biochem 4. Epigenetics

Which of the following statements about epigenetics is false? Environmental stimuli control gene expression. Gene expression is influenced by chemical modifications of the DNA and/or histone proteins. Access to the promoter gene by transcription factors is affected. The DNA sequence is permanently altered.

The DNA sequence is permanently altered. E pigenetics involves reversible changes to the DNA or to histone proteins. These changes, such as adding or removing methyl groups from DNA or acetyl groups from histone proteins, respond to environmental stimuli. Such changes can increase or decrease nucleosome spacing, which can make the promoter of a gene accessible or inaccessible. In this way, epigenetic changes influence gene expression.

An individual who has two alleles of a gene that are different from one another is called ________? Homozygous Heterozygous Homogametic Polyzygous Heterotypical

Heterozygous

Nucleosome consist of double-stranded DNA and histones combined. True False

True

The LEP gene codes for an anorexigenic hormone. Interestingly, breastfeeding has been shown to alter methylation of the promoter of this gene, leading to increased LEP expression. What is likely happening in response to breastfeeding: Breastfeeding increases the methylation of the promoter of the LEP gene, decreasing the spacing between nucleosomes. Breastfeeding decreases the methylation of the promoter of the LEP gene, increasing the spacing between nucleosomes. Breastfeeding decreases the methylation of the promoter of the LEP gene, decreasing the spacing between nucleosomes. Breastfeeding increases the methylation of the promoter of the LEP gene, and the tight packing of the DNA alters binding of RNA polymerase.

Breastfeeding decreases the methylation of the promoter of the LEP gene, increasing the spacing between nucleosomes. When histones wrap up DNA, transcription will be repressed.

Some changes to the DNA do not modify the coding sequence of the DNA but do affect its winding and unwinding from nucleosomes. These changes can increase or decrease the availability of DNA and hence, the transcription of a gene. These are called _________ changes? Genetic Epigenetic Epidermal Hypogenetic

Epigenetic Epigenetic changes result from modifications of the DNA that affect nucleosome spacing and, therefore, transcription. They do not alter the DNA sequence itself.

Which of the following changes can NOT be detected using PCR? Differences in DNA sequence Epigenetic changes Deletions Insertions

Epigenetic changes PCR can enable us to detect any changes in a DNA sequence, such as an incorrect base (A fo C, for example), deleted bases, or inserted bases. It is not affected by changes to the DNA that do not alter the sequence. Thus, it cannot be used to detect epigenetic changes.

Select all of the following that are involved in the process of actively transcribing a gene. Epigenetic modifications to nucleosomes Ribosomes DNA Ligase Transcription Factors Promoters RNA polymerase DNA polymerase

Epigenetic modifications to nucleosomes Transcription Factors Promoters RNA polymerase Epigenetic changes result in modifications of the nucleosomes that affect chromatin packing and transcription. Transcription Factors are specialized proteins that recognize specific promoter sequences and bind to them. Once bound to the promoters, the transcription factors recruit RNA polymerase to the transcription start site. RNA polymerase begins transcribing the gene sequence into a new RNA molecule.

"Nurture affecting Nature:" The study of environmental factors that affect DNA--INHERITIABLE modifications to the genome that do NOT involve changes in nucleotides but to the structure of the nucleosomes. Can increase/decrease gene expression. This is the definition of... Transcription factors Genomics Epigenetics Transcription Translation

Epigenetics Epigenetics deals with changes in phenotype and gene expression patterns that can be passed along across cell generations without a modification of the coding DNA sequence.

Expression is defined as a gene, coded for by a nucleotide sequence made out of protein that is TRANSCRIBED & TRANSLATED into the protein coded for by the gene. True False

False The key here is that nucleotides sequences are NOTmade out of proteins. Nucleotides and proteins are very different kinds of molecules. Nucleotides sequences are composed of nucleotides such as A, C, G, and T (or U).

Proteins that promote coiling of DNA and help prevent DNA strands from "tangling" are called? Histones Enzymes Polymerase Chaperones

Histones The combination of DNA and histone proteins creates nucleosomes. Enzymes are proteins that catalyze chemical reactions. Their names almost always end in the letters "ase". The polymerases are enzymes. Chaperones assist in the folding of other proteins into their proper 3-dimensional shape.

An individual who has two alleles of a gene that are the same as one another is called ________? Homozygous Heterozygous Homotypical Heterogametic Monozygous

Homozygous

The LCT gene codes for Lactase, which is responsible for the breakdown of lactose. Which of the following statements could explain how Lactase activity is increased in the presence of lactose? Lactose blocks RNA polymerase from binding the promoter sequence, facilitating transcription of the LCT gene. Lactose prevents binding of transcription factors at the transcription start site of the LCT gene. The presence of lactose causes nucleosomes to separate, exposing the LCT gene. The presence of lactose causes nucleosomes to pack together tightly, exposing the LCT gene.

The presence of lactose causes nucleosomes to separate, exposing the LCT gene.

What kind of proteins read the promoter region of a gene and send a signal that recruits RNA polymerase so that synthesis of mRNA can begin. Transcription factors RNA polymerase Histones Kinases Release factor

Transcription factors Transcription factors are proteins read the promoter region of a gene and send a signal that recruits RNA polymerase so that synthesis of mRNA can begin. RNA polymerase is the enzyme that transcription factors recruit to transcribe the gene. The DNA double helix is wrapped around histone proteins to form a nucleosome. Kinases are enzymes that add a phosphate group to other molecules. Release factor recognizes the STOP codon in an mRNA and causes the ribosome to release the mRNA and the newly-made protein.

In the organization of DNA into chromosomes, DNA is wrapped around _________ to form nucleosomes. Nucleosomes are organized further to form _____________. RNA; triple helix histones; nucleus histones; chromatin promters ; histones

histones; chromatin DNA is wrapped around proteins called histones to prevent tangling, and the combination of DNA and histone proteins creates nucleosomes. The histones promote coiling of the nucelosomes into a larger chromatin fiber.

What changes can occur to the DNA (ex. methyl groups) and to the histones that will impact gene expression? Select all that apply methylation chromosome replication acetylation splicing

methylation acetylation Methyl groups can be added to DNA (methylation) without altering the DNA sequence. DNA methylation changes the spacing of nucleosomes. Acetyl groups can be added to histones (acetylation) and this also changes the spacing of nucleosomes. Nucleosome spacing affects the transcription of genes. Chromosome replication does not directly affect transcription. Splicing is a step in mRNA processing, which occurs after transcription and which does not directly affect it.

Histone proteins can be chemically modified by addition of an acetyl group. If this causes nucleosomes to pack _________ , the process of ___________ is decreased at those DNA sites. more loosely; transcription more loosely; translation more tightly; transcription more tightly, translation

more tightly; transcription Changes to histone proteins or to DNA that result in tighter nucleosome packing make the DNA less available for transcription. Therefore, transcription is decreased.

The part of the DNA sequence of a gene that regulates the rate of transcription is called the... coding region poly A tail transcript promoter region histone

promoter region A gene must have a promoter region as part of the DNA molecule. The promoter controls the recruitment of RNA polymerase to the DNA and thus, regulates the transcription of the gene.