DNA Structure Replication Functions (Stores and provides copies of genetic material- genes) –...

DNA

• Structure• Replication• Functions (Stores and provides copies of

genetic material- genes)– Blueprint (genes) for Protein Synthesis (Enzymes

and cell building blocks)

Francis Crick

RNA (Ribonucleic Acid)

• Why do we need RNA?• Why can’t DNA directly make proteins?• Where is DNA located? Can it leave? Why

does it stay there?• Where are proteins made?• Temporary copies of parts of the blueprint

• Ribonucleic acid (RNA) – carries DNA’s instructions – acts as an link between DNA in the nucleus and

protein synthesis in the cytoplasm.– plays several different roles in protein synthesis.

Similarities DNA and RNA

• Both are nucleic acids• Both are made up of nucleotides (sugar, base,

phosphate)

DNA versus RNA

DNA versus RNA

Differences between DNA and RNA

DNA RNA

Genes expression is through protein synthesis

Types of RNA

1. Messenger RNA (mRNA) -formed in nucleus from DNA template -Carries copies of instructions for protein synthesis to the ribosomes in cytoplasm (nuclear membrane pores)

2. Ribosomal RNA (rRNA)-along with some proteins make up ribosomes (cytoplasm)

3. Transfer RNA (tRNA)- transport amino acids to ribosomes (cytoplasm)

All types of RNA are formed in the nucleus.

Transfer RNA

Transcription

• Messenger RNA (mRNA) is made from DNA– DNA is template– Complementary RNA is produced– Nucleus (eukaryotic cells)– RNA polymerase (unwinds the DNA and adds

nucleotides to form RNA)– Uracil is paired with adenine

Transcription steps

• RNA polymerase binds to promoter (“start”) region of gene

• RNA polymerase unwinds and separates the two strands of DNA

• RNA polymerase adds complementary RNA nucleotides

• RNA polymerase reaches a sequence of nucleotides on the gene that signals “stop”

• RNA polymerase detaches

Transcription

TranscriptionTemplate versus Nonsense Strand

• http://www.dnai.org/a/index.html

• What does this remind you of?

• Practice creating complementary mRNA

Post-transcription

• Pre-mRNA molecule produced and undergoes processing and editing. – Introns – cut out and

discarded– Exons – remaining pieces

spliced back together to form mRNA

• mRNA travels through nuclear membrane pore into cytoplasm

Transcription leads to Translation

Exon – expressed as a proteinIntron – DNA that isn’t expressed (inhibited)