DNA "The Blueprint of Life"

DNA stands for... DeoxyriboNucleic Acid

● established by James Watson and Francis Crick ● Shape of a double helix

● codes for your genes (traits) ● made of repeating subunits called nucleotides

What is the relationship between GENES and DNA?

What is a gene? A section of DNA, with many bases that codes for a protein Results in a TRAIT

What is a nucleotide? Has three parts: PHOSPHATE DEOXYRIBOSE (sugar) BASE (A,T,G,C) Phosphate Sugar Base

There are two types of Bases Purines (double-ring) – Adenine and Guanine Pyrimidines (single-ring) – Thymine, Cytosine, and Uracil

Base-Pair Rule Adenine Thymine Guanine Cytosine The sides of the DNA ladder are phosphate & sugar held together by hydrogen bonds

Base Pair Rule One side: A T A T C A T G C G G G Other side:

How the Code Works The combination of A,T,G,C determines what traits you might have..... C A T C A T = purple hair T A C T A C = yellow hair

Think of the bases of DNA like letters. Letters form words.... Words form sentences.... *endless combinations

Let's Review What We Know About DNA 1. DNA stands for: De _____ ribo ______ acid 2. What is the shape of DNA? ______________ 3. Who established the structure of DNA? ____________ and ______________ 4. Adenine always pairs with _______________ 5. The sides of the DNA ladder are deoxyribose and _______________

6. Guanine always pairs with _____________ 7. What is the complementary sequence: C A T T A G 8. The two sides of DNA are held together by _______ bonds. 9. DNA is composed of repeating subunits called ______________________ 10. What are the 4 bases that make up the rungs of the DNA ladder? ____________________

RNA RNA = ribonucleic acid. RNA is similar to DNA except: 1. typically has one strand instead of two strands (can be double-stranded – viruses) 2. has uracil instead of thymine 3. has ribose instead of deoxyribose

RNA

Central Dogma There are 3 main processes that define the Central Dogma. 1. Replication – DNA is copied 2. Transcription - RNA is made from DNA 3. Translation - Proteins are made from the message on the RNA

There are two other parts of the central dogma, which are important for viruses Reverse transcription – The process of making a double stranded DNA molecule from a single stranded RNA template through the enzyme, reverse transcriptase. RNA replication - RNA-dependent RNA polymerase is an essential protein encoded in the genomes of all RNA-containing viruses with no DNA stage that have anti-sense RNA. It catalyses (makes happen) synthesis of the RNA strand complementary to a given RNA template.

Central Dogma

DNA REPLICATION the process by which DNA makes a copy of itself (cell division) SEMI-CONSERVATIVE - half of the old strand is saved

DNA Synthesis The synthesis of new DNA strands complementary to both strands of the parental molecule posed an important problem to understanding the biochemistry of DNA replication. Since the two strands of double-helical DNA run in opposite (antiparallel) directions, continuous synthesis of two new strands at the replication fork would require that one strand be synthesized in the 5′ to 3′ direction while the other is synthesized in the opposite (3′ to 5′) direction. DNA is replicated using several enzymes (proteins that do stuff – names usually end in –ase).

DNA 5’ to 3’

DNA Replication 1. DNA helicase unzips the two strands of DNA 2. DNA polymerase III attaches free DNA nucelotides together - But DNA polymerase assembles DNA only in the 5′ to 3′ direction. The new 5’ to 3’ strand is known as the leading strand. How, then, can the other strand of DNA be synthesized? 3. RNA primase attaches a RNA primer to the lagging strand (3’ to 5’). 4. DNA polymerase III can then attach to the lagging strand and copy a short fragment of DNA (Okazaki fragments) 5. The RNA primers are then replaced by DNA by DNA polymerase I. 6. The fragments of DNA are joined together by DNA ligase 7. There are now two complete new strands of DNA

DNA Replication

HOW PROTEINS ARE MADE BY THE CELL What is a protein and why is it important for living systems?

Your body is made up of trillions of cells, of all different kinds: muscle cells, brain cells, blood cells, and more. Inside those cells, proteins are allowing your body to do what it does: break down food to power your muscles, send signals through your brain that control the body, and transport nutrients through your blood. Proteins are building blocks, they make up all that you are.

How Proteins are made by the cell: There are 4 kinds of RNA. 3 of these are used in protein synthesis 1. Messenger RNA (mRNA) – carries an RNA version of a gene to a ribosome in order to make a protein.

RNA carries the "message" to the ribosomes, where proteins are made

4 Types of RNA 2. Transfer RNA (tRNA) – carries amino acids to a ribosome to build a protein. On one end, it has a segment called an anticodon. Each tRNA has an anticodon that matches a specific codon on the mRNA. On the opposite end of the tRNA is an amino acid. When tRNA is made, a specific amino acid is attached depending on what anticodon it has.

tRNA

4 Kinds of RNA 3. Ribosomal RNA (rRNA) forms part of the ribosome. Molecules of rRNA are synthesized in the nucleolus, which contains the genes that encode rRNA. The encoded rRNAs are either large or small. In the nucleolus, the large and small rRNAs combine with ribosomal proteins to form the large and small subunits of the ribosome (e.g., 50S and 30S, respectively, in bacteria). Ribosomal proteins are synthesized in the cytoplasm and transported to the nucleus to be assembled into subunits in the nucleolus. The subunits are then returned to the cytoplasm for final assemblynucleolusgenescytoplasm

rRNA cont In eukaryotes, anywhere from 50 to 5,000 sets of rRNA genes and as many as 10 million ribosomes may be present in a single cell. In contrast, prokaryotes generally have fewer sets of rRNA genes and ribosomes per cell. For example, in the bacterium Escherichia coli, seven copies of the rRNA genes synthesize about 15,000 ribosomes per cell. Differences in rRNA are used to determine evolutionary relationships between bacteria, archaea, and eukaryotes.eukaryotes prokaryotesEscherichia coli

Ribosome Subunits

4 types of RNA 4. siRNA – Small interfering RNA – plays a large role in gene expression

Transcription 1. One of the strands of DNA is used as a template to create a strand of mRNA 2. Requires the enzyme RNA polymerase 3. Transcription always starts at a region called the promoter.

4. Introns are segments of DNA that do not contain genes. Exons are segments that contain genes. 5. Each 3 bases on mRNA is a codon, it corresponds to an amino acid (see codon chart)

Translation 1. Takes the message on mRNA and converts it into an amino acid chain 2. Individual amino acids will join to form a protein. Shapes and composition of protein determine its functionality (hair, enzymes, skin, muscles etc)

Label the image....

DNA amino acids tRNAprotein anticodon codonmRNA ribosome

Steps in Translation 1. The ribosome binds to mRNA at a specific area. 2. The ribosome starts matching tRNA anticodon sequences to the mRNA codon sequence. 3. Each time a new tRNA comes into the ribosome, the amino acid that it was carrying gets added to the elongating polypeptide chain. 4. The ribosome continues until it hits a stop sequence, then it releases the polypeptide and the mRNA. 5. The polypeptide forms into its native shape and starts acting as a functional protein in the cell.

The steps in translation