DNA Profiling/Fingerprints

Forensics DNA Profiling/Fingerprints review for test

what kind of bonds are found between nitrogenous bases ad hold the two halves of DNA together

weak hydrogen bonds

what are the base-pairing rules

• A and T always pair (two hydrogen bonds)

• C and G always pair (three hydrogen bonds)

• in RNA, adenine (A) pairs with the Uracil (U)

what is a chromatin

makes up chromosomes, is a complex of DNA and proteins

what are homologous chromosomes

• paired chromosomes that come from mom and dad

• each parent contributed half of the chromosomes for an individual there is “matching” one with similar genes called a homologous chromosomes

what specifically does DNA code for

specifically proteins

be able to describe DNA replication using the terms helicase, DAN polymerase, primers, unwind/unzip, free nucleotides, hydrogen bonds

DNA is copied in S phase, just before a cell replicates, a couple of enzymes unwind and separate the 2 DNA strands by breaking the weak hydrogen bonds, as DNA is “unzipped” DNA polymerase can ass the new nucleotides to the exposed A, G, C, T bases starting at a primer, each chromatids ends up with identical ones

when working with DNA, 3’ and 5’ are used to indicate ___________ on DNA, which is like a _________________

direction, two way street

DNA polymerase, primer, helicase

• DNA polymerase: copy and makes new DNA

• Primer: tells DNA polymerase where to start

• helicase: unwinds and unzips DNA

what percentage of DNA codes for an individuals traits?

only a small percentage, 1%

how many base pairs are there in DNA found in a human cell?

about 99.9%

list the possible sources for DNA in a crime scene

• usual: blood, sperm, skin

• unusual: saliva, from a cigarette butt or sandwich

• urine

• latent fingerprints under right conditions

what parts of DNA are used to create DNA profiling/fingerprints and why?

STR’s, short sequences of DNA that are repeated in a head-to-tail manner, DNA stutters

outline three steps for removing DNA from a cell sample. name and identify roles of each substance added to cells.

• soap, dissolves the phospholipids in the cell and nuclear membranes because it is basically oil

• salt, added to release the slightly polar DNA from histones

• protease, (dissolves proteins) can be added to help dissolve cell membrane, proteins, enzymes that might attack DNA

• slowly add cold alcohol and DNA rises out of the debris, separates

what 3 substances are added to crime scene DNA when using PCR to make copies for making a DNA “fingerprint”

DNA primers, DNA polymerase, nucleotides

temperature is used to control the copying of DNA for a profile. In PCR, what happens at 95C, 50C, 72C

• 95C: disrupts complimentary base pairing and the two DNA strands come apart

• 50C: complimentary DNA strands can rejoin at this temperature primers will look on and then longer strands will rejoin, primers attach

• 72C: activates DNA polymerase it attaches at the ends of the paired primers and extends, it moves along the single-stranded

what does PCR stand for

polymerase chain reaction