather color.
Black and
White feathers
Erminette

36. Codominance Example
In some chickens, the gene for feather color is controlled by codominance. The allele for black is CB and the allele for white is CW. The heterozygous phenotype is known as erminette.
a. What is the genotype for black chickens? ____
b. What is the genotype for white chickens? ____
c. What is the genotype for erminette chickens ______?
CBCB
CWCW
CBCW

37. CoDominance Example
If two erminette chickens were crossed, what is the probability that:
a. They would have a black chick? ____%
b. They would have a white chick? ____%
Parents: ____ X ____

38. Codominance example CB CW CB CW

39. Codominance example CB CW
CBCB
CBCW CB CW
CBCW
CWCW

40. CoDominance Example
If two erminette chickens were crossed, what is the probability that:
a. They would have a black chick? ____%
b. They would have a white chick? ____%
Parents: ____ X ____ 25 25
CBCW
CBCW

41. Practice problems:
Using XBXB x XbY, answer the following questions (Show the Punnett square):
What proportion/percent of the male children are colorblind?
What proportion/percent of the female children are colorblind?
In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red (R) and (W). The heterozygous genotype is expressed as pink.
What is the phenotype of a plant with the genotype of RR?
What is the phenotype of a plant with the genotype WW?
What is the phenotype of a plant with the genotype RW?

42. Extending Mendelian Genetics Chapter 7
Complex Patterns of Inheritance
Day Two

43. GENES are more complicated than Mendel thought
Some traits have ____________ allele __________
= ____________________
EX: blood type
Allele choices ___ ___ ___
MORE than 2
choices
MULTIPLE ALLELE TRAIT A B O

44. An A allele tells the cell to put “A” glycoproteins on its surface
BLOOD TYPES
An A allele tells
the cell to put
“A” glycoproteins
on its surface

45. different “B” glycoprotein on its surface
BLOOD TYPES
A B allele tells
the cell to put a
different “B” glycoprotein
on its surface

46. the cell NOT to put anything on the surface
BLOOD TYPES
An O allele tells
the cell NOT to put anything on the surface

47. A and B are CO-DOMINANT
A cell with BOTH an
A and a B allele
has BOTH
“A” and “B”
glycoproteins on its surface

48. Blood types are also an example of codominance.
The ABO blood types result from codominant alleles
This blood group consists of 3 different alleles
Dominant A allele
Dominant B allele
Recessive O allele
A and B are equally
dominant

49. PHENOTYPE (BLOOD TYPE)
BLOOD TYPES & ALLELES
GENOTYPE
PHENOTYPE (BLOOD TYPE)
IAIA
IAi
IBIB
IBi ii
IAIB A A B B O AB

50. O ____ can donate to EVERY BLOOD TYPE = _________________
DONOR BLOOD O
____ can donate to EVERY BLOOD TYPE
= _________________
Nothing on surface to recognize as “NOT SELF”
UNIVERSAL DONOR
YOU DON’T HAVE ANYTHING I DON’T HAVE!
Body images modified from:

51. AB can only GIVE to AB BUT . . .
______ can RECEIVE FROM
EVERY BLOOD TYPE
= ____________________ AB
UNIVERSAL RECIPIENT

52. List the genotypes. 4 IAIB List the phenotypes. 4 type AB blood
Ex: Cross Jason who is homozygous for type A blood with Maria who is homozygous for type B blood.
List the genotypes.
4 IAIB
List the phenotypes.
4 type AB blood IA IA IB
IAIB
IAIB IB
IAIB
IAIB

53. Ex: Cross Mike who is heterozygous for type A blood with Lisa who is heterozygous for type B blood.
List the genotypes.
1 IAIB, 1IAi, 1IBi, 1 ii
List the phenotypes.
1 type AB blood
1 type A blood
1 type B blood
1 type O blood
Probability of Heterozygous individual?
75% IA i
IBi IB
IAIB i
IAi ii

54. V. Polygenic traits Traits that are influenced by 2 or more genes
Examples include human height,weight,hair color, eye color, and skin color

55. Epistasis One gene that interferes with the expression of other genes.
Example is with albinism.
One gene interferes with all other genes for pigment production.

56. The environment interacts with genotype.
Phenotype is a combination of genotype and environment.
The sex of sea turtles depends on both genes and the environment
Height is an example of a phenotype strongly affected by the environment.

57. A pedigree is a chart for tracing genes in a family.
Phenotypes are used to infer genotypes on a pedigree.
Autosomal genes show different patterns on a pedigree than sex-linked genes.

58. A circle represents a female A square represents a male
On a pedigree:
A circle represents a female
A square represents a male
A horizontal line connecting a male and female represents a marriage
A vertical line and a bracket connect the parents to their children
A circle/square that is shaded means the person HAS the trait.
A circle/square that is not shaded means the person does NOT have the trait.
Children are placed from oldest to youngest.
A key is given to explain what the trait is.

59. Marriage
Male-DAD
Female-MOM
Has the trait
Female-daughter
Male- Son
Male-Son
Oldest to youngest

60. ff Ff Ff Key: affected male affected female
Steps:
Identify all people who have the trait.
For the purpose of this class all traits will be given to you.
In this example, all those who have the trait are homozygous recessive.
Can you correctly identify all genotypes of this family?
F- Normal
f- cystic fibrosis Ff
Key: affected male affected female
unaffected male unaffected female

61. Several methods help map human chromosomes.
A karyotype is a picture of all chromosomes in a cell.
X Y

62. Karyotypes can show changes in chromosomes.
deletion of part of a chromosome or loss of a chromosome
large changes in chromosomes
extra chromosomes or duplication of part of a chromosome

63. Practice problems
A man with type A blood marries a woman with type A blood. They have the first child with blood type O. What are the genotypes of the father, mother, and baby?
You are blood type O and you marry a person with blood type AB.
Complete the Punnett square for this cross.
List the possible blood types (phenotypes) of your offspring.