1. Mendel and the Gene Idea11
Mendel and the Gene Idea

4. Figure 11.1
Figure 11.1 What principles of inheritance did Gregor Mendel discover by breeding garden pea plants? 4

5. Concept 11.1: Mendel used the scientific approach to identify two laws of inheritance
Mendel discovered the basic principles of heredity by breeding garden peas 5

6. Technique Parental generation (P) Stamens Carpel Results First filial
Figure 11.2
Technique 1 2
Parental
generation
(P) 3
Stamens
Carpel 4
Figure 11.2 Research method: crossing pea plants
Results 5
First filial
generation
offspring
(F1) 6

7. Mendel chose characters that occurred in two distinct forms and created true-breeding lineages7

8. Mendel mated two contrasting, true-breeding varieties, (hybridization)
parents are the P generation
offspring of the P generation are called the F1 generation
F1 individuals self-pollinate or cross- pollinate with other F1, producing the F2 generation 8

9. (true-breeding parents)
Figure
Experiment
P Generation
(true-breeding
parents)
Purple flowers
White flowers
Figure Inquiry: When F1 hybrid pea plants self- or cross-pollinate, which traits appear in the F2 generation? (step 1) 9

10. (true-breeding parents)
Figure
Experiment
P Generation
(true-breeding
parents)
Purple flowers
White flowers
F1 Generation
(hybrids)
All plants had purple flowers
Self- or cross-pollination
Figure Inquiry: When F1 hybrid pea plants self- or cross-pollinate, which traits appear in the F2 generation? (step 2) 10

11. All plants had purple flowers
Figure
Experiment
P Generation
(true-breeding
parents)
Purple flowers
White flowers
F1 Generation
(hybrids)
All plants had purple flowers
Self- or cross-pollination
Figure Inquiry: When F1 hybrid pea plants self- or cross-pollinate, which traits appear in the F2 generation? (step 3)
F2 Generation
705 purple-flowered
plants
224 white-flowered
plants 11

12. Table 11.1
Table 11.1 The results of Mendel’s F1 crosses for seven characters in pea plants 12

13. Table 11.1a
Table 11.1a The results of Mendel’s F1 crosses for seven characters in pea plants (part 1) 13

14. Table 11.1b
Table 11.1b The results of Mendel’s F1 crosses for seven characters in pea plants (part 2) 14

15. Mendel’s Model Mendel’s model to explain the 3:1 F2ratio
1, alternative alleles account for variations in inherited characters
2, for each character an organism inherits two alleles, one from each parent
3, dominant alleles may mask recessive alleles
4, (law of segregation), the two alleles segregate during gamete formation (and end up in different gametes) 15

16. P Generation Appearance: Genetic makeup: Purple flowers PP
Figure
P Generation
Appearance:
Genetic makeup:
Purple flowers PP
White flowers pp
Gametes: P p
Figure Mendel’s law of segregation (step 1) 16

17. P Generation F1 Generation Appearance: Genetic makeup: Purple flowers
Figure
P Generation
Appearance:
Genetic makeup:
Purple flowers PP
White flowers pp
Gametes: P p
F1 Generation
Appearance:
Genetic makeup:
Purple flowers Pp
Gametes: P p
Figure Mendel’s law of segregation (step 2) 17

18. P Generation F1 Generation F2 Generation Appearance: Genetic makeup:
Figure
P Generation
Appearance:
Genetic makeup:
Purple flowers PP
White flowers pp
Gametes: P p
F1 Generation
Appearance:
Genetic makeup:
Purple flowers Pp
Gametes: P p
Sperm from
F1 (Pp) plant
Figure Mendel’s law of segregation (step 3)
F2 Generation P p P
Eggs from
F1 (Pp) plant PP Pp p Pp pp 3
: 1 18

19. Phenotype - physical appearance genotype - genetic makeup19

20. PP (homozygous) Pp (heterozygous) Pp (heterozygous) pp (homozygous)
Figure 11.6
Phenotype
Genotype PP
(homozygous)
Purple 1 3 Pp
(heterozygous)
Purple 2 Pp
(heterozygous)
Purple
Figure 11.6 Phenotype versus genotype pp
(homozygous) 1
White 1
Ratio 3:1
Ratio 1:2:1 20

21. Test Cross Used to tell genotype of individual with dominant phenotype
dominant phenotype crossed with recessive phenotype
Examining offspring determines genotype of dominant individual

22. Dominant phenotype, unknown genotype: PP or Pp? Recessive phenotype,
Figure 11.7
Technique
Dominant phenotype,
unknown genotype:
PP or Pp?
Recessive phenotype,
known genotype: pp
Predictions
If purple-flowered
parent is PP or
If purple-flowered
parent is Pp
Sperm
Sperm p p p p P P Pp Pp Pp Pp
Eggs
Eggs
Figure 11.7 Research method: the testcross P p Pp Pp pp pp
Results or
All offspring purple
½ offspring purple and
½ offspring white 22

23. independent assortment
Figure 11.8
Experiment
P Generation
YYRR
yyrr
Gametes YR yr
F1 Generation
YyRr
Predictions
Hypothesis of
dependent assortment
Hypothesis of
independent assortment
Sperm or
Predicted
offspring in
F2 generation YR Yr yR yr
Sperm YR yr YR
YYRR
YYRr
YyRR
YyRr YR
YYRR
YyRr Yr
Eggs
YYRr
YYrr
YyRr
Yyrr
Figure 11.8 Inquiry: Do the alleles for one character segregate into gametes dependently or independently of the alleles for a different character?
Eggs yr
YyRr
yyrr yR
YyRR
YyRr
yyRR
yyRr yr
Phenotypic ratio 3:1
YyRr
Yyrr
yyRr
yyrr
9 16
3 16
3 16
1 16
Phenotypic ratio 9:3:3:1
Results
315
108
101 32
Phenotypic ratio approximately 9:3:3:1 23

24. Mendel’s law of independent assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation
applies to genes on different, nonhomologous chromosomes or those far apart on the same chromosome 24

25. Degrees of Dominance Complete dominance incomplete dominance
codominance 25

26. P Generation Red CRCR White CWCW Gametes CR CW Figure 11.10-1
Figure Incomplete dominance in snapdragon color (step 1) 26

27. P Generation Red CRCR White CWCW Gametes Pink CRCW F1 Generation
Figure
P Generation
Red
CRCR
White
CWCW
Gametes CR CW
Pink
CRCW
F1 Generation
Gametes CR CW
Figure Incomplete dominance in snapdragon color (step 2) 27

28. P Generation Red CRCR White CWCW Gametes Pink CRCW F1 Generation
Figure
P Generation
Red
CRCR
White
CWCW
Gametes CR CW
Pink
CRCW
F1 Generation
Gametes CR CW
Figure Incomplete dominance in snapdragon color (step 3)
Sperm CR CW
F2 Generation CR
CRCR
CRCW
Eggs CW
CRCW
CWCW 28

29. Multiple Alleles
Most genes exist in populations in more than two allelic forms
For example, the four phenotypes of the ABO blood group in humans are determined by three alleles of the gene: IA, IB, and i.
The enzyme (I) adds specific carbohydrates to the surface of blood cells
The enzyme encoded by IA adds the A carbohydrate, and the enzyme encoded by IB adds the B carbohydrate; the enzyme encoded by the i allele adds neither 29

30. (a) The three alleles for the ABO blood groups and their carbohydrates
Figure 11.11
(a) The three alleles for the ABO blood groups and their
carbohydrates
Allele IA IB i
Carbohydrate A B
none
(b) Blood group genotypes and phenotypes
Genotype
IAIA or IAi
IBIB or IBi
IAIB ii
Figure Multiple alleles for the ABO blood groups
Red blood cell
appearance
Phenotype
(blood group) A B AB O 30

31. Extending Mendelian Genetics for Two or More Genes
Some traits may be determined by two or more genes 31

32. ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ BbEe BbEe Sperm Eggs BBEE BbEE BBEe BbEe BbEE bbEE
Figure 11.12
BbEe
BbEe
Sperm BE bE Be be
Eggs BE
BBEE
BbEE
BBEe
BbEe bE
BbEE
bbEE
BbEe
bbEe Be
BBEe
BbEe
BBee
Bbee
Figure An example of epistasis be
BbEe
bbEe
Bbee
bbee 9
: 3
: 4 32

33. Polygenic Inheritance
Quantitative variation usually indicates polygenic inheritance,
Skin color in humans is an example of polygenic inheritance 33

34. Figure 11.13
AaBbCc
AaBbCc
Sperm
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
Eggs
1 8
1 8
Figure A simplified model for polygenic inheritance of skin color
1 8
1 8
1 64
6 64
15 64
20 64
15 64
6 64
1 64
1 64
Phenotypes:
Number of
dark-skin alleles: 1 2 3 4 5 6 34

35. Describing Continuous Variation
Fig , p.181

36. Nature and Nurture: The Environmental Impact on Phenotype
Sometimes the phenotype depends on environment as well as genotype 36

37. Temperature Effects on Phenotype
This Rabbit is homozygous for allele producing heat-sensitive version of an enzyme in melanin-producing pathway
Melanin is produced in cooler areas of body
Figure Page 179

38. This Siamese cat, raised in a cold environment in Moscow in the late 20s, developed a relatively dark coat. An area on his shoulder was shaved, and the cat wore a warm jacket while the fur was growing back. When the shaved hair grew back in, it was white, the same color as the cat's belly, due to the increased temperature under the jacket. This was not due to scarring, as the hair grew in normally colored later.

40. FF or Ff FF or Ff WW or Ww Attached earlobe Free earlobe
Figure 11.14
Key
Male
Female
Affected
male
Affected
female
Mating
Offspring, in
birth order
(first-born on left) Ff Ff ff Ff
1st generation
(grandparents) Ww ww ww Ww
2nd generation
(parents,
aunts, and
uncles)
FF or Ff ff ff Ff Ff ff Ww ww ww Ww Ww ww
3rd generation
(two sisters) ff FF or Ff
Figure Pedigree analysis WW or Ww ww
Widow’s peak
No widow’s peak
Attached
earlobe
Free
earlobe
(a) Is a widow’s peak a dominant or recessive trait?
(b) Is an attached earlobe a dominant
or recessive trait? 40

41. Parents Normal Aa Normal Aa Sperm A a Eggs Aa Normal (carrier) AA
Figure 11.15
Parents
Normal Aa
Normal Aa
Sperm A a
Eggs Aa
Normal
(carrier) AA
Normal A Aa
Normal
(carrier)
Figure Albinism: a recessive trait aa
Albino a 41

43. Fig , p.183

45. Fig , p.183

46. Sickle-Cell Disease: A Genetic Disorder with Evolutionary Implications
Sickle-cell disease affects one out of 400 African-Americans
Recessive trait caused by a single amino acid substitution in hemoglobin
Symptoms include physical weakness, pain, organ damage, and even paralysis
Heterozygotes -less susceptible to malaria parasite, 46

47. Autosomal Dominant Inheritance example… Achondro-plasia
Fig. 12-5, p.190

48. Achondroplasia Autosomal dominant allele
Homozygous usually leads to stillbirth
Heterozygotes display a type of dwarfism
(short arms and legs relative to other body parts)

49. Huntington Disorder Autosomal dominant allele
Causes involuntary movements, nervous system deterioration, death
Symptoms appear after age 30
People often pass allele on before they know they have it

50. Huntington Disorder

51. Hutchinson-Gilford Progeria
Mutation causes accelerated aging
No evidence of it running in families
Appears dominant
Seems to arise as spontaneous mutation
Usually causes death in early teens

52. Hutchinson-Gilford Progeria
Fig. 12-7, p.191

53. blank