Ch.9

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

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

English has 26 letters

Hawaiian has 2 letters

The binary language of computers uses only two "letters"

0 and 1

"on and Off"

The sequence of only four nucleotides can produce mant different combinations

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

All cells come from pre-exising cells

Cells reproduce by dividing in half

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

Duplication of a parent cell DNA is called Replication

DNA replication begins when DNA helicases seperate the two strands

Hydrogen bond bases are broken

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

DNA Polymerases position Free Nucleotides across complementary nucleotides

Base paring is the Foundation for DNA replication

An Adenine on one strand pairs with thymine on another strand

Cytosine pairs with Guanine

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)

Replication

DNA polyerase mismatch nucleotides once every 10,000 base pairs

Proofreading

DNA repairs enzymes "proofreading"each new daughter strand

replacing mismatched nucleotides

Mistakes

DNA is damages in a number of ways

Spontaneous chemical breakdown at body temperature

Certain chemicals (componets of cigarette smoke)

UV light from sun causes DNA damage

DNA damage leads to uncontrollable cell division and skin cancer.

Types of mutations

Point Mutation

individual nucleotide pairs are removed from the double helix

Insertion Mutation

one or more nucleotide pairs are inserted into DNA double helix

Deletion Mutation

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

Inversion

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

Translocation

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

Tammi Watts

Stormy Hutchinson

Kendra Slaton

Sammy

Genes

Discovered in 1800's

Transformed Bacteria revealed the link between Genes and DNA.

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

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.

Strain R did not cause pneumonia.

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

Carry herritable information

Part of Structures called Chromosomes

Chromosomes are made of DNA and Proteins.

DNA

DNA is made of chains of small subunits called Nucleotides.

Each Nucleotide has 3 components

Phosphate Group

Deoxyribose Sugar

One of Four Nitrogen bases

Thymine

Adenine

Guanine

Cytosine

Biochemist E. Chargaff determined DNA structure

"Chargaffs Rule" 1940

A=T

G=C

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

Discovered DNA as

Long Chains

Has Uniform diameter of 2 nanometers

Is Helical,and twisted like a corkscrew

consist of repeating subunits

DNA is made of two strands of Nucleotides

Sugar-Phosphate backbone

Deoxyribose

Phosphate portions

Nitrogen-containing bases protude inward from sugar-phosphate backbone

Complemtary base pairs

Hydrogen bonds held certain nitrogenous base pairs together

A bonds with T

G bonds with C

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