Bio 313 Iowa State

20,000

complete set of genetic instructions for any organism

• 1. believe all organisms evolved from some dna 
• 2. uses analogy that it flows like a river

• 1. transmission
• 2. molecular
• 3. population

• 1. (also known as classical genetics)
• 2. relation between chromosomes and heredity,
• 3. arrangement of genes on chromosomes
• 4. gene mapping
• 5. focus on INDIVIDUAL ORGANISM

• 1. chemical nature of gene itself
• 2. how genetic information is :
• a. coded
• b. expressed
• c. replicated
• 3. cellular processes such as:
• a. replication
• b. transcription
• c. translation
• 4. gene regulation
• 5. Structure, Organization, Function

• 1. genetic composition of GROUPS of same species and how that changes over time and space
• 2. (study of evolution)

• 1. short generation time
• 2. large but manageable nubmers of progeny,
• 3. adaptability to lab environment
• 4. housed inexpensively

• 1. fruit fly
• 2. mouse 
• 3. zebra fish
• 4. e.coli
• 5. caenorhabditis elegans (nematode)
• 6. Arabidopsis thaliana , (thale cress plant)
• 7. bakers yeast

finding difference in melanosomes in ppl

• A. specific pieces of information travel from various parts of the body to the reproductive organs , from which are passed to embryo
• B. ancient Greeks

• 1. traits acquired by person are passed on by person gentically
• 2. ex/ if practiced french horn then children are talented automatically in french horn

• inside sperm or egg belongs a miniature adult
• (homonculus)

• blending of both maternal and paternal traits (genetic material itself)
• b. gregor mendel disproved this theory with the alleles

• 1. all life is composed of and cells arise only from cells
• 2. is the fundamental structure of life

• 1. all cells contain a complete set of genetic information 
• 2. proven by cutting off the tails of 22 consecutive generations of mice and the next generation still producing a long tail. (August Weismann)

a genes that specifies a characteristic may exist in several forms called alleles.

• 1. primary structure
• 2. double -stranded sequence
• 3. higher order folding helix

• 1. type of tertiary structure
• 2. subjected to strain by being over or underwound
• 3. subject to when dna is circular and no free ends to help destrain

helix wound 10 bp per turn , which is LOWEST energy state

overrotated helixes, overstrained

under supercoiling

• proteins help dna fold into loops and connect to them
• 2. then no more free rotation of ends, and superocoiling occurs :(

• 1. enzymes that add or remove rotations from DNA helix by
• a. temporarily breaking the nucleotide strands
• b. rotating ends around each other
• c. rejoining broken ends
• 2. can fix or worsen the problem

• negatively supercoiled
• A. allows easier separation of DNA
• B. underrtotated (two turns removed), allows faster transcription and replication along with LESS energy

• A. single circular dna
• B. not open relaxed
• C. no histones, but proteins
• D. nucleiod: DNA in a defined clump in cytoplasm

• 1. single, extremely long linear molecule of DNA
• 2. chromosomes in uncondensed in interphase
• 3. packing of eukaryotic DNA is NOT static

• eukaryotic DNA + protein
• A. euchromatin: normal process of condenssation and decondensation in cell cycle
• i. where the majority of transcription takes place
• B. Heterochromatin: remains in highly condensed state throughout cell cycle, even during interphase
• i. majority of chromatin. Found perm. in centromeres, telomeres, predominately in Y chromosome,
• ii. facultative heterochromatin: found in developmental stages
• iii. by a general lack of transcription

• 1. most abundant protein in chromatin
• 2. postively charged proteins of five major types, H1, H2a, H2b, H3, H4
• 3. high % of + charged arginine and lysine
• 4. attracts PO4 on DNA

• 1. simplest form of chromatin
• 2. DA wrapped about 2x around an octamer of 8 histone proteins 2 copies each of H2a, H2b, H3, H4
• 3. like thread wound around a spool
• 4. has "tail" : 11-37 amino acids that extend out from it. this + charged tail interacts w/ DNA to keep the whole structure tightly packed
• 5. H1: binds to 2-22 bp of DNA ; acts as a clamp around DNA
• 6. separated by linker DNA, 30-40 bp varies in size among cell types.
• 7.

1. enxymes called acetyltranferases attach acetyl groups to lysine amino acids on histone tails to LOOSEN DNA winding

• alterations of chromatin structure that are passed on to descendent cells or individuals are frequently referred to as this or EPIGENETICS
• ex/ genomic imprinting

• 1. proper chromosome movement
• 2. binding sites for kintochore
• 3. heterochromatin majorly
• 4. not defined by DNA sequence but by epigenetic changes in chromatin struture.
• 5. Cen H3 in nucleosome versus H3

• 1. serve as capsand stabilization
• 2 ends of replicating ends of chromo.
• 3. telomeric sequences: repeated adenine or thymine nucleotides followed by guanine
• 4. shelterin: (multiprotein compex) binds to telomeres and protects ends of DNA from being inadvertantly repaired as a double strand break in the DNA

the variance of dna depending on which euk cell

variation in DNA, irony that some complex organisms have less (like humans have less than salamanders)

• 1. unique sequence DNA
• 2. moderately repetitive DNA
• 3. highly repetitive DNA

sequences presen only once or few times

• exist in many copies
• almost half the human genome consists of repetitive DNA

• A. moderately repetitive DNA: 150 -300 bp many 1000x's of times
• I. tandem repeat sequences (clustered)
• II. Insterspersed repeat sequences (scattered)
• i. SINE
• ii. LINE
• B. Highly repetitive DNA: < 10 bp 100- 10^6 in presence

• not all bacteria just only circular chromosome:
• 1. some bacteria have DNA on plasmids
• 2. Eukaryotes: some genes are circular DNA ex/ on organelles (mitochondria, chloroplasts)

• 1. genetic info copied
• 2. copies of gen. info separated from each other
• 3. cell must divide

thru binary fission:

• 1. chromosomes separated from cytoplasm by NUCLEAR ENVELOPE
• 2. nuclear matrix: network of protein fibers in nucleus, helps in DNA rep.
• 3. etc

• 1. both carry info for same set of hereditary characteristics
• 2.

• 1. 2 sets of genetic info
• 2. 2n

• 1. single set of chromosomes
• ex/ sex cells
• 2. n

> 2 sets of genetic info

• 1. pair of telomeres
• 2. origins of replication
• 3. centromere

• 1. filaments responsible for moving chromosomes during cell division
• 2. attachment point for these structures is centromere

• 1. kinetochore: assembles on the centromere
•  a, (a multiprotein complex)

• ends of chromosome, play role in stabilization
• b. may contribute to aging , cancer

• DNA synthesis begins
• b. multiple sites on eukaryotic chromosome

• 1. life story of a cell
• 2. parent cells passed to daughter cells

• allow or prohibit the cell's progression to the next stage
• b. allows all cellular processes are in good working order, and hey are necessary to prevent cells with damaged or missing chromosomes from proliferating

• 1. 1st phase of cell cycle: period between ell divsiions, the cell develops, GROWS, and functions
• 2. 3 phases: G1, S, G2
• A. G1: cell grows and produces proteins that's role are necessary for cell division
•  I. G1/S checkpoint holds cell in G1 until all enzymes necessary for the replication of DNA.
• II. may not pass into S phase , instead go to Go phase. (nondividing phase) many cells never enter G0, but some can be held in here indefinitely
• III. S phase: where chromosome is DUPLICATED
•  a. if dna  synthesis is blocked by drug or mutation, then chromosomes will not be duplicated
• IV. at end of S phase , there are now 2 chromatids
• 3. there are critical steps for cell division in this step as well

• 1. period of active cell division
• 2. mitosis, (nuclear division)
• 3. cytokinesis: cytoplasmic division

leads to gametes, number of chromosomes is halved

2 haploid gametes fuse and restore # of chromosomes to its original diploid value

• 1. Meiosis I: cell division (reduction bc # of chromosomes is halved)
• A. Prophase I: lengthy stage in which chromosomes orm homologous pairs an crossing over takes place
• a. crossing over: essential to genetic variation , cross at chiasma
• b. nucelar membrane breaks down
• B. Metaphase I: homologous pairs align along the meaphase plate
• C. Anaphase I: separation of homologous chromosomes
• D. Telophase I: chromosomes arrive a spindle poles and cytoplasm divides
• - INTERMEDIATE- interkinesis: nuclear membrane re-forms around chromosomes clustered at each pole
• 2. Meiosis II: 
• a. equational division
• 3.

• 1. indiv. chromo. may lose or gain parts, 
• 2. order of genes altered

• 1. type of chromosome structure
• 2. centromere is near one end, producing a long arm and a knob, or satellite , at the other end

centromere at or very near end of chromosome

complete set of chromosomes possessed by an organism

• structures that change structure of individual chromosome
• 1. inversion
• 2. deletion
• 3. duplications
• 4. translocation

• 1. tandem dup.: dup. ADJACENT to the original segment
• 2. displaced dup: duplicated farther away from original
• a. can be identical or inverted,

3. can effect phenotype

duplications greater than 1000 bp

allow new genes to evolve.

can be lethal , especially in centromeric region

expression of normally recessive mutations on homologous chromosome lacking the deletion may be expressed when wild-type allele has been deleted (and no longer able to mask recessive allele expression)

1. creates problems if heterozygous,( the inversion doesn't cancel out)

• 1. crossing over in prophase I of meiosis one. 
• 2. so homologous pairs of chromosomes migrate to opposite ends of cells in anaphase  1. although chromosome 1's,2's, etc. line up , the there isn't a certain order as to whether the paternal side or maternal side is on either side.

• protein that allows chromatids to stick together during metaphase in mitosis and meiosis. 
• is not broken in anaphase 1 of meiosis 1 in centromere thanks to shugoshin, a protein that prevenst separation of two sister chromatids during anaphase 1.