1. “You will never change your life until you change something that you do daily”
- John C. Maxwell
“There is nothing in the caterpillar that tells you it I going to be a butterfly”
- Buckminster Fuller
Units of Heredity
Chapter 12

2. Understanding Genetic Disorders
Down Syndrome is caused by an extra chromosome, but how does one pass on an extra chromosome?
Why are color-blindness and baldness typically found only in men?
Are diseases dominant or recessive like other traits?
Do sex chromosomes only code for the sex of the offspring or are their traits associated with each sex chromosome?

3. Discovery of Sex-Linked Traits
Thomas Morgan at Columbia University, 1908
Fruit fly (Drosophila melanogaster)
Model organism
Discovered link between specific trait and ____________
X-linked trait
Discovered crossing over
Genetic recombination

4. Reciprocal Cross
Reciprocal cross: experiment to test the role of _____ on the inheritance of a trait

5. X-Linked Inheritance
X-linked disorders: genetic disorders caused by genes found on the X chromosome
Ex: color blindness
__________ disorder: genetic disorder that does not exist in the presence of a functioning allele
Presence of a defective gene on one allele will result in the expression of the functional allele on the other chromosome
____________ recessive disorder: found on non sex chromosomes
X-linked recessive disorders: found on X chromosome

6. Spermatogenesis and the Sex of the Child
Half of the sperm produced have X chromosome and half have Y chromosome
50% chance of having either a boy or a girl

7. X-linked Recessive Disorders: Color Blindness
Genes that code for red and green absorbing pigments are found close together on the X chromosome
Females have a back-up X chromosome, males do not

9. Check your Understanding
X-linked recessive disorder
Ex. Hemophilia
Father’s genotype X Y
In this situation the mother does not suffer from hemophilia, but her father had hemophilia. The father does not suffer from hemophilia. Predict the chances of having a son with hemophilia.
Mother’s genotype

10. Check you Understanding
X-linked dominant disorder
Ex. Rett syndrome
Father’s genotype X Y
In this situation the mother’s father had Rett syndrome, while her mother did not. The father does not suffer from Rett syndrome. Predict the chances of having a daughter with Rett syndrome.
Mother’s genotype

11. Linked vs. Sex Linked
Linked traits: genes that are located on the ___________________
Sex linked or x-linked traits: genes that are located on the X-chromosome

12. Linked Traits Almost always ________ ________ during meiosis
Linked traits violate the principle of independent assortment

13. Crossing Over and Linked Traits
_______________ chromosomes: chromosomes with a combination of alleles that are different from that of the parent chromosomes
Due to _____________

14. Linked Traits
Genes that are located near each other on the chromosome have a tendency to be inherited together
Ex. Red hair and freckles

15. Autosomal Genetic Disorders
Genetic disorders associated with non-sex chromosomes or autosomes
Autosomal recessive disorder: a genetic disorder that occurs when ______ chromosomes in the pair contain a defective gene
Ex. Sickle cell anemia, Albinism
Autosomal dominant disorder: a genetic disorder that occurs when the offspring receives one defective allele from parent
Typically one of the parents has the disease

16. Genetic Disorders Type Name of Condition Effects
X-linked recessive disorders
Hemophilia
Duchenne muscular dystrophy
Red-green colorblindness
Faulty blood clotting
Wasting of muscles
Inability to distinguish shades of red from green
Autosomal recessive disorders
Albinism
Sickle-cell anemia
Cystic fibrosis
Phenylketonuria
Tay-Sachs disease
Werner syndrome
No pigmentation in skin
Anemia, intense pain, infection
Impaired lung function, lung infections
Mental retardation
Nervous system degradation in infants
Premature aging
Autosomal dominant disorders
Huntington disease
Marfan syndrome
Polydactyly
Brain tissue degradation
Ruptured blood vessels
Extra fingers and toes
Aberrations in chromosome number
Down syndrome
Turner syndrome
Klinefelter syndrome
Mental retardation, shortened life span
Sterility, short stature
Dysfunctional testicles, feminized features
Aberrations in chromosome structure
Cri-du-chat syndrome
Fragile-X syndrome
Mental retardation, malformed larynx
Mental retardation, facial deformities

17. Autosomal Recessive Disorder
__________: a person who does not suffer rom the recessive genetic disorder but who carries an allele for it that can be passed along to their offspring
Ex. Person heterozygous for albinism

18. Autosomal Recessive Disorder
Sickle-cell anemia: defective hemoglobin protein causes
Both mother and father must have at least one allele for sickle cell anemia
25% chance that offspring will get the disease
Sickle-cell anemia

19. Autosomal Dominant Disorder
Ex: Huntington's disease is

20. Tracking Traits
___________: family history used to track genetic conditions

22. Sample Problem = Cystic fibrosis (cc) = Unaffected (CC or Cc) A CC E BG D

23. Sample Problem = Polydactyly (PP or Pp) = Unaffected (pp) F A B C D E? A F ? B C D E

24. Polyploidy
Polyploidy: a condition in which one or more ____________ of chromosomes have been added to the genome of a diploid organism

25. Aneuploidy
Aneuploidy: a condition in which an organism has ______________ chromosomes than normally exist in the species full set
Possibly responsible for % of miscarriages
30% of pregnancies end in miscarriage
Down Syndrome is the result of aneuploidy

26. Down Syndrome

27. Nondisjunction
Nondisjunction: failure in the ___________ of homologous chromosomes (Meiosis 1) or sister chromatids (Meiosis II) during cell division

28. Genetic Disorders in Sex Chromosomes
Genetic disorders associated with sex chromosomes are not inherited but are the result of _______________
Turner Syndrome
Female with single X chromosome
Klinefelter Syndrome
Male with extra X chromosome
XYY Male
Male with extra Y chromosome
XXX Female
Female with extra X chromosome

29. Turner Syndrome Only one healthy X-chromosome Characteristics
Other chromosome is missing or altered
Occurs in 1 of 2,500 human females
Characteristics
____________ between neck and shoulders
Short stature
Often sterile, underdeveloped ovaries

30. Klinefelter’s Syndrome
Extra x-chromosome in human males
Occurs in 1 of 1,000 human males
Characteristics
Underdeveloped testes
Development of some female features
___________ and taller than average
Lower testosterone, infertile

31. Aneuploidy and Cancer
Additional or fewer chromosomes in _________ cells
Occurs during mitosis
Not every cell in the body is affected, as in aneuploidy on sex cells
Almost all _________ are aneuploidy
Not sure if a cause of effect of cancer cells

32. Structural Aberrations in Chromosomes
______________: deviation from the normal
Can occur spontaneously, or as a result of exposure to radiation, viruses, or chemicals
Aberration: deviation from the normal
Deletion:

33. Structural Aberrations in Chromosomes
Deletion: chromosome fragment breaks off and fails to reconnect with the chromosome
Ex: Cri-du-chat syndrome = deletion of section from chromosome 5
___________: chromosome fragment rejoins chromosome in an inverted fashion
Translocation: exchange of pieces from two ___________________ chromosomes
Duplication: section of DNA is duplicated during crossing over
Can have negative effect, but can also be beneficial

34. Cri-du-chat Syndrome Characteristics
Cri-du-chat Syndrome: results from a deletion of chromosome 5
Characteristics
Mental retardation
Improperly developed ______
Small head
Low-set ears
Missing section of chromosome 5

35. Pre-implantation Genetic Diagnostics (PGD)
Screening of genotype of potential embryos prior to in-vitro fertilization (IFV)
Hormones stimulate egg maturation
Egg collection
Fertilization
Removal of embryonic cell during 8-cell stage
Couples with family history of genetic disorders
Parents can choose _____ of child

36. Methods of Fetal Testing
___________________: cells obtained from amniotic fluid of week old fetus
Chorionic villus sampling (CVS): sample taken from placenta tissue at 8-10 weeks of development