1. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Inheritance

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Genetics is the science of heredity These black Labrador puppies are purebred— their parents and grandparents were black Labs with very similar genetic makeups –Purebreds often suffer from serious genetic defects Purebreds and Mutts — A Difference of Heredity

3. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The parents of these puppies were a mixture of different breeds –Their behavior and appearance is more varied as a result of their diverse genetic inheritance

4. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Connection Inbreding causes an increase in abnormalities This is why there are laws about marryin’ yer sister…except in Arkansas

5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The science of heredity dates back to ancient attempts at selective breeding Until the 20th century, however, many biologists erroneously believed that –characteristics acquired during lifetime could be passed on –characteristics of both parents blended irreversibly in their offspring MENDEL’S PRINCIPLES The science of genetics has ancient roots

6. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Modern genetics began with quantitative experiments with pea plants Experimental genetics began in an abbey garden Figure 9.2A, B Stamen Carpel

7. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Definitions heredity: The passing of genetic traits from parent to offspring. dominant Trait: The trait observed in the first generation when parents that have different traits are bred. recessive Trait: A trait that reappears in the second generation after disappearing in the first generation when parents with different traits are bred.

8. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings What did Mendel Do? Mendel experimented with flower color. He crossed plants that had purple flowers with plants that had white flowers. –Result: All the flowers of the “first generation” were purple. –This means purple is a “dominant trait” because it is what showed up. So how do we get white flowers then?

9. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mendel crossed pea plants that differed in certain characteristics and traced the traits from generation to generation Figure 9.2C This illustration shows his technique for cross-fertilization 1 Removed stamens from purple flower White Stamens Carpel Purple PARENTS (P) OFF- SPRING (F 1 ) 2 Transferred pollen from stamens of white flower to carpel of purple flower 3 Pollinated carpel matured into pod 4 Planted seeds from pod

10. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mendel studied seven pea characteristics Figure 9.2D He hypothesized that there are alternative forms of genes (although he did not use that term), the units that determine heredity FLOWER COLOR FLOWER POSITION SEED COLOR SEED SHAPE POD SHAPE POD COLOR STEM LENGTH PurpleWhite AxialTerminal YellowGreen RoundWrinkled InflatedConstricted GreenYellow TallDwarf

11. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings From his experimental data, Mendel deduced that an organism has 2 genes (alleles) for each inherited characteristic –One gene comes from each parent Mendel’s principle of segregation describes the inheritance of a single characteristic P GENERATION (true-breeding parents) F 1 generation F 2 generation Purple flowersWhite flowers All plants have purple flowers Fertilization among F1 plants (F 1 x F 1 ) 3 / 4 of plants have purple flowers 1 / 4 of plants have white flowers Figure 9.3A

12. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A sperm or egg carries only one allele of each pair –The pairs of alleles separate when gametes form –This process describes Mendel’s law of segregation –Alleles can be dominant or recessive GENETIC MAKEUP (ALLELES) P PLANTS F 1 PLANTS (hybrids) F 2 PLANTS PPpp All PAll p All Pp 1/2 P1/2 P 1/2 p1/2 p Eggs P p P PP p Sperm Pp pp Gametes Phenotypic ratio 3 purple : 1 white Genotypic ratio 1 PP : 2 Pp : 1 pp Figure 9.3B

13. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Alternative forms of a gene (alleles) reside at the same place (or locus) on homologous chromosomes Homologous chromosomes bear the two alleles for each characteristic GENE LOCI Figure 9.4 PaB DOMINANT allele RECESSIVE allele Pab GENOTYPE:PPaaBb HOMOZYGOUS for the dominant allele HOMOZYGOUS for the recessive allele HETEROZYGOUS

14. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The inheritance of many human traits follows Mendel’s principles and the rules of probability 9.8 Connection: Genetic traits in humans can be tracked through family pedigrees Figure 9.8A

15. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Family pedigrees are used to determine patterns of inheritance and individual genotypes Figure 9.8B Dd Joshua Lambert Dd Abigail Linnell D_ Abigail Lambert Female Dd Elizabeth Eddy D_ John Eddy ?D_ Hepzibah Daggett ? ? ddDd ddDd Male Deaf Hearing dd Jonathan Lambert

16. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most such disorders are caused by autosomal recessive alleles –Examples: cystic fibrosis, sickle-cell disease 9.9 Connection: Many inherited disorders in humans are controlled by a single gene Figure 9.9A DD dd Normal Dd Normal Dd DD Normal Dd Normal (carrier) Dd Normal (carrier) dd Deaf EggsSperm PARENTS OFFSPRING

17. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A few are caused by dominant alleles Figure 9.9B –Examples: achondroplasia, Huntington’s disease

18. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 9.9

19. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings karyotyping and biochemical tests of fetal cells and molecules can help people make decisions about having babies –Fetal cells can be obtained through amniocentesis Connection: Fetal testing can spot many inherited disorders early in pregnancy Figure 9.10A Amniotic fluid Fetus (14-20 weeks) Placenta Amniotic fluid withdrawn Centrifugation Fetal cells Fluid UterusCervix Cell culture Several weeks later Karyotyping Biochemical tests

20. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chorionic villus sampling is another procedure that obtains fetal cells for karyotyping Figure 9.10B Fetus (10-12 weeks) Placenta Chorionic villi Suction Several hours later Fetal cells (from chorionic villi) Karyotyping Some biochemical tests

21. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Examination of the fetus with ultrasound is another helpful technique Figure 9.10C, D

22. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Genes on the sex chromosomes Most sex-linked human disorders are due to recessive alleles –Examples: hemophilia, red-green color blindness –These are mostly seen in males –A male receives a single X-linked allele from his mother, and will have the disorder, while a female has to receive the allele from both parents to be affected

23. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Color Blindness

24. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A high incidence of hemophilia has plagued the royal families of Europe…because of inbreeding Figure 9.23B Queen Victoria Albert AliceLouis AlexandraCzar Nicholas II of Russia Alexis