DNA, RNA, Protein Synthesis, & Mutations

Edwin Chargaff

Base pairs of DNA

1950

Edwin Chargaff

Rosalind Franklin

X-ray crystallography (showed 2 strands)

1951

Rosalind Franklin

Gregor Mendel

* inherited traits make up an organism’s phenotype
* studied pea plants

1856

Gregor Mendel

Frederick Griffith

Experimented on lab mice to __determine transformation of inherited traits__

1928

Frederick Griffith

Watson and Crick

* Used Franklin’s x-ray pic 3-D model of DNA
* won a nobel peace prize in Sci

DNA

* Stores genetic information
* Found in all cells
* Transmits genetic information to determine traits

Deoxyribonucleic acid

* genetic material located in nucleus of every eukaryotic cell
* made up of double helix

double helix

* 2 strands of linked nucleotides that form a twisted ladder

nucleotides

subunits (monomer) that form DNA

Steps (rungs)

pair of nitrogen bases held together by a __*weak hydrogen bond*__

Sides (backbone)

made up of the ^^sugar (deoxyribose)^^ and a ^^phosphate group^^ held together by a __*strong covalent bond*__

Purines

* Adenine & Guanine
* 2 carbon rings

Pyrimidines

* Cytosine & Thymine
* 1 carbon ring

3’ (prime)

* strand in double helix
* ^^hydroxyl group attached (-OH)^^
* named for carbons on the deoxyribose shape

5’ (prime)

* strand in double helix
* named for carbons on the deoxyribose shape
* ^^has a phosphate group attached^^

transcribes

DNA ___ to mRNA

translated

mRNA is ___ into Amino acids

Proteins

Amino Acids make ___ which express traits (phenotypes)

RNA

* Ribonucleic Acid
* nucleic acid used in genetic info
* contains elements; C H O N P

ribose

* in RNA
* single strand of linked nucleotides containing the 5-carbon sugar (pentose)

cytoplasm

where RNA is located in the cell

Adenine Uracil

cytosine guanine

four nitrogen bases of RNA

mRNA

* Copies instructions from DNA code; carries code out of nucleus to ribosome

messenger RNA

mRNA

rRNA

ribosomes made of protein and RNA

Ribosomal RNA

rRNA

Transfer RNA

tRNA

* t shaped

tRNA

* Carries and transfers a specific amino acid to the amino chain assembled by the ribosome

proteins

* are composed of amino acids
* made by combining 20 amino acids in different combinations

20

how many amino acids are der

ribosomes

proteins are manufactured in ___ located in cytoplasm or attached to the Rough Endoplasmic Reticulum (RER)

cytoplasm

proteins are made by ribosomes located in ___ or attached to the RER

Rough endoplasmic reticulum

proteins are made by ribosomes located in cytoplasm or attached to the ___

functions of proteins

* Fights disease
* builds new body tissue
* enzymes used for digestion and other chemical reacttions are proteins
* component of all cell membranes

transcription

DNA message is transcribed into mRNA & mRNA sent to ribosomes

translation

mRNA is translated into a protein by a ribosome

eukaryotic cell

transcription and translation occur in different places

prokaryotic cell

entire process takes place in the nucleoid region due to no nucleus

transcription

copying of genetic info from DNA to RNA

why DNA is transcribed

* DNA has genetic code for the protein that needs to be made but proteins are made by the ribosomes
* Ribosomes are outside the nucleus in the cytoplasm/attached to the ER

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* DNA is too large to leave nucleus (double stranded)
* RNA can leave the nucleus (single strandedIniti)

Initiation

Elongation

termination

3 stages of transcription


1. Beginning
2. Addition of nucleotides mRNA strand
3. the end/final step

initiation

* beginning of transcription
* occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter (TAC)

promoter

* signals DNA to unwind so the enzyme can “read” the bases on one of the DNA strands in a 3’ to 5’ direction
* enzyme adds RNA nucleotides to a growing RNA strand in a 5’ t 3’ direction

TATA box

Initiation of transcription at a Eukaryotic Promoter

TATA box

* DNA sequence that indicates where a genetic sequence can be read and decoded
* Type of promoter sequence which specifies to other molecules where transcription begins

25-35 base pairs

Eukaryotic genes have a conserved TATA box located ___ before the transcription site of a gene

TATA box

able to define the direction of transcription and also indicates the DNA strand to be read

Transcription factors

proteins can bind the TATA box and recruits RNA Polymerase

RNA Polymerase

enzyme that synthesizes RNA from DNA

elongation

* entire stretch of 1 side of the DNA is transcribed into an RNA molecule
* transcription unit codes for a ^^polypeptide^^

RNA polymerase ll

makes mRNA strand

mRNA

part of DNA temporarily __unzips__ and is used as a template to assemble complementary nucleotides into __

termination

mRNA continues to read the DNA sequence until it reaches a __stop__ signal that ends transcription

terminator

stop signal that ends transcription (ACT, ATT, or ATC)

Pre-mRNA strand

process result in transcription which will require editing

eukaryotic

in __, transcription results in pre-mRNA

Mature mRNA

Pre-mRNA undergoes to yield a final __ strand which leaves the nucleus and goes to the ribosomes

prokaryotes

* in __, transcription results in mRNA
* processing of mRNA does not occur
* transcription and translation can occur simultaneously

RNA splicing

* editing of the initial strand of mRNA (a cut & pase job)
* takes place in eukaryotes

mutations

* A permanent alteration of the DNA sequence which makes up the gene codes
* can occur during DNA Replication
* can be within the genes or affect the entire genome through the chromosomes.

introns

large sections of the mRNA that do not encode for the protein are __spliced out__ of the pre-mRNA strand and remain in the nucleus

exons

sections that code for amino acids to make the protein

splicesome

* exons are spliced tgethe to form a ^^mature mRNA^^ that __leaves the nucleus__ and __travels to the ribosomes__
* removes introns from pre-mRNA

small nuclear ribonucleoproteins (snRNPs)

serves a catalytic function in the splicesome

three

the bases of mRNA are read in groups of __

codon

each group of bases of mRNA are called

5’ cap

* a modified form of a guanine nucleotideto __protect the mRNA from degradation__ and __assists in ribosome binding__

poly-A tail

* protects mRNA molecule from enzymatic degadation
* aids in transcription termination
* export of the mRNA from the nucleus & translation

ribosome

after splicing, the mature mRNA goes thru the pores of the nucleus w/ the DNA code and attaches to a __

complementary

bases of mRNA are __ to the template strand of DNA

translation

making a protein

* decoding of mRNA into amino acids (proteins)

tRNA

part of the translation process of making a protein

* carries specific amino acids from the cytoplasm to the ribosome

anticodon

each tRNA has 3 nucleotides that are complementary to the codon in mRNA called __

ribosomes

mRNA carrying the DNA instructions & tRNA carrying amino acids meet in the ribosome

protein

amino acids are joined together to make a __

polypeptide=___

initiation

elongation

termination

3 stages of translation

initiation

stage of translation

* begins with AUG always

elongation

* codon recognition
* peptide bond formation

termination

a STOP codon is reached and translation stops

Amino acid site

location at which the tRNA pairs up with the mRNA START codon to ensure that the correct amino acid is added to the growing pwptide chain

polypeptide site

locaion at which the amino acid is transferred from the tRNA to the growing polypeptide chain

Exit site

location where the empty tRNA sits before being released back into the cytoplasm to bind to another amino acid and repeat the process

initiation

the beginnign of translation of the mRNA code by the ribosome

elongation

the buildup of a peptide chain by adding one amino acid at a time

termination

* when the translation of the mRNA hits a STOP codon
* the protein chain has been synthesized and released by the ribosome

acquired

* caused by environmental factors or mutagens (such as UV rays, viruses, chemicals etc.)


* occur in somatic cells and are not inherited by offspring. Also not present in all cells.
* type of mutation

germline

* inherited, takes place in gametic cells (egg and/or sperm) – will be found in ALL cells
* type of mutation

point mutation

* Single nitrogen base change (base-pair substitution)
* type of gene mutation

silent mutation

no amino acid change

missense

change in the amino acid

nonsense

code is changed to a stop codon

silent mutation

change in a base pair into another that codes for the same amino acid

missense

* point mutation that still codes for an amino acid, but its __wrong__
* may or may not be harmful

nonsense mutation

* premature code for __stop__ codon
* result: nonfunctional protein

frameshift mutation

* shift in reading frame which changes everything “__*downstream*__”
* caused by insertions or deletions
* can be missense or nonsense

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chromosomal mutations

* occur when a section or sections of the chromosome is changed
* This can occur in several different ways:

\- Deletions - Insertions - Inversions - Translocations