Genetics Exam #2, Chapter 8

The condition known as cri-du-chat syndrome in humans has a genetic constitution designated as ________.

46, 5p-

An autotriploid may arise when three sperm cells are involved in fertilization of a single egg.

False

An individual with Patau syndrome would be called a triploid.

False

Assume that a species has a diploid chromosome number of 24. The term applied to an individual with 25 chromosomes would be triploid.

False

Assume that an organism has a haploid chromosome number of 7. There would be 14 chromosomes in a monoploid individual of that species.

False

Familial Down syndrome can be caused by a translocation between chromosomes 1 and 14.

False

In general, inversion and translocation heterozygotes are as fertile as organisms whose chromosomes are in the standard arrangement.

False

Individuals with familial Down syndrome are trisomic and have 47 chromosomes.

False

Inversions and translocations are without evolutionary significance.

False

Inversions suppress crossing over by providing a chemical imbalance because of breakpoints within certain genes.

False

The term aneuploidy is synonymous with the term segmental deletion.

False

Translocations may be pericentric or paracentric.

False

Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement but one (extra) chromosome 21. Although fertility is reduced in both sexes, females have higher fertility rates than males. Van Dyke et al. (1995; Down Syndrome Research and Practice 3(2): 65-69) summarize data involving children born of Down syndrome individuals. Assume that children are born to a female with Down syndrome and a normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome?

One-half of the offspring would be expected to have Down syndrome.

A paracentric inversion is one whose breakpoints do not flank the centromere.

True

A pericentric inversion includes the centromere.

True

A position effect occurs when a gene's expression is altered by virtue of a change in its position. One might expect position effects to occur with inversions and translocations.

True

An expected meiotic pairing configuration in a triploid would be a trivalent.

True

Assume that a species has a diploid chromosome number of 24. The term applied to an individual with 36 chromosomes would be triploid.

True

Assume that an organism has a diploid chromosome number of 14. There would be 28 chromosomes in a tetraploid.

True

Chorionic villus sampling (CVS) is sometimes preferred to amniocentesis because results can be provided earlier in the pregnancy.

True

Doubling the chromosomes of a sterile species hybrid with colchicine or cold shock is a method used to produce a fertile species hybrid (amphidiploid).

True

Familial Down syndrome is caused by a translocation involving chromosome 21

True

Gene duplications provide an explanation for the origin of gene families.

True

In Drosophila melanogaster (2n = 8), a fly with seven chromosomes could be called a haplo-IV.

True

Nondisjunction is viewed as a major cause of aneuploidy.

True

The chromosomal aberration that causes cri du chat syndrome can be referred to as a segmental deletion.

True

rDNA in eukaryotes is typically redundant.

True

Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement but one (extra) chromosome 21. While there is reduced fertility in both sexes, females have higher fertility than males. Van Dyke et al. (1995; Down Syndrome Research and Practice 3(2):6569) summarize data involving children born of Down syndrome individuals. Given the fact that conceptuses with 48 chromosomes (four #21 chromosomes) are not likely to survive early development, what percentage of surviving offspring would be expected to have Down syndrome if both parents have Down syndrome?

Two-thirds of the surviving offspring would be expected to have Down syndrome.

Although the most frequent forms of Down syndrome are caused by a random error, nondisjunction of chromosome 21, Down syndrome occasionally runs in families. The cause of this form of familial Down syndrome is ________.

a translocation between chromosome 21 and a member of the D chromosome group

The condition that exists when an organism gains or loses one or more chromosomes but not a complete haploid set is known as ________.

aneuploidy

Recently, a gene located on chromosome 3 in humans, FHIT, has been shown to be associated with the significant human malady known as ________.

cancer

A genomic condition that may be responsible for some forms of fragile X syndrome, as well as Huntington disease, involves ________.

various lengths of trinucleotide repeats