DNADNA(Ch 7)(Ch 7)

DeoxyriboNucleic DeoxyriboNucleic

AcidAcid“The Blueprint of Life”“The Blueprint of Life”

DNA StructureDNA Structure

nuclear nuclear DNA is DNA is found in the found in the nucleus of nucleus of cells in cells in chromosomchromosomeses

# of Chromosomes# of Chromosomes

in human somatic cells, 46 in human somatic cells, 46 chromosomes (23 pairs with one chromosomes (23 pairs with one from mom, one from dad)from mom, one from dad)

in human sex cells, only 23 in human sex cells, only 23 chromosomeschromosomes

DNA StructureDNA Structure

mitochondrimitochondrial DNA is a al DNA is a circular loop circular loop and ONLY and ONLY inherited inherited from from mothermother

DNA Structure DNA Structure

composed of smaller units called nucleotides

- phosphoric acid (phosphate)- deoxyribose sugar- nitrogenous base

(Adenine, Thymine, Guanine or Cytosine)

DNA Structure DNA Structure

shape: double helix (twisted ladder)

side/rails: sugar-phosphate backbone

steps/rungs: N bases

Watson & Crick’s Watson & Crick’s double helixdouble helix

Nitrogenous BasesNitrogenous Bases PURINES (big) and PYRIMIDINES (small)PURINES (big) and PYRIMIDINES (small)

A & GA & G C & TC & T purines hydrogen bond with purines hydrogen bond with

pyrimidinespyrimidines

A A == T T C = GC = G

triple bondtriple bond double bonddouble bond

Adenine bonds only to Thymine

Cytosine bonds only to Guanine

Be able to find the Be able to find the complementary DNA strand given complementary DNA strand given a DNA sequence:a DNA sequence:

5’ CCGATTACGGAA 3’5’ CCGATTACGGAA 3’ 3’ ?3’ ?

ANS: GGCTAATGCCTT 5’ANS: GGCTAATGCCTT 5’

Genes and AllelesGenes and Alleles

alleles are alternative forms of a alleles are alternative forms of a gene; one allele from mom, one gene; one allele from mom, one from dadfrom dad

human genome includes the total human genome includes the total amount of DNA in a cellamount of DNA in a cell

only ~1.5% of the DNA is coding only ~1.5% of the DNA is coding (makes proteins) – the rest is (makes proteins) – the rest is “junk DNA”“junk DNA”

Function of DNAFunction of DNA

Hereditary instructions

Chemical code for every trait

“Blueprint” formaking proteins

Chromosome DNA CodeChromosome DNA Code

Genes are segments of DNA segments of DNA that code for a that code for a single traitsingle trait

The code is in sets The code is in sets of 3 (triplicate) of 3 (triplicate) called CODONScalled CODONS

Every codon = 1 Every codon = 1 amino acid in the amino acid in the protienprotien

HairColor

EyeColor

Acid AcidSugar-T-A-SugarAcid AcidSugar-G-C-SugarAcid AcidSugar-C-G-Sugar

DNA code:DNA code: Ccc gga tta ggcCcc gga tta ggc

How many How many amino acids will amino acids will this encode for?this encode for?

= 4= 4

DNA ReplicationDNA Replication

during mitosis – during mitosis – when the when the chromosomes chromosomes double during double during late interphaselate interphase

2N

2N

DNA ReplicationDNA Replication

1. DNA unwinds2. DNA unzips using DNA polymerase

3. Corresponding base pairs

line up 4. DNA reforms 5. Zips back up and winds back up

DNA IdentificationDNA Identification

differences in DNA sequences differences in DNA sequences (lengths, sequences of bases): (lengths, sequences of bases): polymorphismpolymorphism

use VTNR and STR in noncoding use VTNR and STR in noncoding section to identify individualssection to identify individuals

Compare 13 regions to build a bankCompare 13 regions to build a bank Human differ <0.1% from each otherHuman differ <0.1% from each other

According to the Innocence According to the Innocence project, about 200 people who project, about 200 people who have been jailed have been have been jailed have been proven innocent and released proven innocent and released from prison using DNA evidencefrom prison using DNA evidence

DNA IdentificationDNA Identification

Tissue MatchingTissue Matching

- 2 samples with same pattern are - 2 samples with same pattern are same person (crime scene vs. same person (crime scene vs. suspect)suspect)

Inheritance MatchingInheritance Matching

- bands on a child must be - bands on a child must be present in one of the parentspresent in one of the parents

DNA TypingDNA Typing

portions of the DNA molecule contain portions of the DNA molecule contain sequences of bases that are repeated sequences of bases that are repeated numerous times are known as VNTR numerous times are known as VNTR

to a forensic scientist, these tandem to a forensic scientist, these tandem repeats offer a means of repeats offer a means of distinguishing one individual from distinguishing one individual from another through DNA typinganother through DNA typing

Restriction EnzymesRestriction Enzymes

can be thought of as highly can be thought of as highly specialized scissor that cuts a specialized scissor that cuts a DNA molecule when it recognizes DNA molecule when it recognizes a specific sequence of bases.a specific sequence of bases.

PCR TestingPCR Testing

with the with the knowledge of how knowledge of how DNA replicates, DNA replicates, forensic scientist forensic scientist are able to use are able to use PCR to take PCR to take minute quantities minute quantities of DNA and of DNA and multiply it many multiply it many millions of times millions of times to make a larger to make a larger samplesample

ElectrophoresisElectrophoresis

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

substances such substances such as DNA can be as DNA can be separated and separated and characterizedcharacterized

bands and widths are significant in matching samples of DNAbands and widths are significant in matching samples of DNA DNA fingerprinting can DNA fingerprinting can

(a) match crime scene DNA with a suspect, (a) match crime scene DNA with a suspect, (b) determine maternity, paternity, or match to another (b) determine maternity, paternity, or match to another relative, relative, (c) eliminate a suspect, (c) eliminate a suspect, (d) free a falsely imprisoned individual, and (d) free a falsely imprisoned individual, and (e) identify human remains. (e) identify human remains.

CODISCODIS

perhaps the most significant tool to arise perhaps the most significant tool to arise from DNA typing is the ability to compare from DNA typing is the ability to compare DNA types recovered from crime scene DNA types recovered from crime scene evidence to those of convicted criminals evidence to those of convicted criminals

CODISCODIS (COmbined Dna Index System) is (COmbined Dna Index System) is a computer software program developed a computer software program developed by the FBI that maintains local, state, by the FBI that maintains local, state, and national databases of DNA profiles and national databases of DNA profiles from convicted offenders, unsolved crime from convicted offenders, unsolved crime scene evidence, and of missing personsscene evidence, and of missing persons

DNA SourcesDNA Sources

saliva, blood, seminal fluid, skin, saliva, blood, seminal fluid, skin, hairhair

INDIVIDUAL EVIDENCEINDIVIDUAL EVIDENCE

PedigreesDominant trait- a trait seen in every generation Distributed equally between males and females

Recessive trait – seen rarely in a family

Sex-linked trait- seen more in males than females. At least three fold more males than females-Males inherit the gene from MOM-Girls inherit the gene from DAD -- gene found on the X chromosome-So girls have two alleles for the gene-Boys have one allele (NO CARRIERS)-*** Must be able to do pedigrees and calculate -Percent of genotype and phenotype possibilities