Take out your HW: Transcription wkstHomework due tomorrow:

Protein Synthesis wkst

Somewhere on a sheet of scratch paper or in Somewhere on a sheet of scratch paper or in your notes, TRANSCRIBE the following DNA your notes, TRANSCRIBE the following DNA sequence into mRNA:sequence into mRNA:

TAC AGT CCA GCG ATA ATTTAC AGT CCA GCG ATA ATTAUGAUG UCAUCA GGUGGU CGCCGC UAUUAU UAAUAA

TRANSCRIPTION & TRANSLATION: From DNA to Protein Chapter 11, Section 2

Think back to the information contained in your Think back to the information contained in your homework assignment:homework assignment:

1.1. What is produced when the process of What is produced when the process of transcriptiontranscription is complete? is complete?

2.2. What are 2 differences that were listed/shown What are 2 differences that were listed/shown between DNA and RNA?between DNA and RNA?

Genes & Proteins

• What is the function of a gene?

– codes for traits, inherited from parents

• Genes code for specific proteins– Proteins make up muscles, hair, tissues,

enzymes, & pigments

• Protein Synthesis = reading the DNA, forming RNA, using RNA to make the protein (DNA RNA Protein)– Occurs through the processes of

transcription and translation

RNA

• RNA is a nucleic acid (like DNA)

• Differs in structure from DNA:

DNA RNA

Number of Strands 2 1

Nucleotide Sugar Deoxyribose Ribose

Nitrogenous Base Pairs

Thymine(T), Adenine(A), Guanine (G), Cytosine (C)

Uracil (U), Adenine(A),

Guanine (G),

Cytosine (C)

Focusing on RNA

• There are 3 different types of RNA that you will need to know:– mRNA– rRNA– tRNA

Types of RNA• 1. Messenger RNA

(mRNA) – Carries genetic

“message” from DNA to the ribosomes in the cytosol

– “Read” by ribosomes to make proteins

– Contain codons

• 2. Ribosomal RNA (rRNA)– Part of the structure of ribosomes– Ribosome = protein and rRNA

• 3. Transfer RNA• Transfers amino acids to the ribosome to make

protein

Transcription: Getting the message out of the nucleus

• Transcription = enzymes make RNA by copying a portion of DNA in the nucleus

• If a DNA sequence is AATCCGGA, what is the complimentary RNA sequence?

• UUAGGCCU• The mRNA that gets sequenced is sent out of the

nucleus to help make protein

Genetic Code• Sequence of Nitrogenous Bases codes for a

specific Amino Acid that is connected to other amino acids to make a Protein

• Codon = the nitrogenous bases of 3 adjacent nucleotides in mRNA that code for– Start Signal (starts the protein making process)– 1 of 20 different amino acids (parts of a protein)– Stop Signal (stops the protein making process)

• Codons are like 3-letter words– Words contain meaning to us: CAT = – Codons contain meaning in the form of an amino acid CAU = Histidine

•An amino acid can be coded for by more than one codon•20 amino acids combine in different combinations to make various proteins

Translation: Going from the language of bases (AUGC) to proteins

• Translation = using the mRNA to make protein, reading the codons– Takes place at the ribosomes

• The mRNA is “read” in between the 2 sub-units of the ribosome

• tRNA carries the amino acid coded for by the mRNA codons and has an anticodon that pairs up with the mRNA codon– Codon (mRNA) and anticodon (tRNA) follow RNA

base-pairing rules

• Amino acids form peptide bonds between each other to create a long chain of amino acids

Transcription

Amino acids to protein

• Amino acid chains start to fold creating 3-dimensional structures

• Several of these 3-D structures combine to form a functional protein

• These proteins then carry out cellular functions