THE HUMAN GENOME

From Peas and fruit flies to humans…

What is a genome???

All the genetic information (genes) that make up an organism

What makes us human? Analyze human chromosome… Karotype

Picture of all the chromosomes in an organism

Autosomes○ CHROMOSOMES 1-44 (pairs 1-

22)○ Autosomal chromsomes

Sex chromosomes○ Determine a person’s sex (male

XY or female XX)○ Chromosome 45 and 46 (set 23)

DNA

DNA Structure Deoxyribonucleic Acid DNA is a polymer made

up of many monomers called nucleotides

Nucleotide contains: 5-carbon sugar called

deoxyribose RNA contains

RIBOSE sugar instead

Phosphate group One Nitrogenous

base (there are 4 types)

What are these Nitrogenous bases???

Make up the “steps” of the DNA ladder One Step= A Purine + A

Pyrimidine Purines

Double ring structure Adenine Guanine

Pyrimidines Single-ring structure Cytosine Thymine (in DNA only) Uracil (in RNA only)

Nucleic Acids DNA

Double strandDeoxyribose sugarA=TG=C

RNASingle StrandRibose sugarA=UG=CUracil is the

nitrogenous base used instead of THYMINE

DNA Review

The 2 Fates of DNA

DNA Replication(if cell enters cell

division…S-phase)

Protein Synthesis(when cell is doing is normal job-in G1 phase of cell cycle)

DNA Facts All living things have DNA

Prokaryotes-DNA in cytoplasm, simple○ Contain extra DNA called

PLASMIDSEukaryotes-DNA in nucleus,

complex DNA codes for the same 20 amino

acids in ALL living thingsIt is the UNIVERSAL code...all

organisms have the same A,T,G and C bases and the same 20 a.a., just arranged differently

The DNA backbone Putting the DNA

backbone togetherrefer to the 3 and 5 ends

of the DNA○ the last trailing carbon

OH

O

3

PO4

base

CH2

O

base

OPO

C

O–O

CH2

1

2

4

5

1

2

3

3

4

5

5

Sounds trivial, but…this will beIMPORTANT!!

Anti-parallel strands

Nucleotides in DNA backbone are bonded from phosphate to sugar between 3 & 5 carbonsDNA molecule has

“direction”complementary strand runs

in opposite direction

3

5

5

3

Bonding in DNA

….strong or weak bonds?How do the bonds fit the mechanism for copying DNA?

3

5

3

5

hydrogenbonds

Base pairing in DNA Purines

adenine (A)guanine (G)

Pyrimidinesthymine (T)cytosine (C)

PairingA : T

○ 2 bondsC : G

○ 3 bonds

Copying DNA Replication of DNA

base pairing allows each strand to serve as a template for a new strand

new strand is 1/2 parent template & 1/2 new DNA○ semi-conservative

copy process

DNA Replication Large team of enzymes coordinates replication

Let’s meetthe team…

Important Enzymes DNA Helicase

Unzips original DNA strand

DNA PolymeraseAdds nucleotides to the

unzipped sides DNA Ligase

Attaches/glues DNA fragments together on one of the new copies

How does DNA replicate itself?

Template mechanism What is a template??? Like the negative of a photograph

DNA Replication Process of copying the DNA molecule

○ What phase of the CELL CYCLE?S-phase….

2 strands of double helix separate (Unzips)

Each strand acts as a negative for making the new complementary strand

Nucleotides line up one by one following base pairing rules

Enzymes (DNA Polymerase and DNA Ligase) link nucleotides together to form 2 new DNA strands called the daughter strands

Fate #2: Protein Synthesis You already know about this…central

dogma of Biology Just need to know your key players…

The Protein Synthesis Team DNA mRNA tRNA rRNA Codons Anticodons Amino acids Proteins Introns Exons

Central Dogma of Biology

DNAmRNAprotein DNA TRANSCRIBES

to mRNAProcess is called

transcription mRNA TRANSLATES

to proteinsProcess is called

translationmRNA actually makes

amino acids, which come together to make proteins

DNAmRNAamino acids/polypeptide chain (Proteins)

DNA codes for an RNA strand The every 3 bases on the RNA

strand code for a specific amino acidCODON: three sequential

bases that code for a specific a.a. (20 a.a. total)

Amino acid are strung together to make a protein (primary structure)

Change DNA will change RNA which will change amino acids, which change protein

DNAmRNAProtein Transcription

Different form of the same message

DNA makes single stranded RNA (U replaces T)

RNA leaves nucleus Translation

Translate from nucleic acid language to amino acid language

Uses codons, 3-base “word” that codes for specific a.a.○ “code” for an amino

acidSeveral codons make a

“sentence” that translates to a polypeptide (protein)

Start Codons

UAA UGA UAG

Stop Codons

AUG

Three Types of RNA mRNA tRNA rRNA

Three Types of RNA… #1 mRNA (messanger RNA)

RNA transcribed from DNA templateModified in nucleus before if exits

○ RNA splicing: process in which Introns are removed and exons re joined together to make a continuous coding mRNA molecule

Introns○ Internal non-coding regions of DNA and mRNA○ Space fillers/jibberish○ They are cut out of mRNA before it is allowed to

leave the nucleus○ Process is called RNA splicing (processing)

Exons (MOST important part of DNA)○ Coding region of DNA and mRNA that will be

translated (Expressed)○ VERY important part of mRNA…it is carrying the

message from DNA (def can’t cut this out)

Three Types of RNA…#2 tRNA (transfer

RNA)The interpreterTranslate 3-letter

base codes into amino acids

Carries anti-codon on one end (three letters opposite of what is on mRNA)

Carries amino acid on other end

Anti-codon recognizes codon and attaches

Three Types of RNA…#3 rRNA (ribosomal

RNA)Found in ribosomeRibosome composed of 2

subunits:○ Small subunit for mRNA to

attach○ Large Subunit for two

tRNAs to attach“P” site: holds the tRNA

carrying the growing polypeptide chain

“A” site: holds the tRNA that is carrying the next a.a. to be added to the chain

When stop codon (UAA, UAG, UGA) is reached, translation ends and polypeptide is released

MUTATIONS

Mutations

Occur when there is an error in DNA replication

Def: Change in genetic material Mutagens

Physical or chemical agents that cause mutations○ Ex: high energy radiation (x-ray or UV)○ Ex. Chemicals (that are similar to DNA but

cause incorrect base pairing)

MutationAny change in the nucleotide sequence of

DNALarge or small

2 Main typesPoint Mutation

○ Base SubstitutionsFrameshift MutationInsertions or deletions

Base Substitution Replacement of one base or nucleotide with

another Usually do not change amino acid Sometimes causes a change in the protein made Silent Mutation

When a substitution does not cause a change in the protein expressed by a gene

Remember some codons represent the same amino acid

Example: GAA and GAG both code for Glu

Point MutationA point mutation is a simple change in one base of the gene sequence. This is equivalent to changing one letter in a sentence, such as this example, where we change the 'c' in cat to an 'h':

Original: The fat cat ate the wee rat. Point Mutation: The fat hat ate the wee rat.

Insertion or Deletion Nucleotide is removed or added More disastrous mRNA is read as triplet codes

Adding/removing bases changes these three letter codes

Codons downstream from insertion/deletion will be regrouped and probably code for a non-working protein

Result: FRAMESHIFT MUTATIONShift the “reading” frame of the genetic message

Frameshift mutation Original: The fat cat ate the wee rat. Frame Shift: The fat caa tet hew eer at.

Chromosomal Mutations

Involve changes in the number or structure of the chromosome

Chromosomal Disorders

Mechanics of meiosis (where we separate chromosomes) is usually pretty good

But nobody’s perfect…mistakes happen…. Most common problem…

Nondisjunction: when homologous chromosomes fail to separate properly

Literally means “not coming apart”If this occurs, ABNORMAL #s of chromosomes

may find their way into gametes and a disorder of chromosome number may result

Nondisjunction If one of the gametes with an ABNORMAL #

ends up getting fertilized, MAJOR problems!!!Trisomy: “three bodies”

○ Occurs when an autosomal chromosome fails to separate during meiosisWhen do chrm separate?

- Anaphase I and Anaphase 2

○ One gamete ends up with an extra copy of a chromosome and then the fertilized zygote ends up with 3 copies of a chrm instead of 2

○ Example: Downs Syndrome

Chromosomal Mutations May change location of

genes on chromosome Include:

Deletions: loss of part of chromosome

Duplications: produce extra copies of parts of chromosome

Inversions: reverse direction of chromosome

Translocation: when one chromosome breaks off and attaches to another

Mutations NOT always harmful Some alter a protein in a beneficial

way that may help species in a specific environment

If mutation is present in organisms gametes, it may be passed off to off-spring

Mutations are the ULTIMATE source for GENETIC DIVERSITY!!!

What is biotechnology? Here are some hints…

Biotechnology

Manipulation of living organisms or their parts to produce useful products

Main use is to improve human health and food production Seedless fruitsMake insulin

Genetic engineering

The transfer of genes or pieces of DNA from one organism into another organismNew DNA is a combination of pieces from

two different organisms…called recombinant DNA

Used to introduce new characteristics into organisms and populations

Gentically Modified Organisms GMOs

How to make recombinant DNA Use DNA from complex organism (human) and

transfer to a simple organism (bacteria) Uses a PLASMID

Small circular DNA in bacteriaIt is called a VECTOR when used in genetic

engineering

Genetic Engineering Positive/benefits

Make medicine like insulin and vaccines plentiful and inexpensive

Improves crop plants like corn and rice○ Grow faster and

stronger○ Resist disease and

insects○ Genes can be added

to add more vitamins to plants

Negatives/ConsUnknown long term

effects if ingested by humans

Harm native, natural species

Cross pollination between GMOs and wild plants resulting in unwanted hybrids (mockingjays!)

***Decreases genetic variation

DNA Fingerprinting

Not like the fingerprint on your hand

Used to determine the paternity of a child and in forensics (the CSI stuff you see on TV)

The chemical structure of everyone's DNA is the same. Only difference is order of base pairs Too many bases to analyze every

single one, so scientists analyze groups /segments of bases

These patterns do not, however, give an individual "fingerprint," but they are able to determine: If samples are from the same person,

related people, or non-related people. There are a few small fragments in

humans that scientists KNOW vary greatly from individual to individual

They analyze those segments and get a certain probability of a match

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