C5U1

DNA structure

-Antiparallel strands (Opposite directions) -Polarity of strands (3' vs 5' ends) -Strands have complementary base sequences ( Adenine always pairs with thymine Guanine always pairs with cytosine Read DNA from 5 prime to three prime Also write them that way (5 -> 3)) -DNA double helix ( Major groove Minor groove, Ten base pairs per turn (3.4 nm) Distance between bases is .34 nm, Width 2 nm )

Where is DNA found inside Cells?

-Chromosonal (Linear, Circular) -Extrachromosomal (Plasmid, Transposons- DNA regions that can move around, we have them, Mitochondria, Chloroplasts, Satellite )

Approximately how many base pairs comprise one turn of the double helix in DNA?

10

History

1859 charles darwin publishes the origin of species 1866 mendel discovers basic principles of genetics 1969 friedrich miescher identifies "nuclein" 1900s 1990 human genome project begins 1960-90 Explosion of DNA research and technologies James Watson and Francis Crick discover the double helix structure of DNA 1952 rosalind franklin photograph crystals of DNA fibers 1950 erwin chargaff discovered that DNA composition is species specific, chargaff's rules 1944 Oswald avery identifies DNA as the transforming principle 1910- Phoebus Levene proposes tetranucleotide hypothesis, DNA could not carry genetic information 1910- Phoebus levene describes the nucleotide sequence 1901- albrecht kossel isolation and description of nucleobases AGTCU 2000s 2000 first complete genome fruit fly 2002 first mammal genome completed 2003 human genome completed 2013 twins have differences in their genome 2014 epigenetics and personalized medicine

The sugar in DNA is comprised of ____ carbons.

5

When DNA is heated, the hydrogen bonds break and allow the two strands of DNA to separate from one another. Which sequence of DNA would be most resistant to heating, and therefore, stay double stranded longer?

AGGAGCTC

The work of many scientists led to the identification of the nucleotide structure

Cytosine (nitrogen containing base) also called a nitrogenous base Five carbon sugar- phosphate Phosphate Group DNA

Deoxyribonucleic acid (DNA)

Deoxyribose sugar Mostly double stranded Stores information

Nucleosidic bonds are used to link nucleotides together to form nucleic acids.

F

One important way in which RNA differs from DNA is that RNA is missing a key hydroxyl group on its sugar.

F

The most abundant organic molecules in the world are nucleic acids.

F

There are variations in the nitrogenous base and the carbohydrate

Nitrogenous bases --Pyrimidines ----Cytosine ----Thymine ----Uracil --Purines ----Adenine ----Guanine --Sugars ----Deoxyribose -----Ribose

DNA backbone

Phosphodiester bonds create the backbone Phosphates and the pentose sugar alternate in the DNA backbone

Condensation reaction

Phosphodiester linkage

In addition to serving as building blocks of DNA, what other function do nucleotides perform in a cell?

Regulate cell activity

Ribonucleic acid (RNA)

Ribose sugar instead of deoxyribose Base uracil instead of thymine Usually not double stranded Translates information into proteins Regulate gene expression Catalytic activity

Chargaff's rules (1950)

Rule #1 In any species the number of A and T bases are equal and the number of G and C bases are equal

How is the DNA found in the nucleus

Short region of DNA double helix 2 nm Beads on a string from of chromatin 11nm 30-nm chromatin fiber of packed nucleosomes 30nm Section of chromosome in extended form 300 nm Condensed section of chromosome 700 nm Entire mitotic chromosome 1400 nm Only when the cell is undergoing mitosis DDNA spends most time in 300 and 700 nm form

In double-stranded DNA, the base adenine pairs with the base thymine.

T

RNA molecules differ from DNA molecules in the bases that comprise them, their sugars, and their structure.

T

Hydrogen bonds dictate

The pairing of bases

How did Chargaff finding disprove the tetranucleotide theory?

The tetranucleotide theory predicted equal number of ATGC in a given genome and Chargaff found that there was a deviation from this prediction among species

Nucleic acids store, transmit, and help express hereditary information

There are two types of nucleic acids DNA & RNA

The molecule in the accompanying figure is the pyrimidine ____, which is typically found in DNA but not RNA.

Thymine

The two strands of a DNA double helix are held to each other by ____ bonds between nitrogenous bases.

hydrogen

Nucleotides are joined together to make a nucleic acid strand by ____ bonds.

phosphodiester

Monomers are linked by a

phosphodiester bond

Nucleotides are joined together via

phosphodiester bonds

Nucleotides are always added to

the free 3' OH