What organic molecule is DNA?

• Nucleic Acid

Nucleic Acid

• An organic molecule containing hydrogen, oxygen, nitrogen, carbon, and phosphorus

• Examples:• DNA• ????RNA

What differences do you see between DNA and RNA?

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Differences between RNA and DNA

• 1. Sugar in RNA is ribose instead of deoxyribose.

• 2. RNA is generally single stranded, not double stranded.

• 3. RNA contains uracil instead of thymine

RNAIs a disposable copy of a segment of DNA

FUNCTION:Main function is protein synthesis.

Types of RNA

Messenger RNA (mRNA) the RNA molecule that carries the copies of

instructions for assembling amino acids.Ribosomal RNA (rRNA) the RNA that combined with many other proteins,

make up the ribosomes that assemble proteinsTransfer RNA (tRNA) carries amino acids to the ribosomes and matches

them to the coded mRNA

What are the 3 differences between DNA and RNA?

• RNA is a single strand, DNA double

• RNA has ribose sugar in it, DNA has deoxyribose sugar

• RNA has the nitrogenous base uracil,• DNA has thymine

How is RNA made?

• By process called transcription.

• Transcription – process in which segments of DNA serve as templates to produce complementary RNA molecules.

Where transcription occurs

• In prokaryotes it occurs in the cytoplasm

• In eukaryotes it occurs in the nucleus.

Transcription1. The enzyme RNA polymerase attaches to

DNA strand2. RNA polymerase separates the DNA strands3. RNA polymerase uses one strand to assemble

nucleotides into RNA

Where does transcription start?

• The enzyme RNA polymerase binds to special regions on the DNA called promoters.

• Promoters – specific base sequences on the DNA that act as signals to show RNA polymerase where to begin transcription

RNA editing

• Before the RNA can move on to make proteins it must be “edited.”

• Pieces of the RNA are cut out. The pieces that are cut out are called introns.

• The pieces remaining in the RNA are called exons.

What is transcription?

• The process of making RNA from a strand of DNA

• http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

How is RNA used to make proteins?

• The nitrogenous bases act as a code for making proteins

Genetic code – The language consisting of 4 letters (A, C, G, and U) that gives the instructions for building amino acids

The code is read three “letters” at a time, so each “word” is three bases long

codon – the three letter word that corresponds to a single amino acid

• There are 64 different 3 letter combinations of the 4 bases A,T,C and G (so 64 codons)

• But there are only 20 amino acids. Why aren’t there 64 amino acids?

Most amino acids can have more than one codon that codes for them ex. UUA, UUG, CUU, CUC, CUA and CUG all code for the amino acid tryptophan

• There are also codons that that code for the beginning and ending of protein synthesis.

“start” codons – where the reading of the mRNA begins. (The amino acid methionine is a start codon)

“stop” codon- where the reading ends.

*Amino acids bond together to make a polypeptide chain.

**Polypeptides- long chains of amino acids joined together.

• The amino acids in a polypeptide, and the order in which they are joined, determine the properties of the different proteins.

What do codons “code” for?

• Amino Acids

Translation

• After transcription the mRNA strand is ready to start the process of protein synthesis.

• What part of the cell makes proteins?

Ribosomes Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains.

Translation- The decoding of an mRNA message into a protein

(Ribosomes translate the code)

Translation Translation is carried out by ribosomes in the cytoplasm. Step 1: A ribosome attaches to mRNA

Translation

• Step 2: As each codon passes through ribosome, tRNAs bring the proper amino acid to the ribosome.

tRNA• Each tRNA molecule carries just one kind of

amino acid.• Each tRNA has 3 unpaired bases called an

anticodon.• Each tRNA anticodon is complementary to one

mRNA codon

Translation

• Step 3: • The ribosomes attach the amino acids to

the growing chain.

Translation

• Step 4:• The ribosomes helps form a peptide bond

between the first and second amino acid.

Translation

• Step 5:• The ribosome then moves to the next codon

Translation

• Step 6:• Polypeptide chain continues to grow until

ribosome reaches the stop codon

http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/translation.swf

How are proteins related to traits?

Many proteins are enzymes, which catalyze and regulate chemical reactions.

Proteins regulate patterns of growth, patterns of development in humans, and they build or operate different components of a living cell.

The Central Dogma

• Information is transferred from DNA to RNA protein