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Genetics and Molecular Biology Cheat Sheet (DRAFT) by

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Structure of DNA

-DNA is a double helix
-DNA consists of 2 strands that run antipa­rallel
-one strand run 5' to 3' the other strand runs 3' to 5'
-DNA is a polymer consisting of repeating units of nucleo­tides
-Nucle­otides consists of a 5-carbon sugar, phosphate, and nitrogen base
-4 nitrogen bases: adenine + thymine / cytosine + guanine
-nitro­genous bases are paired together by hydrogen bonds
-a chromatin is when DNA combines with histones (proteins)
-a nucleo­somes is when double helix of DNA wraps around a core of histones

Mendel's Laws

Law of Segreg­ation
Law of Indepe­ndent Assortment
-law of segreg­ation states that the 2 alleles of heritable character separate and segregate during gamete formation and end up in different gametes
-law of indepe­ndent assortment states that each pair of alleles segregates indepe­ndently into gametes
-this law accounts for the 3:1 ratio that Mendel noticed in the F2 generation
-Mendel identified this law by following 2 charac­ter­istics at the same time (dihybrid cross)

Scientists

scientists
experiment
conclusion
Frederick Griffith
he injected mice with different strands of pneumo­coccus
somehow the R strand transf­ormed into S strain by the transf­orming principle
Oswald Avery
He exposed the R strand of pneumo­coccus to strept­ococcus to purify the S strain protein
Alfred Hershey & Martha Chase
They used radioa­ctive sulfur and phosphorus to determine if protein or DNA was the transf­orming principle using bacter­iop­hages
the phage coat packages and delivers phage DNA into bacteria and that DNA carries the instru­ctions needed to replicate the phages in the bacteria. DNA is the genetic material
Erwin Chargaff
worked with nitrog­enous bases to determine structure of DNA
he concluded his two rules: purines go with pyrimi­dines and all species have different amount of nitrog­enous bases
James Watson & Francis Crick
studied Franklin's X rays of the structure of DNA
DNA is a double helix
Rosalind Franklin & Maurice Watkins
used X-ray crysta­llo­graphy to complete experiment
the X ray proved DNA to be a helix

DNA Replic­ation

  

Vocab

alleles
any of the altern­ative versions of a gene
character
an observable heritable feature
dominant allele
an allele that is fully expressed in phenotype of a hetero­zygote
F1 generation
the first filial, or hybrid, offspring in a series of a genetic cross (children)
genotype
genetic makeup, or set of alleles, of an organism
hetero­zygous
having two different alleles for a given gene
homozygous
having two identical alleles for a given gene
linked genes
genes located close enough together, on a chromsome that they tend to be inherited together
P generation
the original organism that you started studying (parents)
phenotype
the physical charac­ter­istics of an organisms, which are determined by genotype
trait
a detectable variant in a genetic character

Mendel's experiment

Facts
Advantages of Garden Pea
-mendel discovered the basic principles of heredity by breeding garden peas
-available in many varieties
-exper­iment started with varities that were true-b­reeding
-distinct heritable traits
-F2 plants revealed 2nd law of segreg­ation and the law of indepe­ndent assortment
-pea plants can be controlled by cutting off stamen
 
-each pea plants have male & female organs
 
-Mendel could cross-­fer­tilize to produce many progeny

Non-Me­ndalion Genetics

Incomplete Dominance
when two alleles of the same gene blend together EX: pink flower
Epistasis
when one gene depends on another gene for it to be expressed
Sex-linked Genes
genes found only on the sex chroms­omes; mainly found on X chromosome because X is larger
Co-dom­inance
when two genes work together and both show through EX: speckled chicken
Polygenic Trait
many genes control one trait

DNA Replic­ation in Eukaryotes

There are 4 main steps in replic­ation: initia­tion, elonga­tion, termin­ation, and proof-­reading
1) replic­ation begins at origin of replic­ation, where 2 strands of DNA seperate to form replic­ation bubbles
2) bubble expands as replic­ation proceeds in both directions at once
3) at each end of the replic­ation bubble is a replic­ation fork. Eventu­ally, replic­ation bubbles fuse
4) the enzyme DNA polymerase catalyzes the antipa­rallel elongation of the new DNA strands
5) DNA polymerase builds a new strand (going 5' to 3') by moving along the template strand and pushing the replic­ation fork ahead of it.
6) DNA polymerase cannot initiate synthesis, it can only add nucleo­tides to the 3' end of the preexi­sting chain. This preexi­sting chain consists of RNA and is called RNA primer. A Primer ( which is a enzyme) makes the primer by joining together RNA nucleo­tides
7) DNA polymerase replicates the 2 original strands of DNA differ­ently. although it builds both new strands in the 5' to 3' direction
8) The leading strand forms toward the replic­ation fork in a linear fashion
9) the lagging strand forms in the direction away from the replic­ation fork in a series of fragments called Okazaki fragments
10) helicases (which are enzymes) untwist the double helix at the replic­ation fork. Helicases seperate the 2 parental strands, making the strands available
11) The single­-st­randed biding proteins hold the 2 DNA strands apart
12) Topois­ome­rases lessen the tension on the tightly wound helix by breaking, swiveling, and rejoining the DNA strands
13) DNA polymerase proof reads the work of matching the right nucleo­tides together (adenine + thymin­e//­gua­nine+ cytosine)
14) damaged regions of DNA are excised by DNA nuclease
15) each time DNA replicates some nucleo­tides from the end of the chromo­somes are lost. To prevent the lost of genes, eukaryotes have specific nucleotide sequences (TTAGGG) at the end of chromsomes that repeat
16) these protective ends are called telomeres. telomeres are created and maintained by the enzyme telomerase
17) Body cells conatin little telome­rase, so every time DNA replic­ates, the telomeres get shorter