Proteins

Question 1

Crick’ central dogma

Answer 1

Flow of genetic information whether in prokaryote or eukaryotes is DNA, RNA, protein

Question 2

Why do we need mRNA

Answer 2

DNA cannot get out of the nucleus, it is protected in there

Original recipe le protected, mrna is flushed after usage, has a limited lifespan

Question 3

function difference between RNA and DNA

Answer 3

Pentose sugar
U instead of T
Single strand

Question 4

stem-loop structures of RNA

Answer 4

Sometimes certain parts can be complementary to each other, making it loop,

Question 5

transcription factors

Answer 5

What mRNA is in the cells will reflect the function of the cell, as all cells have the same DNA

What control gene expression linked to the environment

Question 6

promoter

Answer 6

Sequence of dna where rna polymerase will attach to and start transcription

Won’t attach unless transcription factors also attached

Can be very active of not so much

Question 7

terminator sequence

Answer 7

End sequence, causes rna polymerase to detach
Above promoter is upstream, below terminator is downstream

Terminator is transcribed into rna sequence

In eukaryote, it continues past the terminator and then gets cleaves

Poly A helps it bind

Question 8

initiation, elongation and termination

Answer 8

polymerase continues on a bit after termination signal, then cut free

creates cleavage site for endonuclease

Question 9

Where does the energy to form the phosphodiester bonds between ribonucleotides come from?

Question 10

What functions as the actual termination signal?

Answer 10

The transcribed terminator –an RNA sequence- functions as the actual termination signal.

Question 11

difference in termination of transcription between prokaryotes and eukaryotes

Answer 11

mRNA can be immedieatly trsnlated in prokaryotes because there arent ribosomes in nucleus of eukaryots and MRNA needs processing

Question 12

rate of transcription?

Answer 12

20 bases per second.

Question 13

coding strand?

Answer 13

the strand not being transcirbed, mrna is identical to the coding strand

template strand is the one being trasncirbed

Question 14

What is the 5’ cap?

Answer 14

helps protect the mRNA from degradation

after mRNA reaches cytoplasm, the cpa helps as a part of an attach here for ribosomes

Question 15

What is the 3’ untranslated region?

Question 16

two important functions of the poly-A tail?

Answer 16

inhibits degradation of the mRNA
probably helps ribosomes attach to it
also seems to facilitate the export of mRNA from the nucleus
may also stabilize the mRNA so that it exists longer

Question 17

What percent of the human genome do genes comprise?

Answer 17

2%, rest is for structural integrety of the chromosome, and also gene expression

Question 18

Intron

Answer 18

not expressed parts of genes, do not exist in prokaryotes

Question 19

exon

Answer 19

expressed genes of the dna

Question 20

Explain why the coding portion of the average human gene is 1,340 bases, whereas the average total size of a gene is 27,000 bases

Answer 20

because of intron, lots of genes isnt coding

Question 21

splicing hypothesis

Answer 21

presence of introns and extrons enavles a single gene to encode more than one polypeptide depending on which segment of exons are included

always in order, just remove introns, which ones are included

Question 22

the role of introns in DNA fingerprinting

Answer 22

coding genes are mostly all identical, however introns differ massively from person to person

introns resembles a lot a repeat, a stutter, and number of sutters differ from person to person

Question 23

anatomy of the gene

Question 24

Describe the anatomy of the RNA,

Answer 24

intron and extron on mRNA at first, then processing removes intron

Question 25

Describe RNA splicing, and give its importance.

Answer 25

during procession of mRNA, spiceosome binds to mRNA and the intron gets cut, only includes the coding segment (extrons)

only found in eukaryotes

Question 26

Why is the genetic code a triplet code and not doublet

Answer 26

it takes 3 nucleotide to code for 1 amino acid, as there are 20 amino acids, but only 4 nucleotide acid (4^2=16, but 20 amino acids)

alos serves that the code is redundant, so if there are mutations, it can sometimes be unexpressed (silent mutation: always in the 3rd base pair though)

but it still allows for variations through mutation in order to encourage evolution

Question 27

What is the reading frame, why is it important?

Answer 27

always read 3 nucleotide, then 3 nucleotide, then 3…….

serves to know the pattern of reading even without “spaces” between “words”

if mutation shifts readon frame by removing a nucleotide, then almost all amino acids become different and protein becomes useless

frame shift mutation are deletion or insertion

Question 28

What is tRNA, what are the two functions of tRNA? Recognize anticodons

Answer 28

tRNA serves to
chemically links to a particular amino acids with a covalent bond
recognize a specific condon (non-covalent) in mRNA and binds to it (anticodon)

stem and loop structure

Question 29

aminoacyl-tRNA synthetase?

Answer 29

in cytoplasm, creates charged tRNA

site for atp, phosphorylates amino acid, specific tRNA binds to amino acid

anticodon sequence binds by hydrogen bonding, and also other parts of the tRNA

has to be specific because this specific tRNA will bond to a specific condon

Question 30

wobble

Answer 30

reason why there are less tRNA than condon possibilities

condons differing in the third nucleotide creates that there are multiple amino acids wiht different condons, so sometiems tRNA has a last anticodon that can bind to different third codon in order to bind to both AAC and AAG for example. as long as first two are the same, its the same amino acid

last nucleotide on anticodon is wobble position

in anticodon, G binds to C and U on codon
U, A or G
I binds to A C U

Question 31

5 important sites on the ribosome

Answer 31

1) mRNA-binding site

2) A (aminoacyl) site where a tRNA with its bound amino acid enters the ribosome

3) P (peptidyl) site where the growing polypeptide is bound to a tRNA, and

4) the E (exit) site where tRNAs that no longer have a bound amino acid exit from the ribosome

5) catalytic site that forms a covalent (peptide) bond between two amino acids (not shown)

Question 32

translation elongation

Answer 32

amino acids trasnfered to amino acid on the tRNA in the A site
from P to A, A is empty, ribosome moves

Step 1: Codon recognition: An incoming tRNA binds to the codon in the A site

Step 2: Peptide bond formation: The ribosome catalyzes the formation of a peptide bond between the new amino acid and the carboxyl end of the growing polypeptide

Step 3: Translocation: The tRNA at A site is translocated to the P site, taking the mRNA along with it. Meanwhile the tRNA at the P site moves to the E site and is released from the ribosome In this step, the ribsome shifts the mRNA by one codon.

Question 33

translation termination

Answer 33

continue until stop codon rechead
A protein called a release factor binds to the A site
This causes a water molecule to be added to hydrolyze the chain from tRNA in P-site which then releases the polypeptide

Question 34

differences between eukaryotes and prokaryotes transcription and translation.

Answer 34

In prokaryotes (ex E. coli) the process is similar to that of eukaryotes, although translation begins while the gene is being transcribed

Question 35

What determines whether a ribosome is free in the cytosol or bound to rough ER

Answer 35

signal peptide in the cytosol that asks to be taken over to the RER

Question 36

mutations

Answer 36

dont always express, sometimes silent mutation

DNA undergoes many changes in S pahse (replication) and goes through repair systems. if fail of repair, the cell suicide

Point mutation: mutations consisting of one base-pair substitution
either silent mutation,
Missense mutation: a different amino acid is coded
Nonsense mutation: Codon is changed to a ‘stop’ codon before translation is complete – worst case scenario

frameshift mutation: Deletion or addition of 1 or 2 bases completely scrambles the message. If the insertion or deletion results in a new stop codon a truncated or much shortened protein will be synthesized and this is almost invariably non-functional and is referred to as nonsense mutation.

Question 37

5 to 3

Answer 37

energy source to make the covalent bond is the 3 nucleotide phosphae, so you need the phosphate of the 5 end to start

Question 38

initiation

Answer 38

During initiation in eukaryotes, the small ribosomal subunit first binds to the initiator tRNA and its amino acid (methionine, AUG)
The large ribosomal subunit is then added.