13-2 Human Genetic Disorders

Ms. De Los Rios

7th Grade

Human Genetics and Genetic Technology- Course 2

VOCABULARYgenetic disorder- An abnormal condition that a person inherits through genes or chromosomes.

Pedigree- A chart that shows the presence or absence of a trait according to the

relationships within a family across several generations.

Karyotype- A picture of all the human chromosomes in a cell grouped together in pairs and arranged in order of decreasing size.

My Planet Diary pg. 450Doggie Diagnosis-

Maybe you have a dog or know someone who does. Did you know that dogs and humans can have some of the same health problems? It is not uncommon for dogs to have cancer, diabetes, allergies, epilepsy, and eye diseases. Scientists are studying the genes and genetic mutations that cause diseases in dogs in the hopes of better understanding human diseases. Most diseases in dogs are caused by a mutation on one gene. In humans, the mutations can be on multiple genes. The genes that cause diseases in dogs are much easier to find than those in humans. So far, scientists are looking into the genes that cause blindness, cancer, and spinal cord disorders in dogs.

1. Why are scientists studying dog genes to understand human diseases?

2. In what other ways could studying dog diseases be beneficial?

How Are Genetic Disorders Inherited In Humans? Pg. 451

A genetic disorder is an abnormal condition that a person inherits through genes or chromosomes.

Caused by: • Mutations in the DNA of genes

• By changes in the overall structure or number of chromosomes.

Cystic Fibrosis

Cystic fibrosis is a genetic disorder in which the body produces abnormally thick mucus. In the lungs, this can cause difficulty breathing. A person with cystic fibrosis inherits one mutated allele from each parent.

Sickle-Cell Disease

• Sickle-cell disease is caused by a mutation that affects hemoglobin. Hemoglobin is a protein in red blood cells that carries oxygen.

The red blood cells of people with the disease have a sickle, or crescent shape. Sickle-shaped red blood cells cannot carry as much oxygen as normal cells and clog blood vessels. The allele for the sickle-cell trait (S) is codominant with the normal allele (A). A person with one normal allele and one sickle-cell allele (AS) will produce both normal hemoglobin and abnormal hemoglobin. This person usually does not have symptoms of the disease. He or she has enough normal hemoglobin to carry oxygen to cells. A person with two sickle-cell alleles (SS) will have the disease.

Sickle-Cell Disease – Fig. 1 pg. 451

In a person with sickle-cell disease, red blood cells can become sickle-shaped instead of round.

A man has sickle-cell disease. His wife does not have the disease, but is heterozygous for the sickle-cell trait. Use this information to complete the Punnett square. What is the probability that their child will have the sickle-cell disease?__________________________________________________

HemophiliaHemophilia slows or prevents blood clotting so that even small

bumps can cause bleeding. Because hemophilia is caused by a recessive allele on the X chromosome, it is more common in males than females.

Down Syndrome pg. 452

In Down syndrome, instead of a pair of chromosomes, a person inherits three copies of chromosome 21. People with Down syndrome experience some degree of mental retardation and often have heart defects.

Hemophilia is a genetic disorder in which a person’s blood clots very slowly or not at all. People with the disorder do not produce enough of one of the proteins needed for normal blood clotting. The danger of internal bleeding from small bumps and bruises is very high. Hemophilia is called by a recessive allele on the X chromosome. Hemophilia occurs more often in males than in females.

Cross a carrier female, XHXh, with a healthy male, XHY, and complete the Punnett square.

1.What percentage of the offspringWould be normal? ________Would be carriers? ________Would have hemophilia? __________

2. To have a daughter with hemophilia, the father must have the disorder and the mother must have one of twoGenotypes. What are they?____________________________________________________________

Assess Your Understanding pg. 452

1a. Explain- Which of the two major causes of genetic disorders is responsible for Down syndrome? __________________________

____________________________________________________________________________________________________________

b. Infer- Why is hemophilia more common in males? _____________

____________________________________________________________________________________________________________

I got it! Now I know that the two major causes of genetic disorders are _________________________________________________

______________________________________________________

How are Genetic Disorders Traced, Diagnosed, and Treated?

Pg. 453

Tools used by doctors to trace and diagnose genetic disorders are:

PedigreesKaryotypes

Genetic testing

People with genetic disorders are helped through medical care, education, and job training.

Pedigrees and Karyotypes

A pedigree is a chart or “family tree”

that tracks which members of a

family have a particular trait. Circle= Female

Square= Male

A karyotype, a picture of all the

chromosomes in a cell, can be used

to determine whether a person has

the correct number of chromosomes.

PedigreesThis pedigree shows the inheritance of the allele for albinism in three generations of a family.1.Interpret Diagrams- Circle the symbol in the pedigree that represents an albino male.2. Make models- Using what you have learned about pedigrees and pedigree symbols, construct a possible two-generation pedigree for sickle-cell anemia, starting with parents who are both carriers, AS x AS

Genetic Counseling

Couples that have a family history of a genetic disorder may turn to a genetic counselor for advice. They can find out their chances of having a child with the disorder and learn how to prepare to raise him or her. People with genetic disorders face serious challenges. Yet medical treatments, physical therapy, education, and job training programs can help those affected to live active, productive lives.

Assess Your Understanding pg. 455

I get it! Now I know that genetic disorders are traced, diagnosed, and treated by ____________________________________________

_______________________________________________________