Exam 8: Chromosome Mutations: Variation in Number and Arrangement

Translocations may be pericentric or paracentric.

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

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

Inversion heterokaryotypes are often characterized as having reduced crossing over and reduced fertility.Assume that you were examining a strain of organisms you knew to be inversion heterokaryotypes and saw a relatively high number of double chromatid bridges extending between anaphase I nuclei.What would be a likely explanation for this observation? Explain with a labeled diagram.

Describe Bar mutations in Drosophila melanogaster.

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

Clearly illustrate the pairing configuration of an inversion (paracentric)heterokaryotype.

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

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

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 ________.

Provide an example of gene redundancy that occurs in both eukaryotes and prokaryotes.

Under what circumstance can an individual with Down syndrome have 46 chromosomes?

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

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

Name two methods used in genetic prenatal diagnostic testing in humans.

Given that a human normally contains 46 chromosomes,give the chromosome number for each of the following conditions: Turner syndrome (female,no Barr bodies) Klinefelter syndrome (male,one Barr body) Triploid Down syndrome (trisomic) Trisomy 13

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?

Name the polyploid condition that is formed from the addition of an extra set of chromosomes identical to the normal diploid complement of the same species.

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

An individual with Patau syndrome would be called a triploid.