Forensics DNA Chapter 9

Gene

fundamental unit of heredity

DNA

constructed as a very large molecule made by linking a series of repeating units called nucleotides

Nucleotide

composed of a sugar, phosphorus and a nitrogen-containing molecule called a base

4 types of bases

adenine, cytosine, guanine, and thymine

What bases pair with each other?

Adenine—>Thymine

Guanine—>Cytosine

The order in which the base pairs are arranged defines…

the role and function of a DNA molecule

DNA Replication

1) unwinding of the DNA strands in the double helix

2) double helix gets recreated as nucleotides are assembled in proper order (a→t, g→c)

RFLP

(oldest method) consists of hundreds bases in length + longest, needs a lot of evidence

PCR

(25 years) needs little evidence, 15-30 bases, half of RFLP in length

STR

(most recent method) minute evidence, 3-7 bases in length

Concept of Multiplexing

• Abstract and amplify small pieces of STR

Mitochondrial DNA

located outside the cells nucleus and inherited from the mother, multiple individuals (siblings only) can have the same MDNA

Buccal Swab

swabbing the inner mouth with a cotton swab, gives standard/reference DNA, put swab into CODIS to find unknown data that is in system/be put in later

DNA Replication

• begins with the unwinding of the DNA strands in the double helix

• they unwind every A&T get separated every C&G it's separated, then reconnect with other bases to form new double helix’s

Biological Evidence

Hair, blood, semen, saliva, fingernail scrapings, etc… 

Degradation

damages DNA, RFLP degrates more, STR degrates less

Double Helix

is recreated as the nucleotides are assembled in the proper order A with T and G with C two identical copies of DNA emerge fr

Recombinant DNA

a process by which the DNA of an organism is altered by inserting into its fragments of DNA from another organism 

Electrophoresis

materials are forced to move across a gel-coated plate under the influence of an electrical charge

Substances such as DNA can be separated and characterized by…

electrophoresis

What method (PCR, RFLP, STR) is less susceptible to degradation?

STR —> often recovered from bodies or stains that have been subjected to extreme decomposition

T OR F: STR’s are ideal candidates for multiplying by PCR

TRUE

Why is STR better technology?

Most current analysis method is STR

• Less degradation

Polymerase chain reaction is a technique for…

replicating or copying portions of the DNA strand outside of the living cell 

Recombinant DNA is a process by which…

 the DNA of an organism is altered by inserting into its fragments of DNA from another organism 

Portions of the DNA molecule contains sequences of bases that are repeated numerous times. These _____ _______ are for a means of distinguishing one individual from another through DNA typing. Which method of analysis does that?

Tandem repeats, STR

What is the scissor?

DNA molecules are cut up by a restriction enzyme

What method can amplify minute quantities of DNA the technique evolved from another standing of how DNA strands naturally replicate within the cell?

PCR

T OR F: PCR technology can not be applied to RFLP because RFLP strands are too long.

TRUE

**STR as little as ___ picograms of DNA are required 

125

CODIS

is a computer software program developed by the FBI that maintains local state and National databases

Why should biological evidence not be packaged in air tight containers?

because the accumulation of residual moisture is going to contribute to blood destroying bacteria and fungi. place each package separately in its own paper bag 

What makes up the Double Helix?

two linked strands that wind around each other to resemble a twisted ladder in a helix-like shape, each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups (base)