Last minute review flashcards - Bio test 2

Question 1

Explain deacylation

Answer 1

Deacylation is the process of removing acetyl groups from neighbouring histones using the HDAC protein which can bind onto methylated DNA.
It then returns the nucleosomes back to normal and lead to masking of enhancer and promoter sequences of DNA to repress transcription.

Question 2

What is the only thing that can bind to methylated DNA
Why is it important that this binds?

Answer 2

The only thing that can bind onto methylated DNA is the HDAC protein. This must be done to further inhibit transcription by removing acetyl groups from neighbouring histones and returning the gene back to it’s normal off state.

Question 3

Explain the process of in situ studies

Answer 3

For in situ studies the target gene will be taken and its mRNA will be extracted. Then a flourescent probe/complementary DNA strand is going to be made and it’s going to show up in certain tissue/cell regions.

Question 4

Explain the process of in vitro studies

Answer 4

Take out the mRNA from the gene of interest and then use a reverse transcriptase enzyme to form a complenentary cDNA molecule with flouresecent nulcoetides.
Then you are going to place this cDNA in a microarray tray with single-stranded DNA fragments of each gene of interest
Allow them to hybridize and see how they interact with genes

Question 5

Default state of transcription in prokaryotes and eukaryotes

Answer 5

prokaryotes = on
eukaryotes = off

Question 6

What is it the time a protein has in a cell called?

Answer 6

Selective degredation

Question 7

Explain what the regulatory promoter is going to do

Answer 7

Its going to bind transcriptional activator proteins onto enhancer regions and then become bound to the basal mahinery @ core promoter region through a mediator complex forming the transcription initation complex.

Question 8

Regulatory sequence in prokaryotes

Answer 8

Promoter + operator region
-controls transcription of genes

Question 9

Two enzymes coded by the lac operon

Answer 9

-B-galactosidase enzyme
-Lactose permease

Question 10

The amount of cAMP in a cell will determine two factors:

Answer 10

1. the degree of positive regulation (like if lactose is present and induces the repressor protein so it can’t bind the cAMP cells will just increase that degree and make the expression of genes even higher) and it allows for RNA polymerase to bind better
2. whether it will bind to the CRP protein or not

Question 11

What is the gene in humans for lactose metabolism?

What about the enhancer gene for this?

Answer 11

Lactase enzyme
Made by the LCT gene -> produces lactase on chromosome 2

MCM6 is the enhancer gene

Question 12

If someone is lactose intolerant how can you explain this on a genetic level?

Answer 12

Lactose intolerant

Question 13

Galactosemia

Answer 13

Have lactase enzyme
Can’t break down 1/3 enzymes GALE, GALT, GALKI due to mutation in one of these genes

Question 14

Double negative feedback

Answer 14

A lactose molecule binds onto a repressor protein acting as an inducer molecule/allosteric inhibitor.
This is double negative feedback becasue it is inhibiting the negative feedback

Question 15

What did Ellie Metchnikoff propose?

Answer 15

That bacteria has a positive role on the body
Populations that lived on fermented milk lived longer because it would “seed” intestine with lactic acid producing bacteria which lowers pH and kills bad bacteria

Question 16

Disease - can’t produce lactase or digest lactose at all

Answer 16

congential lactase deficiency

Question 17

Where in the small intestine is lactose broken down?

Answer 17

Apical edges

Question 18

3 lactic acid producing bacteria

Answer 18

Lactobacillus
Lactococcus
Bifidobacteria

Question 19

how does repressor protein stop transcription functionally?

Answer 19

Repressor proteins are tetrametric proteins which form a loop in the DNA so that RNA polymerase cannot bind

Question 20

Explain the process of glucose binding to the receptor protein

Answer 20

Kinase receptor proteins exist in monomeric forms. When glucose attaches onto the outer domains its going to pair up and form a dimer. Then the cytoplasmically situated domains are going to phosphorylate each other and bring in cytoplasmic proteins which are going to attach onto the phopshate groups and bring in the glucose transporter protein into the cell membrane.

Question 21

Explain the process of translation enlongation

Answer 21

P=site contains the aminoacyl tRNA charged with the Ser amino acid
charged incoming aminoacyl trna comes into the A-site along with a GTP bound elongation factor attacehd
Once it binds to the mRNA it hydrolyzes the GTP-> GDP and then a confomrational change will occur where the amino acid on P-site will form a condensation reaction and peptide bond to A-site polypeptide chain
THe hydrolyzation of GTP -> GDP will power the movmenet of P-site to E-site
and then incomign A-site will move E-site to out

Question 22

Explain the process of tRNA activation

Answer 22

Using aminoacyl tRNA synthetase, a tRNA molecule will bind onto the active site of the enzyme (20 different types of this enzyme/ amino acid) and then it will use ATP energy to bind a.a onto the 3’ adenine CCA end of tRNA and then release it as a charged aminoacyl tRNA

Question 23

Alternative splicing is of what… in terms of insulin…?

Answer 23

The insulin receptor gene
Skeletal muscle cells: remove exon 11 so have an insulin receptor gene with higher affinity to glucose

Question 24

What is androgen sensitivity?

Answer 24

It is the defect of a single nucleotide which causes error in the androgen receptor protein which responds to testosterone

Question 25

What is the gene responsible for the polar bear mutations?

Answer 25

The mutation in the mc1r gene which codes for the coloured coat and skin colour

A T-> C replacement at codon 298

Question 26

What happens to lactose before it is absorbed into the microvilli in apical membrane of small intestine?

Answer 26

It is first broken down into galactose and glucose with a lactase enzyme

Question 27

Wobble hypothesis

Answer 27

-not following watson-crick base pair rules
-the third nucleotide of the codon is flexible and the first two are stable
-explains the genetic redundancy of a cell because more than one codon can code for a single amino acid

Question 28

What is alternative splicing
What if it doesn’t occur

Answer 28

One gene = many different proteins by removing/keeping certain exons.

Doesn’t occur? nothing really happens, the gene is just transcribed as it normally would be

Question 29

two errors that would make glucose absorption not possible

Answer 29

post-transcriptional error: error in the modifcation of insulin gene

post-translational: error in the insulin receptor gene

Question 30

spirit bear mutations

Answer 30

single nucleotide in mc1r gene replacing T with C at codon 298