1. Forming a New Life
Chapter 3
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2. Genetic testing and engineering
Genomics—the study of functions and interactions of various genes
Genetic testing: Should children be tested?
Would you want to know if you were predisposed for a particular disease?
Are there potential ethical and moral issues with genetic testing?
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3. Conceiving New Life Fertilization
Union of sperm and ovum to produce a single-celled zygote
Also called conception
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4. Two Types of Multiple Births
Monozygotic (MZ)
One egg – One sperm
Identical Twins
Share 100% of genes
Dizygotic (DZ)
Two eggs – Two sperm
More common
Fraternal Twins
Share 50% of genes – just like non-twin siblings
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5. Rise in Multiple Birth Rate
Factors
Rising trend toward delaying childbirth
Increasing use of fertility drugs
Related Risks
Pregnancy complications
Premature delivery and lower birth weight
Infant disability or death
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6. Mechanisms of Heredity: DNA
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7. Determination of Sex
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8. Sex Determination Chromosomes: Coils of DNA carrying genes Autosomes:
22 pairs not related to sexual expression
Sex chromosomes:
1 pair determining sex
XX = female
XY = male
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9. Dominant and Recessive Inheritance
 Heterozygosity, with a dominant allele
Recessive
Homozygosity, with no dominant allele
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10. Trait Inheritance Alleles Polygenic Inheritance
Homozygous: Identical copies of gene
Heterozygous: Different copies of gene
Polygenic Inheritance
Interaction of several genes for a trait
Most traits
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11. Dominant-Recessive Inheritance: Tongue Curling Example
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12. Gene Expression Genotype Phenotype Multifactorial transmission
Actual genetic makeup or allele combinations
Tongue curling ability: DD or Dd
Phenotype
Observable expression of genetic make-up
Product of the genotype
Multifactorial transmission
Experience modifies the expression of a genotype
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13. Inherited Defects Dominant abnormal gene Recessive abnormal gene
Incomplete: Partial dominance
Trait is not fully expressed
Sickle-cell anemia - only some parts of the disease are expressed
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14. Sex-Linked Defects Disorders linked to genes on sex chromosomes
Red/green colorblindness, hemophilia
Affects males and females differently
Carrier
Individual unaffected by disorder but passes on gene to offspring
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15. Chromosomal Abnormalities
Errors in cell division
Result in missing or extra chromosomes
Can occur in sex chromosomes or autosomes
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16. Down Syndrome Trisomy 21 – an extra 21st chromosome
Most common autosomal disorder
Responsible for 40% of moderate to severe mental retardation
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17. Genetic Counseling
Helps prospective parents assess risk of bearing a child with a genetic defect
Karyotype chart shows chromosomal abnormalities
Especially helpful when:
Already have biological children with defect
Family history
Ethnicity
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18. Behavioral Genetics
How does heredity and environment influence traits?
Heritability:
Statistical estimate of heritable influence on trait variance in a population
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19. Measuring Heritability
Family Studies
The degree to which bio-relatives share traits
Adoption Studies
The degree to which adopted children resemble biological relatives or adopted family members
Twin Studies
Concordance: The degree to which MZ and DZ twins resemble each other for a trait
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20. Genotype-Environment (G x E) Correlations
Environment reflects or reinforces genetic differences
Passive: Parents provide environment that fosters trait
Reactive or Evocative: Based on their traits, children evoke different responses from others
Active or Niche Picking: choosing an environment that suits your traits
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21. Nonshared Environment
Development reflects unique environment in which each child grows up
Accidents
Illnesses
Unique interactions with friends or peers
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22. Traits Influenced by Heredity & Environment
Obesity
Intelligence, school achievement
Personality
Schizophrenia
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23. Stages of Prenatal Development
Duration
Germinal
Conception to 2 weeks
Embryonic
2 to 8 weeks
Fetal
8 weeks to birth
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24. Germinal Stage Development
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25. Embryonic Stage Characteristics
Organs and major body systems develop rapidly
Respiratory
Digestive
Nervous
Risk of spontaneous abortion, or miscarriage
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26. Development During Fetal Stage
Organs and body become more complex
‘Finishing Touches’ – toenails, eyelids
Appearance of bone
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27. Maternal Factors Teratogenic: birth defect producing
Nutrition and maternal weight
Drugs & alcohol intake
Nicotine
Caffeine
Maternal illnesses
Sexually Transmitted Diseases (HIV/AIDS)
Maternal age and stress
Outside environmental hazards
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28. Paternal Factors May affect quality of sperm: Exposure to lead
Marijuana or tobacco smoke
Alcohol or radiation
Pesticides
Paternal age
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29. Monitoring Prenatal Development
Ultrasound and Amniocentesis
Chorionic villus sampling CVS)
Embryoscopy
Maternal blood test
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30. Prenatal Care Not evenly distributed among SES, ethnic groups
Includes:
Education
Social services
Nutritional services
 Helps protect the life and health of the infant and mother
Not evenly distributed among SES, ethnic groups
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31. Prenatal Care
Figure 3-11
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32. Preconception care CDC recommendations include: Physical examinations
Vaccinations
Risk screening
Counseling
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