Biology Chapter 18
Which of the following statements are true regarding epigenetics? Choose all that apply.
-Epigenetic changes are transmissible from cell to cell. -Epigenetic changes may be transmitted to offspring. -Variations of gene expression that are unrelated to DNA sequence variants. -Variations are reversible from one generation to the next.
What are the three general rules for genes that follow a Mendelian pattern of inheritance?
-For crosses involving two or more genes, the genes obey Mendel's law of independent assortment -Genes are generally passed unaltered from cell to cell, and from generation to generation -The genes obey Mendel's law of segregation
Indicate the number of Barr bodies resulting from each chromosome composition. XX (normal female): ; X0 (Turner syndrome): ; XXX (triple X syndrome): ; XXY (Klinefelter syndrome): .
1,0,2,1
Diseases that are caused by mutation in human mitochondrial genes affect organs and cells that require high levels of .
ATP
Some people are born with abnormalities in the number of their sex chromosomes. For example, people born with triple X syndrome have three X chromosomes, and those born with Klinefelter syndrome have two X chromosomes and one Y. How does X inactivation proceed in these cases?
All of the X chromosomes are inactivated except for one.
A highly condensed X chromosome is known as a(n) body.
Barr
In a mammalian cell that contains two X chromosomes, one of the X chromosomes will become a(n) .
Barr body
If two X chromosomes are present in a mammalian cell, one of them is converted to a(n)
Barr body.
In genomic imprinting, which genes are silenced?
Genes inherited from either the mother or the father depending on the gene.
How is the Xist gene involved in X inactivation?
It synthesizes RNA, which coats one of the X chromosomes. Proteins then associate with the RNA, promoting compaction into a Barr body.
How is the maternal version of the Igf2 gene silenced in mice?
Methyl groups are attached to the gene, inhibiting transcription.
Which of the following statements about eukaryotic genes is TRUE?
Most, but not all genes, are found in the nucleus
The Xist gene, which is involved in X inactivation, encodes a(n) molecule.
RNA
Which of these sequences plays a critical role in Barr body formation?
The X inactivation center (Xic)
How is X inactivation accomplished?
The Xics are counted, allowing the cell to inactivate all but one X chromosome.
The region on the X chromosome that is known to play a role in Barr body formation is known as the .
X inactivation center
X inactivation is accomplished when all of the ______ are counted, allowing the cell to recognize and inactivate all but one of the X chromosomes.
Xics
The process of X-chromosome inactivation involves the gene ______, which encodes a very long ______ molecule. This molecule coats one of two X chromosomes, thus starting a process that ultimately leads to compaction of the chromosome into a Barr body.
Xist ; RNA
What is the origin of the mitochondria and chloroplasts found in eukaryotic cells?
an ancient endosymbiotic relationship
In statistics, changes in two variables that follow a pattern is termed a(n)
association
Mice that are homozygous for the loss-of-function mutation in the Agouti gene will have ______ fur.
black
Adult, wild-type mice with genotype AA for the Agouti gene will have what color coat hairs?
brown with black tips
Which organelles demonstrate cytoplasmic inheritance?
chloroplast mitochondria
Extranuclear inheritance patterns involve genes located in the and .
chloroplast mitochondria
Mitochondrial and chloroplast genomes are 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
In most plant species, chloroplasts are inherited via the cell, because it contributes most of the cytoplasm to the zygote.
egg
In most plant species, which gamete provides most of the cytoplasm to the zygote?
egg cell
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
What type of inheritance describes genomic imprinting?
epigenetic
The term describes changes in gene expression that are not related to variations of the DNA sequence, yet are transmissible and are reversible?
epigenetics
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:
extranuclear inheritance
What organs are often affected by mutation in human mitochondrial genes?
eyes brain heart kidney muscle
True or false: In general, only genes inherited from the mother are imprinted.
false
X-chromosome inactivation refers to the process that occurs in
female mammals, when the genes of one of the two X chromosomes are not expressed.
The gene Igf2 encodes a(n)
growth hormone.
A Barr body is a(n)
highly condensed X chromosome
In the somatic cells of female mammals, the genes on one of the two copies of the X chromosome are not expressed. This phenomenon is known as X-chromosome .
inactivation
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
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
In most plant species, inheritance of the chloroplast genome follows a(n) inheritance pattern.
maternal
How are mitochondria inherited in humans?
maternal inheritance
The chloroplast genome, which can encode genes that function in the production of pigment, is transmitted to offspring via protoplastids in the cytoplasm of the egg cell. This is an example of what type of inheritance pattern?
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?
maternal inheritance
The marking process that occurs during genomic imprinting is the addition of groups to DNA.
methyl
In a eukaryotic cell, where are genes found?
mitochondria, chloroplasts, nucleus
Female mammals that are heterozygous for X-linked genes, and are thus composed of two types of cells, are known as which of the following?
mosaics
The term is used to describe female mammals that are composed of two different types of cells because they are heterozygous for X-linked genes and experience X inactivation?
mosaics
The calico coat pattern in female cats is an example of
mosaics due to X chromosome inactivation.
In mice, the Igf2 gene inherited from the ______ is not transcribed into mRNA because the DNA is ______.
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 chromosome(s).
one
What types of organs are most likely to be affected by mitochondrial disease?
organs that require high ATP levels
The protein-coding genes in mammalian mitochondrial genome all encode proteins involved in:
oxidative phosphorylation
Most of the genes in the chloroplast genome encode proteins that are involved in .
photosynthesis
The chloroplast genome contains genes that are mostly involved in:
photosynthesis
What is the structure of the mitochondria and chloroplasts genomes?
single, circular DNA molecule
In genomic imprinting, the transcription of the imprinted gene is inhibited because
the DNA is methylated.
In mice, the Agouti gene regulates
the deposition of yellow pigment in hair.
Researchers have identified several mutations that affect the expression of the Agouti gene in mice, including the loss-of-function gene a. For example, mice that are aa homozygotes will have black fur because
the yellow pigment pheomelanin is not produced.
A true association occurs when
two variables follow a pattern.