1. 14-1 Human Heredity Vocabulary: Karyotype Sex chromosome Autosome
Pedigree
Polygenic
Carrier
Key Concept:
How is sex determined?
How do small changes in DNA cause genetic disorders?

2. Human Chromosomes KARYOTYPE
To examine human chromosomes, biologist photograph cells in mitosis when the chromosomes are fully condensed
Cut out the chromosomes from the picture and group them together in pairs
This type of picture is called a
KARYOTYPE

3. Karyotypes A karyotype can tell you THREE things:
Sex (male or female)
Irregular numbers of chromosomes
Any mutations in the chromosomes
Basically: all the chromosomes in a cell are displayed and can be examined for any abnormalities

4. Remember… Humans have 46 chromosomes (23 pair)
2 of them are sex chromosomes  they determine what sex you are
XX = female
XY = male
44 of them are autosomes  they do not determine what sex you are

5. Who determines the sex of a child?
The mother or the father?
THE FATHER!!!!

6. Why does the father determine the sex of the offspring???
Mom is XX, she can donate either one X chromosome or the other X chromosome
Dad is XY, he can donate either an X chromosome or a Y chromosomes.
If the offspring receives the father’s X, it is female
If the offspring receives the father’s Y, it is male

7. The Y chromosome If a Y chromosome is present, the person is male
X chromosomes contain genes necessary for growth/development
No cases of a person born with being 45,0Y
Probably spontaneously aborted (miscarriage)

8. Human Genes
The human genome is the complete set of genetic information
Determines characteristics such as eye color and how proteins function within cells

9. Recessive and Dominant Alleles
Some common genetic disorders are autosomal recessive
This means that you need two recessive alleles (on any of the 44 chromosomes—NOT the sex chromosomes) to express the disease
EX: Cystic Fibrosis
Other genetic disorders are autosomal dominant
Only one allele is needed for the trait to be expressed
EX: Huntington’s Disease

10. From Gene to molecule
In both cystic fibrosis and sickle cell anemia, a small change in the DNA of a single gene affects the structure of a protein, causing a serious genetic disorder

11. Cystic Fibrosis Caused by a recessive allele on chromosome #7
It is an autosomal genetic disorder
Causes digestive and respiratory problems
Death around years of age
How does it happen?
Three bases are deleted from the protein, which removes one amino acid
The protein cannot fold properly anymore, and is destroyed
Result: airway is clogged with mucus

12. Sickle Cell Anemia One DNA base has been changed
Amino acid is valine, instead of glutamic acid
Result=Abnormal hemoglobin

13. Pedigree Chart
Shows how a trait is transmitted from generation to generation
Each row is a generation
Circles represent females
Squares represent males
Shaded in: person expresses that trait
Half shaded in: person is only a carrier
Clear: person does not carry or express that trait
pg. 342

14. Definitions
Carrier= a person who carries the allele for the trait but does not express it
EX: Cystic Fibrosis is an autosomal recessive disorder
Carrier’s genotype= Ff
For a person to have Cystic Fibrosis (genotype=ff), he or she must have inherited an “f” from both parents
Therefore, BOTH parents must be carriers (both Ff)

16. Can’t trace every human trait through a pedigree because some genes are polygenic
Shape of your eyes
Shape of your ears
Height
Eye color
Also, phenotype is influenced by your environment (ex: nutrition & exercise)
Average height is 10cm more than it was in the 1800’s in the US & Europe due to nutritional improvements
Genes that are denied a proper environment in which to reach full expression in 1 generation, can achieve full potential in a later generation (genes are inherited, the environment is not)

17. What makes an allele dominant or recessive?
Gene=sequence of DNA that codes for a protein
Usually:
Dominant alleles code for the correct production of that protein
Recessive alleles code for no/wrong protein production
Heterozygous condition—the normal (dominant) allele will still cause correct protein production

18. Example Cystic fibrosis heterozygotes (Ff)
just one copy of the normal (dominant) allele is enough to supply the cell with the proper proteins to function.
Because of this, the normal allele is considered dominant over the recessive allele
Therefore, a person who is heterozygous does not suffer from Cystic Fibrosis

19. Review… If a person is a carrier for a trait, what does that mean?
They have the allele for the trait but do NOT express it
What is the difference between an autosome and a sex chromosome?
Sex chromosome determines the individual’s sex (2), while autosomes are the rest of the chromosomes (44)

20. Human Blood Groups

21. Blood Groups
Human blood comes in a variety of genetically determined blood groups
Using the wrong blood during a blood transfusion can be fatal
A number of genes help determine blood type but we will focus on two:
ABO blood groups
Rh blood groups

22. Blood Groups—the easy one first
The Rh blood group is determined by a single gene with 2 alleles—positive and negative
The positive allele is dominant
You need two Rh- alleles (Rh-/Rh-) to be Rh negative

23. ABO Blood Groups This is a case of multiple alleles
There are 3 alleles for this gene—A, B, and O.
AND…A and B are codominant!
O is recessive to A and B
Alleles A and B produce antigens (which are carbohydrates) on the surface of red blood cells
O produces NO antigens

24. ABO Blood Groups—the wrong blood can be FATAL
Antigens are recognized by the immune system and induce an immune response
If the wrong blood is transfused, the body will respond to these antigens by producing antibodies
Antibodies are named for what they attack
Antibodies bind to the foreign molecule (the antigen) and blood clumping will occur, which leads to blood clotting, which leads to death

25. ABO Blood Groups If you have blood type A, then you have:
The “A” antigen on the surface or your RBCs
You have anti-B antibodies
You can receive type A blood and type O blood
Remember: Your antibodies are named for what they attack—so if you received type AB or type B blood then clumping would occur.

28. ABO Blood Groups Try this cross
Cross a person who’s genotype is AA with a person who is AB.
Give the possible genotypes and phenotypes

29. Cross a person who’s genotype is AA with a person who is AB.
Gametes= A, A and A, B
Cross: A A A AA AA AB B AB

30. Genotypes= ½ AA, ½ AB
Phenotypes = ½ A, ½ AB

31. 14-2 Human Chromosomes (and 12-4)
Vocabulary:
Sex-linked gene
Sex-influenced gene
Sex-limited gene
Nondisjunction
Key Concepts:
Why are sex-linked disorders more common in males than in females?
What is nondisjunction, and what problems does it cause?
Lou Gehrig: died at 37 of ALS

32. Human Chromosomes
Your chromosomes contain about 30,000 genes and 46 chromosomes
Once thought to be over 100,000 genes
That’s about 3 billion base pairs
Remember: genes on the same chromosome are linked together
They tend to be inherited together

33. Human Genes & Chromosomes
Chromosomes 21 & 22 are the smallest human autosomes
Chromosome 22 contains approximately 43 million DNA bases (approx. 545 genes)
Chromosome 21 contains approximately 32 million DNA bases (approx.225 genes)
1 of these genes is associated with ALS (Amyotrophic Lateral Sclerosis)
Causes a progressive loss of muscle control due to the destruction of nerves in the brain and spinal chord

34. Sex Linked Genes Many sex-linked genes are found on the X-chromosome
What are linked genes?
They can be separated during meiosis through CROSSING OVER
Genes carried on the X or Y chromosome are sex linked because they are on the sex chromosomes
Many sex-linked genes are found on the X-chromosome

35. Sex Linked Genes
The X chromosome has many genes that are important for growth and development
The Y-chromosome only contains a few genes
All X-linked traits are expressed in males
WHY???????
Males only have 1 copy of the X chromosome, while females need 2 copies of the defective gene

36. Sex-Linked Gene Disorders
Colorblindness
3 human genes associated with color vision are located on the X-chromosome
In males, a defective version of any one of these produces colorblindness
Females must receive 2 copies of the allele to be colorblind
XCXc
XCXC
XCY
XcY

37. The Test

38. Sex-Linked Gene Disorders cont.
Hemophilia
2 important genes on the X-chromosome that code for proteins control blood clotting
A recessive allele in either of these 2 genes may lead to hemophilia
“bleeders disease”
Injections of normal clotting proteins prevent death

39. Sex-Influenced Genes A person’s phenotype is affected by their sex
Ex: Pattern Baldness
WOMEN: MEN:
BB: not bald BB: not bald
Bb: not bald Bb: bald
 bb: bald bb: bald

40. X-Chromosome Inactivation
Females have 2 X-chromosomes… if 1 is enough for males, how does the cell “adjust” to the extra x-chromosome in females?
One X-chromosome is randomly switched off
Condenses and is called a Barr body

41. Chromosomal Disorders
Most of the time, the mechanisms that separate human chromosomes in meiosis work very well, but things can go wrong
The most common error: NONDISJUNCTION
The chromosomes fail to separate
The result? Abnormal numbers of chromosomes

42. Nondisjunction Prefixes: dis = absence of / opposite of non = not
Root Word:
Junction = joining together
disjunction = the act of separating
nondisjunction = the act of not separating

47. Examples of Chromosomal Disorders
Down Syndrome
Klinefelter’s Syndrome
Turner’s Syndrome
Triple X Syndrome
                

48. Examples of Nondisjunction resulting in Chromosomal Disorders
Down's Syndrome: 47 chromosomes with 3 #21 chromosomes.
Triple-X Syndrome: 47 chromosomes caused by 3 X chromosomes.
Klinefelter's Syndrome: 47 chromosomes caused by 2 X chromosomes and 1 Y chromosomes.
Turner's Syndrome: 45 chromosomes with 1 X chromosome (caused by the absence of one of the X chromosomes or a Y chromosome).

49. Chromosomal Mutations (from 12-4)
Deletion
Duplication
Inversion
Translocation

50. Chromosomal Mutation (structural change)
Deletion: lose all or part of a chromosome
ABC-DEF AC-DEF
Duplication: segment of a chromosome is repeated
ABC-DEF ABBC-DEF

51. Chromosomal Mutation (structural change)
Inversion: chromosome segment becomes oriented in reverse direction
ABC-DEF ABE-DCF

52. Chromosomal Mutation (structural change)
Translocation: part of 1 chromosome breaks off & attaches to another non-homologous chromosome (segment is usually exchanged)
ABC-DEF ABC-JKL
GH-IJKL GH-IDEF

53. Chromosomal Mutation (change in number)
If an organism is born with the incorrect number of chromosomes
Ex: 47 human chromosomes instead of 46
Result of nondisjunction

54. Down Syndrome 3 copies of chromosome #21
1 in 800 babies in the US is born with this disease
produces mild to severe mental retardation
why should an extra copy of one chromosome cause so much trouble?

55. Klinefelter’s Syndrome
This is a sex chromosomal disorder associated with males.
Nondisjunction causes an extra X chromosome to be passed along during meiosis (XXY).
Resulting male cannot reproduce
Cases have been found in which individuals were (XXXY) or (XXXXY)

56. Turner’s Syndrome
This is a sex chromosomal disorder associated with females.
Nondisjunction causes offspring to inherit only one X chromosome (genotype = XO).
Resulting female is sterile due to underdeveloped sex organs.

57. 14-3 Human Molecular Genetics

58. DNA FINGERPRINTING
DNA fingerprinting is a technique developed to analyze sections of DNA that have little or no known function.
these areas vary widely from one individual to another.
This technique can be used to identify individuals based on banding patterns in the resulting DNA fragments
uses restriction enzymes
proteins that cuts DNA at specific sites along the nucleotide chain (cuts at specific base pairs).
Is used to determine paternity or match a suspect to a crime scene (like on CSI!)

59. THE PROCESS
human DNA is cut with restriction enzymes; this produces DNA fragments of different lengths
mix the DNA fragments with a probe that glows in UV light (the probe will stick to certain segments of DNA)

60. **smaller fragments will travel through the gel faster
run the DNA fragments through a clear gel
negative end
DNA goes in wells at the top
DNA has a "-" charge
· DNA will move to the "+" end of the gel
positive end
**smaller fragments will travel through the gel faster

62. 4. Smaller fragments of DNA will travel
4. Smaller fragments of DNA will travel through the gel faster (remember the
gel is porous).
Large DNA
fragment
negative end
positive end
Small DNA
fragment

63. 5. In order to see these fragments, the gel is viewed under UV light
5. In order to see these fragments, the gel is viewed under UV light. The result: The DNA fragments with the probe attached will glow & you will see a banding pattern
**Because each person's DNA is different, the restriction enzyme will cut the DNA in different places for different people and every person will have a different band pattern.

64. DNA_DetectivePC.exe

65. Gene Therapy
Gene therapy is the process of changing the gene that causes a genetic disorder. This way, the body can make the correct protein or enzyme it needs which eliminates the cause of the disorder.
1st attempt to cure a genetic disorder by gene transfer: 1990
Then, 1999: French girl apparently cured of an inherited immune disorder after cells from her bone marrow were removed, modified in the laboratory, and then placed back in her body

66. Uses a vector to get the “new” DNA inside your cell  viruses are often used cause they infect cells easily.
How does it work?….
1. The virus DNA is modified so it doesn’t cause
disease
2. DNA containing “good” gene is spliced to viral
DNA
The patient is then infected with this newly modified virus particles which should carry the “good” gene into the cells and correct the disorder.

68. Gene therapy today remains a high risk,experimental procedure.
Ethical Questions raised as we learn more about the human genome and gene therapy:
1. If we can manipulate genes to cure disease, does this also give us the right to engineer our bodies? (determine eye color, whether you are tall/short, hair color, sex, blood type...)
2. What will be the consequences if biologists successfully clone human beings?
Science meets Hollywood:
Issues like these were the basis of the movie, GATTACA

69. Review… What is a restriction enzyme?
What is the purpose of gene therapy?
Gene therapy is a process designed to change (replace) the damaged or defective gene with a normal, functional gene.
What is a restriction enzyme?
A restriction enzyme is a protein that cuts DNA at specific sites along the nucleotide chain (cuts at specific base pairs).