Dna flashcards

Purines are larger and have two rings like adenine and guanine. While pyramidines are depicted as smaller and have only one ring like thymine and cytosine. A bonds to T and G to C. There are two H+ bonds between adenine and thymine and three between guanine and cytosine. The teeth are one of the 4 bases (A,T,C,G) The backbone is alternating phosphate and deoxyribose.

You start from where they are bonded to nucleotides and then count clockwise (remember the top of the pentagon is an oxygen and the fifth carbon is bonded to the phosphate). You read in the 5' to 3' direction, 5 prime and 3 prime are the third and fifth carbons which bind to a phosphate connecting deoxyriboses. The two backbones are antiparallel to each other.

The first step is initiation. First the DNA is cut/unwinded down the middle by helicase at the replication origin which forms a replication bubble and if it keeps expanding a replication fork. Helicase breaks apart the H+ bonds between nucleotides (insides of DNA have weak bonds). This unzipped DNA is held apart by single strand binding proteins (SSB's)

Because they do not have DNA (carrier of gentic information). Their DNA replicates into RNA and The RNA (MRNA) is used as a messenger and transcripted for protein sythesis. It is the process in which bacteria take up foreign gentic material and have a change in genotype.

They testes the effects of different strains of bacteria on mouses and found out that if dead virulent strain and living nonvirulent strain were injected in a mouse, the nonvirulent would take up the DNA of the virulent and kill the mouse. Hershey and Chase proved that DNA codes for genes not proteins, because when they used phages (some labelled with sulfur protein capsules and others with phosphorous protein cores) to inject DNA into bacteria only phosphorous labelled DNA entered cells not the sulfur labelled proteins.

It codes for amino acids with each "word/amino acid" code being 3 nucleotides. long which make up proteins through their order and amount (functional or structural proteins). One deoxyribose together with its phosphate and base make a nucleotide. DNA is a polymer of nucleotides. Chargaff's rule is that there must be the same amount of A and T and C and G in a sample of DNA.

Rosalind Franklin rook pictures of the DNA's double helix with x-rays and mixed DNA with water to find nitrogenous bases were on the inside and phosphates and sugar was outside. Watson and Crick used other scientists information to produce a structural model of DNA (they called it a double helix).

They cultured bacteria's DNA with N15 (heavier isotope of nitrogen) and then transferred them to a medium containing n14 (lighter isotope) which showed that when they replicated they used half of the old backbone (containing n15) and half of the new (containing n14) which created medium weight DNA which is half N15 and half N14 on the first replication. That gave evidence that DNA replication is semi-conservative (half is old, half is new). The used a centrifuge to find out the weight

Elongation occurs. Primase inserts RNA sequences called primers which serve as a starting point for polymerase 3 to start work, next DNA polymerase 3 adds free floating nucleotides to the DNA strands (A binds to T, G to C). Next DNA polymerase 1 proof reads the DNA strands and inserts DNA in place of the RNA primers. Then as polymerase works on the lagging strand okazaki fragments form due to the enzyme only being able to work in sections and ligase inserts nucleotides where the fragments form.

It is a semi-conservative process that occurs in the nucleus. First the DNA is cut down the middle by helicase from the replication origin, which breaks apart the H+ bonds between nucleotides (insides of DNA have weak bonds). Next SSb's hold the two strands apart and primase places down short RNA sequences called primers to serve as a starting point for polymerase 3 to work, then polymerase 3 attaches Free floating nucleotides with their appropriate nitrogen bases (AT,CG), Then polymerase 1 proof reads the strands and replaces RNA primers with DNA. Then Ligase joins up okazaki fragments that form in the lagging end as a result of polymerase not being able to work in a straight line with nucleotides and rewinds up the DNA. Last the enzymes dismantle and TERMINATION occurs.

Step 3 is termination. After the okazaki fragments are joined up by ligase, the enzymes (also called the replication machine) on the replication fork dismantle and then termination occurs.

Since DNA replication must occur in the 5'->3' direction and DNA is antiparallel, only one side can replicate DNA fast towards where helicase is cutting this is the leading strand. The opposite side occurs slower and is called the lagging strand due to the fact that it must first wait for helicase to cut and then work in the opposite direction. The replication origin is where helicase starts splitting the DNA and replication begins.

They are protective caps that prevent the shortenning of DNA molecules, helping to postpone the degradation of genes near the ends of DNA molecules. They are like sacrifical end pieces that code for nothing useful.

RNA leaves the nucleus 2. the sugar backbone is ribose (not deoxyribose) 3. It has uracil instead of thymine (T) 4. Its single stranded 5. It can be tRNA, mRNA or rRNA 6. 3 bases code for amino acid (triplet coding = codon).

Transcription, RNA polymerase splits DNA and makes a copy of mRNA then translation in which proteins are made by tRNA bringing amino acids as described by the mRNA in ribosome. Genes produce a polypeptide (protein) and a Genome makes up all the DNA in a cell. The human genome project mapped out the human genome and was completed in 2003 by the international research team. Genes are defined because they make proteins (vestigial genes cannot anymore)

• 1. RNA polymerase starts cutting at the promoter region on the sense strand of DNA (sense strand=the one side that is copied, other side is anti-sense)
• 2. Next, mRNA nucleotides find their appropriate complementary pair and are bound together using RNA polymerase complex (Uracil takes place of thymine) this occurs in the 5'->3' direction.
• 3. When a stop signal/terminator region (nucleotide sequence) is reached transcription stops.
• 4. In eukaryotes ONLY DNA is spliced/processed in this it is given a 5' cap (has a modified G which helps mRNA bind to ribosomes) and a Poly-A tail (strings of A which prevents degredation), RNA spliceosomes remove intron section and joins exons.
• 4. Next, single strand mRNA moves to ribosomes out in the cytoplasm

• The codon is the "code" that is made up of three bases (nucleotides) that codes for one amino acid on mRNA. The three main points are:
• 1. It is redundant- there is more than one code for amino acids (20 total A.A.) and there are four special codes- AUG (methionine which is start) and the 3 stop codes (are actions no A.A)
• 2.The codon is continuous- there are no spaces/punctuation in the code (an insertion or deletion would shift the code forwards or backwards messing up all the start and stop signals and ruining the code)
• 3. The codon is universal- Amino acids and proteins are the same for all organisms (You can eat A.A. from other things and use it to build your body)

• 1. Two ribosomes (made of rRNA) form two subunits (top/bottom bun) and attaches to mRNA
• 2. Initiator codon (AUG) turns on the protein synthesis
• 3. Each tRNA has a specific amino acid that it can hold on one side. The other side of the tRNA has an ANTI-CODON side that matches with the mRNA CODON
• 4. Amino acids get brought by tRNA to the A-site on the ribosome, the ribsome then slides down the mRNA so that the A-site becomes the new P-site. Amino acids are joined (using energy) by peptide bonds, according to code on the mRNA which starts forming a chain.\
• 5. To stop the chain forming a teminator codon (UAA,UAG or UGA) turns the translation synthesis off.

tRNA has a cloverleaf type 3-D structure that includes two important regions. 1. the 3' end attaches to a specific amino acid and then 2. the anticodon (2nd loop) which are exposed bases (nucleotides) that compliment the codon on mRNA. tRNA uses energy to pick up its amino acid. There are fewer than 64 total tRNA molecules, one for each amino acid and each codon. Ex. Tryptophan (A.A.) is carried by the tRNA with the UGG codon.

There are 20 different amino acids. Each one has a amino group (ARM), hydrogen atom, carboxyl group (ARM), central carbon and R group. There differences are due to their R groups and how they interact with the enviroment.

It is a theory that states genetic information only flows in 1 direction DNA -transcription(in nucleus)-> RNA -translation(in cytoplasm)-> protein(tRNA delivers A.A.) or RNA->protein)