Lec 8

Question 1

What was living tissue thought to consist of in the early 20th century?

Answer 1

carbohydrates, fats, and proteins.

Question 2

all enzymes end in ______?

Answer 2

“ase”

Question 3

Where does the word “protein” come from and why?

Answer 3

• -Proteins are by far the most complex molecules in our body
• -The size, complexity, and delicacy of proteins makes them very fragile
• -Seem to be critical for all of the biochemical reactions that take place in our bodies
• -For this reason, the name protein comes from a Greek word meaning ‘of first importance’.

Question 4

What do proteins do?

Answer 4

• -Structural: Help to hold cells and tissue together, e.g. collagen.
• -Enzymes: Catalyze chemical reactions and aid in metabolism, e.g. monoamine oxidase (MAO) breaks down monoamine neurotransmitters (serotonin, dopamine, norepinephrine, epinephrine, etc.), clearing them from the synaptic cleft.
• -Cell signaling: Peptide neurotransmitters, receptors for hormones, and cytokines

Question 5

What are proteins made up of?

Answer 5

Proteins are chains of amino acids. There are 20 different amino acids to choose from, and the specific combination changes the function and structure of the protein

Question 6

How are proteins made?

Answer 6

• -Proteins do not last forever, so your body must not only make new ones as needed, it must also work to replenish old and degraded ones
• -DNA is the recipe that tells your cells how to build proteins (which amino acids to use, and which order to put them in)
• -As long as you have the right number of amino acids in the right order, that is what creates a particular protein

Question 7

Where does gene transcription occur?

Answer 7

cell nucleus

Question 8

What does gene translation occur?

Answer 8

cytoplasm

Question 9

What are genes?

Answer 9

• -segments of DNA that code for particular proteins.
• -so genes are like recipes for proteins. Proteins do all of the work in the cell, but genes tells the cell how to build those proteins

Question 10

What are genes organized into?

Answer 10

Genes are organized into codons. Each codon is 3 nucleotides long, and ‘codes’ for a specific amino acid

Question 11

How many possible codons are there?

Answer 11

There are 43 possible codons (a total of 64), but a lot of them are redundant.

Question 12

What are examples of some codons?

Answer 12

• -AAG codes for the amino acid lysine

- -GAC for aspartic acid

Question 13

DNA cannot directly be made into___________

Answer 13

proteins

–genes code for particular proteins while codons code for a single amino acid

Question 14

How are genes expressed?

Answer 14

• -The DNA molecule partially unravels, exposing the structural gene that is to be transcribed
• -The first process of gene expression is gene transcription. A strand of mRNA is transcribed from one of the exposed DNA strands and carries the genetic code from the nucleus into the cytoplasm of the cell. The sequence of each mRNA strand matches the DNA sequence of that gene. The sole exception to this is that in RNA, thymine is replaced by uracil. Since it’s a 1:1 swap, the meaning of the sequence is not affected
• -The second process of gene expression is when mRNA strands are translated into proteins by ribosomes. The strand of mRNA attaches itself to the ribosome. The ribosome moves along the strand translating each successive codon into the appropriate amino acid, which is added to the protein by a molecule of transfer RNA (tRNA)
• -When the ribosome reaches the end of the messenger RNA strand, a codon instructs it to release the completed protein

Question 15

What is optogenetics?

Answer 15

Transgenic technique that combines genetics and light to control targeted cells in living tissue

Question 16

How was optogenetics discovered?

Answer 16

Based on the fact that there are some kinds of algae that are activated by light-these algae live in deep sea conditions that when its very light out it activates certain cells but when it’s dark out these cells don’t become active
–When scientists transfect these genes into the neurons of an animal’s brain, they could control them with light –you can use blue light (shorter frequency) to excite or inhibit a cell- you can control the animals behavior by shining light

Question 17

What can you use optogenetics for?

Answer 17

You can use optogenetics to determine which cells in a circuit might be implicated in either worsening a disease or remedying a disease and then we can try to find drugs that are more specific and can target those cells to treat illnesses

Question 18

What is epigenetics?

Answer 18

Changes in gene expression related to experience: the environment can switch on or off some genes
-Wide range of experiential factors
–>Chronic stress, traumatic events, drugs, culture, disease impacting brain circuitry
–>Example: born in a hot country, move to a cold climate
Epigenetic changes are adaptive changes (Being in a colder climate is upregulating and downregulating certain genes that are involved in thermoregulation in your body. You can adapt to that new environment)

Question 19

What did Fraga & colleagues discover in 2005 and what do these findings support?

Answer 19

Twins have nearly identical patterns of gene expression early in life, but remarkably different by age 50
–supports epigenetics

Question 20

Why don’t genes necessarily control our behaviour?

Answer 20

Not nature vs nurture, but nature via nurture: Genes load the gun, environment pulls the trigger.
Not all genes are expressed

Question 21

What is the story of Greg and what does this say about epigenetics?

Answer 21

Identical twins, one of them had a typical life and the other one developed a cocaine addiction

• -What made Greg so susceptible to cocaine? How did his identical twin escape similar fate
• -Everyone can do drugs but only 4% of people develop a true addiction
• -Individuals who have experience early life trauma are much more likely to develop mental health disorders and substance use disorders later in life because trauma is an epigenetic factor that can alter gene expression and that combined with your own genes

Question 22

What is the difference between gene mutation and epigenetic changes?

Answer 22

Gene mutations alter meaning

Epigenetic changes alter activity

Question 23

What are genetic mutations?

Answer 23

• -an extra codon at the end of a protein

- -swap of one the nucleic acid base pairs, that alters the meaning of the gene ex. One blue eye and one green eye

Question 24

What are epigenetic changes?

Answer 24

alter the rate at which these genes are expressed. They are either silenced, or allow the gene to be expressed.

Question 25

How do epigenetic changes occur?

Answer 25

• -DNA wrapped around clusters of proteins: histones (Further bundled into chromosomes)
• -Combination of protein and DNA in chromosomes: chromatin
• —>Helps regulate behaviour of genes; keeps them in inactive state (tightly bound)
• —>in gene transcription, when it receives the right instructions from the cell, the chromatin structure will unfurl and it will allow that section of gene to be exposed allowing the gene to be accessible.

Epigenetic changes are signals from the cell to change the physical conformity of that chromatin structure. These histones have epigenetic marks which signal to either unfurl or tighten up

Question 26

What is histone acetylation?

Answer 26

• -an epigenetic mark that relaxes/loosens the chromatin and increases gene transcription.
• -This is stage 1 and 2 of gene expression as well: it exposes that section of the DNA to promote mRNA to bind and you have that complementary base strand which then leaves the cell nucleus

Question 27

What is histone methylation?

Answer 27

an epigenetic mark that tightens/condenses the chromatin and decreases gene transcription

Question 28

How does the environment influence epigenetics exactly?

Answer 28

by regulating the behaviour of epigenetic writers and erasers
–Addition/removal of acetyl and methyl groups can help the brain respond and adapt to environment

These processes can go awry in an environment where you no longer need to silence certain genes or activate certain genes.

Question 29

How does stress affect epigenetics?

Answer 29

When our brain reacts in a very strong way to stressors, or we are constantly pumping out cortisol, it can act to increase or decrease methylation or acetylation depending on where it is in the brain.

Question 30

What does chronic cocaine do?

Answer 30

alter the activity of genes in the brain’s reward center by changing their epigenetic tagging

• -Reconfigures acetyl and methyl tags (Loosens chromatin structure, more prone to activation)
• -Dampens activity of erasers that remove acetyl groups, and writers that add inhibitory methyl groups

Allows them to “remember” rewarding effects of the drug? Relapse?

Can artificially do this – get animals that are more sensitive to effects of cocaine, despite never having had the drug!

Question 31

How can bullying lead to depressive-like behaviour in mice?

Answer 31

–Pair mild-mannered mouse with aggressive mouse; 10 days of ‘bullying’ leads to depressive-like behaviour in mild-mannered mice
–causes increased histone methylation in a large number of genes in the brain’s reward center.
This decreases the transcription of “feel-good” genes.
Treating animals with anti-depressants reverses many of these changes.

Question 32

How can high licking/grooming maternal care in mice affect epigenetics of the offspring?

Answer 32

Offspring less anxious, produce less stress hormone females become high lick/grooming mothers!

Question 33

How can low licking/grooming maternal care in mice affect epigenetics of the offspring?

Answer 33

More DNA methylation in a gene encoding the glucocorticoid receptor

• -Less GR receptor is made in the hippocampus
• -GR has a low affinity for cortisol so it’s the one that when cortisol is flooding the system it’s responsible for shutting down the HPA axis
• -this causes the offspring to become anxious

Question 34

What happens if you take the pups from low licking/grooming to high licking/grooming?

Answer 34

they will develop so that they have a higher tolerance for stress. This shows that genes are not everything