UNIT #10: Protein SynthesisTextbook Chapter 12: DNA & RNA

Below is Frederick ___________________ experiment of 1928. He was trying to find a vaccine for pneumonia by testing bacteria on mice. What do you think happened when he mixed to harmless strains and injected it into the mouse?

Griffith's experiment sparked a debate over whether DNA or protein is responsible for holding hereditary information....for decades scientist's came up with experiments testing both protein and DNA. It was not until this famous experiment from Alfred ___________ and Martha ________ in 1952 with _____________________ did the debate finally come to an end...

Once DNA was established as the macromolecule responsible for holding life's instructions, the now-famous Race of the Double Helix began! There were many, many scientists involved in the discovery of the structure of DNA, but here are just some of the big hitters....

Erwin Chargaff James Watson & Francis CrickRosalind Franklin & Maurice Wilkins1949 1952 1953

DNA stands for ________________________. DNA is composed of units called ____________. Each nucleotide has three parts:

1. __________________________

2. __________________________

3. __________________________ The 5-C sugar found in DNA is deoxyribose. There are four different base pairs in DNA:

1. _____________________

2. _____________________

3. _____________________

4. _____________________

Rosalind Franklin's X-ray diffractions told us the exact width of the double helix.

Erwin Chargaff's Rule that also works due to the base-pairing.

Bases come in two categories based on their structure:

1. _______________: A and G - double rings

2. _______________: T and C - single ring

Complementary Base-Pairing Rules in DNA:

___________ always matches up with ____________.___________ always matches up with ____________.

Complementary base pairs are held together by ________________ bonds.

There are ____ bonds between A and T; there are ____ bonds between C and G.

What do you notice about the orientation of the two strands of DNA nucleotides?

The two strands are said to be ___________________.

During ____ phase of the cell cycle, DNA is replicated in preparation for cell division. How does this happen? There were three models on the table: _____________, ______________, and _______________. An experiment by Meselson and Stahl found the answer...

DNA Replication - the overview:1. DNA must "___________."

2. Each parent strand acts as a ________________.

3. New daughter strands form following the ___________________ rules.

4. Each "daughter" DNA molecule "zips" up.

Enzymes called _______________________ bind to the origins of replication to break the _______________ bonds and "unzip" the DNA.

In eukaryotic cells, there are _______________ origins of replication in order to speed up the process.

The areas where the double helix separates is called the ____________________.

Remember how DNA strands run antiparallel? Well, this poses an interesting problem for DNA replication because new base pairs can only be added in one distinct direction (5' to 3').At the replication fork, enzymes known as _____________________ move along each of the parent strands (in a 5' to 3' direction) adding complementary nucleotides according to the base-pairing rules. There ends up being a ____________ strand that can easily slide along the parent strand without obstacle in the correct direction and a ____________ strand that needs to move section by section resulting in fragments of new DNA. ________________ then needs to attach to the lagging strand and follow along in order to seal up the gaps between the Okazaki fragments.

What happens when a mistake is made? Don't worry! Mistakes happen all the time! Your cells have adapted a __________________ system to try to fix the mistakes.

1. ______________ cuts out the damaged DNA strand. 2. ______________ reattaches to fill in the missing nucleotides. 3. ______________ seals up the free ends to make the strand complete. Proofreading reduces the amount of mistakes in DNA replication to only ___ in every ______________ nucleotides! The human genome is composed of roughly ____ billion nucleotides, so this means that each time replication occurs only _________ mistakes are made.

_________ are sequences of bases in DNA that act as the instructions for life, however it is the ____________ being made that allow life to exist.

Proteins are synthesized differently in prokaryotic cells, than in eukaryotic cells. In prokaryotes, the process is broken down into ___ simple steps (transcription and translation) that take place in the ________________. In eukaryotes, the process is broken down into ____ steps (transcription, RNA processing, and translation), occurring in different locations inside the cell.

Genes are sections of DNA. Each gene corresponds with one _________________.

One DNA strand functions as a template for transcription, which is the synthesis of a complementary messenger RNA (mRNA). The base-pairing rules for DNA synthesis guide transcription, but ____________ (U) takes the place of ____________ (T) in mRNA. The mRNA is read as a sequence of base triplets, called _____________. Each codon specifies an __________________ to be added to the growing polypeptide chain.

There are ___ different amino acids in your body, but there are 43 = ___ different codons.

Each codon corresponds to one amino acid, but one amino acid may have ________ than one codon.

There are three _________ codons (which do not code for an amino acid) and one ___________ codon (which codes for an amino acid _________________).

STEP #1: Transcription In eukaryotic promoter regions, there is the __________ box about 25 nucleotides upstream of the transcription start point. Transcription factor proteins recognize and bind to the DNA. _____________________ binds & the DNA unzips to start transcription. RNA polymerase moves downstream in a 5' to 3' direction creating the mRNA. When RNA polymerase transcribes a terminator sequence, transcription is complete.

The _______________________ is a protein complex that cuts out the introns.The 5' cap and Poly-A tail are necessary to:

1. _______________ the export of the mRNA from the nucleus2. help ______________ the mRNA from degradation3. help ribosome _____________ to the 5' end of the mRNA

STEP #2: RNA processing Cut out the noncoding regions (__________) and splice together the coding regions (__________), then a __________ and a _____________ are added.

STEP #3: Translation __________________ reads the sequence of codons on the mRNA. __________________ (tRNA) will then carry amino acids to the ribosome in the proper sequence to create a polypeptide. The ribosome will only start translation when it comes to a ________ codon (AUG). The ribosome will stop translation when it reaches a _______ codon (UAG, UAA, or UGA). The polypeptide is released and the two subunits of the ribosome dissociates.

A single mRNA molecule can be translated at one time by several ribosomes in clusters called _______________________. How can this help the cell? Translation begins in the cytoplasm with a free ribosome. However if given the cue, the free ribosome can attach to the RER to finish out translation where the polypeptide will be released into the ER's lumen for further processing. Ribosomes can __________ their status from being free to being attached.

The example above shows how a single point mutation has the ability to lead to serious consequences. In this case, sickle cell trait is caused by the accidental switching of a A instead of a T in the gene coding for hemoglobin. This simple change is responsible for Valine to be in the polypeptide instead of glutamic acid.

This type of point mutation is known as a base pair __________________. But luckily not all base pair substitutions have such an effect on a person's health...

What happens when mistakes are made in transcription?...even the best editors in the business make mistakes.

________________ are changes in the genetic material of a cell.

___________ mutations are chemical changes in just one base pair of a gene.

Base-pair Substitutions can lead to: 1. _____________ Mutations - show no change in the amino acid sequence. This usually happens when the mistake is in the "wobble" position (3rd base of the codon) or in an intron that never gets expressed. 2. _____________ - changes one amino for another (like the sickle cell example) 3. _____________ - changes one amino for a stop codon.

Besides a base pair substitution, a point mutation may be a: 1. ______________ = the loss of a base pair 2. ______________ = the addition of a base pair Because mRNA is read as a series of triplets, the addition or deletion of base pairs can result in a shift in the reading frame of the genetic message. We refer to these types of mutations as ___________________ Mutations. Frameshift mutations can have serious consequences resulting in the change of _________ amino acids. These types of mutations usually ends with a protein that is nonfunctional.