CH.8 Bio Quiz

Down syndrome can be the result of _____.

nondisjunction of chromosome 21 during meiosis

A karyotype is most like

photographs of every couple at a high school prom.

How many generations does it take to develop a new plant species by polyploidy?

1

If a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction, the resulting chromosomal abnormality is called _____.

an inversion

During which stage of meiosis could this nondisjunction have occurred?

anaphase II

Which of the following types of organisms commonly demonstrates polyploidy?

flowering plants

You are a medical student and are reviewing a case study about a past patient. The patient was 4 feet 8 inches tall at age 38, was unable to have children, and had an above-average intelligence. The patient also had an irregular number of chromosomes. What diagnosis would you give the patient?

Turner syndrome

In theory, when a nondisjunction for chromosome 18 occurs during meiosis I, four gametes can be produced. If these gametes are fertilized with unaffected gametes from the second parent, what observations would you make concerning the resulting embryos?

Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18.

Jacobsen syndrome, which can cause heart defects, intellectual deficiencies, and bleeding disorders, is caused by a deletion of the terminal end of chromosome 11. What method could you use to determine whether an individual has Jacobsen syndrome?

Perform a karyotype using a person's white blood cells.

Cancer is not usually inherited because

the chromosomal changes in cancer are usually confined to somatic cells.

On average, what percentage of infants born to 45-year-old mothers have Down syndrome?

3%

Each somatic cell in an individual with Down syndrome contains _____ chromosomes.

47

Polyploidy is involved in which of the following examples?

A normal watermelon has 22 chromosomes but seedless watermelons have 33 chromosomes.

Trisomy for most autosomes is fatal, yet trisomy or even tetrasomy (four copies) of the X chromosome is not. What is the explanation for this difference?

Only one copy of the X chromosome is active, regardless of the total number of X chromosomes.

Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not?

Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

Which of the following variations of the sentence "Where is the cat?" is most like a chromosomal deletion?

Where is cat?

Which of the following indicates Turner syndrome?

XO

If Charles gets married and starts a family, which of the following chromosomal abnormalities has an increased chance of occurring in his children?

XXY

Consider the photograph of a karyotype. This is _____.

a photograph of all a person's chromosomes

According to the graph, at what maternal age is the incidence of Down syndrome equal to five times the incidence at age 40?

about 46 or 47

Karyotyping

can reveal alterations in chromosome number.

A fragment of chromosome 21 reattaches to chromosome 21, but in the reverse direction. What is the name given to this change?

inversion

If a chromosome fragment breaks off and then reattaches to the original chromosome but in the reverse direction, the resulting chromosomal abnormality is called a(n)

inversion.

Which of the following statements regarding Down syndrome is false?

Down syndrome is least likely to be seen in the infants of mothers over 40.

Use the graph and your knowledge of Down syndrome to select the three true statements.

Down syndrome is caused by a trisomy of chromosome 21. The incidence of Down syndrome in infants born to mothers under the age of 35 is less than 0.5%. The risk of having a baby with Down syndrome more than doubles for 45-year old mothers compared to 40-year old mothers.

Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?

Extra copies of the other somatic chromosomes are probably fatal.

Which of the following statements about nondisjunction is false?

In mammals, extra copies of the Y chromosome are typically inactivated.

You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication?

In trisomy there would be one extra chromosome; in a duplication, one chromosome would have two copies of a portion of the chromosome.

During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as _____.

nondisjunction

If these four cells resulted from cell division of a single cell with diploid chromosome number 2n = 4, what best describes what just occurred?

nondisjunction

The exchange of parts between nonhomologous chromosomes is called _____.

reciprocal translocation