1. Mechanisms of Genetic Transmission
Genetic information is combined and transmitted by gametes, the reproductive cells of a child’s parent
In the father the gametes are produced in the testicles (each is called a sperm cell)
In the mother they are developed in the ovaries (each is called an ovum or egg cell)

2. Mechanisms of Genetic Transmission (continued)
The sperm and egg cells contain genetic information molecular structure called genes
The genes form threads called chromosomes
Genetic material that the child will inherit from the parent is contained in the chromosomes

3. Mechanisms of Genetic Transmission (continued)
Each human sperm or egg cell contains 23 chromosomes
All other cells of the body contain 46 chromosomes and about 100,000 genes
A single chromosome may contain as many as 20,000 genes

4. DNA The genes are made up of DNA (deoxyribonucleic acid)
DNA have a spiral chemical structure that allows them to divide easily and duplicate DNA molecules
DNA contains the genetic information that directs the form and function of each body cell as it develops

5. DNA (continued)
DNA is shared at conception when a sperm (father) penetrates the egg from the mother
Within a few hours the walls of the sperm cell and the nucleus of the egg cell both begin to disintegrate releasing its chromosomes which join to form a new cell
The new cell formed is called a zygote

6. Meiosis and Mitosis
All cells of the body develop from this original zygote through a process called cell division
The sperm and ova contains only 23 chromosomes making them unique from other body cells
This ensures that when an egg and sperm join to form a new zygote the zygote will contain the complete set of 46 chromosomes (23 pair)

7. The human
body contains
100 trillion
cells.
There is a
nucleus inside
each human
cell (except red
blood cells).
Each nucleus
contains 46
chromosomes,
arranged in
23 pairs.
One
chromosome
of every pair is
from each
parent.
The
chromosomes
are filled with
tightly coiled
strands of
DNA.
Genes are segments
of DNA that contain
instructions to make
proteins— the
building blocks
of life.

8. Meiosis and Mitosis (continued)
The zygote contain the genetic materials from which all of an individual’s cells are formed
The reproductive cells (gametes) divide by a process called meiosis and recombine into a zygote at conception
All other cells will develop from the zygote through a simpler division called mitosis

9. Meiosis and Mitosis (continued)
Mitosis involves:
1. 23 pairs of chromosomes of a cell duplicate themselves and divide into two identical sets
2. The two sets of chromosomes move to opposite sides of the cell
3. A new wall forms between them, resulting in two new identical cells containing the same set of chromosomes, genes and DNA

10. Gametes and Zygote Sperm Sperm Ovum Gametes (reproductive cells)
Fertilization
Zygote

11. The Process of Meiosis for Sperm Cells
Cell with 46 chromosomes (only one pair of homologous
chromosomes is shown here). Each member of the pair has begun to replicate similar to
mitotic cell division.
First meiotic cell division
begins, but does not proceed
as in mitosis. Instead of the
replicated chromosome splitting
apart, one member of each
homologous pair becomes a
part of the first-generation
daughter cell.
The second meiotic division
proceeds after the first is completed;
now the replicated chromosome
acquired in the first-generation
daughter cell splits apart.
Each of the four gametes
produced by the two-step process
now has acquired one member
of the pair of homologous
chromosomes.

12. The Process of Mitosis
Each daughter cell now has a pair of chromosomes that is identical to the original pair
Cell nucleus with a pair of chromosomes
Chromosomes split
and replicate to produce
two identical pairs
The pairs separate, and the cell divides

13. GENOTYPE AND PHENOTYPE
GENOTYPE: Set of genetic traits a person inherits; a person’s inborn capacity or potential
PHENOTYPE: Set of traits a person actually displays, resulting from a combination of the person’s genotype (potential) and life experiences that modify that potential

14. Individual Genetic Expression (continued)
Examples of phenotype may include a certain height, intelligence score, shyness
Phenotype results from all the interactions of the person’s genotype with the environment from conception onward

15. Genes (dominant and recessive)
Genes are inherited in pairs (one from each parent)
Dominant gene--in a paired set of genes, the gene with the greater influence in determining physical characteristics
Recessive gene--in a paired set of genes, the gene that influences or determining physical characteristics only when no dominant gene is present

16. Genes (dominant and recessive) continued
A dominant gene will influence a child’s phenotype even if it is paired with a recessive gene
A recessive gene must be paired with another recessive gene to be able to influence the phenotype
If paired with a dominant gene its influence is blocked

17. Genes (dominant and recessive) continued
Eye color--blue eyes (recessive trait), brown eyes (dominant trait)
a child’s eyes will remain blue only if they have received the appropriate blue-producing gene from both parents
If they received it from only one parent or from neither they will end up with brown eyes (dominant)

18. Genes (dominant and recessive) continued
Genes may take on two or more alternatives forms called alleles
a person who inherits two identical alleles for a particular trait is homozygous for that trait
if they inherit two different alleles for the trait it is heterozygous

19. Polygenic
Blood type and eye color have a limited number of distinct ways of transmission
height, weight, skin color, personality, behavioral traits are polygenic (involve many genes)
Environment influence them in important ways (can diet and change weight)

20. Determination of Sex
One pair of chromosomes among the 23 is largely responsible for determining whether a child is male or female
In women the pair of chromosomes is XX
In men the pair is XY
all eggs cells contain a single X chromosome
a sperm cell may contain either an X or Y

21. Determination of Sex (continued)
If a Y bearing sperm fertilizes the egg, a male (XY) zygote develops
If a X bearing sperm fertilizes the egg a female (XX) zygote develops

22. Genetic Abnormalities
Sometime too many or too few chromosomes transfer (or transfer a defective gene) to newly forming zygote
This may affect a child mentally, physically or both
Inheriting too many or too few chromosomes is usually fatal

23. Genetic Abnormalities (continued)
In a few cases children with a missing or an extra chromosome survive
Down syndrome--caused by extra 21st chromosome or transfer or part of the 21st on to another chromosome

24. Genetic Abnormalities (continued)
Characteristics of Down’s Syndrome
almond shaped eyes, round head
stubby hands and feet
may have abnormal heart and intestinal tract
facial deformities
vulnerable to diseases such as leukemia
as they age fall behind developmentally

25. Genetic Abnormalities (continued)
Usually levels out at the moderately retarded level
most live until middle adulthood
they are able to do simple routines and hold these type of jobs
more frequent in mothers over the age of 35

26. FREQUENCY OF DOWN SYNDROME (PER 1000)
Relationship Between Maternal Age and the Incidence of Down Syndrome
100 90 80 70 60
FREQUENCY OF DOWN SYNDROME (PER 1000) 50 40 30 20 10 15 20 25 30 35 40 45 50
MATERNAL AGE (YEARS)

27. Pictures of Down’s syndrome individuals

28. Down Picture #2

29. An adult Down’s person

30. Genetic Abnormalities (continued)
Klinefelter Syndrome--
results from inheriting an extra chromosome (usually an X) resulting in an XXY pattern
affects males (they are sterile, have small testes)
have normal intelligence
affect about 1/800

31. Klinefelter Syndrome is caused by a chromosome variation involving the sex chromosomes. The person with Klinefelter Syndrome is a male who, because of this chromosome variation, has a hormone imbalance. While Dr. Harry Klinefelter accurately described this condition in 1942, it was not until 1956 that
other researchers reported that many boys with this description had 47 chromosomes in each cell of their bodies instead of the usual number of 46. This extra sex (X) chromosome causes the distinctive make-up of these boys. All men have one X chromosome and one Y chromosome, but sometimes a variation will result in a male with an extra X. This is Klinefelter Syndrome and is often written as 47,XXY. There are other, less common variations such as 48,XXYY; 48,XXXY; 49,XXXXY ; and XY/XXY mosaic. All of these are considered Klinefelter Syndrome variants.

32. Klinefelter Karotype

33. Klinefelter individual

34. Genetic Abnormalities (continued)
Turner syndrome--
results from having only one sex chromosome (X0) affecting females
will develop learning disabilities
not fully sexually differentiated
are very short as adults (4 and 5 ft.)
have webbed necks
ears are set lower than usual

35. Adults with Turner syndrome are short, averaging around four feet, eight inches in height. But girls with Turner syndrome
don't start life as very short individuals - they become short over time, growing more slowly than their sisters and friends
with each passing year. Studies have shown that a medicine called recombinant human growth hormone, or GH, can
improve the height of girls with Turner syndrome. However, these studies have tended to start GH treatment around age 9
or later, after years of deteriorating growth. So, even with treatment, many girls remain shorter than would be expected
based on the heights of their parents. The purpose of this new study is to determine if GH started at a young age can
prevent the growth failure typical of girls with Turner syndrome. In addition, the study will monitor all participants for
development of ear infections and hearing loss, problems that trouble many girls with Turner syndrome.

36. A Turner’s syndrome infant

37. A Turner’s syndrome teen

38. Disorders from Abnormal Genes
Three types of genetic disorders:
1. dominant gene disorder
2. recessive gene disorder
3. multifactorial gene disorder
Dominant gene disorder require only one abnormal gene from either parent to affect a child

39. Disorders from Abnormal Genes (continued)
Huntington disease (dominant gene disorder)
gradual deterioration of the central nervous system, causing mental retardation and uncontrollable movements
appear when person is in their 30’s or 40’s
always fatal

40. Disorders from Abnormal Genes (continued)
Recessive gene disorder--
can occur when the fetus inherits a pair of recessive genes, one from each parent
Cystic Fibrosis--involves production of thick mucus, clogging the lungs
causes delayed growth and sexual maturation, shortened life and vulnerable to infections

41. Disorders from Abnormal Genes (continued)
Sickle-Cell Disease--red blood cells take on a sickle shape instead of a round shape
These cells get caught in the blood vessels cutting off circulation, reducing oxygen supply causing pain
have bacterial infections
degeneration of organs (due to lack of oxygen)
few live past 40 years of age

42. Disorders from Abnormal Genes (continued)
Tay-Sachs Disease--disease of the nervous system (chemical imbalance)
about age 6 months will show poor tolerance for sudden loud noises, seem weak and slow to develop
lead to seizures, deafness and blindness
most die by age 3

43. Disorders from Abnormal Genes (continued)
Phenylketonuria (PKU)--occurs in 5-10/1000, inability to utilize an amino acid called phenylalanine (found in milk, meat) and needed for normal growth
increases in levels of phenylalanine in the blood and spinal fluid affects the brain causing deterioration of cognitive functioning and mental retardation

44. Disorders from Abnormal Genes (continued)
Multifactorial disorders--
result from a combination of genetic and environmental factors
Neural tube defects--result when the tube enclosing the spinal cord fails to close completely or normally
Sometimes the upper part of the brain is absent or underdeveloped

45. Disorders from Abnormal Genes (continued)
Causes include heredity and environmental aspects such as pollutants, poor nutrition, diseases (diabetes)
geographical background and racial/ethic background)
British Isles has the highest
U.S. highest is in the the Appalachian region

46. Disorders from Abnormal Genes (continued)
Cleft palate/lip--when the upper lip and/or roof of the mouth fail to grow resulting in a split or “cleft”
If severe may lead to difficulties breathing, speaking, hearing and eating
surgery can usually repair the problem

47. Disorders from Abnormal Genes (continued)
Congenital heart disease--structural and/or electrical abnormalities in the formation of the heart
medication and surgery can usual correct

48. Prenatal Diagnostic Techniques
Diagnostic techniques after conception but before birth
Ultrasound--high frequency sound waves are projected through the mother’s womb
Waves bounce off the fetus creating a television image of the size, shape, and position of the fetus

49. Prenatal Diagnostic Techniques (continued)
Ultrasound can be used to:
determine age of fetus
multiple pregnancies
physical defects in internal/external organs
determine Down’s Syndrome (extra fold of skin on the neck)

50. Prenatal Diagnostic Techniques
Amniocentesis--performed at weeks 14-18
Using, ultrasound a slender needle is inserted through the mother’s abdomen into the uterus and the amniotic sac and a sample of amniotic fluid is withdrawn
Fluid contain the cells which hold the genetic makeup of the fetus
can be used to determine if they have abnormal chromosomes

51. Prenatal Diagnostic Techniques (continued)
Amniocentesis
It can also determine disorders such as Down’s Syndrome, neural tube defect and sex of the baby

52. Prenatal Diagnostic Techniques (continued)
Chorionic Villus Sampling (CVS)
tests for most of the same disorders as amniocentesis does
performed between the 8th & 10th week of pregnancy
involves collecting and analyzing tissue by inserting a catheter through the vagina into the uterus between the uterine lining and the chorion (surrounds the embryo, becomes the placenta later)

53. Prenatal Diagnostic Techniques (continued)
This technique lets parents know very early whether the fetus has inherited any serious defects
primary risk of procedure is miscarriage
Fetoscopy--inserting a fetoscope (telesopic type fiber optic lens through the abdomen into the uterus to observe the amniotic fluid, placenta, and fetus
performed 15th-18th week

54. Prenatal Diagnostic Techniques (continued)
Fetoscopy is used to observe already identified problems or to confirm other prenatal tests
Maternal Serum Alpha Fetoprotein
test measuring the amount of alpha-fetoprotein (AFP) in the mother’s blood
performed 15th-18th week
fetoprotein is produced by the fetus and passes from the amniotic fluid through the placenta into the mother’s bloodstream

55. Prenatal Diagnostic Techniques (continued)
High level of AFP are associated with various problems as anencephaly (lacking a brain), spina bifida, and Down’s Syndrome
Percutaneous Umbilical Blood Sampling (PUBS)
experimental method of sampling fetal blood by guiding a needle through the mother’s abdomen and uterus and umbilical vein
performed between the 18th and 36th week

56. Prenatal Diagnostic Techniques (continued)
Used to diagnosis numerous conditions, such as Down Syndrome, neural tube defects, cystic fibrosis)

57. Risk of Selected Genetic Disorders
Chromosomal
Down Syndrome
Klinefelter syndrome (XXY)
Fragile X syndrome
Turner syndrome (XO)
Dominant Gene
Polydactyly
Achondroplasia
Huntington disease
Recessive Gene
Cystic fibrosis
Sickle-cell disease
Tay-Sachs disease
X Linked
Hemophilia
Multifactorial
Congenital heart disease
Neural tube defect
Cleft lip/cleft palate
1/800
1/800 men
1/1,200 male births
1/2,000 female births
1/3,00 women
1/ /100
1/2,300
1/15, /5,000
1/2,500 white persons (risk of being a carrier is 1/25)
1/625 African Americans (risk of being a carrier is 1/10)
1/3,600 Eastern European Jews(risk of being a carrier is 1/30 - 1/300)
1/2,500 male babies
1/125
1 - 2/1,000
1/1, /5,000
Sources: ACOG (1990); Blatt (1988); Diamond (1989(; Hagerman (1996); Selekman (1993); Stratford (1994).

58. Who Should Seek Prenatal Counseling?
1. Couples who already have a child with some serious defect such as Down syndrome, spina bifida, congenital heart disease, limb malformation, or mental retardation
2. Couples with a family history of a genetic disease or mental retardation
3. Couples who are blood relatives (first or second cousins)
4. African Americans, Ashkenzzi Jews, Italians, Greeks, and other high-risk ethnic groups
5. Women who have had a serious infection early in pregnancy (rubella or toxoplasmosis) or who have been infected with HIV
6. Women who have taken potentially harmful medications early in pregnancy or habitually use drugs or alcohol
7. Women who have had X rays taken early in pregnancy
8. Women who have experienced two or more of the following: stillbirth, death of a newborn baby, miscarriage
9. Any woman thirty-five years or older
Source: Adapted from Fienbloom & Forman (1987) p. 129

59. Behavior Genetics
Behavior genetics--is the study of how genetic inheritance (genotype) and environmental experience jointly influence physical and behavioral development (phenotype)

60. Behavior Genetics (continued)
Four concepts of behavior genetics
range of reaction-the range of possible phenotypes that an individual with a particular genotype might exhibit in response to the specific sequence of environmental influences they experience
influences as neighborhood, child’s family, school and community etc.

61. Behavior Genetics (continued)
Canalization--tendency of genes to narrowly restrict the development of certain phenotypic characteristics to a single or relatively limited number of outcomes in spite of environmental pressures toward other outcomes
early perceptual-motor (crawling, sitting up are canalized)

62. Behavior Genetics (continued)
Others include personality, temperament, intellectual functioning
Gene-Environment Relationship-
patterns of interaction between a newborn infant and his caregiving environment and the extent to which that pattern supports the expression and development of the child’s inborn traits

63. Behavior Genetics (continued)
Examples include:
shyness
athletic ability
parents may display their own genetically inherited traits that support the development of similar traits in their children

64. Behavior Genetics (continued)
A passive gene-environment relationship-
if support for the development of traits come from others (parents and family members)
Evocative gene-environment relationship-
displayed by child of certain traits evokes support from others

65. Behavior Genetics (continued)
Active gene-environment relationship--
when a child with a particular trait actively seeks out support from others with similar traits (sports, etc.)