Question 1

In what way can defective transposable elements alter genomes even if they cannot mobilize? (Select all that apply. )
A)Crossing-over between transposable elements on the same chromosome can result in a deletion or an inversion.
B)Crossing-over between transposable elements on nonhomologous chromosomes can result in a reciprocal translocation.
C)Genes located between two transposable elements could be moved to a nonhomologous chromosome.
D)Proteins produced by the defective transposable elements introduce point mutations in other areas of the genome.

Accepted Answer

The answer of In what way can defective transposable elements...

Question 2

What is true about reciprocal translocation heterozygotes and inversions? (Select all that apply. )
A)The amount of DNA in the genome remains the same.
B)The genes at the boundaries may be disrupted, while those in the middle are most likely unaffected.
C)Up to 50% of gametes may be unbalanced, resulting in semisterility.
D)They are both used to make Balancer chromosomes.

Accepted Answer

The answer of What is true about reciprocal translocation heterozygotes...

Question 3

An individual with which type of chromosomal rearrangement is expected to have the lowest fertility?
A)chromosomal duplication
B)pericentric inversion
C)translocation heterozygote
D)translocation homozygote
E)paracentric inversion

Accepted Answer

A translocation heterozygote has one normal set of chromosomes and one set with a translocation, leading to problems during meiosis and resulting in reduced fertility due to the production of unbalanced gametes.

Question 4

Turner syndrome (XO)is a sex chromosome aneuploidy.Of the effects listed below, which one is not usually seen in this syndrome?
A)unusually short stature
B)infertility
C)skeletal abnormalities
D)unusually long limbs

Accepted Answer

Turner syndrome (XO) typically presents with short stature, infertility, and skeletal abnormalities, but not with unusually long limbs.

Question 5

Which can result in Down syndrome? (Select all that apply. )
A)nondisjunction resulting in an extra chromosome 21
B)a reciprocal translocation between acrocentric chromosomes 14 and 21
C)deletions of a segment of chromosome 21
D)having the triploid number of chromosomes

Accepted Answer

Down syndrome is most commonly caused by nondisjunction leading to an extra chromosome 21 (trisomy 21). It can also result from a Robertsonian translocation involving chromosome 21, such as a translocation between chromosomes 14 and 21. Deletions of chromosome 21 or triploidy do not typically result in Down syndrome.

Question 6

What is true in translocation heterozygotes?
A)At the borders of translocations, genes that are normally located on different homologs appear to be linked.
B)Fertility is reduced because only alternate segregation results in balanced gametes.
C)The translocation chromosome is used as a balancer because it cannot cross over with a normal chromosome.
D)Crossing over between normal and translocation chromosomes results in an inversion.

Accepted Answer

In translocation heterozygotes, genes that are normally located on different homologs appear to be linked due to the rearrangement of genetic material.

Question 7

What might result from movement of transposable elements in a species' genome? (Select all that apply. )
A)The level of expression of one or more genes could be changed.
B)A gene could be moved from one chromosome to another.
C)A segment of DNA could be duplicated or deleted.
D)The rate of point mutation could increase.

Accepted Answer

Transposable elements can influence gene expression by inserting themselves near or within genes, potentially altering their expression levels. They can also facilitate the movement of genes between chromosomes or cause duplication or deletion of DNA segments. However, they do not directly increase the rate of point mutations, which are typically single base changes in the DNA sequence.

Question 8

Which segregation pattern in a translocation heterozygote is likely to result in a normal zygote after fertilization?
A)alternate
B)adjacent-1
C)adjacent-2
D)nondisjunction

Accepted Answer

Alternate segregation in a translocation heterozygote is likely to result in a normal zygote after fertilization because it separates homologous centromeres into different gametes, leading to gametes with balanced genetic material.

Question 9

Which is not an example of euploidy?
A)Seedless watermelons have three copies of each chromosome.
B)A normal human has two copies of each chromosome.
C)A human with Down syndrome has three copies of chromosome 21.
D)Commercially grown strawberry plants have eight copies of each chromosome.

Accepted Answer

Euploidy refers to changes in the whole set of chromosomes, whereas an individual with Down syndrome has an extra copy of only one chromosome (chromosome 21), making it an example of aneuploidy, not euploidy.

Question 10

During mitosis, if all of the chromosomes in a diploid cell fail to separate and instead segregate into one daughter cell, the result will be what?
A)one monoploid daughter cell and one triploid daughter cell
B)one 2x-1 daughter cell and one 2x+1 daughter cell
C)two 2x daughter cells
D)only one tetraploid daughter cell

Accepted Answer

This scenario describes a failure in chromosome segregation during mitosis, leading to one daughter cell receiving all the chromosomes (doubling its chromosome number) and the other receiving none. This results in one tetraploid daughter cell, as all chromosomes are segregated into a single cell, doubling its original diploid number.

Question 11

Which is a mechanism by which transposable element mobilization may be controlled by the cell? (Select all that apply. )
A)blocking transcription of transposable element genes
B)blocking translation of transposable element transcripts
C)alternative splicing of transposable element transcripts
D)synthesizing an enzyme that removes transposable elements from the genome
E)increasing the mutation rate of transposable element DNA sequences

Accepted Answer

Cells can control transposable elements by blocking their transcription, translation, or through alternative splicing, which can prevent their mobilization.

Question 12

Which sex chromosome aneuploidy is not usually seen in live births?
A)XO
B)XXY
C)YO
D)XXX

Accepted Answer

YO aneuploidy, which would theoretically result from a sperm with no sex chromosome fertilizing an egg, is not compatible with life and thus not seen in live births. All other options listed (XO, XXY, XXX) are known aneuploidies that can result in live births, with Turner syndrome (XO), Klinefelter syndrome (XXY), and Triple X syndrome (XXX) respectively.

Question 13

Which is a characteristic of retrotransposons, but not of DNA transposons?
A)include a gene that encodes reverse transcriptase
B)may be present in a genome from one to millions of times
C)found only in humans
D)may not have a function in their host
E)have short DNA sequences that are inverted repeats of each other on the ends

Accepted Answer

Retrotransposons are characterized by their ability to encode the enzyme reverse transcriptase, which is not a feature of DNA transposons. This enzyme allows retrotransposons to transcribe their RNA back into DNA, which can then integrate into the genome.

Question 14

What might be the outcome of repeated duplications of one or a few genes in a species' genome?
A)tetraploidy
B)semisterility
C)the presence of gene families
D)repetitive DNA that is of no use to the cell
E)fusion of segments of two chromosomes into one

Accepted Answer

Gene duplication events can lead to the formation of gene families, where multiple copies of a gene exist within the genome. These copies can diverge over time, potentially taking on new functions or enhancing the organism's ability to produce certain proteins.

Question 15

What is a reason that aneuploidy in sex chromosomes is generally better tolerated than aneuploidy in autosomal chromosomes in humans?
A)In somatic cells, most of the genes on only one X chromosome are transcriptionally active.
B)Autosomal aneuploidy leads to heart defects and death in utero.
C)Y chromosome duplication results in only minor changes in testosterone levels.
D)Sex chromosome aneuploids may occur as the result of fertilization, but extra sex chromosomes are removed from the developing embryo during subsequent mitosis.
E)Any change in autosome number results in increased susceptibility to infection.

Accepted Answer

In somatic cells, most of the genes on only one X chromosome are transcriptionally active, which means that having an extra X chromosome does not significantly increase the gene dosage. This mechanism, known as X-inactivation, helps to mitigate the effects of having an extra sex chromosome, making aneuploidy involving sex chromosomes generally better tolerated than aneuploidy involving autosomes.

Question 16

In Drosophila, a gynandromorph, which is composed of equal parts of male and female tissue, results from
A)an XX female losing one X chromosome during the first mitotic division after fertilization.
B)an egg carrying an X chromosome fertilized by a Y-carrying sperm.
C)a normal egg fertilized by both an X-carrying sperm and a Y-carrying sperm.
D)the fusion of a female embryo with a male embryo.

Accepted Answer

Gynandromorphs in Drosophila can result from an XX female losing one X chromosome during the first mitotic division after fertilization, leading to a mosaic organism with both male (XO) and female (XX) cells.

Question 17

On the island of Madeira, two populations of house mice have accumulated different Robertsonian translocations.Which are true about these two populations of mice? (Select all that apply. )
A)They have fewer chromosomes than mice in other areas of the world.
B)They are isolated from each other geographically.
C)If mice from different populations mate, their offspring are sterile.
D)Mice from different populations are unable to mate with each other.
E)They are becoming extinct because of semisterility.

Accepted Answer

The two populations of house mice on the island of Madeira have accumulated different Robertsonian translocations, which means that they have fewer chromosomes than mice in other areas of the world. They are also isolated from each other geographically, which means that they are unable to mate with each other. If mice from different populations do mate, their offspring are sterile.

Question 18

Which is not an example of aneuploidy?
A)monosomy
B)tetraploidy
C)trisomy
D)nullisomy

Accepted Answer

Tetraploidy refers to a condition where an organism has four complete sets of chromosomes, which is a type of polyploidy, not aneuploidy. Aneuploidy involves a chromosome number that is not an exact multiple of the haploid number, such as monosomy, trisomy, and nullisomy.

Question 19

Triploid organisms usually result from
A)the union of monoploid and diploid gametes.
B)nondisjunction during mitosis.
C)propagation of fused cell lines.
D)a fertilization event that involves three monoploid gametes.
E)normal fertilization of gametes produced by triploid parents.

Accepted Answer

Triploid organisms typically result from the union of a monoploid (n) gamete and a diploid (2n) gamete, leading to a triploid (3n) organism.

Question 20

One similarity between DNA transposons and retrotransposons is that
A)during transposition, both go through an RNA form that is copied back into DNA.
B)both can encode an enzyme required for mobilization.
C)transposition results in movement of the original transposon to a different place in the genome.
D)they both have poly-A segments at one end.

Accepted Answer

Both DNA transposons and retrotransposons can encode enzymes necessary for their mobilization, such as transposase for DNA transposons and reverse transcriptase for retrotransposons.

Quiz 13: Chromosomal Rearrangements and Changes in Chromosome Number

In what way can defective transposable elements alter genomes even if they cannot mobilize? (Select all that apply. )

What is true about reciprocal translocation heterozygotes and inversions? (Select all that apply. )

An individual with which type of chromosomal rearrangement is expected to have the lowest fertility?

Turner syndrome (XO) is a sex chromosome aneuploidy.Of the effects listed below, which one is not usually seen in this syndrome?

Which can result in Down syndrome? (Select all that apply. )

What is true in translocation heterozygotes?

What might result from movement of transposable elements in a species' genome? (Select all that apply. )

Which segregation pattern in a translocation heterozygote is likely to result in a normal zygote after fertilization?

Which is not an example of euploidy?

During mitosis, if all of the chromosomes in a diploid cell fail to separate and instead segregate into one daughter cell, the result will be what?

Which is a mechanism by which transposable element mobilization may be controlled by the cell? (Select all that apply. )

Which sex chromosome aneuploidy is not usually seen in live births?

Which is a characteristic of retrotransposons, but not of DNA transposons?

What might be the outcome of repeated duplications of one or a few genes in a species' genome?

What is a reason that aneuploidy in sex chromosomes is generally better tolerated than aneuploidy in autosomal chromosomes in humans?

In Drosophila, a gynandromorph, which is composed of equal parts of male and female tissue, results from

On the island of Madeira, two populations of house mice have accumulated different Robertsonian translocations.Which are true about these two populations of mice? (Select all that apply. )

Which is not an example of aneuploidy?

Triploid organisms usually result from

One similarity between DNA transposons and retrotransposons is that