DEP Chapter 3 Presentation

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  • 1. Chapter 3 Heredity and Environment Dr. M. Davis-Brantley
  • 2. The Genetic Code
    • Development that is dynamic, ongoing, interactional, and unique; just four chemicals are the basic building blocks of the genetic code
  • 3. What Are Genes?
    • Genes are made up of DNA the complex protein code of genetic information
    • DNA directs the form and function of each body cell as it develops
  • 4. What Are Genes, cont.
    • Each molecule of DNA is called a chromosome
    • Chromosomes contain instructions to make all the proteins a living being needs
    • The packet of instructions is called a genome
    • Each person has 23 sets of chromosomes, or 46 chromosomes
    • The human genome contains 30,000 genes
  • 5. The Beginnings of Human Life
    • Gamete reproductive cell that directs process by which genetic information combined and transmitted
    • Father gametes sperm
    • Mother gametes ovum
  • 6. Zygote and Genotype
    • Male and female gametes fuse and become a zygote
    • Zygote begins process of duplication and division immediate
      • two reproductive cells have now become one
    • Genotype the genetic information from the 46 chromosomes
      • set at human conception and endures through life
  • 7. Sex Determination and Sex Ratio
    • 23 rd pair is the chromosome pair that determines the zygotes sex
    • Female the 23 rd pair is composed of XX chromosomes
      • Females are composed of XX so they will only produce XX
    • Male the 23 rd pair is composed of XY chromosomes
      • Males are composed of XY so they can offer either X or Y
      • Therefore, critical factor in determination of sex is which sperm penetrates the ovum first
  • 8. Sex Determination and Sex Ratio, cont.
    • 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
  • 9. Sex Determination and Sex Ratio, cont.
    • Other factors include
      • rarely, male sperm may only carry either X or Y
      • sometimes a womans 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
  • 10. Multiple Zygotes
    • Monozygotic twinsidentical twins (or quadruplets) originate from one zygote
      • share identical instructions
      • possibility of cloning
      • 1/3 of twins monozygotic
      • Video-- Black/White Twins
  • 11. Multiple Zygotes, cont.
    • Dizygotic twinsfrom 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
  • 12. Multiple Zygotes, cont.
    • Dizygotic twins
      • women in late 30s 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
  • 13.
    • The zygote contains a complete set of instructions to create a person
    • Complex instructions on duplication, cell division, and differentiation
    Duplication, Division, and Differentiation
  • 14. 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 genes
  • 15. 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 persons phenotype
      • when genes interact this way, all the involved genes contribute fairly equally
  • 16.
    • Nonadditive genesphenotype 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
    Dominant and Recessive Genes
  • 17. From Genotype to Phenotype, cont.
    • 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
  • 18. Behavior Genetics
    • Behavior genetics study of effects of genes on behavior
  • 19.
    • A gamete with more than or less than 23 chromosomes creates a zygote with chromosomal abnormalities
      • most likely variable that creates chromosomal abnormalities is mothers age (over 35)
      • fathers age (over 40) also a variable
    Chromosomal Abnormalities
  • 20.
    • Most zygotes with chromosomal abnormalities never come to term
      • spontaneous abortion occurs in about one-half of all fetus with chromosomal abnormalities
    Chromosomal Abnormalities, cont.
  • 21.
    • Three chromosomes at gene #21 (trisomy-21)
    • Syndrome a cluster of distinct characteristics that occur together in a given disorder
    Down Syndrome
  • 22.
    • Location of sex chromosome
    • Kleinfelters syndrome XXY
      • seemingly normal child has delayed puberty
    • Turners Syndrome
    • Fragile X syndrome
      • hanging on by a thread (mutated gene)
      • intensifies from generation to generation
    Abnormalities of the 23rd Pair
  • 23. Dont worry about the following slides for the test. They are for additional information only and to help you understand the concepts better.
  • 24.
  • 25. 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 zygotes 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
  • 26. Duplication and Division, cont.
    • by birth, your original zygote has duplicated and divided into 10 trillion cells . . . by adulthood, its 100 trillion cells
    • Every cell carries an exact copy of the complete genetic instructions inherited by the one-celled zygote
  • 27. 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
  • 28. Differentiation, cont.
    • 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 expressed
  • 29.
    • Genes direct the creation of 20 amino acids that produce thousands of proteins forming the bodys structure and directing biochemical functions
      • proteins of each body cell are continually affected by other proteins, nutrients, and toxins that influence the cell functioning
    More Complications
  • 30. More Complications, cont.
    • genetic imprinting tendency of certain genes to be expressed differently when inherited from mother than from father (tagging)
      • some of the genes which influence height, insulin production, and several forms of mental retardation affect a child differently depending on which parent they came from
  • 31. From Genotype to Phenotype
    • Every psychological characteristic is genetically influenced
    • Every psychological characteristic and personal trait is affected by the environment
  • 32. Behavior Genetics
    • Behavior genetics study of effects of genes on behavior
      • personality patterns, psychological disorders, and intellectual abilities
  • 33. 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
  • 34. Alcoholism, cont.
    • Not simply a biochemical reactionit 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)
  • 35.
    • 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
    Chromosomal and Genetic Abnormalities


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