Chapter 5

Question 1

Dutch hunger winter.

Answer 1

-By the winter of 1944-1945, Europe had suffered from 4 years of war. The winter was bitter cold, and food was scarce. The area of the western Netherlands was under control of the Nazi army, which created a blockade that prevented food from getting to the area. People were surviving on about 30% of their normal caloric intake. By the time food returned to the area, in May of 1945, about 20,000 people had died

Question 2

Epigenetics

Answer 2

-refers to specific alterations of gene expression, which can be inherited but are not changes in DNA sequence.

Question 3

Epigenomics

Answer 3

Broader term, referring to heritable changes in the ways that genes are expressed, without changes in DNA sequence, across the whole genome.

Question 4

Epigenome

Answer 4

-uses chemical tags that affect the structural packaging of DNA or mat silence parts of me genome, thereby alrering gene expression and subsequent protein production (Fig. 5-1)
-Surprisingly, these modificarions can be passed on from generarion to generation.
-As the cell divides, the chemical modifications stay with me parental DNA; these modifications can be altered by interactions with the environment, including factors such as parental diet and exposure to environmental toxins.
-The modifications that science knows most about are DNA methylation, histone modification, and the interaction of microRNAs with the genome.

Question 5

Methylation

Answer 5

-the addition of a chemical tag called a methyl group to me cytosine base in me DNA sequence irself (see Fig. 2-3).
-The presence of methylation turns off expression of me gene or genes mar are methylated.
-studies of this process found that methylacion of a gene’s promoter silences that gene’s expression.
-When a cell divides, methyl-copying enzymes add methyl tags to newly replicated strands of DNA, based on the methyl tags on the template strand.
-The DNA sequence and the methyl tags are passed on to each daughter strand.
-New studies of genome-wide methylation have revealed that methylation may be more complex than originally thought.
-Methylation may have a profound impact on several regulatory elements, altering transcription in ways beyond just silencing the promoter

Question 6

Histone
Modification

Answer 6

-The DNA double helix winds around histone proteins, which give it structure and stability, allowing the DNA to form chromosomes.
-Histone (or chromatin) modification involves changes to the proteins around which the DNA double helix winds
-Chemical tags attach to the “tails” of the histones and can alter how tightly the DNA is packaged by adjusting the tension with which it winds.
-When the DNA is wound tightly around the histones, some sequences of DNA may not be available for transcription, so no protein will be made from that sequence.
-The gene will appear “turned off.”
-When the DNA is loosened, a gene that was hidden may suddenly be able to interact with the cell’s protein-making machinery and appear to be “turned on.”
-In this way, histone modification and DNA methylation can turn gene expression on and off (Fig. 5-2).

Question 7

microRNAs (miRNAs)

Answer 7

-small single-stranded pieces of RNA that can bind to messenger RNA, making it double stranded and preventing protein production.
-miRNA can just turn off gene expression.
-These single-stranded pieces of RNA are only 20 to 30 bases long, and they do not encode protein.
-Sometimes they are included as contributing to epigenomic changes.

Question 8

developmental plasticity

Answer 8

-the ability of the environment to cause different phenotypes from the same genotype

Question 9

Microbiome

Answer 9

-composed of all the microorganisms and their genomes living in and on a person in peaceful coexistence.
-These various organisms, often called “normal flora,” are different in number and type for every human (even identical twins) and include those that live in the mouth, the gastrointestinal tract, the nose and sinuses, the vagina, and on the skin.
-These organisms collectively are unique to every person

Question 10

agouti gene (Avy)

Answer 10

-Mammals, like us, carry the agouti gene (.4vy). Mice carrying twO copies of the dominant agouti alleles are yellow and obese, but Au] can be methylated (or turned off) to varying degrees. Mice born with variations in methylation vary in color according to the level of Av] activity. Mice with mottled coats will be produced when Ary activity varies from cell to cell.
-The work by these and other scientists has demonstrated that epigenetic changes are maintained through mitosis and are passed on in the germline during meiosis.
Figure 5–3

Question 11

developmental windows

Answer 11

having too little or too much food could result in epigenetic changes mat cause disease, both in me person affected and their offspring.

Question 12

Nutrigenomics
Figure 5-1

Answer 12

The study of the interaction of nutrition and the genome is called nutrigenomics.

Question 13

Summary

Answer 13

• Epigenetics refers to specific alterations of gene expression, which can be inherited but are not changes in DNA sequence.
• Nutrigenomics is the study of the interaction of nutrition and the genome.
• Epigenetic changes are maintained through mitosis and are passed on in the germline during meiosis.
• Three mechanisms of epigenetic changes are methylation, histone modification, and microRNAs.
• Methylation turns off expression of the gene or genes that are methylated.
• When the DNA is wound tightly around histories, some sequences of DNA may not be available for transcription, so no protein will be made from that sequence.
• MicroRNAs bind to messenger RNA, making it double stranded; this binding prevents the process of
translation.
• Epigenetic events also have been shown to change the expression of suppressor genes and oncogenes.
• The areas in and around oncogenes are often hypomethylated, leading to an increase in their expression. • Tumor-suppressor gene areas are hypermethylated, which silences the expression of these genes.
• The microbiome is composed of all the microorganisms and their genomes living in and on a person
in peaceful coexistence.

Question 14

1. What did we learn from the Dutch hunger winter?
   a. Nutrition events have impacts on future generations.
   b. Fetal development is affected by overnutrition.
   c. Underfeeding an infant results in a low body mass index throughout life.
   d. When food is limited, parents will choose to feed their children rather than themselves.

Answer 14

A

Question 15

2. What happens in the process of methylation?
   a. Histone proteins are rearranged.
   b. Genes are silenced due to binding with micro RNA.
   c. Oncogenes are activated.
   d. Gene expression is turned off.

Answer 15

D

Question 16

3. When the area around oncogenes is hypomethylated, what happens to gene expression?
   a. Gene expression increases.
   b. Gene expression stays the same.
   c. Gene expression decreases.
   d. Genes are no longer expressed.

Answer 16

A

Question 17

4. How does bisphenol A (BPA) cause epigenetic changes?
   a. BPA directly increases gene expression.
   b. BPA can alter the production of microRNAs.
   c. BPA alters caloric intake, which can lead to epigenetic changes in future generations.
   d. BPA contaminates drinking water directly, leading to kidney disease.

Answer 17

B

Question 18

5. What did we learn from studies with agouti mice?
   A.Mother mice exposed to plastics produced offspring more likely to get kidney disease.
   B. Mice with the agouti gene turned off were yellow and obese.
   C. When mother mice were fed higher levels of supplements, their offspring were browner, leaner, and healthier.
   D. Supplements such as folic acid, zinc, and the amino acid methionine result in lower levels of methylation.

Answer 18

C

Question 19

6. How does the microbiome interact with the environment?
   a. The microbiome is similar to the genome in that it is stable from birth.
   b. Major dietary changes can alter the microbiome.
   c. Identical twins have virtually identical microbiomes.
   d. Colon cleansing will eliminate the microbiome.

Answer 19

B

Question 20

Case Study
Aamuun and Asad are refugees from Somalia currently living in Albuquerque, New Mexico. Aamuun was pregnant when the couple arrived. During the first 4 months of Aamuun’s pregnancy, she lived on very meager food portions. After arriving in the United States, her diet improved greatly. She gave birth to a healthy girl of normal birth weight. The family is having some difficulty adjusting to their new home, but they are receiving help and support from their new community. Fortunately, they will continue to have access to health care as their baby grows and develops.
1. How might Aamuun’s meager food intake affect the long-term development of their baby?
2. How does this case illustrate potential epigenetic changes?
3. Will Aamuun’s and Asad’s grandchildren be at an increased risk of disease due to epigenetic changes? Why or why not?
4. What can health-care professionals do to support this family?

Answer 20

1. Potential higher risk of obesity and health problems such as cardiovascular disease later in life.
2. Diet potentially affects fetus gene expression as the fetus was not given proper nutrition in her first 4 months of development which can cause epigenetic changes.
3. Yes, they will be at increased risk for these epigenetic changes because epigenetic changes are maintained through mitosis and meiosis so it affects sex cells and therefore progeny.
4. Health care professionals can support by recommending a diet that is conducive to methylation.

-1. Aamuun’s Meager food might affect the child to be malnourished. The child will get imbalanced nutrition and lack of protein results in changes in the epigenetic factor of DNA activation.

2. Lack of inadequate diet interferes with the mechanism of the epigenetic process. The potential changes of methylation, histone modification and decoded of microRNA result in a change of the epigenetic process. Methylation of DNA leads to repression of the gene. Histone proteins present around the DNA alters the DNA package and results in turn off the genes. MicroRNA a single-stranded membrane that does not encode with the protein leads to genome changes. Altogether results in genomic changes.
3. Yes. Aamuun and Asad’s grandchildren are at high risk of developing cancer due to tp epigenomic changes. Lack of protein in genes(histone cells), loss or damage to the cell division, unregulated cell growth results in Carcinogenesis. As the gene is inherited from one generation to another generation, the normal cell growth is converted into cancer cells.
4. Health care professionals help them by improving their diet and nutrition and thereby reduces the risk of cancer. Educate them about the importance of antioxidants and technology that reverses the changes in the gene pattern. Health care professionals also support them by providing appropriate environmental and biological factors that prevent the development of cancer.