Chromosomes - GRE Subject Test: Biochemistry, Cell, and Molecular Biology
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Which of the following choices might occur due to a chromosomal translocation?
Which of the following choices might occur due to a chromosomal translocation?
All of the given choices describe potential outcomes of chromosomal translocations. A translocation event occurs when recombination occurs between non-homologous chromosomes. The result is two chromosomes, each with genetic material from two different sets of genes that are generally kept separate.
Being present in a new environment may affect the expression of a gene (either an increase or decrease). Also, it is possible for translocations to occur in the middle of genes. The result of this could be newly formed non-functional (broken) genes or gene fusions between two coding regions that were originally separate. These alterations of gene expression have been implicated in many human diseases, including various cancers.
All of the given choices describe potential outcomes of chromosomal translocations. A translocation event occurs when recombination occurs between non-homologous chromosomes. The result is two chromosomes, each with genetic material from two different sets of genes that are generally kept separate.
Being present in a new environment may affect the expression of a gene (either an increase or decrease). Also, it is possible for translocations to occur in the middle of genes. The result of this could be newly formed non-functional (broken) genes or gene fusions between two coding regions that were originally separate. These alterations of gene expression have been implicated in many human diseases, including various cancers.
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Which chromosome abnormality affects chromosome 21?
Which chromosome abnormality affects chromosome 21?
Down syndrome is also referred to as trisomy 21. In about one in every 900 births, the child has an extra copy of the 21st chromosome.
Klinefelter syndrome is the result of a male being born with two X chromosomes and one Y chromosome. A deletion on the short arm of chromosome 5 causes Cri-Du-Chat syndrome; these children have respiratory problems and distinctive facial features. Williams syndrome is the result of genetic material missing from chromosome 7—in particular the gene for elastin, which causes disorders of the circulatory system and heart. A missing or incomplete X chromosome causes Turner syndrome. People who have Turner syndrome develop as females.
Down syndrome is also referred to as trisomy 21. In about one in every 900 births, the child has an extra copy of the 21st chromosome.
Klinefelter syndrome is the result of a male being born with two X chromosomes and one Y chromosome. A deletion on the short arm of chromosome 5 causes Cri-Du-Chat syndrome; these children have respiratory problems and distinctive facial features. Williams syndrome is the result of genetic material missing from chromosome 7—in particular the gene for elastin, which causes disorders of the circulatory system and heart. A missing or incomplete X chromosome causes Turner syndrome. People who have Turner syndrome develop as females.
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In the human population, what is the chance that a baby is born with a chromosomal abnormality (due to aneuploidy, deletions, or translocations)?
In the human population, what is the chance that a baby is born with a chromosomal abnormality (due to aneuploidy, deletions, or translocations)?
About 
newborns have a chromosomal abnormality, whether due to inheritance or as a result of meiotic events such as nondisjunction.
About
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of human pregnancies are spontaneously aborted in the first three months of development. Of these, what percent of the unsuccessful pregnancies are due to chromosomal abnormalities?
Nearly half of all spontaneously aborted pregnancies are due to chromosomal abnormalities. This includes aneuploidy (an excess or loss of 1+ chromosomes), deletions (a loss of a piece of a chromosome), and translocations (the transfer of one chromosome piece to another).
Nearly half of all spontaneously aborted pregnancies are due to chromosomal abnormalities. This includes aneuploidy (an excess or loss of 1+ chromosomes), deletions (a loss of a piece of a chromosome), and translocations (the transfer of one chromosome piece to another).
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Which of the following histone proteins is NOT in the nucleosome core of chromatin?
Which of the following histone proteins is NOT in the nucleosome core of chromatin?
DNA exists in the condensed chromatin form in order to fit into the nucleus. Negatively charged DNA loops twice around positively charged histone proteins to form a nucleosome bead. This nucleosome core is made up of two proteins each of histones H2A, H2B, H3 and H4.
H1 is the only histone protein that is not in the nucleosome core, and ties the nucleosome beads together in a string. H1 is located on the nucleosome exterior and help link DNA to the other proteins of the histone structure.
DNA exists in the condensed chromatin form in order to fit into the nucleus. Negatively charged DNA loops twice around positively charged histone proteins to form a nucleosome bead. This nucleosome core is made up of two proteins each of histones H2A, H2B, H3 and H4.
H1 is the only histone protein that is not in the nucleosome core, and ties the nucleosome beads together in a string. H1 is located on the nucleosome exterior and help link DNA to the other proteins of the histone structure.
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What is a telomere?
What is a telomere?
Telomeres are located at the ends of chromosomes and primarily serve the function of protecting the chromosome from degradation and fusion with neighboring chromosomes. The centromere is the site of attachment of two sister chromatids. Telomeres are not proteins; they are simply specialized portions of DNA. The sex chromosomes contain telomeres, but are only known as the sex chromosomes, allosomes, or chromosome 23.
Telomeres are located at the ends of chromosomes and primarily serve the function of protecting the chromosome from degradation and fusion with neighboring chromosomes. The centromere is the site of attachment of two sister chromatids. Telomeres are not proteins; they are simply specialized portions of DNA. The sex chromosomes contain telomeres, but are only known as the sex chromosomes, allosomes, or chromosome 23.
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The __________ is the end of a chromosome that is elongated by an enzyme known as __________.
The __________ is the end of a chromosome that is elongated by an enzyme known as __________.
Telomeres are the non-coding terminal ends of chromosomes, which help maintain the integrity of the chromosome and prevent it from being degraded. During normal DNA replication, the ends of the telomeres are not replicated and, therefore, must be lengthened by a different process. Telomerase is an enzyme that uses reverse transcription to extend the telomere.
Centromeres are the regions of chromosomes that link sister chromatids. Extendase function is observed in some polymerases, and involves extending the DNA strand beyond the template (typically by the addition of an adenine nucleotide).
Telomeres are the non-coding terminal ends of chromosomes, which help maintain the integrity of the chromosome and prevent it from being degraded. During normal DNA replication, the ends of the telomeres are not replicated and, therefore, must be lengthened by a different process. Telomerase is an enzyme that uses reverse transcription to extend the telomere.
Centromeres are the regions of chromosomes that link sister chromatids. Extendase function is observed in some polymerases, and involves extending the DNA strand beyond the template (typically by the addition of an adenine nucleotide).
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Which of the following would be affected by inhibiting a cell's ability to perform reverse transcription?
Which of the following would be affected by inhibiting a cell's ability to perform reverse transcription?
The only choice that involves a process that uses reverse transcription is the lengthening of telomeres. Telomerase is an enzyme that uses reverse transcription to extend telomeres after replication. mRNA splicing and post-translational modifications do not directly use the process of reverse transcription.
The only choice that involves a process that uses reverse transcription is the lengthening of telomeres. Telomerase is an enzyme that uses reverse transcription to extend telomeres after replication. mRNA splicing and post-translational modifications do not directly use the process of reverse transcription.
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You have discovered a new species of fish with a diploid number of 116. The gametes of this organism, just like human gametes, are haploid. You also discover that each gamete has 2 sex chromosomes, and sex of the zygote is determined by various combinations of the 4 possible sex chromosomes. What is the number of autosomes in a gamete of this new species?
You have discovered a new species of fish with a diploid number of 116. The gametes of this organism, just like human gametes, are haploid. You also discover that each gamete has 2 sex chromosomes, and sex of the zygote is determined by various combinations of the 4 possible sex chromosomes. What is the number of autosomes in a gamete of this new species?
If the diploid number is 116, 
haploid number in the gamete. Subtract 2 sex chromosomes, gives 56 autosomes in the gamete. This required knowing the distinction between autosomes and sex chromosomes and remembering to work from the haploid number since we are asked how many autosomes are in a gamete, not in an adult.
If the diploid number is 116,
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Which of the following are not true about homologous pairs of chromosomes?
Which of the following are not true about homologous pairs of chromosomes?
The alleles on the chromosome are not the same. The gene loci is the same, but which allele a chromosome carries depends on the donor. For example, if the maternal parent had blue eyes and the paternal parent had green eyes, then at the gene for eye color there could be 2 different alleles in their progeny.
The alleles on the chromosome are not the same. The gene loci is the same, but which allele a chromosome carries depends on the donor. For example, if the maternal parent had blue eyes and the paternal parent had green eyes, then at the gene for eye color there could be 2 different alleles in their progeny.
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During interphase, the genome is packed into chromatin, a complex of DNA and protein that orders the DNA. Most of the chromatin is loosely packed but certain regions a highly condensed. What is this condensed chromatin called?
During interphase, the genome is packed into chromatin, a complex of DNA and protein that orders the DNA. Most of the chromatin is loosely packed but certain regions a highly condensed. What is this condensed chromatin called?
During interphase, DNA is complexed with protein into a structure called chromatin. Euchromatin refers to chromatin that is loosely packed. Heterochromatin refers to chromatin that is highly condensed, and largely unavailable for transcription.
During interphase, DNA is complexed with protein into a structure called chromatin. Euchromatin refers to chromatin that is loosely packed. Heterochromatin refers to chromatin that is highly condensed, and largely unavailable for transcription.
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Which of the following is an example of epigenetic inheritance?
Which of the following is an example of epigenetic inheritance?
Epigenetic inheritance is a term that describes heritable changes in gene expression that are not caused by DNA sequence. Purine dimers, mismatched bases, and the coding regions of genes are all describe information that is contained within the DNA sequence. Histone methylation patterns, however, are not contained within the DNA. This heritable information has various effects on gene expression that is not due to the sequence of DNA, thus making it an example of epigenetic inheritance. Expression patterns based on histone methylation affect the accessibility of a DNA sequence and the ability of RNA polymerase to bind the sequence for transcription, silencing a gene without actually altering it.
Epigenetic inheritance is a term that describes heritable changes in gene expression that are not caused by DNA sequence. Purine dimers, mismatched bases, and the coding regions of genes are all describe information that is contained within the DNA sequence. Histone methylation patterns, however, are not contained within the DNA. This heritable information has various effects on gene expression that is not due to the sequence of DNA, thus making it an example of epigenetic inheritance. Expression patterns based on histone methylation affect the accessibility of a DNA sequence and the ability of RNA polymerase to bind the sequence for transcription, silencing a gene without actually altering it.
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Commonly, _________ of histones leads to the silencing of genes.
Commonly, _________ of histones leads to the silencing of genes.
Out of the choices, only methylation of histones is commonly associated with the silencing of genes. Proteins known as histone methyltransferases bind a methyl group to amino acids in the histone, most commonly lysine or arginine. The result is a change in chromatin structure, most commonly blocking transcription sites and preventing expression.
Acetylation of histones is often found in activated genes. Phosphorylation of histones has been seen in DNA regulation, but it is unclear whether or not this modification affects the expression of genes.
Out of the choices, only methylation of histones is commonly associated with the silencing of genes. Proteins known as histone methyltransferases bind a methyl group to amino acids in the histone, most commonly lysine or arginine. The result is a change in chromatin structure, most commonly blocking transcription sites and preventing expression.
Acetylation of histones is often found in activated genes. Phosphorylation of histones has been seen in DNA regulation, but it is unclear whether or not this modification affects the expression of genes.
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Physical barriers between euchromatin and heterochromatin that often block enhancers from interacting with promoters, subsequently preventing transciption, are best characterized as which of the following?
Physical barriers between euchromatin and heterochromatin that often block enhancers from interacting with promoters, subsequently preventing transciption, are best characterized as which of the following?
The correct answer is insulators. Insulators are regions of DNA that serve as boundary elements, preventing the formation of euchromatin from heterochromatin. Mediators and chromosomal looping promote transcription factor recruitment to the DNA and promoter-enhancer interactions. Nuclear lamins provide structure to the nuclear envelope.
The correct answer is insulators. Insulators are regions of DNA that serve as boundary elements, preventing the formation of euchromatin from heterochromatin. Mediators and chromosomal looping promote transcription factor recruitment to the DNA and promoter-enhancer interactions. Nuclear lamins provide structure to the nuclear envelope.
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One mechanism by which the cell can stably alter gene transcription is through DNA _________, which will repress expression of the gene that is altered. This is an example of an epigenetic modification.
One mechanism by which the cell can stably alter gene transcription is through DNA _________, which will repress expression of the gene that is altered. This is an example of an epigenetic modification.
Methylation is one of the most common epigenetic modifications that can be made to DNA sequences, and it typically results in repression of transcription at that site. This is typically achieved by modifying activity of the promoter region of a given gene.
Methylation is one of the most common epigenetic modifications that can be made to DNA sequences, and it typically results in repression of transcription at that site. This is typically achieved by modifying activity of the promoter region of a given gene.
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Which of the following best describes the mechanism by which histone acetylation results in increased transcriptionof a given chromosomal segment?
Which of the following best describes the mechanism by which histone acetylation results in increased transcriptionof a given chromosomal segment?
Acetylation induces a change directly to the histone; the histone is typically positively charged and thus has a high level of interaction with the negatively charged DNA. Acetylation makes the histone less positive, and therefore it is less attracted to the DNA. This reduced interaction reduces the tight coiling of DNA around the histones, and transcriptional machinery has more access to the strand to increase transcription of genes at those sites.
Acetylation induces a change directly to the histone; the histone is typically positively charged and thus has a high level of interaction with the negatively charged DNA. Acetylation makes the histone less positive, and therefore it is less attracted to the DNA. This reduced interaction reduces the tight coiling of DNA around the histones, and transcriptional machinery has more access to the strand to increase transcription of genes at those sites.
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Histones are proteins that bind to and order the DNA into tight clusters, making it inaccessible to transcription machinery. How does the cells loosen the interaction of the histone and DNA.
Histones are proteins that bind to and order the DNA into tight clusters, making it inaccessible to transcription machinery. How does the cells loosen the interaction of the histone and DNA.
By adding acetyl groups to the positively charged histone tails, the cell can loosen the binding of DNA to a histone since DNA is largely negatively charged. This DNA can now be accessed by transcription machinery such as RNA polymerase. In this way acetylation of histones promotes transcription of genes on that piece of DNA. Deacetylation does the opposite - replaces positive charges onto histones so that they can interact more tightly with the DNA, ultimately suppressing expression of the DNA.
By adding acetyl groups to the positively charged histone tails, the cell can loosen the binding of DNA to a histone since DNA is largely negatively charged. This DNA can now be accessed by transcription machinery such as RNA polymerase. In this way acetylation of histones promotes transcription of genes on that piece of DNA. Deacetylation does the opposite - replaces positive charges onto histones so that they can interact more tightly with the DNA, ultimately suppressing expression of the DNA.
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Bees use enzymes called DNMT1 and DNMT3 (DNA methyltransferases) to create epigenetic changes that differentiate social castes at a common site pattern. What is this type of epigenetic change called?
Bees use enzymes called DNMT1 and DNMT3 (DNA methyltransferases) to create epigenetic changes that differentiate social castes at a common site pattern. What is this type of epigenetic change called?
CpG (cytosine-phosphate-guanine) methylation is a common type of epigenetic change caused by this set of enzymes. In this case, the bees use this to create difference castes of bees out of the same shared genome.
CpG (cytosine-phosphate-guanine) methylation is a common type of epigenetic change caused by this set of enzymes. In this case, the bees use this to create difference castes of bees out of the same shared genome.
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Which term refers to a picture of the chromosomes of a single cell, arranged in descending order of size?
Which term refers to a picture of the chromosomes of a single cell, arranged in descending order of size?
A karyotype is produced by staining and photographing the chromosomes of a dividing cell. Pictures of the individual chromosomes are cut out and arranged in descending order of size. The chromosomes occur in homologous pairs that are similar in both staining patterns and size and have similar genetic material.
Physiological imaging is the visual representation of the functions of an organ, for example its blood flow, electrical activity, metabolism, and oxygen uptake. Radionuclide reflux imaging is a nuclear medicine scan used to determine whether an infant has gastroesophageal reflux. Phage type involves distinguishing subgroups of bacteria by the type of bacteriophage associated with that specific bacterium. Chromatography is the separation of two or more chemical compounds by their removal at different rates based on differential absorption and solubility.
A karyotype is produced by staining and photographing the chromosomes of a dividing cell. Pictures of the individual chromosomes are cut out and arranged in descending order of size. The chromosomes occur in homologous pairs that are similar in both staining patterns and size and have similar genetic material.
Physiological imaging is the visual representation of the functions of an organ, for example its blood flow, electrical activity, metabolism, and oxygen uptake. Radionuclide reflux imaging is a nuclear medicine scan used to determine whether an infant has gastroesophageal reflux. Phage type involves distinguishing subgroups of bacteria by the type of bacteriophage associated with that specific bacterium. Chromatography is the separation of two or more chemical compounds by their removal at different rates based on differential absorption and solubility.
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