Forensics:DNA
FALL SEMESTER 2024
INSTRUCTOR: Mrs. Michele Buxton
28 October 2024
DNA is in every nucleated cell of the human body .
● Can be extracted from:
○ Blood (only white cells)
○ Semen
○ Urine
○ Bone
○ Hair follicles (tube where hair grows)
○ Saliva
Cells
Cells are the basic functional and structural element of all living things .
● Chromosomes
○ Found in the nucleus of cells .
○ Made up of long-chain DNA molecules .
○ Inherited from both parents .
○ Humans have 46 chromosomes .
● Chromosomes to DNA
○ Every chromosome is made up of DNA .
○ Genes are portions of DNA that code for specific proteins .
○ Humans have about 35,000 genes .
DNA
1
, ● If all the DNA in a human body was put end to end how long do you think the strand
would be ?
○ It would reach the sun and back more than 600 times - 55,800,000,000 miles .
○ DNA is made of four bases that are paired and held together w/ hydrogen
bonds .
○ Each base contains the element nitrogen , and are referred to as nitrogenous
bases .
Nitrogenous Bases
● Adenine (A) always bonds with Thymine (T)
○ Adenine and thymine are connected w/ two hydrogen bonds .
● Cytosine (C) always bonds with Guanine (G) .
○ Cytosine and guanine are connected with three hydrogen bonds .
■ Referred to as “base pairs”
Nucleotides
● Each nitrogenous base is connected to a sugar molecule and a phosphate group .
○ This makes up a nucleotide unit .
■ DNA is arranged in a double helix (twisted ladder) .
● The average DNA molecule contains approx. 100 million nucleotide groups .
○ In humans, the order of these nucleotide bases is 99.9% the same .
○ The unique sequence of the other 0.1% makes each human (except identical
twins) “one of a kind” .
■ Referred to as “junk DNA” .
DNA History
● DNA was first identified in 1869 by Swiss chemist Friedrich Mieshcer .
○ In 1953, James Watson, Francis Crick, and Rosalind Franklin were credited
w/ discovering DNA’s 3d double helix shape .
● In 1985, Alec Jefferys, a professor in England changed the world forever by
inventing a new method of identifying people - DNA fingerprinting .
2
FALL SEMESTER 2024
INSTRUCTOR: Mrs. Michele Buxton
28 October 2024
DNA is in every nucleated cell of the human body .
● Can be extracted from:
○ Blood (only white cells)
○ Semen
○ Urine
○ Bone
○ Hair follicles (tube where hair grows)
○ Saliva
Cells
Cells are the basic functional and structural element of all living things .
● Chromosomes
○ Found in the nucleus of cells .
○ Made up of long-chain DNA molecules .
○ Inherited from both parents .
○ Humans have 46 chromosomes .
● Chromosomes to DNA
○ Every chromosome is made up of DNA .
○ Genes are portions of DNA that code for specific proteins .
○ Humans have about 35,000 genes .
DNA
1
, ● If all the DNA in a human body was put end to end how long do you think the strand
would be ?
○ It would reach the sun and back more than 600 times - 55,800,000,000 miles .
○ DNA is made of four bases that are paired and held together w/ hydrogen
bonds .
○ Each base contains the element nitrogen , and are referred to as nitrogenous
bases .
Nitrogenous Bases
● Adenine (A) always bonds with Thymine (T)
○ Adenine and thymine are connected w/ two hydrogen bonds .
● Cytosine (C) always bonds with Guanine (G) .
○ Cytosine and guanine are connected with three hydrogen bonds .
■ Referred to as “base pairs”
Nucleotides
● Each nitrogenous base is connected to a sugar molecule and a phosphate group .
○ This makes up a nucleotide unit .
■ DNA is arranged in a double helix (twisted ladder) .
● The average DNA molecule contains approx. 100 million nucleotide groups .
○ In humans, the order of these nucleotide bases is 99.9% the same .
○ The unique sequence of the other 0.1% makes each human (except identical
twins) “one of a kind” .
■ Referred to as “junk DNA” .
DNA History
● DNA was first identified in 1869 by Swiss chemist Friedrich Mieshcer .
○ In 1953, James Watson, Francis Crick, and Rosalind Franklin were credited
w/ discovering DNA’s 3d double helix shape .
● In 1985, Alec Jefferys, a professor in England changed the world forever by
inventing a new method of identifying people - DNA fingerprinting .
2
