What organic molecule is DNA?
-
Upload
charity-stanton -
Category
Documents
-
view
18 -
download
0
description
Transcript of What organic molecule is DNA?
Nucleic Acid
• An organic molecule containing hydrogen, oxygen, nitrogen, carbon, and phosphorus
• Examples:• DNA• ????RNA
What differences do you see between DNA and RNA?
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
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.
• http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf
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
• 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.
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 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 4:• The ribosomes helps form a peptide bond
between the first and second amino acid.
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.