DNA, Genes and Genetics

What is DNA?

-DNA Stands for DeoxyriboNucleic Acid

-DNA is the hereditary material inherited from past generations

-The vast majority ( >99%) of your DNA is in the nucleus of your cells

DNA Structure-DNA’s structure is known as

a double helix. (Think of a twisted ladder)

-The helix is composed of two strands

-The sides of the ladder (red in the picture) are composed of alternating deoxyribose sugar and phosphate molecules

-The rungs of the ladder are composed of nucleotides held together by hydrogen bonds

NucleotidesAdenine and guanine are known as purines

Cytosine and thymine are known as pyrimidines

A always binds to TC always binds to G

Watson and Crick

James Watson Francis Crick-“Discovered” the structure of DNA in 1953

-Used the knowledge of many other scientists to determine the structure

-Awarded the Nobel prize in 1962 for DNA’s structure*

What are Genes?Genes are segments of DNA responsible for the production of a functional protein.

Every person has two copies of each gene,one inherited from each parent.

Genes are responsible for your traits! Ex. widow’s peak, skin tone, etc

Environment can be a factor in traits as well*

ChromosomesChromosomes are compact molecules of

DNA

A human set of chromosomes contains 23 pairs

23rd pair are your sex chromosomes

Karyotype

Sex chromosome abnormalitiesXXX – Triple X syndrome (1 in 1000)

-little to no effectXXY – Klinefelters syndrome (1 in 1000)

-often infertile, taller, slight reading/ learning impairment, increased breast tissueXYY – XYY syndrome (1 in 1000)

-increased growth velocity-severe acne? -slight developmental delays

(reading and writing)

So how we get from DNA to Protein?

TranscriptionDNA is copied into messenger

RNA (mRNA) by an enzyme called RNA polymerase in the nucleus

RNA is identical to DNA except Thymine (nucleotide) is replaced by Uracil

RNA is single stranded

Transcription

TranslationmRNA is then exported to the

cytoplasm and processed further by other enzymes to remove the “junk” DNA called introns

The final mRNA is transported to ribosomes where translation occurs.

Ribosomes read the mRNA in multiples of 3 nucleotides called codons

For example:5’ AUGCCCUCAGAG 3’

Codon Table

AUG, AUA, and GUA -causes the protein to STOP being translated

AUG (Methionine)-required to START translation

TranslationEach codon signals the cell to

retrieve and add an amino acid to a growing chain of amino acids using transfer RNA (tRNA).

AA sequence = Protein!Once the entire mRNA

sequence is read and translated into amino acids the chain of AA’s is released

This chain of AA’s folds and contorts into a structure called its tertiary structure*

Finally a functional protein!