1. Patterns of Inheritance
Beyond Mendel
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2. Mendel and the Garden Pea
Advantages of Garden Pea for research:
Many hybrids previously produced.
Large number of true-breeding varieties.
Small and easy to grow.
Short generation time.
Sexual Organs enclosed in flower.
Self-fertilization
Cross fertilization
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3. TestCross
If you cross a plant with an unknown genotype (PP or Pp) with a homozygous recessive individual, the two possible genotypes will yield different results.
pp x PP = 100% (Pp)
pp x Pp = 50% (pp) : 50% (Pp)
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4. Mendelian Inheritance
Phenotype Considerations
Continuous Variation
The greater the number of genes influencing a character, the more continuous the expected distribution of character variation will be.
Example: eye color, hair color, height
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5. Phenotypic Considerations
Incomplete Dominance
Heterozygotes are intermediate in color.
Ex: four o’clock flowers
RR=red
WW=white
RW=pink
Environmental Effects
Degree of allele expression may depend on the environment.
Ex: lung cancer gene and smoking
Epistasis
One gene interferes with the expression of another gene.
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6. Multiple Alleles: ABO Blood Group
Codominance - No single allele is dominant, and each allele has its own effect.
ABO Blood Groups
Human gene that encodes enzyme that adds sugar molecules to lipids on the surface of red blood cells.
IB adds galactose
IA adds galactosamine
i adds no sugar
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7. Chromosomes and Inheritance
A trait determined by a gene on the sex chromosome is said to be sex-linked.
In Drosophila, sex is determined by the number of copies of the x chromosome.
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8. Human somatic cells normally have 23 pairs of chromosomes.
Human Chromosomes
Human somatic cells normally have 23 pairs of chromosomes.
Divided into seven groups characterized by size and shape.
22 pairs of autosomes
1 pair of sex chromosomes
XX = Female
XY = Male
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9. Karyotype
A karyotype is an organized profile of a person's chromosomes
Picture is taken of chromosomes during prophase of mitosis.
They are cut out and matched up using size, banding patterns, and centromere position
Helps scientists quickly identify chromosomal alterations that may result in a genetic defects.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

10. Copyright © McGraw-Hill Companies Permission required for reproduction or display
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies