DNA: A Code for Life

DNA and Protein Synthesis

- DNA (TRANSCRIPTION)-mRNA- (TRANSLATION) -PROTEIN

Mutations

--Additions and Deletions are known as frameshift mutations because when they occur everything in the sequence from then on is messed up! → These are much worse because now every amino acid will be wrong because every codon is wrong. ---Substitutions are known as point mutations because only a single nucleotide is changed.

Base-Pairing

-A (adenine) is always paired with T (thymine) - C (cytosine) is always paired with G (guanine) -A=T -C=G

Proteins

-DNA codes for proteins via genes (one gene codes for one protein) -Proteins are responsible for every process occurring in any cell -They are fundamental to the immune system and function in vaccines

DNA and Protein Synthesis: Overview

-DNA contains the genetic information to make amino acids -Amino acids combine to make proteins -These proteins determine the physical traits of an organism and control cellular functions. -Proteins do everything, and DNA gets all the credit!

What is DNA?

-DNA or Deoxyribonucleic acid contains the genetic code of all life -A huge double-stranded molecule made up of nucleotides -Each nucleotide is composed of a sugar (deoxyribose), a phosphate group, and one of four bases:

The Genetic Code

-However, each codon codes for only ONE specific amino acid. -Finally, the genetic code is universal because nearly every organism uses the same set of codons to code for the same amino acids.

Reading DNA

-In order to "read" a specific stretch of DNA scientists need many copies of the sequence they are interested in. -They need to artificially "replicate" the DNA. -They do this by mimicking the natural DNA replication

DNA and Mutations

-Mutations are any changes that take place in DNA: Can be spontaneous or caused by mutagens ex: Chemicals, high temperatures, UV light, radiation Can change the genetic code, and be replicated when forming new body cells. In sex cells, can be passed on to offspring. Mutations can be neutral, beneficial, or harmful ex: Blue eyes - a mutation that occurred 6,000 -10,000 years ago, can be traced back to one ancestor

Substitution

-Replace just one letter: THE DOG BIT THE CAT vs THE DOG BIT THE CAR

The Genetic Code -- Codons

-The four bases of DNA and RNA are read in groups of three (called a CODON.) -Therefore, there are 64 possible codons. -The start codon (AUG) also codes for the amino acid methionine, thus every protein begins with methionine. -There are three stop codons (UAA, UAG, or UGA).

DNA Structure

-The two parallel strands of DNA are connected by hydrogen bonds linking the base pairs -The DNA "ladder" is twisted into a spiral called the "double helix"

Base-Pairing Rules

-These rules mean that when the sequence of As, Ts, Cs, and Gs is known on one strand, the sequence on the other complementary strand is also known. -One strand serves as a template for the other. -This property is what allows a new DNA molecule to be built that is identical to the original.

The process of Transcription

1) DNA unzips 2) mRNA (messenger ribonucleic acid) copies info from DNA using base pairings RNA is different from DNA Single stranded, not double stranded Instead of deoxyribose, it has ribose instead of Thymine, it uses Uracil 3) Carries the genetic code from the nucleus to the ribosome in the cytoplasm

The process of Translation

1) Ribosomes attach to mRNA and starts reading the codons 2) tRNA (transfer RNA) - carries amino acids and attaches them to the growing protein chain 3) When protein production is complete, the ribosome releases the protein chain

Cellular DNA Replication Occurs in Three Steps

1)-Proteins unwind the DNA helix and separate the hydrogen bonds connecting the bases of the two strands. 2)-DNA polymerase uses each strand as a template to build another new strand. 3)-Semiconservative replication—there are now two new DNA double helices, each of which has one old and one new strand.

Translation

: information in RNA is converted into the order of amino acids in a protein (cell cytoplasm the ribosomes reads the sequence)

Insertion

Add just one letter (E): ex) THE DOE GBI TTH ECA T

Frameshift mutations

Additions and Deletions are known as frameshift mutations because when they occur everything in the sequence from then on is messed up! → These are much worse because now every amino acid will be wrong because every codon is wrong.

Deletion

Delete just one letter (T): ex) THE DOG BIT HEC AT

Overview of Gene Expression

Genetic information flows from DNA to RNA to protein during gene expression, which occurs in two steps: first transcription and then translation. The transcription of a protein-coding gene produces an mRNA molecule, which is then transported to the cytoplasm, where translation occurs and the protein is made with the help of ribosomes.

point mutations

Substitutions are known as point mutations because only a single nucleotide is changed.

coding

a-t g-c ***A-U***

Transcription:

information in DNA is converted to RNA language (takes place in nucleus)

What is Gene Expression

proteins (what make us us) are produced through gene expression: the process by which genes are transcribed into RNA and then translated to make proteins .

Semiconservative replication—

there are now two new DNA double helices, each of which has one old and one new strand.