AP Bio Unit 6

Genotype

your genes

Phenotype

what you look like

Gene expression

the process by which D N A directs protein synthesis, includes two stages: transcription and translation

_____ is the bridge between genes + protein synthesis

RNA

Transcription

going from DNA to RNA

messenger RNA or mRNA

the RNA that you actually use to make proteins

What are responsible for translation

ribosomes

Whats the extra step in eukaryotic cells of transcription + translation?

pre mRNA is processed into mRNA

What can begin before transcription is finished in prokaryotes?

translation of mRNA

What separates transcription from translation in a eukaryotic cell?

the nuclear envelope

A primary transcript

The initial RNA transcript from any gene prior to processing

Whats the general order of transcription + translation (happens except in viruses)

DNA to RNA to proteins

Triplet code

a series of nonoverlapping, three-nucleotide words

the nitrogenous bases

Adenine, Thymine, Guanine, Cytosine, Uracil

What nucleotide base is unique to RNA

uracil

What nucleotide base is unique to DNA

Thymine

What are the base pairs

A - T/U
C - G

DNA has 2 strands

5 prime strand
3 prime strand

Template strand

provides a template for ordering the sequence of complementary nucleotides in an RNA transcript

How do your enzymes read the strands

from 3' to 5'

RNA polymerase makes

RNA

DNA polymerase makes

DNA

Any polymerase will read

3' to 5' & make 5' to 3'

Codons

the mRNA base triplets

coding strand

The nontemplate strand that

Complementary strand

changes to what it binds to, also goes from "5' to 3'" to "3' to 5'"

RNA sequence

just og strand but the T turns into U

RIBOSOMES read ______ and create ________

5' to 3' and create amino acid chains that don't have that type of directionality

Start/stop codons

tells you when the protein is starting & when it is ending

If you get stop code then

that means ribosomes will stop forming proteins

DNA polymerase is ____ maintenance, it needs a ____

high maintenance, it needs a primer

RNA polymerase is _____ maintenance, it ____ need a _____, it just _______

low maintenance, it doesn't need a primer, it just comes & separates DNA

RNA polymerase is all

self contained

Promoter

tells DNA polymerase where to sit to attach & make RNA

3 stages of transcription

initation
elongation
termination

Initiation

where it 1st comes & sits

Elongation

makes RNA

termination

detaches when done

Promoters are usually really

long
- they are long stretches of noncoding areas

Promoters are what ____ is looking for when it wants to come & sit

RNA

Transcription factors come help

RNA polymerase bind

TATA box

Whole bunch of TATATATA (like 36) & RNA polymerase is like thats where I sit

Nucleotides are added to

the 3′ end of the growing RNA molecule

The 5′ end receives a

modified nucleotide 5′ cap

The 3′ end gets a

poly-A tail

what do modifications of the pre-mRNA molecule do

They seem to facilitate the export of m R N A to the cytoplasm
They protect m R N A from hydrolytic enzymes
They help ribosomes attach to the 5′ end

What is 5' cap like?

the helmet to protect mRNA from harm

What is Poly A Tail like

padding on the butt

Introns

The noncoding segments in a gene

Exon

coding portions of DNA or RNA

Spliceosomes

remove introns

What do splicesosomes consist of

a variety of proteins and several small R N A s that recognize the splice sites

The RNA of the spliceosome do what

catalyze the splicing reaction

How does genetic info flow during translation

from mRNA to protein

What helps a cell translate an mRNA message into protein

transfer RNA (tRNA)

tRNA

job is to transfer amino acids to growing polpeptide

Translation

changing languages from RNA to protein

Do you need tRNA to make proteins

yes

How do ribosomes make proteins

By feeding mRNA thru the top & bottom of ribosome & it will read every single base & codon & then make a polypeptide chain

Where do ribosomes get amino acids?

tRNA

What is at the bottom of tRNA

an anticodon

Every 3 bass on mRNA is a

codon

the tRNA knows wwhicch codon it is looking for bc

at every single bottom of tRNA is an anticodon

How does an anticodon relate to a codon

It fits like a puzzle piece to a codon

Why is the anticodon there?

There for the tRNA to recognize which codon it is looking for

What does the amino acid correspond with?

The codon

What is the shape of tRNA

It is just a RNA strand that is twisted into a 3 dimensional shape
- the have 5' to 3' ends

what causes the tRNA to twist & fold into a 3D molecule

hydrogen bonds

rRNA

what ribosomes are made of

Ribosome

proteins + rRNA

mRNA

what you got from proteins to make protein

3 binding sites for tRNA

P site
A site
E site

P site

holds the tRNA that carries the growing polypeptide chain
- does the actual work

A site

holds the tRNA that carries the growing polypeptide chain
- next block, waits for its turn

E site

the exit site, where discharged tRNAs leave the ribosome

3 stages of translation

initaton
elongation
termination

Intiation factors job

to airlift large subunit & set it down where its supposed to go
- then you are ready to go

3 steps of elongation

codon recognition (uses energy)
peptide bond formation
translocation (uses energy)

Where are amino acids added to

the C-Terminus

During elongation what does the tRNA do after it donates amino acids

bc it is empty it then leaves to go pick up another o the same amino acid

When does elongation stop

when a stop codon in the mRNA reaches the A site

What protein does the A site accept

a release factor

Release factor

causes additon of H2O molecule instead of an amino acid
- this releases the polypeptide, & translation assembly comes apart

Once you get a stop codon

everything comes apart & protein becomes free

Where are ribosomes found

cytosol + ER

Where is ER connected directly to

nucleus

mRNA goes directly from ER to

nucleus to make proteins

Do ribosomees in ER + cytosol have a difference?

no

Where does polypeptide synthesis always begin?

in the cytosol

Synthesis finishes in the cytosol unless

the polypeptide signals the ribosome to attatch to the ER

Signal peptide

They mark polypeptides destined for the ER or for secretion

If you start making proteins outside ER,

it gets label to tell other transport proteins where to take it

Mutations

changes in genetic info of a cell
- any change in RNA, DNA, etc

Point mutations

changes in just 1 nucleotide pair of a gene
- you only change 1 base, 1 nucleotide pair

2 general categories of point mutations w/in a gene

- single nucleotide pair substitions
- nucleotide pair insertions or deletions

Silent mutations

no effect on the amino acid produced by a codon bc of redundancy in the genetic code

Missense mutations

still code for an amino acid, but not the correct amino acid
- diff base + amino acid

Nonsense mutation

change an amino acid codon into a stop codon; most lead to a nonfunctional protein

How many base changes do silent mutations have?

1 base change

Why do silent mutations exist?

Bc we have a lot of codon repeats that code for the same exact amino acid