chapter 6-questions

Which of those two major causes is responsible for Down syndrome?

A change in the overall number of chromosomes

What is a pedigree?

A chart that tracks which members of a family have a particular trait

Why are pedigrees helpful in understanding genetic disorders?

A pedigree allows scientists and genetic counselors to infer how a genetic disorder is passed from one generation to the next.

What is a karyotype?

A picture of all the chromosomes in a cell, arranged in pairs

Explain what factors might work together to enable a great soccer player to kick a ball a long distance.

Athletic build and coordination may be inherited abilities that work together with environmental factors of practice, instruction, and exercises that strengthen muscles.

Which method would be the best way of producing a plant similar to the one you already have? Explain.

Cloning; many houseplants can be cloned by cutting the stem from one plant and putting the stem in soil.

How are the cells of a person with Down syndrome different from those of a person without the disorder?

Each of the cells of a person with Down syndrome has three copies of chromosome 21; normal cells have two copies of chromosome 21.

How many human blood types are there? Summarize how blood type is inherited.

Four: A, B, AB, and O; the alleles for blood types A and B are codominant, and the allele for blood type O is recessive. Type A blood results from two A alleles or one A and one i; type B blood results from two B alleles or one B and one i; type AB blood results from one A allele and one B allele; and type O results from two i alleles.

Identify the two major causes of genetic disorders in humans.

Mutations in DNA or changes in the overall structure or number of chromosomes

Aaron has blood type O. Can either of his parents have blood type AB? Explain your answer.

No; blood type AB has the genotype I AI B, while blood type O has the genotype ii. Each of his parents passed on an i allele, so neither could have blood type AB.

Are a person's characteristics determined only by genes? Explain.

No; genes and the environment interact to determine many of a person's characteristics.

Would a karyotype reveal the presence of sickle-cell disease? Why or why not?

No; sickle-cell disease is not related to the number of chromosomes in a cell.

Explain how red- green colorblindness is inherited. Why is the condition more common in males than in females?

Red-green colorblindness is determined by a recessive allele on the X chromosome. The condition is more common among males because males need to inherit only one recessive allele to express the trait, while females need two.

List three methods that scientists can use to develop organisms with desirable traits.

Selective breeding, cloning, and genetic engineering

Briefly describe each method.

Selective breeding—crossing two individuals to obtain particular characteristics; cloning producing an organism with the same genes as another organism; genetic engineering—transferring genes from one organism into the DNA of another

Identify three patterns of inheritance in humans. Give an example of a trait that follows each pattern.

Single genes with two alleles: widow's peak; single genes with multiple alleles: blood type; and multiple genes: skin color

What are two applications of DNA technology?

Studying the human genome and DNA fingerprinting.

Contrast the sex chromosomes found in human females and human males.

The Y chromosome is much smaller than the X chromosome. Females have two X chromosomes, and males have an X and a Y chromosome.

Sam has hemophilia. Sam's brother, mother, and father do not have hemophilia. Draw a pedigree showing who has the disorder and who is a carrier.

The square for Sam should be completely shaded, indicating that he has the disease. Sam's mother's circle should be half-shaded, indicating that she is a carrier. The squares for Sam's father and brother should be blank.

What are the functions of the sex chromosomes?

To carry genes that determine whether a person is male or female, and to carry other traits

Do you think DNA fingerprinting would be useful in solving crimes? Explain your reasoning.

Yes, DNA fingerprinting would be useful because each person's DNA is unique, so scientists could identify people involved in