Chapter Three:

1. Chapter Three: Heredity and Environment

2. Development that is dynamic, ongoing, interactional, and unique The Genetic Code The Genetic Code Development that is dynamic, ongoing, interactional, and unique; just four chemicals are the basic building blocks of the genetic codeThe Genetic Code Development that is dynamic, ongoing, interactional, and unique; just four chemicals are the basic building blocks of the genetic code

3. Genes are made up of DNA DNA directs the form and function of each body cell as it develops Each molecule of DNA is called a chromosome What Genes Are

4. Chromosomes contain instructions The packet of instructions is called a genome Each person has 23 sets of chromosomes The human genome contains 30,000 genes

5. The Beginnings of Human Life Gamete Father gametes�sperm Mother gametes�ovum The Beginnings of Human Life Gamete�reproductive cell that directs process by which genetic information combined and transmitted Father gametes�sperm Mother gametes�ovumThe Beginnings of Human Life Gamete�reproductive cell that directs process by which genetic information combined and transmitted Father gametes�sperm Mother gametes�ovum

7. Male and female gametes fuse and become a zygote Zygote begins process of duplication and division Genotype�the genetic information from the 46 chromosomes Zygote and Genotype Zygote and Genotype Male and female gametes fuse and become a zygote Zygote begins process of duplication and division -two reproductive cells Genotype�the genetic information from the 46 chromosomes -set at human conception and endures through lifeZygote and Genotype Male and female gametes fuse and become a zygote Zygote begins process of duplication and division -two reproductive cells Genotype�the genetic information from the 46 chromosomes -set at human conception and endures through life

8. Sex Determination and Sex Ratio Of 22 out of 23 pairs of human chromosome, the matching chromosomes are very closely matched The 23rd pair is different in females, it is designated XX in males, it is designated XY Sex Determination and Sex Ratio Of 22 out of 23 pairs of human chromosome, the matching chromosomes are very closely matched -but not identical -some genes come in slight, normal variations called alleles The 23rd pair is different -in females, it is designated XX -in males, it is designated XYSex Determination and Sex Ratio Of 22 out of 23 pairs of human chromosome, the matching chromosomes are very closely matched -but not identical -some genes come in slight, normal variations called alleles The 23rd pair is different -in females, it is designated XX -in males, it is designated XY

9. Females always contribute one X Males will have 1/2 of the sperm contributing an X and the other half contributing a Y Females always contribute one X Males will have 1/2 of the sperm contributing an X and the other half contributing a Y Critical factor in determining the sex of a zygote is which sperm reaches the ovum first Females always contribute one X Males will have 1/2 of the sperm contributing an X and the other half contributing a Y Critical factor in determining the sex of a zygote is which sperm reaches the ovum first

10. Other factors include rarely, male sperm may only carry either X or Y sometimes a woman�s uterus either unusually alkaline or acid, giving either an X or Y sperm an advantage in a stressful pregnancy XY embryos are more likely to be expelled than are XX embryos in a spontaneous abortion, or miscarriage Other factors include -rarely, male sperm may only carry either X or Y -sometimes a woman�s uterus either unusually alkaline or acid, giving either an X or Y sperm an advantage -in a stressful pregnancy XY embryos are more likely to be expelled than are XX embryos in a spontaneous abortion, or miscarriage -current sex ratio in United States is 52 males to 48 femalesOther factors include -rarely, male sperm may only carry either X or Y -sometimes a woman�s uterus either unusually alkaline or acid, giving either an X or Y sperm an advantage -in a stressful pregnancy XY embryos are more likely to be expelled than are XX embryos in a spontaneous abortion, or miscarriage -current sex ratio in United States is 52 males to 48 females

11. Multiple Zygotes Monozygotic twins�identical twins (or quadruplets) originate from one zygote Dizygotic twins�from two separate zygotes Multiple Zygotes Monozygotic twins�identical twins (or quadruplets) originate from one zygote -share identical instructions -possibility of cloning -1/3 of twins monozygotic Dizygotic twins�from two separate zygotes -Dizygotic births occur once in every 60 births, and occur as frequently as 1 in 6 pregnancies, but usually only 1 twin develops past embryo stage Dizygotic twins -women in late 30�s are three times more likely to have dizygotic twins -as menopause approaches, ovulation becomes irregular with some cycles producing no ovas and others producing multiple ovas -share no more genes than other offspring (about 50 percent) -50 percent of the time one twin is maleMultiple Zygotes Monozygotic twins�identical twins (or quadruplets) originate from one zygote -share identical instructions -possibility of cloning -1/3 of twins monozygotic Dizygotic twins�from two separate zygotes -Dizygotic births occur once in every 60 births, and occur as frequently as 1 in 6 pregnancies, but usually only 1 twin develops past embryo stage Dizygotic twins -women in late 30�s are three times more likely to have dizygotic twins -as menopause approaches, ovulation becomes irregular with some cycles producing no ovas and others producing multiple ovas -share no more genes than other offspring (about 50 percent) -50 percent of the time one twin is male

12. Duplication, Division, and Differentiation The zygote contains a complete set of instructions to create a person Complex instructions on duplication, cell division, and differentiation

13. Duplication and Division Zygote begins duplication and division within hours after conception the 23 pairs of chromosomes duplicate the single cell in the zygote splits down the middle the zygote�s outer membrane surrounds two cells Duplication and Division Zygote begins duplication and division within hours after conception -the 23 pairs of chromosomes duplicate, forming two complete sets of the genetic code for that person (zygote) -these two pair sets move toward the opposite sides of the zygote and the single cell in the zygote splits down the middle -the zygote�s outer membrane surrounds two cells, each containing a complete set of the original genetic code -these two cells then duplicate and divide to become four, then eight, and so onDuplication and Division Zygote begins duplication and division within hours after conception -the 23 pairs of chromosomes duplicate, forming two complete sets of the genetic code for that person (zygote) -these two pair sets move toward the opposite sides of the zygote and the single cell in the zygote splits down the middle -the zygote�s outer membrane surrounds two cells, each containing a complete set of the original genetic code -these two cells then duplicate and divide to become four, then eight, and so on

14. by birth, your original zygote has duplicated and divided into 10 trillion cells . . . by adulthood, it�s 100 trillion cells Every cell carries an exact copy of the complete genetic instructions inherited by the one-celled zygote by birth, your original zygote has duplicated and divided into 10 trillion cells . . . by adulthood, it�s 100 trillion cells Every cell carries an exact copy of the complete genetic instructions inherited by the one-celled zygote by birth, your original zygote has duplicated and divided into 10 trillion cells . . . by adulthood, it�s 100 trillion cells Every cell carries an exact copy of the complete genetic instructions inherited by the one-celled zygote

15. Differentiation At the 8-cell stage a third process, differentiation, occurs Cells begin to specialize Differentiation Not just any cell found in the zygote can become a person At the 8-cell stage a third process, differentiation, occurs Cells begin to specialize -they take different forms -they reproduce at different rates, depending on where in the growing mass they are located Differentiation Not just any cell found in the zygote can become a person At the 8-cell stage a third process, differentiation, occurs Cells begin to specialize -they take different forms -they reproduce at different rates, depending on where in the growing mass they are located

16. Certain genes affect differentiation by switching some genes on and others off Genotype Certain genes affect differentiation by switching other genes on and others off so that the other genes produce the right proteins at the right times�on-off switching mechanisms Genotype�inheritance that can be observed or is expressedCertain genes affect differentiation by switching other genes on and others off so that the other genes produce the right proteins at the right times�on-off switching mechanisms Genotype�inheritance that can be observed or is expressed

17. Gene - Gene Interactions Multifactoral traits Polygenetic traits These are affected by on-off switching mechanisms, additive genes, and dominant-recessive genes Gene - Gene Interactions Multifactoral traits�inherited traits produced by interaction of genes and environment Polygenetic traits�inherited traits produced by gene interaction These are affected by on-off switching mechanisms, additive genes, and dominant-recessive genesGene - Gene Interactions Multifactoral traits�inherited traits produced by interaction of genes and environment Polygenetic traits�inherited traits produced by gene interaction These are affected by on-off switching mechanisms, additive genes, and dominant-recessive genes

18. Additive Genes Additive genes each additive gene contributes to the trait when genes interact this way, all the involved genes contribute fairly equally Additive Genes Additive genes�one of a number of genes affecting a specific trait -each additive gene contributes to the trait -skin color and height are determined by them -every additive gene has some impact on a person�s phenotype -when genes interact this way, all the involved genes contribute fairly equallyAdditive Genes Additive genes�one of a number of genes affecting a specific trait -each additive gene contributes to the trait -skin color and height are determined by them -every additive gene has some impact on a person�s phenotype -when genes interact this way, all the involved genes contribute fairly equally

19. Dominant and Recessive Genes Nonadditive genes dominant-recessive pattern X-linked genes Dominant and Recessive Genes Nonadditive genes�phenotype shows one gene more influential than other genes This is also referred to as the dominant-recessive pattern -gene showing the most influence is referred to as dominant -gene showing the least influence is referred to as recessive X-linked genes�located on X chromosome -if recessive gene is X-linked, that it is on the X chromosome is critical -female has one X chromosome and one Y; males have only 2 X -females� recessive genes can be counterbalanced by Y chromosome, but males� recessive genes can not because they have only the X chromosome -if X-linked gene recessive, may cause color blindness, many allergies, several diseases, and learning disabilities Dominant and Recessive Genes Nonadditive genes�phenotype shows one gene more influential than other genes This is also referred to as the dominant-recessive pattern -gene showing the most influence is referred to as dominant -gene showing the least influence is referred to as recessive X-linked genes�located on X chromosome -if recessive gene is X-linked, that it is on the X chromosome is critical -female has one X chromosome and one Y; males have only 2 X -females� recessive genes can be counterbalanced by Y chromosome, but males� recessive genes can not because they have only the X chromosome -if X-linked gene recessive, may cause color blindness, many allergies, several diseases, and learning disabilities

20. Genetic Diversity Every person is unique

21. Mechanisms of Genetic Diversity Since each gamete contains only 23 chromosomes, why is every conception genetically unique? 8 million chromosomally different ova x 8 million of the same = 64 trillion different possibilities of children from each couple

22. Health Benefits of Genetic Diversity Genetic diversity safeguards human health Minute differences can affect the ability to stave off certain diseases Genetic diversity maintains the species

23. From Genotype to Phenotype Every psychological characteristic is genetically influenced Every psychological characteristic and personal trait is affected by the environment Genotype Phenotype From Genotype to Phenotype Every psychological characteristic is genetically influenced Every psychological characteristic and personal trait is affected by the environment Genotype�genetic potential Phenotype�combination of genetic potential and expression -we are all carriers of the unexpressed genes -we can pass them along through the sperm or ovaFrom Genotype to Phenotype Every psychological characteristic is genetically influenced Every psychological characteristic and personal trait is affected by the environment Genotype�genetic potential Phenotype�combination of genetic potential and expression -we are all carriers of the unexpressed genes -we can pass them along through the sperm or ova

24. Behavior Genetics Behavior genetics�study of effects of genes on behavior Behavior Genetics Behavior genetics�study of effects of genes on behavior -personality patterns, psychological disorders, and intellectual abilitiesBehavior Genetics Behavior genetics�study of effects of genes on behavior -personality patterns, psychological disorders, and intellectual abilities

25. Senility Caused by Alzheimer�s Disease Most common and feared type of senility is Alzheimer�s disease Can be genetic�but only when �early-onset� If �late-onset,� may be a combination of genes and environment Senility Caused by Alzheimer�s Disease Most common and feared type of senility is Alzheimer�s disease -amyloid B protein accumulates in the brain, leading to dysfunction and destruction of brain cells and disruption of the mind Can be genetic�but only when �early-onset� If �late-onset,� may be a combination of genes and environment -other predictors may include hypertension, diabetes, high cholesterol, diet, exercise, not smoking, weight control, mental alertness, and physical healthSenility Caused by Alzheimer�s Disease Most common and feared type of senility is Alzheimer�s disease -amyloid B protein accumulates in the brain, leading to dysfunction and destruction of brain cells and disruption of the mind Can be genetic�but only when �early-onset� If �late-onset,� may be a combination of genes and environment -other predictors may include hypertension, diabetes, high cholesterol, diet, exercise, not smoking, weight control, mental alertness, and physical health

26. Alcoholism Inherited biochemistry makes some people highly susceptible to alcohol addiction Not simply a biochemical reaction Culture counts Alcoholism Inherited biochemistry makes some people highly susceptible to alcohol addiction -addictive pull can be overpowering, or weak, or something in the middle -may explain ethnic variations Not simply a biochemical reaction�it is psychological and physical, and biological; thus alcoholism is polygenetic, with alcoholics inheriting a combination of biochemistry-affecting and temperament-affecting genes Culture counts too(whether alcohol is present in environment)Alcoholism Inherited biochemistry makes some people highly susceptible to alcohol addiction -addictive pull can be overpowering, or weak, or something in the middle -may explain ethnic variations Not simply a biochemical reaction�it is psychological and physical, and biological; thus alcoholism is polygenetic, with alcoholics inheriting a combination of biochemistry-affecting and temperament-affecting genes Culture counts too(whether alcohol is present in environment)

27. Chromosomal and Genetic Abnormalities We now give attention to these because we can recognize disruptions of normal development origins of genetic and chromosomal abnormalities misinformation and prejudice add to problems of people with these abnormalities

28. Chromosomal Abnormalities A gamete with more than or less than 23 chromosomes creates a zygote with chromosomal abnormalities Most zygotes with chromosomal abnormalities never come to term Chromosomal Abnormalities A gamete with more than or less than 23 chromosomes creates a zygote with chromosomal abnormalities -most likely variable that creates chromosomal abnormalities is mother�s age (over 35) -father�s age (over 40) also a variable Most zygotes with chromosomal abnormalities never come to term spontaneous abortion occurs in about one-half of all fetus with chromosomal abnormalitiesChromosomal Abnormalities A gamete with more than or less than 23 chromosomes creates a zygote with chromosomal abnormalities -most likely variable that creates chromosomal abnormalities is mother�s age (over 35) -father�s age (over 40) also a variable Most zygotes with chromosomal abnormalities never come to term spontaneous abortion occurs in about one-half of all fetus with chromosomal abnormalities

29. Down Syndrome Three chromosomes at gene #21 (trisomy-21) Syndrome�a cluster of distinct characteristics that occur together in a given disorder

30. Abnormalities of the 23rd Pair Location of sex chromosome Kleinfelters syndrome�XXY Fragile X syndrome Abnormalities of the 23rd Pair Location of sex chromosome Kleinfelters syndrome�XXY -seemingly normal child has delayed puberty Fragile X syndrome -hanging on by a thread (mutated gene) -intensifies from generation to generationAbnormalities of the 23rd Pair Location of sex chromosome Kleinfelters syndrome�XXY -seemingly normal child has delayed puberty Fragile X syndrome -hanging on by a thread (mutated gene) -intensifies from generation to generation

31. Genetic Testing and Genetic Counseling (table 3.2) Individuals with a parent, sibling, or child with a serious genetic condition known to be dominant or recessive Couples with history of early spontaneous abortions, stillbirths, or infertility Couples from the same ethnic group or subgroup�especially if closely related Women over 35 and men over 40

32. The Process of Genetic Counseling Counselor constructs couples� family history Some tests provide information before conception The Process of Genetic Counseling Counselor constructs couples� family history -charts patterns of health and illness over generations Some tests provide information before conceptionThe Process of Genetic Counseling Counselor constructs couples� family history -charts patterns of health and illness over generations Some tests provide information before conception

33. Other tests are prenatal (table 3.3) alpha-fetoprotein assay ultrasound (AKA sonogram) amniocentesis chorionic villi sampling pre-implantation testing gamete selection Other tests are prenatal -alpha-fetoprotein assay -ultrasound (AKA sonogram) -amniocentesis -chorionic villi sampling -pre-implantation testing (used in in vitro fertilization) -gamete selection; ova/and or sperm are screened to select ones free of particular problems Other tests are prenatal -alpha-fetoprotein assay -ultrasound (AKA sonogram) -amniocentesis -chorionic villi sampling -pre-implantation testing (used in in vitro fertilization) -gamete selection; ova/and or sperm are screened to select ones free of particular problems

34. A Basis for Decision Many want to know ahead of time Some do not There is a more knowledge of what is to come�or not

35. Alternatives If both partners are carriers of a serious condition or are at high risk because of age or family characteristics, they may turn to in-vitro fertilization (IVF) gamete intrafallopian transfer (GIFT) zygote intrafallopian transfer (ZIF) artificial insemination donor (AID) postponement of pregnancy until promising treatments are further developed