AP Bio DNA and RNA unit

Nucleotide

one nitrogenous base, one deoxyribose sugar, and one phosphate group

Nitrogenous bases have 2 categories

pyrimidines and purines

pyrimidines

cytosine, thymine, and uracil

single 6-membered ring structure

purines

adenine and guanine

double ring structure (one 5-membered ring and one 6-membered ring)

Cytosine always pairs with

guanine

Adenine always pairs with

Thymine (DNA)

Uracil (RNA)

Deoxyribose

5 carbon sugar

1’ is attached to the

nitrogenous base

5’ is attached to the

phosphate

phosphate

attached between the 5’ carbon of one nucleotide and the 3’ carbon of the next

base pairs are held together by

hydrogen bonds

hydrogen bonding is important because

weak bonds are easily able to separate for copying

the backbone of each strand are the

sugar and phosphate

the two strands are

antiparallel

antiparallel

the 3’ end of one strand faces the 5’ end of the other strand

don’t go in the same direction

two strands of DNA are twisted together to form the

double helix structure

prokaryotes

contain a singular circular chromosome (contain one circular loop of DNA)

prokaryotes are able to transmit ___ to each other

plasmids

Eukaryotic

linear chromosomes

DNA wraps around histone protein

nucleosomes make up chromatin fiber

coils tightly during mitosis

helicase

an enzyme which unzips the DNA at the origins of replication by breaking hydrogen bonds between base pairs

uses ATP hydrolysis

ATP hydrolysis

Breaks phosphate off of ATP to make ADP & release energy

Topoisomerase

enzyme that prevents strands from recoiling

prevents strands from getting tangled

DNA polymerase

requires RNA primers to initiate DNA synthesis (can only add in one direction

leading strand

5’ strand adds nucleotides continuously toward the replication fork

lagging strand

joins fragments on the lagging strand

DNA ligase

joins the fragments on the lagging strand

Prokaryotic DNA replication

same basic process but there is a single origin of replication that proceeds in both directions

Does DNA replication occur quickly

YES

semi-conservative

each new DNA consists of one strand from the original DNA and one new strand

result of DNA replication

produces two identical copies of the DNA strand

Central Dogma of biology

DNA encodes RNA, RNA encodes proteins

Transcription

copying or transcribing of the information in the DNA onto an mRNA

RNA processing

changes made to the transcribed RNA somewhat before it leaves the nucleus

Translation

how the mRNA is translated at the ribosomes to produce chains of amino acids that will be folded into proteins

mRNA

messenger RNA

what does mRNA do?

carries genetic info from the nucleus to the ribosomes

tRNA

transfer RNA

what does tRNA do?

aids in bringing the correct amino acid to the ribosome to build the proteins

rRNA

ribosomal RNA

what does rRNA do?

a structural component of ribosomes that is produced in the nucleolus; structural component

Step 1 Transcription

cell signal must first start to unwind the DNA in the nucleus at the gene that needs transcribed

Step 2 Transcription

one strand of DNA will be the template and RNA bases will bind to it

Choice of template strand

differs for each gene

can start with leading or lagging strand (only one will be used)

Step 3 Transcription

RNA polymerase unzips and rezips the DNA

Step 4 Transcription

promoter tells the RNA where it should start from (called the TATA box)

Addition of RNA bases proceeds in the __’ to __’ direction

5’ to 3’ direction

Elongation

occurs a the RNA bases are added

Step 5 Transcription

DNA sequence on the gene signals the termination of transcription adds the poly-A tail

RNA Processing Step 1

5’ capping

helps protect mRNA from degradation

RNA Processing Step 2

addition of poly-A tail at 3’ end signals it is ready to leave nucleus and go to cytoplasm

Introns

(noncoding parts of the gene) are cut out, in the trash

Exons

(expressed parts of the gene) spliced back together & mRNA leaves nucleus

Translation mRNA

codes every three bases for one amino acid

Translation ribosomes

are where it all happen

Translation tRNA

bring the correct amino acids to the template

Translation every 3 nitrogen bases code for

a specific amino acid

codon

every 3 nitrogen bases

start codon for every protein

AUG

Initiation

mRNA is transported to cytoplasm

attaches to a ribosome

start codon is read first

tRNA brings anti-codons

Elongation

ribosome moves along the mRNA strand

read the codons of mRNA in order

tRNA brings anti-codons and donates amino acid

repeats for each codon

Termination

when the stop codon is reached translation stops

mRNA leaves the ribosome

polypeptide chain folds into 3-dimensional shape