Genetics Exam 4

Select all of these that are true of chloroplast DNA.

1. A typical chloroplast genome is about 100,000 - 200,000 bp in length. 2. Many chloroplast proteins are encoded by nuclear genes.

Select all of these that are human diseases caused by genomic imprinting.

1. Angelman syndrome 2. Prader-Willi syndrome

Which of the following are examples of epigenetics?

1. DNA methylation. 2. Localization of histone variants. 3. Chromatin remodeling. Covalent histone modification.

Which proteins represent histone modifying enzymes that have been associated with epigenetic changes in cancer cells?

1. Histone methyltransferase 2. Histone acetyltransferase 3. Histone kinase

Which changes occur following the binding of Xist RNAs to the Xi?

1. Histone variant macroH2A is incorporated into the nucleosomes along the Xi. 2. Recruitment of DNA methyltransferases to Xi. 3. Covalent modification of specific sites in histone tails. 4. Recruitment of protein complexes to Xi.

Select all of these that are true of mitochondrial genes.

1. Human mtDNA carries relatively few genes. 2. Mitochondrial DNA contains both coding and noncoding regions. 3. Most mitochondrial proteins are encoded by nuclear genes.

Select all of the true statements regarding genomic imprinting.

1. The marking of alleles can be altered from generation to generation. 2. Genomic imprinting is permanent in somatic cells.

The X-inactivation center consists of which two genes?

1. Xist 2. Tsix

In the experiment carried out by Davidson, Nitowsky, and Childs, which outcome would support the Lyon hypothesis?

All nine clones expressed either the fast or sloe G-6-PD protein but not both.

The inactivated X chromosome in the somatic cells of mammals is called a ____.

Barr body

What accounts for the molecular mechanism of imprinting of the Igf2 gene?

Differential methylation during oogenesis and spermatogenesis.

True or false: Because epigenetics refers to heritable changes in gene expression, all epigenetic changes are examples of transgenerational epigenetic inheritance.

False

True or false: Epigenetic changes due to PcG complexes are transient and only present during development.

False

True or false: Gene regulation may be related to epigenetic events such as binding of transcription factors to certain genes, which induce permanent mutations in the DNA.

False

True or false: Gene regulation may be related to epigenetic events such as the binding of transcription factors to certain genes, which induce permanent mutations in the DNA.

False

True or false: Smoking cigarettes induces the formation of lung cancer only by causing genetic mutations in tumor suppressor genes.

False

Select all of these that are phases of X chromosome inactivation.

Initiation Maintenance Spreading

Match the phases of X chromosome inactivation with the correct description.

Initiation - one of the two X chromosomes is targeted for inactivation. Spreading - Inactivation begins at the Xic region and continues in both directions along the X chromosomes. Maintenance - The inactivated X chromosome is replicated as a Barr body and compaction is continued from embryonic development through adulthood

Which species achieves dosage compensation by inactivating the paternally derived X chromosome in all somatic cells of a female?

Marsupial mammals

If the expression of genes in the offspring directly influences their traits, the genes are transmissible from generation to generation, the genes segregate during gamete formation, and the genes of the trait segregation independently, then the genes follow ____ inheritance patterns.

Mendelian

Genes located on chromosomes are called nuclear genes because they are located in the cell ____.

Nucleus

____ promote cancer by increasing transcription of genes that regulate division.

Oncogenes

Which statement best describes how X chromosomes are inactivated in female mammals?

One X is randomly inactivated in each cell at an early stage of embryonic development.

Which genes on the X chromosome are able to escape the effects of X chromosome inactivation on female mammalian cells?

Pseudoautosomal genes

Patterns of imprinting are maintained in what type of cells throughout development?

Somatic

In the case of the Igf2 gene, which copy is expressed in the offspring?

The allele from the father.

How do transcription factors contribute to epigenetic modification?

Transcription factors recruit chromatin modifying proteins, such as DNA methyltransferase.

True or false: The epigenetic modifications that lead to silencing of an X chromosome are lost and reestablished following each cell division.

True

True or false: The genes located in mitochondria and chloroplasts do not exhibit Mendelian patterns or inheritance.

True

Which of the following statements regrading X chromosome inactivation is true?

X chromosome inactivation occurs during embryogenesis in females.

What is the primary role of the X-inactivation center (Xic)?

X-chromosome inactivation

What happens when pluripotency factors stimulate the expression of Tsix?

Xist is inhibited

The genome located in the nucleoid of the mitochondrion or chloroplast consists of a ____ chromosome.

circular, double-stranded DNA

Population of cells that are all derived from a single cell are called

clone

Chloroplasts evolved from an endosymbiotic relationship between ____.

cyanbacteria and eukaryotic cells.

The methylation of a previously unmethylated site is called ____.

de novo methylation

What term explains the variation of gene expression that is not related to the variation of the DNA, is transmissible and is reversible?

epimutation

The Hardy-Weinberg equilibrium is used as a null hypothesis, ie if a population is in Hardy-Weinberg equilibrium, then ___.

evolutionary change is not occurring in this population

An offspring receives genetic material located in the mitochondria. This is an example of ____ inheritance.

extranuclear

In a form of epigenetic inheritance called ____, a segment of nuclear DNA is marked in a non-permanent way that alters gene expression throughout the life of the individual.

genomic imprintint

Polycomb group (PcG) complexes epigenetically influence development by ____ various genes.

inhibiting

The genome of a chloroplast is ____ than the genome of a mitochondrion.

larger

The size of a human mitochondrial chromosome is ____ the size of a typical bacterial chromosome.

less than 1%

The methylation of hemimenthylated sites is called ____.

maintenance methylation

Chloroplasts and mitochondria are inherited through the cytoplasm of the egg. This type of extranuclear is called ____.

maternal inheritance

Mitochondria may have evolved from an endosymbiotic relationship between ____.

purple bacteria and eukaryotic cells

X chromosomes are randomly inactivated during embryonic development. This is also called ____.

the Lyon hypothesis

The PcG complex attaches three methyl groups to lysine at position 27 in histone H3 in a process known as ____. This mark represses gene expression.

trimethylation

A statistically significant correlation coefficient means that ____.

two variables have true association

How do chemicals found in cigarette smoke induce cancer?

1. by causing epigenetic changes. 2. By mutating genes.

Which of the following is an example of epigenetic inheritance?

Methylation of DNA that occurs in an oocyte

A female with Turner syndrome (XO) would have how many Barr bodies in her cells?

None

In inactivation of an X chromosome is an ____ event.

epigenetic

Human mitochondrial diseases, such as Leber hereditary optic neuropathy, are usually ____ inherited.

maternally.

At the molecular level, one way genomic imprinting is regulated is by DNA

methylation

The mice in the figure are heterozygous, Igf2 Igf2, yet they have different phenotypes due to genomic imprinting. What is this phenomenon called?

monoallelic expression

In humans with a typical constitution of chromosomes, X-chromosome inactivation induces dosage compensation by randomly inactivating one of the X chromosomes in the somatic cells of ____.

females

The inactivation of an X chromosome occurs in ____.

females mammals

A species that produces two kinds of gametes, with unequal distribution of cytoplasmic organelles, is said to be a ____ species.

heterogamous

The variegation of the leaf shown in the image can be explained by ____.

heteroplasmy

Which statements are examples of how environmental factors may function as epigenetic regulations?

1. Body differences between queen bees and worker bees caused by dietary differences. 2. Vernalization occurs when certain flowering plants are exposed to colder temperatures during the previous winter. 3. Exposure to tobacco smoke has been shown to alter DNA methylation and covalent modifications of specific genes in lung cells.

List the events of X chromosome inactivation in the correct sequence putting the first event at the top.

1. Chromosomes pair briefly beginning at the Tsix gene. 2. All pluripotency factors and CTCFs are shifted to one of the two X chromosomes. 3. The Tsix gene of the chromosome without pluripotency factors and CTCfs is inhibited; the inactivated chromosomes is coated with Xist RNA. 4. Xist RNA recruits proteins that epigenetically modify specfific sites within the Xi.

Which of the following are factors that can cause a change in the size of a population from one generation to the next?

1. Diseases 2. Predators 3. Natural disasters

Which of the following statements regarding X inactivation are true?

1. Expression of Tsix from both X chromosome inhibits the expression of Xist. 2. When the Xist gene is inactive the X chromosome is active. 3. In very early embryos, both X chromosomes are active.

What are the three ways that PRC1 may inhibit transcription?

1. Nucleosomes in the target gene may form knot-like structures. 2. Direct interaction with transcription factors. 3. Covalent modification of H2A by attraction of ubiquitin molecules.

Which of these statements are true for human mitochondrial diseases?

1. They usually affect cells that require high levels of ATP. 2. They are usually chronic degenerative disorders. 3. They often exhibit varying degrees of severity within families.

Mutations in chromatin-modifying proteins may contribute to cancer by causing ___.

1. closed chromatin to inhibit expression of tumor suppressors. 2. open chromtain to overexpress oncegenes

DNA methylation of CpG islands, covalent histone modification and/or chromatin remodeling may induce cancer by ___.

1. increasing the expression of oncogenes. 2. decreasing the expression of tumor suppressor genes.

If a correlation coefficient suggests a positive correlation between DNA methylation and disease severity, then possible explanations could be that ___.

1. the disease leads to changes in DNA methylation 2. an environmental agent produced both DNA methylation and the disease independently 3. DNA methylation causes the disease

Founder Effecr

A group of individuals from a larger population can migrate to a new area and establish a colony, which will be highly susceptible to genetic drift.

In birds males are ZZ and females are ZW. Studies have shown that male birds express twice as much gene product of some Z-linked genes. What does this suggest?

Z-linked genes are not dosage compensated in birds.

A genetic disease in which cells divide uncontrollably is ___.

cancer

The theory that explains the evolution of some eukaryotic organelles such as chloroplasts and mitochondria is called the ____ theory.

endosymbiosis

Trans-epigenetic mechanisms are more commonly found in ____.

1. single-celled eukaryotes 2. bacteria

Which of the following are environmental factors that promote epigenetic changes?

1. temperature 2. diet 3. toxins

What is genomic imprinting?

A form of epigenetic inheritance in which a segment of DNA is marked in a way that it alters gene expression.

Are epigenetic changes potential drug targets for cancer treatment?

Yes, because oncogenes and tumor suppressor genes can be regulated epigenetically.

An RNA that does not encode a polypeptide is a ____ RNA.

non-coding

In a mitochondria, genetic material is located in a region called the ____.

nucleoid

A mutation in a chromatin-modifying protein that contributes to cancer would likely be associated with ___.

open chromatin around on oncogene