Human Heredity

Exceptions to the RulesPedigreesKaryotypes

Ethics

Examples of Dominant Disorders

• Dwarfism• Polydactyly and Syndactyly• Hypertension• Hereditary Edema

• Chronic Simple Glaucoma – Drainage system for fluid in the eye does not work and pressure builds up, leading to damage of the optic nerve which can result in blindness.

• Huntington’s Disease – Nervous system degeneration resulting in certain and early death. Onset in middle age.

• Neurofibromatosis – Benign tumors in skin or deeper• Familial Hypercholesterolemia – High blood cholesterol and propensity for heart

disease• Progeria – Drastic premature aging, rare, die by age 13. Symptoms include limited

growth, alopecia, small face and jaw, wrinkled skin, atherosclerosis, and cardiovascular problems but mental development not affected.

Examples of Recessive Disorders

• Congenital Deafness• Diabetes Mellitus• Sickle Cell anemia• Albinism• Phenylketoneuria (PKU) – Inability to break

down the amino acid phenylalanine. Requires elimination of this amino acid from the diet or results in serious mental retardation.

• Galactosemia – enlarged liver, kidney failure, brain and eye damage because can’t digest milk sugar

• Cystic Fibrosis – affects mucus and sweat glands, thick mucus in lungs and digestive tract that interferes with gas exchange, lethal.

• Tay Sachs Disease – Nervous system destruction due to lack of enzyme needed to break down lipids necessary for normal brain function. Early onset and common in Ashkenazi Jews; results in blindness, seizures, paralysis, and early death.

Exceptions to the Rules

Incomplete Dominance

• The heterozygous is a blend between the dominant and recessive.

RR = red rr = white Rr = pink

Codominance

• The heterozygous condition, both alleles are expressed equally

• Sickle Cell Anemia in Humans

NN = normal cells

SS = sickle cells NS = some of each

Polygenic• More than one gene contributes to the

trait so there can be many phenotypes

Multiple Alleles

• There are more than two alleles for a trait

• Blood type in humans

• Blood Alleles?– A, B, O

• Blood Types?– Type A, Type B, Type AB, Type O

Rules for Blood Type• A and B are codominant

– AA = Type A– BB = Type B– AB = Type AB

• A and B are dominant over O– AO = type A– BO = type B– OO = type O

Can You see the Number?

Colorblindness is an X-linked recessive trait.

X-linkedTraits found on the X chromosome

Pedigrees

How to Construct a Pedigree?

• A Pedigree is a visual showing the pattern of inheritance for a trait. (Family tree)

• Symbols and Rules:

• Male = Female =

• Affected = Unaffected =

• Link parents together with a line and then make a vertical line to connect to offspring.

Is this trait dominant or recessive?

Note that the trait can appear in offspring of parents without the trait.

Is this trait dominant or recessive?

Note that the trait appears in every generation and ½ the offspring of an affected heterozygote are expected to show the trait.

Karyotypes

Karyotypes

• Maps of chromosomes

• 22 homologous pairs of human chromosomes

• Sex Chromosomes are the 23rd pair of chromosomes that determine the sex of an individual.

Changes in Chromosome Number and Structure

Down syndrome is caused by a change in chromosome number.

Chromosome Non-Disjunction in Meiosis

Down syndrome (trisomy 21)

The Frequency of Chromosome Non-Disjunction And Down Syndrome Rises Sharply with

Maternal Age

The phenomenon is clear – the explanation isn’t.

Karyotype

1 2 3 4 5

6 7 8 9 10

16 17 18 19 20

Karyotype of a normal female

21 22 23

11 12 13 14 15

1 2 3 4 5

6 7 8 9 10

16 17 18 19 20

Karyotype of a normal male

21 22 23

11 12 13 14 15

Karyotype Practice

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

21 22 23

Down Syndrome Male

Karyotype Practice

Klinefelter Male

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

21 22 23

Karyotype Practice

Turner Syndrome Female

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

21 22 23

Karyotype Practice

XYY Syndrome Male

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

21 22 23

Ethics

Pre-Implantation Genetic Diagnosis (PGD)

Removing a cell for diagnosis from a human embryo.

Amniocentesis and Chorionic Villus Sampling

Many new techniques for learning about individual genes rather than whole chromosomes are available or under development.

If you were to test your DNA…who does it belong

to?12. In the film, a person could have a

potential romantic partner sequenced. Discuss the positive and negative aspects of having this technology available to prospective mates.

If you were to test your DNA…who does it belong

to?16. You are an employer and know from

genetic testing that the most qualified applicant for the job has a 70% chance of developing Multiple Sclerosis in one year's time. Would you hire this person? Why or why not?

Gene Therapy

p-GLO Gene

Choose the sex of your child

Picking your Kid’s Traits

14. During a scene in GATTACA, Vincent’s parents visited a doctor who specialized in child conception to select for the best traits for his future brother. They hoped that his brother would have the best possible chances for a successful life. Some of the traits mentioned in GATTACA included intelligence, height and any possibility of inheritable diseases. If you decided to have a child one day and are given the opportunity to select for special traits, would you do so? Explain why or why not.

Picking your Kid’s Traits

15. Wouldn't every parent want to ensure that their child was perfect and had the attributes of physical attractiveness, intelligence and athletic prowess to be able to do whatever he or she wanted in life? If so, why is the society portrayed in this film so devoid of happiness, vitality and fun?

Dolly• In 1996, Ian Wilmut

cloned Dolly from an adult sheep.

CopyCat• In February 2002,

researchers from Texas A & M reported the live birth of a cloned tabby.

• Researchers are interested in using cloned cats in AIDS research, since feline AIDS is a good model for human AIDS.

Noah

Cloning

18. Cloning is a process in which you make a genetically identical organism. People say that this could be cool others say it is messing with Mother Nature. If you had the opportunity to clone yourself, would you do it and why?

Cloning

19. If a couple had a baby who died and could not have any more babies, but had the opportunity to clone their baby, should they be allowed to clone it?

Stem Cell Research

Stem Cell Research

20. Stem cell research is another ethical issue. Stem cells are cells from an early embryo that can become any type of cell like a heart, lung, liver, or skin cell. The reason people are researching these cells are because you can actually grow new tissues and organs to replace damaged ones. For instance, it may be possible to grow a new set of lungs for someone dying of lung cancer. The ethical issue with this type of research is that in order to get this type of stem cells you have to destroy an embryo so it will never grow into a person. Do you think this research should be done? Why or why not?

GATTACA

17. What would you say to a friend who believed themselves to be solely a product of their DNA and with no true freedom?

GATTACA

13. The technology to do what was done in the movie is definitely possible within the next fifty years. Do you think that Vincent’s world could eventually happen in America? Why?