Bio Exam 4 (final exam) CH 15-17

answer with defination

What was the Hershey-chase experiment

They determined that inside genes/cells there was DNA and not proteins by injecting radioactive material into the genes that either would show proteins (35S tag) or DNA (32P tag) of which DNA was present

what are the three components of a nucleotide

phosphate group (5’ end), a nitrogenous base (A,T,C,G) and a sugar (3’ end)

how does complementary base pairing work

A with T

C with G

connected together via hydrogen bonds. there is a template strand that is created which allow for these new bases to be added on

what holds the nucleotides together

phosphodiester bonds

what are the names for the 2 strands of DNA

Parental (template) and daughter strand

why is DNA antiparell

it has 2 strand that run in the opposite direction. one runs 5’→3’ while other runs 3’→5’

what were the three types of DNA syntheses that were looked at to determine how DNA replication occurs

semiconservative replication

conservative replication

dispersive replication

what is semiconservative replication

parental stand separates (unzips) and each on the strand is used as a template foe a new strand

now it has one old strand and one new strand

what is the conservative replication

the parental model serves as a template for an entirely new strand

one daughter has 2 old strand while other has 2 new strands (like cloning)

what is the dispersive replication

the parental strand cuts into sections

one strand has parts of new and old intertwined

what model for DNA replication was supported

semiconservative replication model

what shape does DNA make

double helix

how many replication bubbles does bacteria have

one because it is circular DNA

how many replication bubbles does DNA have

as many as it wants cause it is one long strand

what is the replication fork

location at which the bubble end meets the DNA that is not untwisted yet by helicase

what does DNA helicase do

unzips the DNA parent strand and creates the replication bubble by breaking the hydrogen bonds

what are the SSBPs used for

attach inside he replication bubble that is formed to help keep it open. stabilizes the structure

what does topoisomerase do

while the bubble gets formed, tension is in the still coiled DNA and it cuts and rejoins the DNA to help release this tension. also helps keep the DNA from breaking

what does DNA polymerase do

this is what physically makes the new daughter DNA strand by attaching the new nucleotide bases to its correct match. It only works in the 5’→3’ direction and needs primers to tell it where to start

what does primase do

it places primers on the leading and lagging strand to tell DNA polymerase where to start working at

on leading strand, it only needs to place one primer and it will work continuously

on the lagging strand, it has to place multiple primers as DNA polymerase has to work in the “opposite direction” then DNA is getting unzipped. has to keep moving backwards

what doe DNA ligase do

it glues the Okazaki fragments that are made on the lagging stand together

what is the leading strand

the strand that gets build in the 5’→3’ direction. gets made in one continuous motion

what is the lagging strand

the strand that gets built in the 3’→5’ direction. has to get made in many small fragments called Okazaki fragments

what is the replisome

multiprotein molecular machinery responsible for the replication of DNA

what is a telomere

a tail that is created on the end of the parent strand of DNA where new DNA is not make on the daughter stand. these are caused from the lagging strand getting made in pieces

this is problematic as the DNA keeps getting shorter

what is an example of a telomerase

cancer cells as it allows them to keep growing

what is responsible for proofreading the DNA

DNA polymerase

what error does UV light cause

production of an extra thymine (thymine dimers) which cause a kink in the DNA

What is nucleotide excision repair

fixes errors that occur within the DNA by recognizing the error then removing the damaged section

what is the central dogma of biology

DNA→ RNA→ proteins

who discovered the mRNA was found carrying a copy of the DNA message

Jacob and Monod

what does RNA polymerase do

synthesizes RNA (makes the RNA via the DNA)

what scientist discovered that there was 64 3 codon code for reading the mRNA template strand

Gamow and then Crick and Brenner confirmed

what occurs between DNA and RNA

transcription - making a copy of the information

what occurs between RNA and proteins

translation - interpreting language into proteins

where does transcription occur in eukaryotes

in the nucleus

where does translation occur for eukaryotes

in the cytoplasm

what is a codon

a triplet code that codes for a certain protein. there are 64 possible codons for the 20 amino acids. several codons code for the same amino acid

where is the codon located on

the mRNA strand

who assigned what each codon coded for

Nirenberg and Leder

how does DNA help create the message for these codons

the DNA holds all the information of which the RNA strand is built off of. The DNA base pairs are translated into the RNA base pairs of which now allows the codons to be read to code for the proteins

what is the start codon

AUG (methionine)

what are the stop codons

UGA, UAA, UAG

what does the genetic code entail (4)

redundant - more than one codon for amino acids

unambiguous - only one codon for only that AA

nearly universal - shared by all organisms

without punctuation - no breaks in-between the code

what is it called when information flows backwards from RNA back to DNA

reverse transcriptase which is problematic

define point mutation

one or a a small number if base changes that occur. they are permeant changes to the DNA

what are the types of point mutation and define all (4)

Missense mutations - change an amino acid in the protein. codes for wrong amino acid

silent mutations - does not change what amino acid gets coded for from reduadancy

frameshift mutations - shift the reading frame altering all the following codons (base gets added or removed)

nonsenses mutations - change in codon that codes for a stop codon when it should not

how do point mutations impact the fitness of an organism (3) and what are most common

1. beneficial - increase the fitness of the individual

2. neutral - have no effect on the individual

3. deleterious - mutations decrease the fitness of the organism

most of the point mutations are neutral or deleterious

what are the chromosome mutations and their definitions (4)

Inversion - segment breaks off of chromosome, flips around and rejoins on

Translocation - a section breaks off and reattached to another chromosome

Deletion - a segment of chromosome is lost

Duplication - a segment is present in may copies

How can chromosome mutations be seen

karyotype

what does transcription do

RNA molecule is made from DNA in a similar fashion that DNA replication is done. Only the template strand is needed in order to create the RNA molecule

decodes the message hidden in DNA into RNA

How does the RNA polymerase work

De novo - does not need template strand to get going

what much attach to the DNA in bacteria before it can start having an mRNA strand built off of it

a sigma must bind

what are the three stages of transcription and translation

initiation, elongation, termination

describe what happens in initiation in transcription

the RNA polymerase attaches to the promoter (part of the DNA that allows the RNA polymerase to attach before the part that gets coded)

describe what happens in elongation in transcription

the RNA strand starts to be be build and grows longer. As it grows longer it peals away from the template strand and exits the RNA polymerase. The DNA now recoils and exits the polymerase too

describe what happens in termination in transcription

the RNA polymerase reaches a set of bases in the DNA template called the terminator which tells it to stop coding. the RNA polymerase detaches from the DNA and the new RNA molecule

what is mRNA

Messenger RNA which is the carrier of information that encodes the amino acid sequence. (this was the RNA that was created in transcription)

besides the code for the amino acids what is mRNA made of

introns (white noise) and exons (physical code)

what is the process of removing the introns

RNA splicing via spliceosomes

explain the process of RNA splicing

introns are removed via spliceosomes, a cap is placed on the 5’ end and poly A-tail are placed on the 3’ end. this is no the completed mRNA molecule ready to go to translation

how is transcription different in prokaryotes and eukaryotes

prokaryotes - a sigma is required for the RNA polymerase to bind to the promoter. it allow occurs in the cytoplasm which is the same place where translation take place

eukaryotes - occurs in the nucleus and RNA polymerase is able to just bind to promoter

what are ribosomes used for

they are used in the process of translation to take the code out of mRNA to amino acids. comprised of a small and large subunit. small subunit attaches to the mRNA

what are polyribosomes

when many ribosomes attach to the same mRNA stand to make the same AA chain more than once

what is tRNA

transfer RNA that uses anticodons to pull the code out of mRNA and make the protein chain

consisted of loops and stem the house the anticodon to the mRNA. additionally has a CCA sequence that is able to grab the corresponding AA to the sequence

what is the anticodon

the opposite code (bases) than is on the mRNA

what is translation

taking mRNA into the amino acid sequence with the use of tRNA in the ribosome

how many tRNAs are there

only 40 because of redundancy. found from crick in the wobble hypothesis

what are the sites that tRNA go into in the ribosome

A site - acceptor site

P site - where peptide bonds form

E site - where tRNA exits

explains what happens in initiation in translation

starts with the AUG codon, the small subunit binds to the mRNA strand via ribosomal binding site (rRNA) upstream of start codon, large subunit attaches on top, a tRNA is in the A-site and starts to move to the P-site

explains what happens in elongation in translation

tRNA works its way through the A, P, E sites building the AA chain longer and longer. everything moves one at a time to the empty site (not an all at once movement)

explain what happens in termination in translation

stop codon is reached which NO tRNA codes for but rather a protein aka release factor enters the A site and causes the 2 subunits of ribosomes to detach.

what is translocation

how the ribosome moves down the mRNA strand from elongation factors

after termination in translation, what is the last thing that happens

the amino acid chain is now folded into a protein with the help of molecular chaperones to help complete the chain