Biology Exam 2

2.1-2.6

The Central Dogma

Gene Expression

DNA → mRNA → Protein

Transcription

DNA copied to make mRNA

Translation

mRNA read to make a protein

translate a sequence of amino acids

protein coding regions of DNA

copied into an mRNA molecule that is used as instructions to make proteins

non-coding DNA

some produces functional RNA

some are regulatory sequences

functional RNA

not used to make protein, but has a biological role

regulatory sequences

help determine when, how a gene will be copied

DNA functions

stores RNA and protein-encoding information; transfers information to daughter cells

stable

RNA functions

carries protein-encoding information; helps to make proteins; catalyzes some reactions

unstable

DNA structure

double-stranded

RNA structure

single-stranded

DNA nucleotide bases

Adenine, Thymine, Guanine, and Cytosine

RNA nucleotide bases

Adenine, Uracil, Guanine, and Cytosine

DNA sugars

deoxyribose and hydrogen

RNA sugars

ribose and OH

RNA polymerase steps

Initiation

Elongation

Termination

Initiation

RNA polymerase binds to control region of DNA

Promoter

helps to initiate the process of transcription with signals

Signals

encoded in the DNA to tell RNA Polymerase where to start and stop

activators

need to be bonded to control regions of the DNA

chromatin

DNA + Histones

Histones

protein complexes responsible for packing DNA

keep DNA organized

hold information to determine ‘open’ or ‘closed’ state of DNA

open

copied or used region of DNA-Euchromatin

closed

not copied or used-Heterochromatin

Euchromatin

loosely coiled

Heterochromatin

tightly coiled

Transcription factor

protein that binds to DNA and regulates gene expression

activate expression

need to bind

Repressors

silence expression and needs to be removed

General Transcription Factors (GTFs)

need to bind to DNA to guide RNA polymerase to bind

RNA plymerase

only reads DNA 3’ → 5’ direction

builds mRNA 5’ → 3’ direction

doesn’t proofread or correct mistakes

Elongation

adding nucleotides to a new DNA strand

template strand

strand that’s being copied in transcription

Termination

RNA polymerase reaches terminator sequence for some genes the mRNA transcript falls away from the DNA template and RNA polymerase

helper protein pulls it away

mRNA during termination

completely detached itself from DNA

either fall off or be pulled away from the DNA

mRNA sequence is translation

it’s translated into an amino acid sequence in the cytoplasm or Rough ER

the genetic code

all organism utilize it the same for representing the 20 amino acids

allows ribosomes from any organisms to produce specific proteins from any mRNA molecule

properties of the genetic code

triplet, non-overlapping, degenerate, unambiguous, punctuated, and universal

triplet

3 bases code for 1 amino acid

(in the RNA form)

non-overlapping

the sets of 3 are read sequentially

punctuated

tells the ribosome where to start and stops

start codon

AUG

stop codons

3

UAA, UAG, UGA

degenerate

the genetic code is redundant; most amino acids have more than 1 codon

unambiguous

codons are exclusive; each specifies only 1 amino acid

universal

the same codons specify the same amino acids ands stop codons in ALL organisms

rRNA

ribosomal RNA

makes up ribosomes, builds proteins

tRNA

transfer RNA

translates the genetic code into the appropriate amino acid

anticodon region

matches to codon on mRNA molecule using complementary base pairing

methionine

first amino acid ALWAYS

small ribosome subunit

binds with AUG codon using complementary base pairing

initiation factors

responsible for assembly of the initiation complex

large subunit joins the complex

the loaded tRNA is now the P site of the large subunit

E

exist site (unloaded tRNA leaves from this location)

P

polymerization site (amino acids are joined together her to form a polymer)

A

access site (new loaded tRNA enters the ribosome in this location)

large subunit catalyzes two reactions

breaks bonds between tRNA in P site and its amino acid

peptide bond forms between that amino acid and the amino acid on tRNA in the A site

if rRNA is destroyed

the activity stops

first tRNA releases its methionine

moves into the E site and dissociated from the ribosome

then tRNA can become loaded again with another amino acid in the cytoplasm

during elognation

steps are repeated as polypeptide elongates

translation ends when

a stope codon enters the A site

ribosome falls of the mRNA

the completed polypeptide is released

have many ribosomes working

on 1 mRNA transcript to amplify synthesis

after termination

protein is then folded

protein synthesis

each ‘valve’ is an important step in getting the right protein

mutation

change in the DNA structure or base sequence of a gene

can occur in RNA replication

intrinsic mutations

factors inside the cell

extrinsic

factors from the external environment

DNA mutations

defective protein or an inability to make certain proteins, can cause diseases

point mutations

change in 1 base pair of DNA

types of point mutations

silent, missense (conservative, non-conservative), nonsense, frameshift (insertion, deletion)

silent mutation

change in the DNA base pair (no affect), but the amino acid stays the same

conservative missense mutation

amino acid does change, but the new amino acid has the same chemical properties

usually small changes to protein structure and function

non-conservative missense mutation

amino acid does change, but the new amino acid has different chemical properties

will change the way a protein folds and how it interacts with other molecules (drastic folding changes)

Nonsense mutation

amino acid does change to a stop codon

ranges from no effect to drastic…depends on location of mutation

Frameshift mutation

addition or deletion of a single DNA base

changes how the mRNA is read (new reading frame for sets of 3 bases/codons

more significant effects on final protein because every amino acid downstream of the mutation is affected

various affects with changes in amino acids

no effect, reduced functionality, loss of function, and gain of function (rare)

loss or gain of fuction

one of the two ways organelles evolve

cystic fibrosis

genetic disease caused by a channel protein mutation

differential gene expression

expression of different by cells with the same genome

Transcription Factors (TF)

are a component that determines which genes are expressed

-bind to control region of gene

reongnize sequence of base pairs on DNA strand

Activators

help general transcription factors and RNA polymerase assemble

Repressor

blocks general transcription factors and RNA polymerase

expressed genes

only occurs if both activators are present and the repressor is absent

little/no transcription

only one activator present

no transcription

activators present and repressor is present

Lactose Intolerance

lactase gene prevents bind of TFs → lactase gene not expressed → can’t digest lactose

Lactase Persistance

a mutation in the control region of the lactase gene the prevents methylation → lactase continues to be expressed → can digest lactose

Non-polar Hormone path to nucleus

cell membrane→ nuclear membrane→ finds protein binding partner→ hormone protein initiate gene expression of target genes

Polar Hormone path to nucleus

bind to signa receptor on cell membrane→ initiates signal pathway in cytoplasm with secondary messengers→ signal cascade at then end…allows it to enter nucleus and bind to DNA to regulate gene expression

signal cascade

a transcription factor changes conformation (shape)

increased translation of genes

can be increased in response to growth cues and other signaling molecules

c-Myc transcriptional activator had a mutation it is always active

the genes would always be expressed even in the absence of growth factors causing inappropriate gene expression

MNK1, a translational activator had a mutation and could NOT be activated

the mRNA that it targets would no longer have increased translation into a protein

mutation on inactive translation

it wouldn’t change but would make less protein

cell theory

1. The cell is the most basic unit capable of exhibiting the characteristics of life

2. All living organisms are composed of one or more cells

   1. All cells arise from pre-existing cells (through the process of Mitosis and cytokinesis)

zygote

a fertilized egg

life begins as

a single cell

-undergoes many rounds of cell division to make trillions of cells

reasons for cell division

development, cell replacement, and repair

Development

from a single cell into a multicellular adult