2. Genetics
Study of inheritance, the stability and variance of inheritance patterns
Gregor Mendel, “The Father of Genetics”
Worked with the garden pea plant using cross pollination
What would happen if we all had the exact same DNA sequences? What if we had extremely divergent DNA sequences?
What determines which genes we inherit from our mother and father?

3. Genetic Terms
Gene-basic unit of inheritance, arranged in a linear sequences on a chromosomes
Allele-alternative forms of a gene; alleles contain genetic information that is expressed as traits.
Examples of traits are flower color, seed shape, plant height etc.
Each trait can have a different version (allele); flower color can be purple or white, we use one letter for the trait flower color, but change whether it is upper or lower case

4. Genetic Terms
Dominant- 1 copy of allele results in expression of trait, always use a capital letter to show it is dominant, ex. A
Recessive-requires 2 copies of same allele to get expression of trait, always use lower case letter to show it is recessive, ex. a
If purple is dominant to white flowers, how would you write your alleles?

5. Genetic Terms
Homozygous Dominant-2 same copies of dominant allele, get expression of dominant trait, AA
Heterozygous Dominant-1 copy of dominant allele, 1 copy of recessive, still get dominant trait expression, Aa
Homozygous recessive-2 copies of recessive allele, get expression of recessive trait, aa

6. Genetic Terms Genotype-genes of an organism
Phenotype-physical appearance of the organism
True or False: The phenotype of an organism is dictated by the genotype of that organism
True breed lineage vs. hybrid offspring
P, F1, F2 Generation

7. Genetic Terms
Monohybrid cross-a cross that only predicts the genotype and phenotype for one trait, ex. plant flower color
Dihybrid cross-a cross that predicts the genotype and phenotype of 2 traits, ex. plant flower color and height

8. Predicting Gametes
If an organism has the genotype BB, how many different gametes can it make? 1: B
When predicting gametes, keep in mind that each gamete must have 1 complete set of instructions
Cc DDEE GgHh
2: C, c : DE 4: GH, Gh, gH, gh
KKLlMM TTUUVV AaBBCc

9. Mendel’s Early Genetic Experiments: Monohybrid Cross
Crossed a true breed purple flower plant with a true breed white flower plant P generation PP x pp P-purple p-white Pp F1 generation, all purple heterozygous dominant Crossed the F1 generation with each other Pp x Pp F2 generation PP, Pp, Pp, pp Genotypic Ratio 1 PP: 2 Pp :1 pp Phenotypic Ratio 3 purple: 1 white

10. Mendel’s Law of Segregation
Mendel continued his monohybrid crosses (1000s) for 7 different traits
Average ratio for all traits studied was always about 3:1
The Law of Segregation:
Each individual has 2 of every gene (alleles) for each trait
These genes (alleles) will separate from each other during meiosis into different gametes.
Fertilization gives each new individual 2 alleles for each trait

11. A a b B A B A b a B a b

12. Genetics Problem
In parrots, alleles for blue feathers are dominant to alleles for yellow.
Cross a heterozygous dominant blue feathered parrot with a yellow feathered parrot

13. Monohybrid Genetics Problem
B b Bb bb b
Genotypic ratio 1 Bb : 1 bb
Phenotypic ratio 1 Blue : 1 yellow

14. Genetics Problem
Rhinoceroses can be born without a horn, the recessive condition.
Cross 2 heterozygous dominant rhinoceroses. Can they produce a baby rhino without a horn?

15. Monohybrid Cross H h HH Hh hh H h H-horn present h-no horn
Genotypic Ratio 1 HH: 2 Hh : 1 hh
Phenotypic Ratio 3 with horns : 1 no horn

16. Mendel’s Early Genetic Experiments: Dihybrid Cross
Mendel noticed that all purple flower plants were tall and all white flower plants were short
Could you ever see a purple short plant or a white tall plant?
Crossed a homozygous dominant tall purple flower plant with a homozygous recessive short white flower plant

17. Mendel’s Early Genetic Experiments: Dihybrid Cross
P generation AABB x aabb
F AaBb
F AaBb x AaBb
4 by 4 punnett square
Phenotypic ratio 9 purple, tall: 3 purple, short: 3 white, tall: 1 white, short

18. Mendel’s Early Genetic Experiments: Principle of Independent Assortment
The results from the many dihybrid crosses allowed him to develop the
Principle of Independent Assortment-gene pairs (traits) are independent of each other and are sorted into different gametes
Exception: Linked genes; they always sort together into same gamete

19. A a b B
Diploid (2N) A B A b a B a b
Haploid (1N)

20. Genetics Problem: Dihybrid Cross
In panthers, black fur is dominant to yellow fur.
A recessive gene results in the absence of claws.
Predict the offspring of a cross between a heterozygous black panther with no claws and a yellow panther that is heterozygous for claws

21. Genetics Problem: Dihybrid Cross
B-black fur b-yellow fur
C-claws c-no claws
bC bc
BbCc
Bbcc
bbCc
bbcc Bc bc
Genotypic Ratio 1:1:1:1
Phenotypic Ratio 1:1:1:1

22. Punnett Square and Probabilities
What is the probability from the following cross that any offspring will have unattached earlobes or attached earlobes?
The probability of inheriting a specific allele is like flipping a coin and occurs every time parents have an offspring

23. Mendel’s Early Genetic Experiments: Test Cross
If you have a purple flower, what are the possible genotypes?
PP or Pp
How do you decide? Do a Test Cross using a white flower plant
PP x pp = all offspring are Pp (purple)
Pp x pp = ½ offspring are Pp (purple)
½ offspring are pp (white)

24. Human Genetics
The study of inheritance and prediction of genes in humans
Very difficult, many genes involved
Small sample size, few offspring
Mate by chance, live in diverse environments
Long life span makes it difficult to track genes in different generations

25. Human Genetics: Understanding a Pedigree
Pedigree-a chart of genetic connections between individuals; family tree that tracks genes/diseases
Single genes can be followed by constructing pedigrees
Square=male circle=female
Shaded =affected non-shaded=not affected
A line between a circle + square=mating
Lines from the mating=offspring

26. Human Inheritances Patterns
Autosomal Recessive Inheritance-gene is located on autosome; 2 copies of gene required for expression of disease/trait; 1 copy=carrier, not affected
Albinism, cystic fibrosis, sickle cell anemia, phenylketonuria, methemoglobinemia, Niemann-Pick disease

27. Effects of Autosomal Recessive Disorders

28. Autosomal Recessive Inheritance
F-normal, no cystic fibrosis f-cystic fibrosis
What are the chances of offspring from 2 heterozygote parents for the cystic fibrosis gene having the disease?
Parents are carriers
F f FF Ff ff F f
25% (1 out of 4) will have cystic fibrosis
What are the genotypic/phenotypic ratios?

29. Human Inheritances Patterns
Autosomal dominant inheritance- gene is located on autosome; 1 copy of gene results in expression of disease/trait
Ex. Achondroplasia, Huntington’s, Osteogenesis Imperfecta, polydactyly, progeria, sperocytosis

30. Autosomal Dominant Inheritance
P-polydactyly (extra fingers/toes) p-normal
What are the chances of offspring from a cross of 2 heterozygous parents for polydactyly also having the condition?
P p PP Pp pp P p
75% (3 out of 4) chance of having polydactyly
What is the genotypic/phenotypic ratios?

31. Variations to Mendelian Inheritance Patterns: Multiple Alleles
Codominance
2 alleles are not dominant to each other, and if both are present both are expressed
Ex. Blood Groups- ABO blood typing
A dominant to O, but not to B
B dominant to O, but not to A
O recessive

32. Codominance: Blood Typing
There are 6 genotypes that express 4 different blood phenotypes
Phenotype Genotype
Type A AA, AO
Type B BB, BO
Type AB AB
Type O OO

33. Codominance: Blood Typing
What does a blood typing do? Why is blood called A, B, AB, or O?
Based on the different sugars found on red blood cells ex. Type A blood has A sugars on RBCs
What type of sugars does AB or O have?
Why do we need to type blood?

34. Codominance: Blood Typing Problems
Cross a person with type O blood with one that has type AB blood
Give phenotypic and genotypic ratios

35. Codominance: Blood Typing ProblemsAO BO A B
Genotypic Ratio 1 AO : 1 BO
Phenotypic Ratio 1 Type A : 1 Type B

36. Codominance: Blood Typing Problems
Type B blood male and a Type O blood female never produce a Type O blood child.
Is this possible? Why or why not?

37. Codominance: Blood Typing Problems
Type B blood can be BB or BO*
O O BO B
Genotypic Ratio All are BO
Phenotypic Ratio All are Type B
*this genotype would produce a Type O offspring

38. Blood Type Problem BO OO O
If father’s genotype is BO, it would be possible to get an O blood type child
B O BO OO O
Genotypic ratio: 1 BO: 1 OO
Phenotypic ratio: 1 type B: 1 type O blood

39. Variations to Mendelian Inheritance Patterns
Incomplete Dominance-one allele isn’t complete dominant to the other; heterozygotes are intermediate in phenotype
Snap dragon flower color: R-red, r-white
RR x rr = Rr all offspring are pink
What happens when 2 pink flower plants are crossed? Give phenotypic and genotypic ratios Rr Rr

40. Incomplete Dominance
R-red r-white Rr-pink
R r R r RR Rr rr

41. Pleiotropy
Expression of alleles (for 1 trait) has positive or negative effects on other traits Ex. Sickle cell mutation
Affects the protein hemoglobin which carries O2
Insufficient O2 will cause RBCs to sickle and eventually burst anemia
Secondary effectsheart/lung damage, kidney/heart failure, skull deformation, mental impairment

42. Pleiotropy: Marfan Syndrome
Single gene mutation affects 2 or more distinct and unrelated traits
mutation of fibrillin gene

43. Incomplete Penetrance
Polydactyly  extra fingers/toes
Autosomal dominant disorder which exhibits incomplete penetrance
A dominant allele sometimes does not determine the phenotype
Some who inherit polydactyly allele are phenotypically normal

44. Pleiotropy: Sickle Cell Anemia
Homozygous for condition die in early 40s, no cure, extremely debilitating
Severe anemia, poor circulation, physical weakness, impaired mental function, spleen damage
Why is this mutation maintained?
Protection/resistance against malaria
S-no sickle cell s-sickle cell (recessive)
SS-no sickle cell, no resistance
Ss-no sickle cell, resistance
ss-sickle cell, resistance
Heterozygote advantage

45. Sickle Cell Anemia Genetics Problem
Cross 2 heterozygous dominant parents together.
How many children would have sickle cell?
How many children would not?
How many children are resistant to malaria? How many are not?

46. Sickle Cell Anemia Genetics Problem
Parents are Ss-do not have sickle cell
S s SS Ss ss S s
3 children do not have sickle cell, 1 does
3 children protected, 1 is not

47. Epistasis
When one gene pair masks/prevents another gene pair’s expression
Ex. Labrador fur color
B-black fur b-brown fur
E-melanin deposited e-no melanin
The recessive genotype of “ee” will cause no melanin deposition, thus the resulting fur coat will be yellow, even when “B or b” alleles are present

48. Continuous Variation in Traits
Multiple genes are responsible for the phenotype of an organism  polygenic inheritance
Skin and eye color, height
A great deal of variation exists resembling a bell shaped curve
Look at human height; a few genes regulate height, but there exists a normal amount of variation
What factors contribute to height?

50. Environmental Effects on Phenotype: Multifactorial Traits
Fur color on Siamese cats or Himalayan rabbits-heat sensitive enzyme that produces melanin
Flower color on Hydrangea Plant-influenced by acidity of soil
Height of Yarrow plant cuttings-varies depending on elevation planted

51. Continuous Variation in Traits
Genetics allows us to predict genotypes of organisms, but there are many external and internal factors that influence the actual phenotype of those organisms  cleft lip/palate, clubfoot, hypertension, diabetes, schizophrenia, allergies, cancers
An individual’s phenotype is the outcome of the complex interaction among all its genes and environment in which it lives
G x E interaction

52. Sex Determination in Humans
Determined by the 23rd pair on chromosomes
XX-female XY-male
A female only makes eggs that carry the X chromosome
A male makes sperm that contain either the X or Y chromosome
Males are haploid for the X chromosome, females are diploid

53. Sex Determination in Humans
Sex is determined by the Y chromosome
Up until about 7 weeks, an embryo has a uncommitted reproductive duct system
This duct system will develop into testes/penis if a Y chromosome is present
This is due to the expression of the SRY gene located on the Y chromosome
No Y chromosome duct system forms into ovaries/uterus
Faulty SRY  phenotypic female, sterile

54. Human Inheritance Patterns
X-linked recessive-gene is located on the X chromosome; 2 copies of gene required for expression in females, 1 copy in males results in expression. XX vs XY
Ex. Fragile X syndrome, hemophilia, color blindness, muscular dystrophy, Menkes syndrome, adrenoleukodystropy

55. X-linked Recessive Inheritance Problem
What type of offspring would a colorblind man and woman who is a carrier for CB have?

56. X-linked Recessive Inheritance Problem
Female-Cc not colorblind Colorblind male-c
But CB is X-linked XCXc XcY
Xc Y
XCXc
XCY
XcXc
XcY XC Xc
Female offspring ratio 1 CB: 1 no CB
Male offspring ratio 1 CB: 1 no CB

57. X-linked Recessive Inheritance Problem
Can a female with muscular dystrophy ever have a son who does not have MS?
Can a male with hemophilia have a daughter who is not affected with the disease?

58. X-linked Recessive Genetics Problem
M-no MS m-has MS
XM Y
XMXm
XmY
XmXM Xm
No, all male offspring would have MS

59. X-linked Recessive Genetics Problem
H-no Hemophilia h-Hemophilia
Xh Y
XHXh
XHY
XhY XH
Yes, female offspring would not have hemophilia, but are carriers for the gene