NUCLEIC ACIDS AND PROTEIN SYNTHESIS. QUESTION 1. DNA. QUESTION 2. To store and transmit the genetic information that tells cells which proteins to make and when to make them. QUESTION 3. They form the structural units of cells and help control chemical processes within cells.
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To store and transmit the genetic information that tells cells which proteins to make and when to make them
They form the structural units of cells and help control chemical processes within cells.
The nucleotide. They are arranged in two long complementary chains.
A nitrogen-containing base, a sugar molecule called deoxyribose, and a phosphate group.
Adenine, abbreviated A
Guanine, abbreviated G
Cytosine, abbreviated C
Thymine, abbreviated T
Purines: Adenine and Guanine. Have two carbon rings
Pyrimidines: Cytosine and Thymine. Have a single carbon ring.
James Watson and Francis Crick in 1953.
The alternating deoxyribose sugar and phosphate molecules which are linked together by covalent bonds.
Two Views of the DNA backbone
The backbone is shown in yellow in this diagram. Notice that there are two backbones, one for each of the strands of nucleotides
They are covalently bonded to the deoxyribose sugar and then to the complementary nitrogen base in the other strand by hydrogen bonds.
Guanine from one nucleotide strand will always pair with cytosine from the other strand using three hydrogen bonds and adenine from one strand will pair with thymine from the other using two hydrogen bonds.
The process of copying DNA in a cell.
The two nucleotide chains separate by unwinding, and each chain serves as a template for a new nucleotide chain.
Red color is the new strand.Blue color is the original strand.
The point at which the two nucleotide chains separate
They separate the two complementary chains of nucleotides in the DNA molecule by moving along the molecule and breaking the hydrogen bonds between the complementary bases.
Bind to a separated chain of nucleotides, move along the separated chain and assemble a new chain using free nucleotides in the nucleus and the separated chain as a template.
The complementary nature of the two chains of nucleotides that make up the DNA molecule. If the original chain of nucleotides has a nitrogen base sequence of CATCAA the other assembled beside it would be GTAGTT.
Red color is the new strand,blue color the original strand. The red box is showing the complementary bases mentioned in the last slide.
It proceeds in opposite directions on each original strand. Replication begins simultaneously at many points along one original strand and at just one point on the other original strand.
Direction of Replication
Two new exact copies of the original DNA molecule. Each molecule has one original strand of nucleotides and a copied complementary strand.
Original DNA strands opened up
Two new molecules of DNA each with one old and one new strand
Replication is very accurate, only about one error in every 10,000 paired nucleotides.
Enzymes that proofread DNA and repair errors
A variety of agents, including chemicals, ultraviolet radiation and other forms of radiation.
The transfer of genetic information from the DNA in the nucleus to the site of protein synthesis on the ribosomes.
The sugar in RNA is ribose in DNA it’s deoxyribose. RNA has the nitrogen base Uracil (U) instead of Thymine as in DNA
Messenger RNA (mRNA) - carries genetic information from DNA in the nucleus to the ribosome.
Transfer RNA (tRNA) -each binds to a particular amino acid and brings it to the ribosome
The process by which genetic information is copied from DNA to mRNA
RNA polymerase. Makes RNA copies of specific sequences of DNA
A specific region of DNA that marks the beginning of that part of the DNA chain that will be transcribed.
The DNA unwinds and the RNA polymerase binds at a particular site on the DNA. The initial binding site is called the "promoter region".
That portion of the DNA molecule (only one of the two nucleotide strands) that is copied by RNA polymerase.
The nitrogen base sequence on the template chain and complementary base pairing by RNA polymerase.
Nitrogen base sequence on DNA
Complementary base pairing on mRNA
The termination signal - a specific sequence of nucleotides on the template that marks the end of a gene.
The RNA polymerase
Transcripts - different types of RNA molecules including mRNA, tRNA, and rRNA. The mRNA may have further processing occur. Noncoding regions called introns are removed and the remaining coding regions called exons are spliced together.
Amino Acids. Twenty different kinds.
It’s three dimensional structure, which is determined by its amino-acid sequence.
Levels of protein structure that determine the function of a protein.
Triplets of nucleotides in mRNA that determine the sequence of amino acids in proteins
A sequence of three nucleotides on a mRNA molecule. It codes for one specific amino acid. There are 64 codons.
The codon that causes a ribosome to start translating an mRNA molecule into a protein. It is always the nitrogen base sequence AUG. The codons that cause translation to cease. There are three.
That all organisms are related.
The process of assembling proteins from information encoded in mRNA. It begins when a mRNA molecule leaves the nucleus and migrates to a ribosome.
A sequence of three nitrogen bases on the tRNA molecule that are complementary to a codon on a mRNA molecule. It actually pairs with the codon on mRNA.
The complementary base pairing between codons on mRNA and anticodons on tRNA
Composed of rRNA and proteins. Make up 2 subunits. Found free in the cytosol and attached to the endoplasmic reticulum.
Ribosomes found free in the cytosol produces proteins used inside the cell. Those attached to the E.R. produce proteins used in the cell membrane or outside of the cell.
mRNA holding site
One site holds a mRNA transcript so its codons can be read by tRNA. The other two sites (P and A sites) hold tRNA molecules so that their attached amino acids can be bonded to the growing chain.
mRNA binding site
Methionine. Only initially. It may be removed later.
A stop codon.
Yes. Many can. They may form a chain known as a polysome.
Review of Protein Synthesis: Transcription and Translation