1. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Chapter 3 Forming A New Life: Conception, Heredity, and Environment

2. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. How Fertilization Takes Place  Fertilization  Union of sperm and ovum to produce a zygote.  Also called conception  Zygote:  One-celled organism resulting from fertilization.  Duplicates itself by cell division to create a baby 3-2

3. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. How Fertilization Takes Place  Women  At birth, have 2 million ova in their ovaries, each contained in a follicle.  During ovulation, when sexual maturity is attained, a mature follicle is ruptured and the ovum is expelled from the ovary. 3-3

4. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. How Fertilization Takes Place  Men  Several hundred million sperm are produced in the testicles each day.  Sperm enter the vagina through ejaculation and attempt to reach the cervix.  Few will arrive in the fallopian tubes where fertilization takes place. 3-4

5. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Infertility  Inability to conceive a baby after 12 months of trying.  Women’s fertility begins to decline in the late 20s.  Men’s fertility begins to decline in the late 30s. 3-5

6. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 3.1 - Common Causes of Infertility in Men and Women 3-6

7. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 3.1 - Common Causes of Infertility in Men and Women 3-7

8. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Treatments for Infertility Hormone Treatment Drug Therapy Surgery 3-8

9. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Alternative Ways to Parenthood  In vitro fertilization (IVF) - Increases the likelihood of multiple, usually premature, births.  In vitro maturation (IVM) - Diminishes the likelihood of multiple births.  Performed earlier in the monthly cycle  Makes hormone injections unnecessary 3-9

10. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Alternative Ways to Parenthood  Male infertility  Intracytoplasmic sperm injection (ICSI)  Artificial insemination  Artificial insemination by a donor (AID)  Gamete intrafallopian transfer (GIFT)  Zygote intrafallopian transfer (ZIFT)  Surrogate motherhood  Surrogate - Fertile woman impregnated by a prospective father by artificial insemination. 3-10

11. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Mechanisms of Heredity  Heredity  Genetic transmission of heritable characteristics from parents to offspring.  Genetic code  Sequence of bases within the DNA molecule.  Set of rules that govern the formation of proteins that determine the structure and functions of living cells. 3-11

12. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Figure 3.1 - DNA: The Genetic Code 3-12

13. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Genetic Code  Chromosomes: Coils of DNA that consist of genes.  Genes: Small segments of DNA located in definite positions on particular chromosomes.  Functional units of heredity  Located in a definite position on chromosome  Human genome: Complete sequence of genes in the human body. 3-13

14. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Cell Division  Meiosis  Type of cell division which the sex cells undergo when they are developing.  Crossing Over  Each sex cell ends up with only 23 chromosomes.  Mitosis  Process by which the nonsex cells divide in half over and over again.  DNA replicates itself, so that each newly formed cell has the same DNA structure as all the others. 3-14

15. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Genotypes and Phenotypes  Phenotype: Observable characteristics of a person.  Genotype: Genetic makeup of a person, containing both expressed and unexpressed characteristics. 3-15

16. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Patterns of Genetic Transmission  Dominant and recessive inheritance  Every offspring gets a pair of alleles for each characteristic, one from each parent.  Alleles: Two or more alternative forms of a gene that can occupy the same position on paired chromosomes and affect the same trait.  Homozygous: Possessing two identical alleles for a trait.  Heterozygous: Possessing differing alleles for a trait. 3-16

17. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Patterns of Genetic Transmission  Polygenic inheritance  Pattern of inheritance in which multiple genes at different sites on chromosomes affect a complex trait.  Traits may also be affected by mutations.  Mutations: Permanent alterations in genes or chromosomes.  Multifactorial transmission  Combination of genetic and environmental factors to produce certain complex traits. 3-17

18. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Epigenesis  Mechanism that turns genes on or off and determines functions of body cells.  Chemical molecules that are attached to a gene.  Epigenetic changes can respond to environmental factors such as nutrition, sleep habits, stress, and physical affection.  Epigenetic modifications may be heritable. 3-18

19. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 3.2 - Some Birth Defects 3-19

20. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 3.2 - Some Birth Defects 3-20

21. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 3-21 Table 3.2 - Some Birth Defects

22. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Dominant or Recessive Inheritance of Defects  Dominant traits  Achondroplasia - Type of dwarfism  Huntington’s disease  Recessive traits  Tay-Sachs  Sickle-cell anemia - Can be incomplete dominance  Incomplete dominance: Pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait. 3-22

23. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Sex-Linked Inheritance of Defects  Sex-linked inheritance: Pattern of inheritance in which certain characteristics carried on the X chromosome inherited from the mother are transmitted differently to her male and female offspring.  Certain recessive disorders are linked to genes on the sex chromosomes.  Male and female children affected differently.  Carriers - Heterozygote females who carry one bad copy of a recessive gene and one good one. 3-23

24. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Figure 3.3 - Genetic and Chromosomal Abnormalities 3-24

25. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Chromosomal Abnormalities  Errors in cell division  Extra or missing chromosome  Triple X syndrome  Klinefelter syndrome XXY  Turner syndrome XO  Down syndrome: Chromosomal disorder characterized by moderate-to-severe mental retardation and by such physical signs as a downward-sloping skin fold at the inner corners of the eyes. 3-25

26. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 3.3 - Genetic and Chromosomal Abnormalities 3-26

27. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Genetic Counseling  Clinical service that advises prospective parents of their probable risk of having children with hereditary defects.  Karyotype - Chart that can show chromosomal abnormalities.  Indicates whether a person who appears normal might carry a genetic defect that could be transmitted to a child. 3-27

28. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Relative Influences of Heredity and Environment  Behavioral genetics: Quantitative study of relative hereditary and environmental influences on behavior.  Heritability: Statistical estimate of contribution of heredity to individual differences in a specific trait within a given population at a particular time. 3-28

29. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Relative Influences of Heredity and Environment  Measuring heritability - Estimating how much of a trait is due to genetics and how much is the result of environmental influences.  Types of heritability studies  Family studies - Measure the degree to which biological relatives share certain traits.  Whether the closeness of the familial relationship is associated with the degree of similarity 3-29

30. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Relative Influences of Heredity and Environment  Adoption studies - Look at similarities between adopted children and their adoptive parents.  Studies on twins - Compare pairs of monozygotic twins with same-sex dizygotic twin.  Concordant - Describing the tendency of twins to share the same trait or disorder. 3-30

31. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. How Heredity and Environment Work Together  Developmental system - From conception on, a combination of constitutional, social, economic, and cultural factors help shape development.  More advantageous circumstances and experiences lead to increased likelihood of optimum development. 3-31

32. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Reaction Range and Canalization  Reaction Range: Potential variability, depending on environmental conditions, in the expression of a hereditary trait.  Canalization: Limitation on variance of expression of certain inherited characteristics.  Highly canalized traits - Eye color, for example, strongly programmed by genes with little opportunity for variance in their expression.  Cognition and personality are not highly canalized. 3-32

33. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Genotype-Environment Reaction  Genotype-environment interaction: Effect of the interaction between genes and the environment on phenotypic variation.  Genotype-environment correlation: Tendency of certain genetic and environmental influences to reinforce each other; may be passive, reactive (evocative), or active.  Also called genotype-environment covariance  Genetically similar children often develop differently depending on their home environments. 3-33

34. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Genotype-Environment Reaction Parents, who provide the genes that predispose a child toward a trait, also tend to provide an environment that encourages the development of that trait. Passive Children with differing genetic makeups evoke different responses from adults. Reactive or evocative As children grow older, they select experiences consistent with their genetic tendencies. Niche picking - Tendency to seek out environments compatible with one’s genotype. Active 3-34

35. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Nonshared Environment  Nonshared environmental effects: Unique environment in which each child grows up, consisting of distinctive influences or influences that affect one child differently from another.  Effects of experience on development  Interactions of parenting  Nonfamilial influences  Broader context in which families live 3-35

36. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Characteristics Influenced by Heredity and Environment  Physical and physiological traits - Monozygotic twins more concordant than dizygotic twins in risk for medical disorders.  Obesity: Extremely overweight in relation to age, sex, height, and body type.  Intelligence - Heredity exerts a strong influence on general intelligence and lesser extent on specific abilities such as memory, verbal, and spatial ability. 3-36

37. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Characteristics Influenced by Heredity and Environment  Personality - Genes directly linked with specific aspects of personality.  Temperament: Characteristic disposition, or style of approaching and reacting to situations.  Psychopathology - Evidence for a strong hereditary influence on such mental disorders as schizophrenia, autism, alcoholism, and depression. 3-37

38. Copyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Characteristics Influenced by Heredity and Environment  Schizophrenia: Neurological disorder marked by:  Loss of contact with reality  Hallucinations and delusions  Loss of coherent, logical thought  Inappropriate emotionality 3-38