a&p lab DNA, RNA

Deoxyribonucleic acid, or DNA is a large organic molecule composed of two chains of

nucleic acids.

Each nucleic acid molecule is composed of many individual molecules called

nucleotides

Nucleotides are composed of three subunits:

a phosphate group, deoxyribose (five-carbon) sugar, and one of four nitrogenous bases.

Purines are composed of

two nitrogen containing rings and one of two nitrogenous bases called adenine and guanine.

pyrimidines have one

nitrogen-containing ring and one of two nitrogenous bases called thymine and cytosine.

Nucleotides are linked by

covalent bonds between their sugar-phosphate groups to form the nucleic acid strand.

two nucleic acid strands

make up a DNA molecule, bound to each other by hydrogen bonds between the purine and pyrimidine bases.

thymine (T) always pairs with

adenine (A),

guanine (G) always pairs

with cytosine (C)

DNA replication is a necessary process when a cell needs to reproduce. Replication begins with an enzyme,

DNA helicase

the enzyme used to reattach new nucleotides after the DNA has been unzipped

DNA polymerase

why replication is considered “semi-conservative”

Replication is considered semi-conservative because each strand is half of the old nucleic acid strand and the other half is a new nucleic acid strand. 

protein

a large molecule that consists of one or more polypeptide molecules that are bound together to form a single functional unit. Proteins are required by all living organisms for both structure and function of tissues and organs

polypeptide

a molecule that is a string of bound amino acids. Polypeptides are made by taking the information stored in DNA through the two-step process of protein synthesis.

. The two steps of protein synthesis are

trascription and translation

Transcription takes the information coded in DNA and

converts it to a strand of mRNA in the nucleus

Translation then takes the strand of mRNA

and uses it as a template to build a protein.

Mutations that occur during

replication impact protein synthesis

Mutations can be

silent, beneficial, or harmful.

mutation is a mistake in

base pairing during replication

silent mutations cause

no change in the amino acids during protein synthesis.

benificail mutations create

genetic varibility

harmful mutations cause proteins to

not function normally

DNA

The information to construct polypeptides in DNA is contained in structural genes. A structural gene is a particular segment of DNA that codes for a single polypeptide or a portion of a polypeptide. Remember, each three-letter combination of nucleotides in DNA is called a triplet

RNA

a single strand of nucleic acids used as a messenger to carry the information from DNA to the site of protein synthesis. It also controls the process of protein synthesis. RNA differs structurally from DNA by containing ribose sugar in its sugar-phosphate backbone, and containing uracil instead of thymine.

Messenger RNA

is a single strand of RNA that is a complementary copy of the gene on DNA. mRNA dictates the primary structure of the polypeptide by directing the placement of individual amino acids. Each three-letter combination in mRNA is called a codon, and is complementary to a DNA triplet.

Transfer RNA

binds with a particular amino acid and transports that amino acid to the site of protein synthesis. There are two active ends on tRNA. One end of the molecule has an “anticodon,” which is a complementary copy of a codon on the mRNA. The other end of the tRNA molecule has a region which temporarily binds it to the specific amino acid it transports.

Ribosomal RNA

Also known as a ribosome, rRNA is a large molecule consisting of large and small subunits. rRNA attaches to an mRNA molecule and aligns the anticodon on tRNA with an appropriate codon on mRNA. Adjacent amino acids on tRNA are then joined together to form a growing polypeptide

Amino Acids

the structural units, or building blocks, of polypeptides and proteins. There are twenty amino acids used to build polypeptides. Eleven of those amino acids are synthesized by the body and are called non-essential. Nine amino acids are called essential, because they cannot be synthesized by the body and must come from a balanced diet.

transccription

takes place in the nucleus.

Each three-letter combination in mRNA is called a

codon

During, the nucleotides in DNA are used to create complemetary sequence of nucleotides in

mRNA

The nucleotides used to construct the mRNA should contain

ribose sugar and uracil instead of thymine

The second step of protein synthesis is

translation and takes place in the cytoplasm of the cell

Each codon in mRNA codes for the placement of a single and specific

amino acid

The anticodon is a

complementary copy of the codon on mRNA, and an exact copy of the triplet on DNA, except that uracil replaces thymine.

During the second step of protein synthesis, nucleotide in mRNA are used to create the primary structure of a

polypeptide

What amino acids would be coded for by the mRNA and carried to the site of protein synthesis by tRNA?

look at the complementary mRNA, then use the amino acid reference chart to figgure it out

What type of bond functions to hold adjacent amino acids together?

peptide

the final product of translation

polypeptide

tRNA only carriers the

Amino acid

The amino acid needed is determined by the

Codon

Enzymes from the ribosome then form a

Peptide bond between the two adjacent amino acids