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Ch.9

Hydrogen Bonding

By : Tammi Watts

Stormy Hutchinson

Nitrogen-containing bases protude inward from sugar-phosphate backbone

Ladder like structure of the two DNA strands are twisted into Double Helix

Complemtary base pairs

G bonds with C

A bonds with T

Hydrogen bonds held certain nitrogenous base pairs together

DNA is a Double Helix

DNA is made of two strands of Nucleotides

Sugar-Phosphate backbone

Phosphate portions

Deoxyribose

Discovered DNA as

consist of repeating subunits

Is Helical,and twisted like a corkscrew

Has Uniform diameter of 2 nanometers

Long Chains

Roslind Franklin and Maurice Wilkins studied DNA structure using X-Ray scattering

Genes and DNA

DNA

Each Nucleotide has 3 components

One of Four Nitrogen bases

Biochemist E. Chargaff determined DNA structure

G=C

A=T

"Chargaffs Rule" 1940

Cytosine

Guanine

Adenine

Thymine

Deoxyribose Sugar

Phosphate Group

DNA is made of chains of small subunits called Nucleotides.

Genes

Part of Structures called Chromosomes

Chromosomes are made of DNA and Proteins.

Carry herritable information

Discovered in 1800's

Transformed Bacteria revealed the link between Genes and DNA.

F. Griffith worked with 2 strains of Streptococcus Pneumoniae Bacteria.

Living R stain bacteria were transformed by genetic material released by the S strain

Avery,Mcleod, and MCarty (1940's)

The transforming molecule from the S strain was DNA

Strain R did not cause pneumonia.

Strain S caused pneumonia when injected into mice, killing them. He then made a sample of heat-killed S Strain and mixed it with R Strain....this combination caused death as well through pneumonia.

By

Sammy

Kendra Slaton

Stormy Hutchinson

Tammi Watts

Mutations

Types of mutations

Translocation

a chunck of DNA (often very large) is removed from one chromosome and attached to another

Inversion

A piece of DNA is cut out of chromosome, turned around,and reinserted into gap

Deletion Mutation

one or more nucleotide pairs are removed from the DNA double helix

Insertion Mutation

one or more nucleotide pairs are inserted into DNA double helix

Point Mutation

individual nucleotide pairs are removed from the double helix

Mistakes

DNA is damages in a number of ways

UV light from sun causes DNA damage

DNA damage leads to uncontrollable cell division and skin cancer.

Certain chemicals (componets of cigarette smoke)

Spontaneous chemical breakdown at body temperature

Proofreading

DNA repairs enzymes "proofreading"each new daughter strand

replacing mismatched nucleotides

Replication

DNA polyerase mismatch nucleotides once every 10,000 base pairs

DNA Replication

Duplication of a parent cell DNA is called Replication

Hydrogen bond bases are broken

DNA Polymerases position Free Nucleotides across complementary nucleotides

If one strand reads ATG, the other reads TAC

The two resulting DNA molecules have one old parental strand and a new strand (semiconservative replication)

Cytosine pairs with Guanine

An Adenine on one strand pairs with thymine on another strand

Base paring is the Foundation for DNA replication

A second strand of new DNA is synthesized along each seperated strand .

DNA replication begins when DNA helicases seperate the two strands

Each of two daughter cells gets an exact copy of parents cells genetic information.

Cells reproduce by dividing in half

All cells come from pre-exising cells

DNA Encodeing

Within a DNA strand, Four types of bases can be arranged in any liner order,and this sequence is what encodes genetic information.

The genetic code is analogous to languages

A 10 nucleotide sequence can code for greater than 1 million different combinations

The sequence of only four nucleotides can produce mant different combinations

The binary language of computers uses only two "letters"

"on and Off"

0 and 1

Hawaiian has 2 letters

English has 26 letters

small sets of letters combine in various ways to make up different words