DNA and RNA Replication Transcription and Translation Griffiths

DNA and RNA Replication, Transcription and Translation

Griffith’s Experiment

Avery’s Experiment

Hershey-Chase Experiment

A typical Bacteriophage –

Bacteriophage infection cycle

The 3 Key Roles of DNA Storing genetic information. Copying genetic information. Transmitting genetic information.

DNA is 2 long polymers of covalently bonded nucleotides wound around each other and attracted to each other by hydrogen bonds.

The 4 bases are the Purines (adenine and guanine) and the Pyrimidines (Thymine and Cytosine)

Guanine bonds with Cytosine. The three bonds are hydrogen bonds!

Adenine bonds with Thymine. Here there are two hydrogen bonds.

A diagram of DNA

The three components of DNA are the phosphate group, sugar and a nitrogen containing base

Chargaff's rules state that DNA from any cell of all organisms should have a 1: 1 ratio of guanine to cytosine and adenine to thymine.

Rosalind Franklin and her X-Ray diffraction picture of DNA

Watson and Crick – 1953. DNA is 2 chains wound around each other, each chain going in opposite directions. The two chains are held together with hydrogen bonds.

Prokaryote vs. Eukaryote DNA.

Eukaryotic chromosomes contain DNA wrapped around proteins called histones. Each package of 8 histones is called a nucleosome

The strands are complementary in the sense that each strand can be used to make the other half by the sequence of base pairing.

Prokaryote DNA replication

Eukaryotes – DNA replication occurs at many places and proceeds in two directions until each chromosome is copied.

DNA Replication is carried out by a series of enzymes. DNA Polymerase joins individual nucleotides to produce a new DNA molecule

Gene – coded DNA instruction for the production of a protein.

Protein Synthesis an overview http: //www. youtube. com/watch? v=su. N-s. V 0 c. T 6 c

The three main types of RNA

DNA and RNA nucleotides are very similar in structure.

A central tenet of biology describes the two-step process, transcription and translation, by which the information in genes flows into proteins: DNA → RNA → protein.

Because there is no nucleus to separate the processes of transcription and translation, when bacterial genes are transcribed, their transcripts can immediately be translated

Transcription and translation are spatially and temporally separated in eukaryotic cells; that is, transcription occurs in the nucleus to produce a pre-m. RNA molecule

Transcription – the production of RNA molecules from parts of the DNA molecule

Promoters are regions of DNA that tell RNA polymerase where to start. Similar signals tell RNA polymerase to stop

. The pre-m. RNA is processed in the nucleus to remove the introns and splice the exons together into a translatable m. RNA. That m. RNA exits the nucleus and is translated in the cytoplasm.

The steps of pre-m. RNA splicing (intron removal)

The basic building block of a protein is the amino acid.

There are 20 amino acids; each one differs in its R group. Below are four amino acids showing the differences in R groups.

Amino acids are joined together in proteins by peptide bonds.

The language of RNA to the language of protein: The genetic code is a triplet code in which three nucleotides in RNA specify one amino acid in protein.

Translation is the process of decoding an m. RNA message into a polypeptide chain. It all starts with m. RNA

Ribosomes, the organelles on which the m. RNA is translated, consist of two subunits, each of which contains r. RNA and ribosomal proteins.

t. RNA’s bring amino acids to the ribosomes during translation to be assembled into polypeptide chains.

Adding an Amino Acid to t. RNA The correct amino acid is added with the help of an enzyme.

Initiation of Translation

Translation begins when an m. RNA attaches to a ribosome. Each codon is matched by an anticodon with t. RNA. The t. RNA brings in the correct amino acid for that codon.

Elongation of the polypeptide chain begins by the appropriate t. RNA binding to the codon in the A site of the ribosome

At a stop codon, a release factor reads the triplet, and polypeptide synthesis ends

Several ribosomes can translate an m. RNA at the same time, forming what is called a polysome.

http: //www. youtube. com/watch? v=5 i. S 4 CRPPDus

genetics, a mutation is a change of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal genetic element.

A frameshift mutation (also called a framing error or a reading frame shift) is a genetic mutation caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that is not divisible by three.

Cystic Fibrosis is an example of a frame shift mutation.

Shaking Vest treatment for Cystic Fibrosis. The vest helps to loosen the thick mucus and allow some of it to be expelled from the lungs.

Chromosomal Mutations This involves changes in the number or structure of chromosomes.

Down syndrome (DS) or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21.

Polyploidy in Plants. Certain fruits have been developed that have are triploid, (3 N) or tetraploid (4 N). The extra chromosomes cause the fruit to be larger and stronger than the normal 2 N or diploid plant.

Operon An operon is a group of genes that operate together

Lac genes in E. coli. When lactose is not present, the repressor binds to the operator region preventing transcription.

Eukaryotic Gene Regulation The TATA box helps to position RNA polymerase by marking a point just before transcription. Promoters are found just before the TATA box.

Transcription factors – a protein that binds to a specific DNA sequence, controlling the transcription of m. RNA. They can either activate or block RNA polymerase.

RNA interference – small RNA molecules connected to proteins form a Silencing complex. This complex destroys any m. RNA it meets with that has a complementary code.

Hox genes Control the differentiation of cells and tissues in the embryo.

Homeotic genes cause the development of specific structures in plants and animals. i. e. they are involved in determining where , when and how body segments develop in flies.

Pax 6 gene from a mouse inserted onto a fruit fly causes eyes to grow in unusual places.