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| Passing along of traits from one generation to the next. |
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| The study of heredity (genes). |
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| Set of instructions (described by DNA that a child receives from each parent. |
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Work:1856-18-1863
Austria
Scientist and Monk
• Educated in a monastery
• Became a monk and joined the local science club
– Counted the number of offspring in crosses involving pea plants |
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| Early Ideas About Heredity-1600's |
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Definition
• British farmers tried similar crosses
• Noted that some had stronger tendency to pass traits to offspring. |
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• White X purple flowers
– All offspring were purple
– F2 = white and purple |
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Many varieties available
– Previous work done with them
– Small and grow quickly
– If left alone they will self pollinate
-Easy to cross pollinate |
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| Mendel's Experimental design |
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Definition
True Breeding varieties-only one type of gene for each trait.
EX: purple vs. white flowers |
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Definition
-P Generation (parental) 1st
-F1 Generation (filial) 2nd
-F2 Generation (filial) 3rd
-From two members of F1
-Self pollinate |
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Definition
Purple X White flowers.
-all of the F1 was purple.
-Dominant trait (expressed in F1 (purple)
-Recessive trait (not expressed by the F1, white) |
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Self Fertilize F1
3:1 ratio between dominant and recessive
Had been done before but Mendel counted the offspring and discovered this ratio. |
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F2=Disguised 1:2:1 Ratio
-1 "true breeding" dominant
-2 non "true breeding" dominant
.Purple
-1 "true breeding" recessive
.White |
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Each individual has two factors (genes) for each trait.
Homozygous and Heterozygous |
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Both genes are different.
-The dominant gene is expressed by the recessive trait is still carried and can be passed on. |
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Alternative forms of a gene.
ex:white or purple
p or P |
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| The actual alleles present |
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| The likelihood of getting one particular genotype in the offspring. |
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Determines the genotype of an individual expressing a dominant trait.
EX: PP 25% (homozygous dominant)
Pp 50% (heterozygous dominant)
pp 25% (homozygous recessive) |
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| Mendel's First Law: Law of Segregation |
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Definition
Somatic Cells contain two copies of each gene (alleles).
Only one per gamete. Gametes combine randomly.
Dominant masks recessive allele.
Alleles must seperate during meiosis |
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| Mendel's Second Law:Law of Independent Assortment |
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Definition
Determined while working with dihybrid crosses.
-working with two traits at the same time.
-Genes located on different chromosomes are inherited independently. |
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| Mendel's theory was considered a big flop True or False? |
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Definition
| True. Scientist weren't looking for anything. Didn't discover all traits. Theory was rediscovered in 1900, 16 yrs after Mendel's death. |
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Definition
When offspring exhibit a phenotype intermediate to that of both parents
• Ex. Snapdragons
• NOT blending
– The original traits come back in F |
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Sometimes more than two alleles exist for a given trait in a population of
individuals |
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A & B are proteins that cover the RBC surface
• Equally dominant
• “O” means absent
• Chromo #9 |
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(universal receiver)
– IAIB |
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Definition
– Cell surface marker on RBC
– 85% is Rh+
– Rh- mother bears an Rh+ fetus
• During child birth blood crosses
• Mom begins make Rh- to attack Rh+
t Involves 45 different antigens on the surface of RBC that are controlled by 2
closely linked genes on chromosome 1.
t Maternal antibodies can cross the placenta and destroy fetal red blood cells.
t The risk increases with each pregnancy. |
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Definition
Sometimes one trait is determined by several genes and multiple alleles Continuous variation for the trait within a population
– Ex. Human height |
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Definition
When an allele effects more than one trait
• One gene has many effects
• Genes work together in an interrelated web |
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| Examples of Pleiotrophic Effects |
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Definition
Cystic fibrosis-– Clogged blood vessels
– Overly sticky mucus
– Salty sweat
– Liver and pancreas failure
– Etc.
– Protection against cholera
• Disease that kills through profound fluid loss
Sickle-cell anemia-Protection from maleria
Fragile-X syndrome-One gene, but phenotype includes
• Lower IQ
• Abnormally long faces
• Large, protuberant ears
• Large testicles in males |
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Definition
– Two separate genes that effect each other
– Must have a homozygous recessive gene to produce white corn
• Gene A
– allows purple pigment to be deposited on seed coat
• Gene B
– Produces purple pigment |
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Definition
– Some alleles are heat sensitive
– Different pigmentation during seasonal weather changes.
• Ex. Arctic Fox |
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| What other structures besides chromosomes divide and segregate? |
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Definition
Centrioles
Mitchondria
Cholorplasts |
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Definition
– 1900
– Rediscovered Mendel’s work
– Similar chromosomes paired during meiosis |
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Definition
– 1902
– Chromosomal theory of inheritance
– Scientists were still skeptical! |
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Definition
– Drosophilia melanogaster (Fruit Fly)
• New generation every 12 days
– 1910
– Found a white eyed male mutant
• Red is normal
• White X Red
– F1 were all red eyed
• red is dominant
– F2 produced white eyed flies
• All the white eyed flies were made
– Crossed F1 female with the original white eyed male.
• White eyed female!
"• Sex Linked Trait"
– Attached to the X and Y chromosomes that determine sex.
– Y chromosome has very few functional genes
– Genes are carried on chromosomes, and Mendel’s laws are true
– Many mutations!
• Small wings
– same chromo as white eye
– Crossing over!!
• Short wings
• Short legs
• Black body
• Curved wings
– Nobel prize in 1934 |
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Definition
– Problem w/ genes that make proteins located on X chromo
– Most are recessive |
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Definition
X-linked condition
Faulty blood clotting
• Group of proteins |
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Term
| Duchenne Muscular Dystrophy |
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Definition
X-linked condition
– Wasting of muscles (2-10 yrs) |
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Term
| Red-green color blindness |
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Definition
X-linked condition
Color blind
– Male = 8%
– Female = 0.5% |
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Term
| Autosomnal recessive disorder |
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Definition
– Sickle Cell anemia
– Cystic Fibrosis
– Tay-Sachs |
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Term
| Autosomnal Dominant disorder |
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Definition
Polydactyly
• Extra fingers or toes
• Ernest Hemmingway’s cats
– Huntington Disease
• Brain tissue degeneration |
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Definition
– Down Syndrome
• Mental retardation
– Turner syndrome
• Sterile
• Short
– Kleinfelter syndrome
• Feminized features |
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Term
| Aberations in chromo structure |
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Definition
Fragile-X Syndrome
• Mental retardation |
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Term
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Definition
Humans have 46 chromosomes (23 pairs)
– Vary in size shape and appearance |
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Definition
– Photographing of chromosomes
– An individual’s particular array of chromosomes |
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Definition
– During meiosis, the homologous chromosomes (sister chromatids) do not separate
properly
– Leads to aneuploidy |
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Definition
| Having an abnormal number of chromosomes |
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| Nondisjunction Involving Autosomes |
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Definition
Monosomics
Trisomics
Down Syndrome |
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Definition
| one of a particular chromo |
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Definition
– Trisomy 21
– mental impairment & physical defects |
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Definition
| Female who is sterile but usually normal in other respects |
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| XXY "Klinefelter Syndrome” |
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Definition
Sterile male
• female body characteristics
• diminished mental capacity in some
• 1/500 male births |
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Definition
• Nonviable and fails to develop
• Humans cannot survive with out the X chromosome |
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Definition
• Sterile female
• short
• webbed neck
• immature sex organs
– No changes during puberty.
• Mental abilities are low to normal
• 1/5,000 female births |
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Term
| X chromosomes fail to separate during meiosis |
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Definition
• XX gametes.
• “O” gametes |
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Term
| When Y chromosomes fail to separate during meiosis |
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Definition
– YY gametes
– “O” gametes |
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Definition
• Fertile male of normal appearance
• 1/1,000 male births
• 20x higher in prison and mental institutions
• However, most don’t develop patterns of antisocial behavior |
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Definition
• Accidental changes in genes
• Almost always bad
• Recessive allele |
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Definition
Family trees
• Indicate inheritance of the mutation.
• Used to study human heredity (genetic disorders) |
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Definition
– 1920’s
• Chromos contain genetic info
– 1930s & 1940s
• DNA is the genetic info
• Genes bring about the production of protiens |
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Definition
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Term
1928: The Griffith Experiment
Streptococcus pneumoniae (Bacteria) |
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Definition
Smooth Strain (polysaccharide coat)
-Killed mice
Rough Strain (no coat)
-No effect
Coat needed for infection.
However,dead smooth + live rough = mice died Hereditary info could thus be passed from dead cells to live ones! |
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Definition
| DNA can be passed from dead strains of a pathogenic bacterium to transform a non-virulent strain into one that is pathogenic. |
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| 1944: The Avery Experiments |
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Definition
Oswald Avery
Same as Griffith, but removed protein.
–Chromos are made of protein (Histones) and DNA
–Transforming activity
•Not Reduced- when protein removed
–by lipid and protein extraction
–by protein or RNA-digesting enzymes
•Stopped- when DNA removed
–by DNA-digesting enzymes |
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Term
| 1928: The Griffith Experiment-end result |
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Definition
Demonstrated conclusively that DNA is the hereditary material!!
–Not protein (common belief) |
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Term
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Definition
-DNA is inserted into the host cell’s DNA as if they were the cells own genes
-DNA >>>> RNA |
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Definition
–“Retroviruses”
–To infect cells
•DNA from the RNA
•The DNA copy may then insert into the host cell's DNA.
•Permanent!
–RNA>>>>DNA |
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Term
| 1952: Hershey- Chase Experiment |
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Definition
Avery’s results were not widely accepted.
–Most still thought genes were protein
Alfred Hershey & Martha Chase
Radioactive labels to mark DNA and protein of viruses. |
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Term
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Definition
| •Radioactive phosphorus (32P) |
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Definition
| •Radioactive sulfur (35S) |
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Term
–DNA
•Radioactive phosphorus (32P)
–Protein Coat
•Radioactive sulfur (35S) |
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Definition
-Infected bacteria using r/a labels
–New viruses made by bacteria contained the r/a phosphorus (32P) but not the sulfur.
-DNA is the genetic material! |
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Term
| 1957: Fraenkel-Conrat Experiment |
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Definition
Ċ-Heinz Fraenkel-Conrat
Ċ-RNA-containing viruses
¡VWhy: nucleic acids = genetic material
-RNA from one virus was crossed with the protein of another similar virus
¡VHybrid virus painted on tobacco leaf
¡VProtein of offspring was from the original RNA |
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Term
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Definition
Late 1950's
-Nucleic Acid accepted as the genetic material
-Structure still unknown |
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Term
| Chargaff-DNA always had equal amounts of: |
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Definition
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Definition
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Definition
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•Amounts of adenine equaled thymine and cytosine equaled guanine
–A=T
–G=C |
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Definition
A Regular Structure.
Suggested Base-Pairing. |
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Definition
1953
X-Ray Visioned DNA=Helix |
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Definition
–James Watson—23-year-old American, one year out of graduate school
–Francis Crick—35-year-old English graduate student
•Connected the ideas of a helix with base-pairing.
•DNA
–Sugar-phosphate backbone
–Base-pairing
–Double helix
•They also suggested a mechanism by which DNA was able to copy itself |
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| How the DNA Molecule Replicates: |
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Definition
Nitrogenous Bases
–“nucleotides”
–A,T ,G,C
Complementary Base Pairs
–ATTGCAT
–TAACGTA
Semiconservative Replication
–When DNA copies itself
–Each existing strand serves as a template for a new complementary strand
–One new, one old |
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Term
| 1958 :The Meselson Stahl Experiment |
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Definition
Matthew Meselson & Franklin Stahl
Semiconservative replication was tested using 14N and the heavy isotope 15N.
Exp.
–Parental
•All heavy strands (15N)
•Placed in medium of light (14N) |
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| 1958 :The Meselson Stahl Experiment Results: |
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Definition
–F1
•Light & heavy
–F2
•Light & heavy
•Both light |
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Definition
-enzyme
-oversees the operation
-Replaces complementary nucleotides on parent strands. |
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Definition
-Unzips DNA-1000 nucleotides at a time
-•Replication Fork. |
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Definition
–Enzyme
–Bonds sugar-phosphate backbone |
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Term
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Definition
–minimized by DNA polymerase proofreading
–Bacterial polymerase
•1/100,000 mistakes
•1/1,000,000 kept |
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Term
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Definition
A.Mutation = permanent change in DNA sequence
How does the checking mechanism know which strand is correct?
–Binding Protiens
•which strand is older
B.Almost all cancers begin as a mutation that is passed along at replication.
1. somatic cells
2. rate is low
–After decades of accumulated mutations, cells can become malignant.
C.Heritable Mutations
–Germ-line cells
•Divide to become egg/sperm
–Create genetic diversity! |
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Definition
| –Hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism. |
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Definition
–Strands of amino acids (20 different) joined by peptide bonds.
–Every protein has a unique amino acid sequence. |
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Transcription
Making Protein |
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Definition
–DNA >> RNA >> protein
•RNA is a
–“blueprint” copy of DNA
–Messenger RNA (mRNA)
–Ribosomal RNA (rRNA)
–Transfer RNA (tRNA) |
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Term
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Definition
•1. Transcription
–mRNA is made in the nucleus
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2. Translation
–mRNA leaves the nucleus and directs the production of a protein molecule. |
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Definition
–1. RNA polymerase
•binds to the DNA at the promoter
•moves along the DNA molecule
–2. mRNA is made
•nucleotide sequence is complementary to DNA
•But, Thymine is replaced with Uracil
•A=U
•G=C |
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Term
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Definition
–Adenine = Thymine
–Guanine = Cytosine
–Double strand
–The sugar is deoxyribose |
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Definition
–Adenine = Uracil
–Guanine = Cytosine
–Single strand
–The sugar is ribose |
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Definition
| Site where the RNA polymerase first binds to DNA. |
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Definition
| Moves down DNA in steps of 3 nucleotides |
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Definition
–Each block = an amino acid
–codon |
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Definition
–mRNA sequence that corresponds to the 3-nucleotide sequence on DNA
–Ex. AUG/GCU/UAA
64 possible codons
–Same for all |
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Translation
Ribosomes (Ribo) |
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Definition
–Make proteins
–Follow mRNA blueprint
–In the cytoplasm
–Made of
•proteins
•rRNA |
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Term
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Definition
– nticodon at one end
•a sequence of three nucleotides complementary to a mRNA codon.
–Amino Acid (AA) at other end
•corresponds with the codon of the mRNA |
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Definition
–tRNA
•brings the correct amino acid into position along the mRNA molecule (held by ribo)
–Ribosome
•proceeds along mRNA,
•next AA is added to peptide chain.
–When finished
•ribo falls apart
•completed protein released |
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Term
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Definition
–Prokaryotic DNA
•continuous sequence of genes with no interruptions.
–Eukaryotic DNA
•Exons-gene sequences that code for amino acids
•Introns- intervening, nonusable sequences of nucleotides
–must be removed from mRNA before translation can occur.
–97% of your DNA!!! |
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Definition
–multiple copies of each gene!
–Most genes
–Clusters of almost identical sequences
–Few to several hundred |
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Term
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Definition
–50,000 segments of CACACACAC.….
–Primates Alu repeat
•280 base pairs
•1 million times!
•10% of your DNA
•DNA virus?
–Selfish DNA
•Only purpose is to copy itself |
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Term
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Definition
–genes that jump from one position to another on a chromosome,
–preventing expression of gene sequence.
–no functional role
•“molecular parasites”
•May transfer genetic properties such as resistance to antibiotics.
•45% of human genome! |
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Term
| Mutations in Germ-line Tissues |
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Definition
| –Only when a mutation occurs within a germ-line cell is it passed to subsequent generations |
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Term
| Mutations in Somatic Tissues |
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Definition
–Changes in somatic cells are not passed on from generation to generation.
–A somatic mutation may have drastic effects on the individual in which it occurs.
–Ex. Lung Cancer |
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Term
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Definition
| –Point mutations are changes in the hereditary message of an organism that involve only one or a few base pairs of the coding sequence |
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Definition
| •Identity of a base changes |
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Definition
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Definition
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•If insertion or deletion throws the reading of the gene message out of register
–Some mutations may arise spontaneously, while others are the result of exposure to mutagens. |
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| Changes in Gene Position–Transposition |
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Definition
.Individual genes may move from one place to another
•Its expression or the expression of neighboring genes may be altered |
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Term
| –Chromosomal Rearrangements |
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Definition
•Large segments of chromosomes in eukaryotes may change their relative locations or undergo duplication
•Usually has drastic effects on the expression of the genetic message |
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Definition
| –Agents thought to cause cancer. |
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Term
| Chemical Carcinogenesis Theory |
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Definition
| –The suspicion that chemicals contribute to the incidence of cancer |
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Term
| Cancer and Mutation-Early Ideas |
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Definition
–John Hill
•English physician (1761)
•chemical carcinogenesis theory
–Noted unusual tumors of the nose in heavy snuff users.
–He believed that it was from the tobacco
–Observations in 1775 by Sir Pott, a London surgeon, suggested a relationship between soot and tar and scrotal cancer in chimney sweeps.
Demonstrating that Chemicals Can Cause Cancer
–In 1915, a Japanese doctor found tar applied to rabbits caused cancer.
–Since that time, it has been shown repeatedly that smoking cigarettes introduces tar into the lungs, leading to an increased rate of lung cancer.
Carcinogens Are Common
–Numerous chemicals have been found to be carcinogenic.
–They are all mutagens, capable of inducing changes in DNA. |
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