CH 18: Homework
In a female mammal heterozygous for an X-linked recessive allele, what proportion of somatic cells will express the recessive allele? - 0% - 100% - 25% - 50%
50%
What is a Barr body? - An inactive cell that is produced during oogenesis in female mammals - A highly condensed X chromosome - An imprinted gene only found in females - A maternal cell that transports gene products into the developing egg - A region on the X chromosome that is essential for compaction
A highly condensed X chromosome
Which of the following are common types of molecular changes that result in epigenetic effects on gene expression? - DNA methylation - Chromatin remodeling - DNA translocation - DNA mutation - Localization of histone variants - Covalent histone modification
DNA methylation; chromatin remodeling; localization of histone variants; covalent histone modification
What is the origin of the mitochondria and chloroplasts found in eukaryotic cells? - Membrane-bound vesicles that broke off from the nucleus - An ancient endosymbiotic relationship - An ancient infection with a virus - Membrane-bound vesicles produced by the Golgi apparatus
an ancient endosymbiotic relationship
In statistics, changes in two variables that follow a pattern is termed a(n) ______. - correspondence - association - causation - concordance
association
A highly condensed X chromosome is known as a(n) _____ body.
barr
Adult, wild-type mice with genotype AA for the Agouti gene will have what color coat hairs? - All yellow - All black - All brown - Yellow with brown tips - Brown with black tips
brown with black tips; the yellow pigment is sandwiched between layers of black pigment, giving a brown color along most of the hair shaft. No yellow pigment is synthesized near the tip of the hair.
An example of X-chromosome inactivation is found in some female cats, which have a coat color containing randomly distributed patches of black and orange fur. This is called the _____ pattern of coat color.
calico
Which of the following phenotypes is directly associated with X-chromosome inactivation? - Skin pigmentation in humans - Body size in male mice - Calico coat pattern in female cats - Shell coiling in snails - Leaf color in four o'clock plants
calico coat pattern in female cats
What is an example of mosaicism? - Dextral coiling in snails - Dwarfism in mice - Calico coat pattern in cats - White chloroplasts in the four-o'clock plant
calico coat patterns in cats
Which of the following characterize an epigenetic effect? - Causes a change in gene expression - Leads to changes in the DNA sequence - Has no effect on gene expression - The change must be passed from cell to cell
causes a change in gene expression; the change must be passed from cell to cell
Which organelles demonstrate cytoplasmic inheritance? - The nucleus - Chloroplasts - The endoplasmic reticulum - Mitochondria - The Golgi apparatus
chloroplasts; mitochondria
Mitochondrial and chloroplast genomes are typically composed of a single, _____ _____ molecule.
circular; DNA
The cells of humans and other mammals have the ability to _____ their X chromosomes, and are therefore able to inactivate all but one of them.
count
Thomas Hunt Morgan recognized that some genes in Drosophila violated the law of independent assortment. He proposed that such genes were located on the same chromosome and that new combinations of alleles could be created only if _____ _____ during meiosis.
crossing over
Mitochondria and chloroplasts are found in eukaryotic cells because of an ancient _____ event, in which a prokaryotic cell engulfed another prokaryotic cell. It is for this reason that these organelles contain their own genetic material.
endosymbiotic
Genomic imprinting is an example of a phenomenon called _____ inheritance.
epigenetic
Th term which describes changes in gene expression that are not related to variations of the DNA sequence, yet are transmissible and are reversible, is _____.
epigenetic
The process of X-chromosome inactivation is an example of a(n) _____ change that occurs during embryonic development in female mammals. This leads to silencing of one of the two X chromosomes found in somatic cells.
epigenetic
What type of inheritance describes X-chromosome inactivation? - Epistatic - Mendelian - Mitochondrial - Extranuclear - Epigenetic
epigenetic
What type of inheritance describes genomic imprinting? - Epigenetic - Mendelian - Epistatic - Mitochondrial - Extranuclear
epigenetic
Which of the following statements are true regarding epigenetics? - Epigenetic changes are transmissible from cell to cell. - Variations of gene expression that result from DNA mutations - Variations of gene expression that are unrelated to DNA sequence variants - Variations are reversible from one generation to the next. - Epigenetic changes may be transmitted to offspring.
epigenetic changes are transmissible from cell to cell; variations of gene expression that are unrelated to DNA sequence variants; variations are reversible from one generation to the next; epigenetic changes may be transmitted to offspring
The inheritance pattern observed for genes that are located outside the cell nucleus, in mitochondria or chloroplasts, is called _____ inheritance.
extranuclear
Transmission of genes located outside of the cell nucleus is known as: - polygenic inheritance - extranuclear inheritance - Mendelian inheritance - epistatic inheritance
extranuclear inheritance
True or false: Epigenetic changes that occur in an individual are permanent during its lifetime.
false; while some epigenetic changes are relatively permanent during the life of an individual, others are reversible
X-chromosome inactivation refers to the process that occurs in ______. - all mammals, in which the genes of all X chromosomes are not expressed - male mammals, in which the genes of the single X chromosome are not expressed - female mammals, when the genes of one of the two X chromosomes are not expressed - female mammals, when the genes of both of the X chromosomes are not expressed
female mammals, when the genes of one of the two X chromosomes are not expressed
What are the three general rules for genes that follow a Mendelian pattern of inheritance? - Genes are generally passed unaltered from cell to cell, and from generation to generation. - For crosses involving two or more genes, the genes obey Mendel's law of independent assortment. - The genes obey Mendel's law of segregation. - The genes interact in an additive way to produce a phenotype.
genes are generally passed unaltered from cell to cell, and from generation to generation; for crosses involving two or more genes, the genes obey Mendel's law of independent assortment; the genes obey Mendel's law of segregation
Individuals may have the same genotype but very different phenotypes as a result of ______. - epistasis - polygenic inheritance - genomic imprinting - genetic linkage
genomic imprinting
The gene Igf2 encodes a(n) ______. - neurotransmitter - transcription factor - enzyme - growth hormone
growth hormone
In the somatic cells of female mammals, the genes on one of the two copies of X chromosomes are not expressed. This phenomenon is known as X-chromosome _____.
inactivation
Why don't imprinted genes follow a Mendelian pattern of inheritance? - Imprinted genes are inherited only maternally because they are found on the mitochondrial genome. - Individuals may have the same genotype but different phenotypes because the offspring expresses only the maternal or paternal allele. - The genes are linked on the same chromosome, violating Mendel's law of independent assortment. - The genes do not separate during meiosis, violating Mendel's law of segregation.
individuals may have the same genotype but different phenotypes because the offspring expresses only the maternal or paternal allele
One of the first imprinted genes to be identified was a gene in mice called Igf2. This gene encodes a growth hormone called _______ - like growth ______ 2 (Igf2)
insulin; factor
How does DNA methylation inhibit gene expression? - It causes mutations in the gene. - It prevents the initiation of transcription. - It prevents binding of repressor proteins. - It attracts activator proteins to the promoter. - It causes chromatin to become more compact.
it prevents the initiation of transcription; it causes chromatin to become more compact
When two genes are located close to one another on a chromosome, they tend to be transmitted together. This phenomenon is known as _____.
linkage
Which phenomenon describes the presence of two genes very close to each other on the same chromosome, and which are transmitted together as a unit? - Linkage - Epistasis - X inactivation - Genomic imprinting - Pleiotropy
linkage
In a particular plant, the pigmentation of the offspring depends exclusively on the pigmentation of the female parent. This phenomenon is known as _____ inheritance.
maternal
In humans, mitochondria are inherited through a type of uniparental inheritance called _____ inheritance.
maternal
How are mitochondria inherited in humans? - Maternal inheritance - Epigenetic inheritance - Biparental inheritance - Mendelian inheritance - Paternal inheritance
maternal inheritance
What is the phenomenon called in which a trait of the offspring is solely determined by the value of the trait in the female parent because it is passed on via the organelles in the egg cell? - Gene linkage - Genomic imprinting - Maternal effect - Maternal inheritance - Epistasis
maternal inheritance
The marking process that occurs during genomic imprinting is the addition of _____ groups to DNA.
methyl
The transcription of a gene can be altered by the attachment of _____ groups to the bases of DNA.
methyl
How is the maternal version of the Igf2 gene silenced in mice? - The gene is found in mitochondria, which are only inherited from the father. - Compaction of one of the X chromosomes into a Barr body silences the gene. - Methyl groups are attached to the gene, inhibiting transcription. - Methylation is erased from the gene, inhibiting transcription.
methyl groups are attached to the gene, inhibiting transcription
The molecular mechanisms of epigenetics are varied. The most common types are: DNA _____, chromatin _____, covalent _____ modification, and localization of histone variants.
methylation; remodeling; histone
Extranuclear inheritance patterns involve genes located in the _____ and _____.
mitochondria; chloroplasts
In a eukaryotic cell, where are genes found? - the Golgi apparatus - the plasma membrane - mitochondria - chloroplasts - the endoplasmic reticulum - the nucleus
mitochondria; chloroplasts; the nucleus
The calico coat pattern in female cats is an example of ______. - extranuclear inheritance - paternal inheritance due to genomic imprinting - mosaicism due to X-chromosome inactivation - gene interaction due to linkage
mosaicism due to X-chromosome inactivation
Which of the following statements about eukaryotic genes is TRUE? - Only a few genes are found in the nucleus. - About half of the genes are found in the nucleus. - All genes are found in the nucleus. - Most, but not all genes, are found in the nucleus.
most, but not all genes, are found in the nucleus
In mice, the Igf2 gene inherited from the ______ is not transcribed into mRNA because the DNA is ______. - mother; methylated - father; mutated - mother; mutated - father; methylated
mother; methylated
Mendelian inheritance is characterized by three general rules: 1. Except in the case of rare _____, genes are passed unaltered from generation to generation; 2. Each gene obeys Mendel's law of _____; and 3. During crosses, two or more genes obey Mendel's law of independent _____.
mutation; segregation; assortment
In humans and other mammals, X chromosomes are counted. This process ensures that any normal somatic cell contains _____ active X chromosomes(s).
one
What does the expression of the Igf2 gene depend on in mice? - Parental origin, with only the paternal gene expressed - Parental origin, with only the maternal gene expressed - Alleles inherited from both parents, with only the dominant gene expressed - Alleles inherited from both parents, with only the mutant gene expressed
parental origin, with only the paternal gene expressed
In mice, the Igf2 gene is imprinted in such a way that only the _____ allele is expressed.
paternal
What is the structure of the mitochondria and chloroplasts genomes? - Multiple, linear DNA molecules - Single, circular DNA molecule - Single, linear DNA molecule - Single, linear RNA molecule - Multiple, circular RNA molecules
single, circular DNA molecule
Which of the following statements best describes epigenetic changes during the life of an individual? - All epigenetic changes are permanent and irreversible. - Some epigenetic changes are permanent while others are reversible. - All epigenetic changes are transient and reversible.
some epigenetic changes are permanent while others are reversible
Which of the following statements is true regarding a female mammal that is heterozygous for an X-linked gene? - Three fourths (3/4) of the somatic cells will express one of the two alleles. - All of the somatic cells will express one of the two alleles. - All of the somatic cells will express both of the two alleles at the same time. - Some of the somatic cells will express one allele, the others will express the other allele.
some of the somatic cells will express one allele, the others will express the other allele
Leaf pigmentation in four-o'clock plants is inherited via the chloroplast genome. A female plant with variegated leaves is crossed with a male plant with white leaves. What is the result of this cross? - All offspring will have white leaves. - Half of the offspring will have variegated leaves, and the other half will have white leaves. - All offspring will have green leaves. - Some offspring will have green leaves, some will have white leaves, and some will have variegated leaves. - All offspring will have variegated leaves.
some offspring will have green leaves, some will have white leaves, and some will have variegated leaves
In genomic imprinting, the transcription of the imprinted gene is inhibited because ______. - the DNA is methylated - the Xist transcript binds to the gene - the DNA is phosphorylated - a transcription factor controlling gene expression is phosphorylated
the DNA is methylated
Imprinted genes do not follow a Mendelian inheritance pattern because ______. - individuals with imprinted genes are mosaics with different expression patterns in different somatic cells - the DNA sequence is altered in each generation - the alleles from the parents are expressed differently
the alleles from the parents are expressed differently
In this diagram, what is the b+ allele linked to? - The c+ allele - There is no linkage. - The c allele - The b allele
the c+ allele
In mice, the Agouti gene regulates ______. - the deposition of yellow pigment in hair - the transcription of cell cycling proteins - the inheritance pattern of mitochondria - the sex of the individual - the size of the individual
the deposition of yellow pigment in hair
Which of the following hypotheses did Thomas Hunt Morgan propose for the unexpected results he obtained when studying transmission of genes in Drosophila? - The likelihood of a crossover between genes is related to how far apart they are on the chromosome. - Crossing over occurs during meiosis, allowing chromosomes to create new allele combinations. - Alleles of different genes on the same chromosome are always inherited together. - Genes located on the same chromosome are more likely to be inherited together, violating Mendel's law of independent assortment. - Some genes are located on extranuclear DNA and follow a maternal inheritance pattern, violating Mendel's law of segregation.
the likelihood of a crossover between genes is related to how far apart they are on the chromosome; crossing over occurs during meiosis, allowing chromosomes to create new alle combinations; genes located on the same chromosomes are more likely to be inherited together, violating Mendel's law of independent assortment
The process that is directly affected by the attachment of methyl groups to the bases of DNA is ______. - conjugation - transcription - translation - replication
transcription
For most genes, DNA methylation silences genes by inhibiting the initiation of ______ or by causing the chromatin in a region to become more ______. - translation; compact - translation; open - transcription; open - transcription; compact
transcription; compact
True or false: An epigenetic effect causes a change in gene expression without altering the sequence of DNA.
true
True or false: As a result of genomic imprinting, individuals with the same genotype may have different phenotypes.
true; genomic imprinting represses the allele inherited from one parent. As a result of this repression, individuals with the same genotype may have different phenotypes.
A true association occurs when ______. - two variables are studied at the same time - one variable is caused by another variable - one variable is independent of another variable - two variables follow a pattern
two variables follow a pattern
