chapter 13 - epigenetics and gene expression

Question 1

what is a genome

Answer 1

• the complete set of genetic / hereditary information that is encoded in ones dna

Question 2

what is gene expression

Answer 2

• the production of a protein using the information endowed in a gene
• copying information from DNA into mRNA (transcription) and then translating the message into a series of amino acids to form a protein

Question 3

what is DNA

Answer 3

• deoxyribonucleic acid
• molecule in the nucleus of a cell that determines the types of protein that a cell can make
• 2 chains of nucleotides, contains deoxyribose sugar and ACGT

Question 4

what is a histone

Answer 4

• a special protein around which DNA is coiled to form chromatin

Question 5

what is chromatin

Answer 5

• a tangled network of DNA in the nucleus of a cell that is not dividing
• dividing: when the cell is about to divide the coiled chromatin becomes more tightly coiled

Question 6

what are chromosomes

Answer 6

• ‘super coiled’ structures that are large enough to be see with a light microscope
• 23 pairs of chromosomes (46 overall)

Question 7

what are genes

Answer 7

• the factor that determines a hereditary characteristic (part of a chromosome)

Question 8

what is epigenetics

Answer 8

• altering gene expression without changing the gene structure (make certain genes more or less likely to be expressed / inherited)

Question 9

what is the study of epigenetics

Answer 9

• to determine how genome function is affected by mechanisms that regulate the way genes are processed

Question 10

what are epigenetics changes

Answer 10

• environmental factors

- trans-generational effects

Question 11

what are epigenetic factors

Answer 11

• compiles that attach to, or ‘mark’ DNA
• interact with genetic material but do not change the underlying DNA sequence
• chemical tags, indicating what, where and when genes should be ‘turned on’ or expressed

Question 12

what is an epigenome

Answer 12

• the sum of all the factors that determine when, where and which genes are ‘turned on’ or expressed
• helps control which genes are active in a particular cell and which proteins will be produced

Question 13

what are the changes in chromatin

Answer 13

• regulates genes epigenetically, the way in which chromatin is wrapped around the histone may change gene expression

Question 14

changes in histones that affect chromatin

Answer 14

• acetylation and methylation

Question 15

what is acetylation

Answer 15

• the addition of the acetyl group (CH3CO) to the histone protein, enhances gene expression
• more open / loosely bound chromatin, enhances transcription (produces more of the gene / it is expressed)

Question 16

what is methylation

Answer 16

• addition of the methyl group (CH3) to the histone that results in the inhibition of gene expression
• chromatin is more tightly bonded making it harder for it to bond with the DNA strand, stops transcription and no gene product is made / it isn’t expressed

Question 17

what are some environmental changes

Answer 17

• child abuse: affect DNA methylation patterns, result in poor health and mental problems of adults
• exercise: beneficial and changes to the pattern of epigenetic tags in muscle and fat tissue occur
• high stress environment: exposure to high stress during infancy results in them being stressed themselves

Question 18

explain some transgenerational effects

Answer 18

• obesity: altering the pregnant mothers diet can modify the offsprings DNA
• UV light: causes damage to DNA in surface layer of skin, damaging the order of or removing AGCT letters
• addictive behaviour: pre-exposure to drugs during adolescence can prime future offspring to display signs of predisposition to addiction

Question 19

explain twin studies and genetics

Answer 19

• individuals with identical genes, similar upbringings but who experience different life outcomes due to epigenetics and environments factors
• studies show identical twins who have different tolerances to pain, depression, diabetes, breast cancer shows they have different states of methylation
• in each case genes that are switched on in one twin are off in the other
• can be due to environmental differences once growing up

Question 20

explain famine and epigenetics

Answer 20

• studies of children and grandchildren of pregnant women who endured starvation in WW2 and in China 50’s revealed they tended to be smaller and more prone to diabetes and psychosis
• famine strikes but you can’t instantly alter your genes
• epigenetics changes all you to alter genes of your children which makes them best suited to new circumstances (can last 2-3 generations hoping by then that the situations have changed)