Transcription and Translation: Protein

synthesis

What we already know…

DNA encodes the information to make proteins

DNA cannot leave the nucleusProtein synthesis occurs outside

of the nucleus, on a ribosome

DNA encodes the information to make RNA.........and RNA molecules function together to make protein

                                                                                                                                                     

How does it happen?

Structure of RNA

Single stranded Built of nucleotide

5-Carbon Sugar = ribose sugar

Phosphate Group Nitrogenous base:

Adenine, Uracil, Guanine, and Cytosine

NO THYMINE IN RNA

3 Types of RNA

Messenger RNA (mRNA) DNA cannot leave the nucleus so mRNA carries

information to ribosomes for protein production Transfer RNA (tRNA)

brings specified amino acids from the cytoplasm to the ribosomes where the protein chain is made

Ribosomal RNA (rRNA) the ribosome and protein

3 Types of RNA

Transcription

DNA mRNA

Transcription Process by which a molecule of DNA is

copied into a complementary strand of mRNA

Occurs in the nucleus

How does it happen?

1. DNA unzips and exposes one gene as a template

2. A complementary strand of RNA is formedo A – Uo G – C

3. mRNA strand exits the nucleus and moves into the cytoplasm

4. The two strands of DNA re-attach and recoil

Transcription movie http://learn.genetics.utah.edu/units/basics/transcribe/

Try it yourself …

Transcribe Strand 1 of the DNA molecules below 1 - T T A G G A C T G C A A T T G

2 - A A T C C T G A C G T T A A C

1 - C A G T C C G A A C G T T T A

2 - G T C A G G C T T G C A A A T

Answers

A A U C C U G A C G U U A A C

G U C A G G C U U G C A A A U

Translation

mRNA protein

Translation

Process by which the mRNA is “read” and a protein is created from amino acids

Occurs at the ribosome

Steps of Translation

1. mRNA moves to the ribosomes

2. the rRNA on the ribosome binds to the mRNA and starts “reading” codons.

Codons – 3 letter code that specifies a particular amino acid.

start codon = AUG stop codon = UAA, UAG, or UGA

3. AUG binds to the first anticodon of tRNA

4. tRNA transfer amino acids until the rRNA reaches a stop codon on the mRNA

5. the ribosome releases the protein and the mRNA protein to be used by the cell mRNA to synthesize more protein molecules

Movie of Translation

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter15/animations.html#

mRNA-amino acid chart

Try it yourself!

DNA template strand

DNA: TACGATCGAACGTAT mRNA codon: tRNA anticodon: Amino Acids :

mRNA Activity Here is a strand of mRNA. Arrange your tRNA

molecules to determine the sequence of Amino Acids that this mRNA codes for. AUG CUA UCA UCA UAU GGA GUA ACU

AGU UUU CGC AUU CCG CAU ACA CGG GUU

CUC CCU CAC AGG UGG GGG UGU CUA ACC

UUA CCC GCA UCG UAA

Mutations

Mutations lead to mistakes in the proteins being made.

Mutations can happen during DNA replication and change the “blueprint of the cell”

Or

During transcription or translation so a wrong protein or no protein is made

Types of mutation

Point mutation- one nucleotide changes Frameshift mutation- an insertion or deletion

of a nucleotide that changes all codons after that point

Chromosomal mutation- all of the genes on a certain chromosome can be affected. Or change the location of genes on the chromosome.

Transcription

The information in the DNA not only contains amino acid (aa) sequences, it also has “junk” DNA. Exon: RNA that codes for a.a. Intron: junk RNA/DNA

Enzymes in the nucleus snip out the exon and the RNA molecule is protected and sent outside of the cell.

mRNA splicing

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter15/animations.html