1. Invitation to the Life Span by Kathleen Stassen Berger
Chapter 2 – Genes and Prenatal Development
These colors actually are a template design in PPT, but match the scheme of the book…do you agree? If so, this will be an easy formatting task. The cover has been revised to reflect the new title “Invitation to the Life Span”. I’ve been waiting to get it, that’s why this slide has been delayed getting to you…but I didn’t want to wait any longer. So the cover needs to be swapped in/out when it arrives. Lastly, I got rid of the chapter outline…as it’s repetitive. Do you agree?
PowerPoint Slides developed by
Martin Wolfger and Michael James
Ivy Tech Community College-Bloomington

2. The Beginning of Life DNA (deoxyribonucleic acid): Chromosomes:
Molecule that contains the chemical instructions for cells to manufacture various proteins
Promotes growth and sustains life
Chromosomes:
Molecules of DNA
DNA consists of 46 chromosomes arranged in 23 pairs

3. The Beginning of Life Gametes: Zygote: Genes:
Reproductive cells (sperm and ova)
Each gamete consists of 23 chromosomes.
Zygote:
Two gametes (sperm and ovum) combine and produce a new individual with 23 chromosomes from each parent.
Genes:
Specific sections of a chromosome that carry instructions via four chemicals.
Chemicals are organized in four pairs (AT, TA, CG, GC).
Each person has about 3 billion pairs.

4. The Beginning of Life

5. Genetic Variations and Similarities
Genes are passed down from generation to generation
Genotype:
An organism’s genetic inheritance, or genetic potential
Unique for each organism
Phenotype:
The observable characteristics of an organism, including appearance, personality, intelligence, and all other traits.

6. Genetic Variations and Similarities
Many genes are identical for every human being.
Some genes vary slightly in their codes from one person to another.
Allele:
Variation of a gene or any of the possible forms in which a gene for a particular trait can occur.
Effects of variations vary greatly from causing life-threatening conditions to having no detectable effect at all.

7. The Human Genome Genetic Diversity Genome: Distinguishes each person
Allows the human species to adapt to pressures of the environment (e.g. climate changes, illnesses).
Genome:
The full set of genes that are the instructions to make an individual member of a certain species
Similarity between two people: 99.5%
Similarity between humans and chimpanzees: 98%
Similarity between humans and every other mammal: 90+%

8. Human Genome Project and HapMap
Found “only” about 20,000 genes in humans
Exact number is unknown
HapMap:
International project trying to spot all variations in the human genome
Found 11 million variations among the billion chemical pairs

9. Siblings and Twins Sibling Similarities Monozygotic (identical) twins:
Each sibling gets abut 10,000 genes from each parent.
Millions of variations and billions of combinations are possible.
Full siblings are not necessarily alike.
Monozygotic (identical) twins:
Originate from one zygote that splits apart very early in development.
Incomplete split results in conjoined twins.
Same genotype but slight variations in phenotype are possible due to environmental influences.

10. Siblings and Twins Dizygotic (fraternal) twins
Result from fertilization of two separate ova by two separate sperm.
Dizygotic twins have half their genes in common and occur twice as often as monozygotic twins.
Incidence is genetic and varies by ethnicity and age.

11. Male and Female Humans usually possess 46 chromosomes.
44 autosomes and 2 sex chromosomes
Females: XX
Males: XY
Sex of offspring depends on whether the father’s Y sperm or X sperm fertilizes the ovum.

12. Male and Female

13. Genetic Interactions Almost every trait is: Regulator genes
polygenic (affected by many genes)
multifactorial (influenced by many factors)
Regulator genes
Direct the interactions of other genes, controlling their genetic expression, duplication, and transcription
Responsible for differences between species

14. Additive Heredity Additive genes
Genes that add something to some aspect of the phenotype
Effects of additive genes add up to make the phenotype
Example: Height is affected by the contributions of about 100 genes

15. Dominant-Recessive Heredity
Dominant gene is far more influential than the recessive gene (non-additive).
Dominant gene can completely control the phenotype with no noticeable effect of recessive gene.
Genes for blood type B and Rh-positive blood are dominant.
Effect of recessive genes can sometimes be noticed.
Dominant brown eye gene and recessive blue eye gene can result in hazel eyes.

16. Carrier
A person whose genotype includes a gene that is not expressed in the phenotype
Unexpressed gene occurs in half of the carrier’s gametes and is passed on to half of the carrier’s offspring
Offspring can be carrier or express the gene in the phenotype (e.g. when unexpressed gene is inherited by both parents)

17. Heritability
Statistical term that indicates what portion of the variation in a particular trait within a particular population is inherited.
Example: 90% of the height differences among children of the same age is genetic.
Environment can affect the expression of inherited genes.

18. Genetic Problems Chromosomal Abnormalities Down Syndrome (Trisomy-21)
Three copies of chromosome 21
Specific facial characteristics (thick tongue, round face, slanted eyes)
Hearing losses, heart abnormalities, muscle weakness, short stature
Slow to develop language
Accelerated aging (cataracts, dementia, certain forms of cancer common at age 40)

19. Genetic Problems Abnormalities of the Sex Chromosomes
Turner Syndrome (X only):
Unusually short, underdeveloped female organs, infertile
Slow to develop
Problems in spatial understanding
Klinefelter Syndrome (XXY):
Symptoms include learning problems and infertility
Boy’s penis does not grow during puberty and fat accumulates around the breast area
Sometimes not recognized until adulthood

20. Genetic Problems Gene Disorders Dominant Disorders
Half of the offspring of parents with a dominant disorder will have the disorder.
Most dominant disorders begin in adulthood (fatal dominant childhood conditions cannot be passed on).
Many dominant disorders have relatively mild or variable symptoms.
Tourette syndrome
Some who inherit the dominant gene exhibit uncontrollable tics and explosive outbursts
Most have milder, barely noticeable symptoms

21. Genetic Problems Recessive Disorders
Millions of different types, lethal conditions are rare
Sickle-cell trait
Offers some protection against malaria
African carriers are more likely than non-carriers to survive
Cystic fibrosis
More common among people with northern European ancestors
Carriers may have been protected against cholera

22. Genetic Problems

23. Sex-Linked Conditions
All X-linked conditions are more common in boys; girls are likely to be protected by their second X
Fragile X Syndrome
Most common form of inherited mental retardation
Additional symptoms include muscle weakness, shyness, and poor social skills
Hemophilia
Blood clotting is inhibited
Blood transfusions can save children’s lives
Color blindness
Most common sex-linked condition
Often passed on because it is not debilitating

24. Sex-Linked Conditions

25. Advising Prospective Parents
Genetic Counseling
Consultation and testing by trained professionals
Enables prospective parents to learn about their genetic heritage, including harmful conditions that may be passed on to their offspring
Ethical Guidelines
Test results are kept confidential
Decisions regarding sterilization, adoption, abortion, or carrying a pregnancy to term are made by the clients

26. Advising Prospective Parents

27. Presenting the Facts Potential genetic counseling issues
Prospective parents must base some decisions on odds
Tests often reveal that more tests are needed
False positives and false negatives
True positives may cause additional stress

28. PKU: A Success Story Phenylketonuria (PKU) Recessive condition
Results in inability to metabolize phenylalanine (amino acid found in many foods)
Buildup of phenylalanine causes brain damage, progressive mental retardation, and other symptoms
Early testing and a special diet usually results in normal development

29. From Zygote to Newborn Three main periods of prenatal development
Germinal Period (first two weeks after conception): rapid cell division and beginning of cell differentiation
Embryonic Period (3rd through 8th week): basic forms of all body structures develop
Fetal Period (9th week until birth): fetus grows in size and matures in functioning

30. The Germinal Period
Zygote begins duplication and division within hours of conception
Development of the placenta
Organ that surrounds the developing embryo and is attached to the wall of the uterus
Sustains life via the umbilical chord (nourishes organism and carries waste products away)
Implantation (about 10 days after conception)
Developing organism burrows into the placenta that lines the uterus
Organism grows rapidly
Pregnancy can be detected due to new chemicals in the mother’s urine

31. The Germinal Period

32. The Germinal Period

33. The Embryonic Period Embryo
Developing human organism from about the 3rd through the 8th week after conception
Begins when the primitive streak appears down the middle of the cell mass
Primitive streak becomes the neural tube and later forms the brain and spine of the CNS
Head takes shape
Eyes, ears, nose, and mouth form
Heart begins to pulsate
Extremities develop and webbed fingers and toes separate

34. The Embryonic Period

35. The Fetal Period
Fetus
Developing human organism from the start of the 9th week after conception until birth
Genitals form and sex hormones cause differences in fetal brain organization
Cephalocaudal and proximodistal growth
Heartbeat detectable via stethoscope
All body parts and systems complete prenatal development
Cortex is not fully mature at birth (e.g. prefrontal lobes)
Brain at birth is far bigger than any other part of the baby

36. The Fetal Period Age of viability
Age at which a preterm newborn may survive outside the mother’s uterus if medical care is available
About 22 weeks after conception
Brain is able to regulate basic body functions (e.g. breathing)
Chances of survival increase with each day after the 22-week mark

37. The Fetal Period

38. Birth
Fetal brain signals the release of hormones to trigger the female’s uterine muscles
Labor begins
Average duration for firstborn babies: 12 hours
Quicker labor for later-born babies
Apgar scale
Quick assessment of newborn’s heart rate, breathing, muscle tone, color, and reflexes
Completed twice (1 minute and 5 minutes after birth)
Score of 0, 1, or 2 in each category
Desired score: 7 or above

39. Birth

40. Traditional and Modern Birthing Practices
Home births
Hospital births
Doula
Woman who helps with labor, delivery, breast-feeding, and newborn care
May be related to lower rate of cesarean sections

41. Cesarean Section (C-Section)
Surgical birth
Fetus can be removed quickly
Rates and reasons for c-sections vary greatly
Lower rates in poorer countries (emergencies)
Higher rates in richer countries (planned for the convenience of mother and/or obstetrician)
1/3 of births in the United States
Less trauma for the newborn but slower recovery for the mother
Subsequent cesarean deliveries may be necessary

43. Medical Intervention
Infant mortality has decreased due to better medical care
1900: 5%
Today: <1 in 200
Childbirth has become safer for mothers
Death rate in poorest nations: 1 in 20 women
Excessive medical care also has disadvantages
Increase in unnecessary c-sections is associated with higher rate of low-birth weight babies

44. Low Birthweight Low birthweight (LBW) Very low birthweight (VLBW)
Less than 2,500 grams (5½ pounds) at birth
United States
Steady increase in LBW over the past 25 years
8% of newborns are seriously underweight
More susceptible to teratogens, higher birth risks, lower survival rate
Very low birthweight (VLBW)
Under 1,500 grams (3 pounds, 5 ounces) at birth
Extremely low birthweight
Under 1,000 grams (2 pounds, 3 ounces) at birth

46. Preterm or Slow Growing?
Birth that occurs at 35 or fewer weeks after conception
Usually associated with low birthweight
Small for gestational age (SGA)
Birthweight is significantly lower than expected, given the time since conception
Suggests impairment throughout prenatal development and serious problems

47. Causes of Low Birthweight
Genetic factors
Maternal illness
Exhaustion
Infection
Malnutrition
Drug use
Multiple births

48. Mothers, Fathers, and a Good Start
The Father’s Role
Supportive father helps mother stay healthy
Father can decrease or increase mother’s stress (affects fetus)
Most fathers are helpful to their pregnant wives
Two way street: Pregnant mothers should support, involve, and encourage fathers

49. The Importance of Close Contact
Birth complications can have lingering impact on later life
Mothers and fathers should help with early caregiving if newborn must stay in the hospital
Kangaroo care
Child-care technique in which the mother of a low-birthweight infant holds the baby between her breasts
Allows baby to hear mother’s heartbeat and feel her body heat
Research confirms beneficial effects

50. Postpartum Depression
Sadness and inadequacy felt by 8-15% of new mothers in the days and weeks after giving birth
Symptoms range from baby blues to postpartum psychosis
Depressed mothers find baby care burdensome and may think about mistreating the infant
Paternal involvement can have beneficial effect
Some fathers are depressed themselves
Causes for Postpartum Depression vary

51. Bonding Parent-Infant Bond
The strong, loving connection that forms as parents hold, examine, and feed the newborn
Early skin-to-skin contact is not essential
Cross-fostering in monkeys
Newborns are removed from their mothers and raised by another female or male
Strong and beneficial relationship sometimes develops

52. Nature, Nurture, and the Phenotype
Four general research conclusions
Genes affect every aspect of human behavior
Nongenetic influences begin at conception and continue lifelong, sometimes altering genetic instructions
Most environmental influences on children raised in the same home are NOT shared, partly because parents treat each child differently
Children , adolescents, and adults “niche-pick,” choosing environments that are compatible with their genetic inheritance

53. Nearsightedness or Myopia
“High” (more severe) and “low” (less severe) nearsightedness
Low nearsightedness runs in families and is associated with minor variations in the Pax6 gene
Environment also plays a role
Increase in nearsightedness among East Asian schoolchildren
Increased schoolwork may have caused nearsightedness in children with a Pax6 allelle

54. Alcoholism Alcoholism probably has a genetic basis
Genes can cause an overpowering addictive pull in some people
Environmental conditions can modify the genetic effects
Nature and nurture must combine to create an alcoholic
Fetal Alcohol Syndrome (FAS)
A cluster of birth defects that may occur in the child of a woman who drinks alcohol while pregnant
Includes abnormal facial characteristics, slow physical growth, and retarded mental development

55. Prenatal Teratogens
Substances and conditions that can impair prenatal development and result in birth defects or even death
Not all teratogens can be avoided
Structural abnormalities are obvious at birth
Behavioral teratogens
Affect the child’s developing brain
Can cause developmental retardation, hyperactivity, and learning disabilities
Effects do not become evident for months or years

57. Significant Factors Genetic Vulnerability
Some zygotes carry genes that make them vulnerable
Certain genes increase likelihood of cleft lip in Japanese people
Some women do not metabolize folic acid well
Increases rates of neural-tube defects (e.g. spina bifida)
Folic acid was added to many foods in the United States and Canada and rates have decreased

58. Significant Factors Timing of Exposure
Critical period: time when a body part develops
First two months for structural abnormalities
Often before woman knows she is pregnant
Time when most spontaneous abortions occur
Sensitive period: time when teratogens can interfere with recent growth

60. Significant Factors Amount of Exposure
Threshold effect: Certain teratogens are relatively harmless until exposure reaches a certain level
Bisphenol A (BPA)
Chemical compound used to make clear plastic
Small doses are harmless but threshold for humans is unknown
Pregnant mothers should avoid plastic containers and dishware
Prescription drugs
Vitamin A
High doses can be harmful

61. Resolving Uncertainties
Pregnancy does not have to be an anxious time
Good prenatal care can
teach women what they can do to have healthy babies
save lives
reassure parents that all is well