chapter 14 mendel and the gene idea [ mendelian genetics: the scientific study of heredity and...
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Chapter 14Mendel and the Gene Idea
[Mendelian genetics: The scientific study of heredity and hereditary variation]
van Leeuwenhoek (17th century)de Graaf (17th century)Early 19th century – blending theory
14.2Crossing pea plants (“genetic crosses”) – Gregor Mendel(19th century)
Discrete heritable factors
14.3Mendel tracked heritable characters for three generations
Both purple and white=flowered plants appear in the F2 generation in a ratio of approximately 3:1
Sweet pea flowers
14.4 Alleles, alternative versions of a gene
Table 14.1 Results of Mendel’s F1 Crosses for Seven Characters in Pea Plants
14.5 Mendel’s law of segregation (Layer 1)
14.5 Mendel’s law of segregation (Layer 2)
14.6 Genotype versus phenotype
Round and wrinkled peas
SS or Ss
ss
14.7A testcross
14.8Testing two hypotheses for segregation in a dihybrid cross.
Do alleles sort independently?
Recombinant phenotypes
14.9 Segregation of alleles and fertilization as chance events
1) Black fur in mice (B) is dominant to brown fur (b). Short tails (T) is dominant to long tails (t). What proportion of the progeny of the cross BbTt multiply BBtt will have black fur and long tails?
A) 6/16B) 8/16C) 9/16D) 3/16E) 1/16
2) Tallness (T) is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color. A dwarf red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals?
A) TtRr - tall and pinkB) ttRr - dwarf and pinkC) TtRr - tall and redD) TTRR - tall and redE) ttrr - dwarf and white
14.10 Incomplete dominance in snapdragon color
Carnation
Pleiotropic effects of the sickle-cell allele in a homozygoteSingle gene multiple effects
14.14 The effect of environment of phenotype
Norm of reaction for a genotype:The range of phenotypic possibilities due to environmental influence
AcidAlkaline
14.13.A simplified model for polygenic inheritance of skin color.(Mating between individuals who are heterozygous for all three genes)
Three separately-inherited genes affect the darkness of skin
Multiple genes single effect
14.11.Multiple alleles for the ABO blood groups.
Blood types are the result from various combinations of three different alleles (IA, IB and i)
14.15 Pedigree analysis
14.15 Pedigree analysis
Large families provide excellent case studies of human genetics
AlbinismCystic fibrosisHuntington’s disease
14.19Testing a fetus for genetic disorders
See Chapter 14 Review (p. 282-283)
• Concept 14.1. Two laws of inheritance (Mendel)
• Concept 14.2. Applying the law of probability to Mendelian genetics.
• Concept 14.3. Inheritance patterns are often more complex than predicted by Mendelian genetics.
• Concept 14.4. Many human traits follow Mendelian patterns
• Also look at tips for solving genetic problems (p. 283).
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