MOLECULAR GENETICS

what is DNA? 23 and me http://www.forbes.com/sites/danmunro/2013/12/02/class-action-law-suit-filed-against-23andme/#52ee367c59c6

History (1): The transforming principle

History (2): Hershey & Chase Experiment

Central Dogma of Molecular Biology DNA  RNA  protein

DNA contains all the genetic information about an organism. Regions on DNA that code for specific attributes are called genes. 3) In order for the information within a gene to be useful, it has to be translated into proteins.

The end proteins determine individual traits!

What makes good genetic material? Stable source of information Ability to replicate accurately Capable of change

Watson and 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*

Why care? - genes are segments of DNA responsible for the production of a functional protein. - genes are responsible for your traits! Ex. widow’s peak, skin tone, etc Environment can be a factor in traits as well* - Every person has two copies of each gene, one inherited from each parent.

Genes Genes are units of heredity that are passed on from parent to offspring. Genes give specific instructions for one characteristic. One gene = one polypeptide (not really…)

Genome *the complete genetic makeup of an organism, its total DNA sequence*

C value = total amount of DNA in the haploid (1N) genome Varies widely from species to species and shows no relationship to structural or organizational complexity. Examples C value (bp)  48,502 T4 168,900 HIV-1 9,750 E. Coli 4,639,221 Lilium formosanum 36,000,000,000 Zea mays 5,000,000,000 Amoeba proteus 290,000,000,000 Drosophila melanogaster 180,000,000 Mus musculus 3,454,200,000 Canis familiaris 3,355,500,000 Equus caballus 3,311,000,000 Homo sapiens 3,400,000,000

Problem: Measured linearly, the Escherichia coli genome (4.6 Mb) would be 1,000 times longer than the E. coli cell. The human genome (3.4 Gb) would be 2.3 m long if stretched linearly. *this stuff needs to get organized!

Organization of DNA 1.a) Supercoiling DNA double helix is twisted in space about its own axis, a process is controlled by topoisomerases occurs in circular and linear DNA molecules b) Looped domains

Different levels of organization 1. Prokaryotic chromosomes - most contain one double-stranded circular DNA chromosome - others consist of one or more chromosomes and are either circular or linear - arranged in arranged in a dense clump (nucleoid)

2. Viral chromosomes TMV T2 bacteriophage single or double-stranded DNA or RNA circular or linear surrounded by proteins TMV T2 bacteriophage

3. Eukaryotic chromosomes because we have A LOT of DNA in each cell it needs to be packaged in a specific way

Chromosomes are compact molecules of DNA A human set of chromosomes contains 23 pairs 23rd pair are your sex chromosomes Karyotype

Where are your genes?

Eukaryotic chromosome structure Chromatin: - non-condensed complex of DNA and chromosomal proteins, about twice as much protein as DNA Two major types of proteins Histones abundant, basic proteins with a positive charge that bind to DNA evolutionarily conserved 2. Non-histones - all the other proteins associated with DNA - differ markedly in type and structure

Packing of DNA into chromosomes Level 1 Winding of DNA around histones to create a nucleosome structure. Level 2 Nucleosomes connected by strands of linker DNA like beads on a string. Level 3 Packaging of nucleosomes into 30-nm chromatin fiber. Level 4 Formation of looped domains.