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Gregor MendelGregor Mendel Austrian monk, Austrian monk,
gardener, scientistgardener, scientist First acknowledged to First acknowledged to
study study heredityheredity – the – the passing on of passing on of characteristics from characteristics from parents to offspringparents to offspring
TraitsTraits – characteristics – characteristics that are inheritedthat are inherited
Father of Father of geneticsgenetics – the – the branch of biology that branch of biology that studies hereditystudies heredity
The PeasThe Peas
Mendel chose garden peasMendel chose garden peas They reproduce sexually, so They reproduce sexually, so
they have both male and they have both male and female sex cells, called female sex cells, called gametesgametes
Pollen and egg unite in a Pollen and egg unite in a process called process called fertilizationfertilization
Fertilization results in a Fertilization results in a fertilized cell, called a fertilized cell, called a zygotezygote, , that develops into a seedthat develops into a seed
The Peas MateThe Peas Mate Pollination is the transfer of Pollination is the transfer of
pollen grains from a male pollen grains from a male reproductive organ to a reproductive organ to a female productive organfemale productive organ
Both male and female organs Both male and female organs are close together in the are close together in the same pea flowersame pea flower As a result, peas normally self-As a result, peas normally self-
pollinatepollinate This is what Mendel wanted in This is what Mendel wanted in
most casesmost cases Mendel also removed the Mendel also removed the
male organ and dusted pollen male organ and dusted pollen on flower of another planton flower of another plant Called cross-pollinationCalled cross-pollination
Mendel’s PeasMendel’s Peas
Mendel’s peas had Mendel’s peas had been self-pollinating been self-pollinating for a long timefor a long time
This meant that the This meant that the tall ones had been tall ones had been tall for a long time tall for a long time and the short ones and the short ones had been short for had been short for generations generations Called purebredsCalled purebreds
Mendel’s Monohybrid Mendel’s Monohybrid CrossesCrosses Mendel performed cross-Mendel performed cross-
pollination with a tall pea pollination with a tall pea plant (6 foot purebred) and plant (6 foot purebred) and a short pea plant (2 foot a short pea plant (2 foot purebred) – these are the purebred) – these are the parental generation (Pparental generation (P11))
HybridHybrid – offspring of parents – offspring of parents that have different forms of that have different forms of a trait a trait
All of the offspring grew as All of the offspring grew as tall as the tall parent – first tall as the tall parent – first filial generation (Ffilial generation (F11)) The “short trait” seemed to The “short trait” seemed to
disappear disappear
Monohybrid CrossesMonohybrid Crosses
Mendel let his F1 Mendel let his F1 plants self pollinateplants self pollinate Second filial Second filial
generation (Fgeneration (F22))
He counted over He counted over 1000 plants1000 plants About 75% were tallAbout 75% were tall About 25% were About 25% were
shortshort Ratio of 3:1Ratio of 3:1
Monohybrid CrossesMonohybrid Crosses Mendel did these same Mendel did these same
types of crosses for 7 types of crosses for 7 traitstraits Seed shape: round vs. Seed shape: round vs.
wrinkledwrinkled Seed color: yellow vs. Seed color: yellow vs.
greengreen Flower color: purple vs. Flower color: purple vs.
whitewhite Flower position: axial vs. Flower position: axial vs.
terminalterminal Pod color: green vs. yellowPod color: green vs. yellow Pod shape: inflated vs. Pod shape: inflated vs.
constrictedconstricted Plant height: tall vs. shortPlant height: tall vs. short
backback
The Rule of Unit Factors The Rule of Unit Factors Mendel concluded that each organism has two Mendel concluded that each organism has two
factors that control each of its traitsfactors that control each of its traits We now know these factors are We now know these factors are genesgenes and that and that
they are located on chromosomesthey are located on chromosomes Alternate forms of genes are called Alternate forms of genes are called allelesalleles Each of Mendel’s traits had two forms of genes – Each of Mendel’s traits had two forms of genes –
two allelestwo alleles One comes from mother, one from fatherOne comes from mother, one from father
The Rule of DominanceThe Rule of Dominance Some alleles are Some alleles are dominantdominant
over over recessiverecessive alleles alleles Dominant alleles cover Dominant alleles cover
recessive recessive allelesalleles In genetics, capital letters are In genetics, capital letters are
used to express dominant used to express dominant alleles and lower case letters alleles and lower case letters are used to express recessive are used to express recessive allelesalleles Ex: “T” for tall allele, “t” for Ex: “T” for tall allele, “t” for
short alleleshort allele So what will a “TT” plant look So what will a “TT” plant look
like?like? A Tt plant?A Tt plant? A tt plant? A tt plant?
Earlobes, Forelock, Dimples, Earlobes, Forelock, Dimples, Straight thumb, Bent Pinky, Straight thumb, Bent Pinky, Mid-digit hairMid-digit hair
The Law of SegregationThe Law of Segregation Mendel’s first law of Mendel’s first law of
heredityheredity Every individual has Every individual has
two alleles of each two alleles of each gene and when gene and when gametes are gametes are produced, each produced, each gamete receives one gamete receives one of these allelesof these alleles
So how did this work So how did this work in Mendel’s Fin Mendel’s F2 2
generation ? generation ?
PhenotypesPhenotypes
Two organisms can Two organisms can look alike on the look alike on the outside, but have outside, but have different allele different allele combinationscombinations
PhenotypePhenotype is the is the way an organism way an organism looks and behaveslooks and behaves ex: yellow seeds can ex: yellow seeds can
be TT or Ttbe TT or Tt
GenotypesGenotypes The allele combination an The allele combination an
organism contains is known organism contains is known as its as its genotypegenotype You can’t always see this You can’t always see this
because of dominiancebecause of dominiance TT and Tt are different TT and Tt are different
genotypesgenotypes An organism is An organism is homozygoushomozygous
for a trait if the two alleles for a trait if the two alleles for the trait are the samefor the trait are the same Ex: TT or ttEx: TT or tt
An organism is An organism is heterozygousheterozygous for a trait if for a trait if the two alleles for the trait the two alleles for the trait are differentare different Ex: Tt Ex: Tt
Mendel’s Dihybrid CrossesMendel’s Dihybrid Crosses
Mendel crossed peas that differed from Mendel crossed peas that differed from each other in two traitseach other in two traits
He crossed plants that were homozygous He crossed plants that were homozygous for round yellow seeds (RRYY) with for round yellow seeds (RRYY) with plants that were homozogous for green plants that were homozogous for green wrinkled seeds (rryy) wrinkled seeds (rryy)
FF11 generation generation All plants produced round, yellow seedsAll plants produced round, yellow seeds
What was dominant?What was dominant?
The Second Generation The Second Generation (F(F22))
Let FLet F11 plants self- plants self-pollinate (were pollinate (were heterozygous for two heterozygous for two traits) traits)
He got all four He got all four combinations in a combinations in a certain ratiocertain ratio Round, yellow – 9Round, yellow – 9 Round, green – 3Round, green – 3 Wrinkled, yellow – 3Wrinkled, yellow – 3 Wrinkled, green - 1Wrinkled, green - 1
The Law of Independent The Law of Independent AssortmentAssortment
Mendel’s second law of Mendel’s second law of heredityheredity
Genes for different traits Genes for different traits are inherited are inherited independently of each independently of each otherother Inheritance of one trait has Inheritance of one trait has
no influence on another traitno influence on another trait Instead of a ratio of Instead of a ratio of
9:3:3:1, what would the 9:3:3:1, what would the dihybrid cross have looked dihybrid cross have looked like?like?
Punnett SquaresPunnett Squares 1905, Reginald 1905, Reginald
Punnet, English Punnet, English biologist created a biologist created a shorthand way of shorthand way of finding EXPECTED finding EXPECTED proportions of possible proportions of possible genotypes in the genotypes in the offspring of a crossoffspring of a cross
Monohybrid crosses Monohybrid crosses See overheadSee overhead
Dihybrid crossesDihybrid crosses See overheadSee overhead
ProbabilityProbability
Reality is rarely like a Punnett squareReality is rarely like a Punnett square When you toss a coin, what’s the When you toss a coin, what’s the
likelihood it will be heads?likelihood it will be heads? You toss 20 heads in a row, what’s the You toss 20 heads in a row, what’s the
likelihood the next will be heads?likelihood the next will be heads? TOSS COINSTOSS COINS ASSIGNMENTASSIGNMENT
P. 262, Problem-Solving LabP. 262, Problem-Solving Lab P. 276, Connection to MathP. 276, Connection to Math
Section 1 ReviewSection 1 Review What structural features of pea plants made What structural features of pea plants made
them suitable for Mendel’s genetic studies? them suitable for Mendel’s genetic studies? What are genotypes of a homozygous and a What are genotypes of a homozygous and a
heterozygous tall pea plant?heterozygous tall pea plant? One parent is homozygous tall and the other is One parent is homozygous tall and the other is
heterozygous. How many offspring will be heterozygous. How many offspring will be heterozygous? heterozygous?
How many different gametes can an RRYy parent How many different gametes can an RRYy parent form? What are they?form? What are they?
What is the law of segregation?What is the law of segregation? What is the law of independent assortment?What is the law of independent assortment? What is the rule of dominance? What is the rule of dominance? In garden peas, the allele for yellow peas is In garden peas, the allele for yellow peas is
dominant to the allele for green peas. Suppose dominant to the allele for green peas. Suppose you have a plant that produces yellow peas, but you have a plant that produces yellow peas, but you don’t know whether it is homozygous you don’t know whether it is homozygous dominant or heterozygous. What experiment dominant or heterozygous. What experiment could you do to find out?could you do to find out?
Genetic VariationGenetic Variation Crossing over during meiosis provides Crossing over during meiosis provides
variabilityvariability How many different kinds of gametes How many different kinds of gametes
can a pea plant produce? can a pea plant produce? Each cell has 7 pairs of chromosomesEach cell has 7 pairs of chromosomes
Each can line up at the equator in two Each can line up at the equator in two different ways and separate by segregationdifferent ways and separate by segregation
22nn = 2 = 277 = 128 possible combinations = 128 possible combinations without crossing overwithout crossing over
When you include the egg, 128 x 128 = When you include the egg, 128 x 128 = 16,384 different combinations of 16,384 different combinations of offspringoffspring
Genetic VariationGenetic Variation In humans, how many possible In humans, how many possible
combinations are there in a single sperm combinations are there in a single sperm or egg?or egg?
222323 = 8,388,608 combinations = 8,388,608 combinations How many possible combinations with How many possible combinations with
fertilizationfertilization 8,388,608 x 8,388,608 = 7.04 x 108,388,608 x 8,388,608 = 7.04 x 101313
(over 70 trillion) (over 70 trillion)
Genetic RecombinationGenetic Recombination With crossing over, additional With crossing over, additional
variation is added providing an almost variation is added providing an almost endless amount of variation possibleendless amount of variation possible
This reassortment of chromosomes This reassortment of chromosomes and the genetic information they and the genetic information they carry, either by crossing over or by carry, either by crossing over or by independent segregation of independent segregation of homologous chromosomes is called homologous chromosomes is called genetic recombinationgenetic recombination
Variation is the raw material that Variation is the raw material that forms the basis for evolution to act on forms the basis for evolution to act on
NondisjunctionNondisjunction Go back to Go back to anaphase I anaphase I The failure of homologous chromosomes to The failure of homologous chromosomes to
separate properly during meiosis is called separate properly during meiosis is called nondisjunctionnondisjunction
In one type of nondisjunction, two kinds of In one type of nondisjunction, two kinds of gametes resultgametes result One with an extra chromosome (trisomy)One with an extra chromosome (trisomy)
Trisomy 21 – Down syndromeTrisomy 21 – Down syndrome One missing a chromosome (monosomy, usually don’t One missing a chromosome (monosomy, usually don’t
survive)survive) One exception – Turner syndrome, female is XO One exception – Turner syndrome, female is XO
NondisjunctionNondisjunction The other type of nondisjunction The other type of nondisjunction
involves a total lack of involves a total lack of separation of homologous separation of homologous chromosomeschromosomes Gamete inherits a complete diploid Gamete inherits a complete diploid
set set Zygote has Zygote has polyploidypolyploidy
Not uncommon in plants – often Not uncommon in plants – often larger and healthier larger and healthier chrysanthemum (tetraploid, 4chrysanthemum (tetraploid, 4nn)) Wheat (hexaploid, 6Wheat (hexaploid, 6nn) ) Apples (3Apples (3nn) )
There are even chemicals that There are even chemicals that help plant breeders do this help plant breeders do this artificiallyartificially
Gene LinkageGene Linkage Genes that are close Genes that are close
together on a together on a chromosome are often chromosome are often inherited togetherinherited together Crossing over rarely Crossing over rarely
works for just one geneworks for just one gene These genes are said to These genes are said to
be be linkedlinked So chromosomes, not So chromosomes, not
genes follow Mendel’s genes follow Mendel’s independent independent assortmentassortment
Chromosome MappingChromosome Mapping
Crossing over occursCrossing over occurs Geneticists use the Geneticists use the
frequency of crossing frequency of crossing over to map the over to map the relative position of relative position of genes on a genes on a chromosomechromosome Genes that are further Genes that are further
apart are more likely apart are more likely to have crossing over to have crossing over occuroccur
Chromosome MappingChromosome Mapping
Suppose there are 4 genes on a chromosome Suppose there are 4 genes on a chromosome – A, B, C, D– A, B, C, D
Frequencies of recombination as follows:Frequencies of recombination as follows: Between A & B: 50% (50 map units)Between A & B: 50% (50 map units) Between A & D: 10% (10 map units) Between A & D: 10% (10 map units) Between B & C: 5% (5 map units)Between B & C: 5% (5 map units) Between C & D: 35% (35 map units)Between C & D: 35% (35 map units)
These give a relative distance between genesThese give a relative distance between genes A -10 units- D -35units- C -5 units- B (whole A -10 units- D -35units- C -5 units- B (whole
thing is 50 units) thing is 50 units)
Section 2 ReviewSection 2 Review How are the cells at the end of meiosis different How are the cells at the end of meiosis different
from the cells at the beginning of meiosis?from the cells at the beginning of meiosis? What is the significance of meiosis to sexual What is the significance of meiosis to sexual
reproduction?reproduction? Why are there so many varied phenotypes Why are there so many varied phenotypes
within a species such as humans?within a species such as humans? How does meiosis support Mendel’s law of How does meiosis support Mendel’s law of
independent assortment?independent assortment? What is crossing over? What is crossing over? How can you use crossing over to map a How can you use crossing over to map a
chromosome? chromosome? What are linked genes?What are linked genes?
What is DNA?What is DNA? DNA contains the complete DNA contains the complete
instructions for instructions for manufacturing all the manufacturing all the proteins for an organismproteins for an organism
DNA achieves its control by DNA achieves its control by determining the structure of determining the structure of proteinsproteins
The moral - DNA codes for The moral - DNA codes for PROTEINSPROTEINS
Let’s start with an Let’s start with an animated touranimated tour
Alfred Hershey & Martha Alfred Hershey & Martha ChaseChase
For a long time, many scientists believed For a long time, many scientists believed protein was the genetic material protein was the genetic material Protein is more complex than DNAProtein is more complex than DNA
1952, Hershey & Chase experimented 1952, Hershey & Chase experimented with radioactively labeled viruses with radioactively labeled viruses (bacteriophages) made only of protein & (bacteriophages) made only of protein & DNADNA DNA was labeled with DNA was labeled with
one isotope one isotope Protein with a different Protein with a different
isotope isotope
Hershey & ChaseHershey & Chase Bactriophages inject genetic material into bacteria, Bactriophages inject genetic material into bacteria,
causing the bacteria to create more bacteriophagescausing the bacteria to create more bacteriophages Hershey & Chase “followed” the radioactively Hershey & Chase “followed” the radioactively
labeled viruseslabeled viruses Discovered that DNA was the genetic material Discovered that DNA was the genetic material
being injected into the bacteriabeing injected into the bacteria
Structure of NucleotidesStructure of Nucleotides DNA is a polymer of DNA is a polymer of
nucleotidesnucleotides Nucleotides have 3 partsNucleotides have 3 parts
A simple sugar (deoxyribose in A simple sugar (deoxyribose in DNA)DNA)
A phosphate group A phosphate group A nitrogenous baseA nitrogenous base
4 possible nitrogenous 4 possible nitrogenous bases in DNAbases in DNA Adenine (A)Adenine (A) Thymine (T)Thymine (T) Guanine (G)Guanine (G) Cytosine (C)Cytosine (C)
Watson & CrickWatson & Crick In 1953, published a paper In 1953, published a paper
proposing that DNA is made of proposing that DNA is made of two chains of nucleotides held two chains of nucleotides held together by nitrogenous basestogether by nitrogenous bases Hydrogen bonds hold Hydrogen bonds hold
strands together (weak)strands together (weak) A only bonds with T, C only A only bonds with T, C only
bonds with Gbonds with G DNA is a double helixDNA is a double helix Also correctly described now Also correctly described now
DNA replicatesDNA replicates Won the Nobel PrizeWon the Nobel Prize
DNA- Common ThreadDNA- Common Thread DNA is the same among ALL DNA is the same among ALL
organisms with DNAorganisms with DNA The differences come with the The differences come with the
different sequences of the four bases different sequences of the four bases Like different words meaning different things, Like different words meaning different things,
even though the letters are the sameeven though the letters are the same The more alike the sequences, the more The more alike the sequences, the more
related he organisms arerelated he organisms are
Replication of DNAReplication of DNA
Without replication, Without replication, new cells (after new cells (after mitosis) would only mitosis) would only have half the DNA of have half the DNA of their parentstheir parents
All organisms All organisms undergo DNA undergo DNA replicatonreplicaton
How DNA ReplicatesHow DNA Replicates Due to complementary base Due to complementary base
pairing, “knowing” the pairing, “knowing” the sequence of one strand helps sequence of one strand helps you predict what the other you predict what the other will look likewill look like
Replication begins when an Replication begins when an enzyme breaks the hydrogen enzyme breaks the hydrogen bonds between basesbonds between bases Called “unzipping” the Called “unzipping” the
DNADNA Cells have stockpiles of Cells have stockpiles of
nucleotides and these bond nucleotides and these bond with the newly exposed baseswith the newly exposed bases Done by a set of enzymes Done by a set of enzymes
called DNA polymerasescalled DNA polymerases
How DNA ReplicatesHow DNA Replicates Each DNA strand has 2 Each DNA strand has 2
ends, labeled the 5’ and ends, labeled the 5’ and and the 3’ end. and the 3’ end. Replication proceeds in Replication proceeds in
the 5’the 5’ 3’ direction 3’ direction Each new strand formed is Each new strand formed is
a complement of one of a complement of one of the parents strandsthe parents strands Half old, Half new - called Half old, Half new - called
semiconservative semiconservative replicationreplication
Genetic continuity is Genetic continuity is maintainedmaintained
Section 1 ReviewSection 1 Review Describe the structure of a nucleotide.Describe the structure of a nucleotide. How do the nucleotides in DNA bond with each How do the nucleotides in DNA bond with each
other within a strand? How do they bond with other within a strand? How do they bond with each other across strands?each other across strands?
Explain why the structure of a DNA molecule is Explain why the structure of a DNA molecule is often described as a zipper.often described as a zipper.
How does DNA hold information?How does DNA hold information? The sequence of nitrogenous bases on one strand The sequence of nitrogenous bases on one strand
of a DNA molecule is GGCAGTTCATGC. What of a DNA molecule is GGCAGTTCATGC. What would be the sequence of bases on the would be the sequence of bases on the complementary strand?complementary strand?
In general, describe the steps that occur during In general, describe the steps that occur during
DNA replication.DNA replication.
Genes & ProteinsGenes & Proteins The information in DNA is put to work through the The information in DNA is put to work through the
production of proteinsproduction of proteins Some proteins become important structuresSome proteins become important structures Other proteins (enzymes) control chemical reactionsOther proteins (enzymes) control chemical reactions Remember that proteins are polymers of amino Remember that proteins are polymers of amino
acids acids The sequence of nucleotides The sequence of nucleotides
determines the string of amino acids determines the string of amino acids and the proteinand the protein
RNARNA RNA differs from DNA in RNA differs from DNA in
3 ways:3 ways: RNA is single stranded RNA is single stranded
(DNA is double)(DNA is double) The sugar in RNA is ribose The sugar in RNA is ribose
(DNA is deoxyribose)(DNA is deoxyribose) Instead of thymine, RNA Instead of thymine, RNA
contains the base uracilcontains the base uracil 3 types of RNA3 types of RNA
Messenger RNA (mRNA)Messenger RNA (mRNA) rRNArRNA tRNAtRNA
TranscriptionTranscription In the nucleus (if cell is In the nucleus (if cell is
eukaryotic), enzymes make an eukaryotic), enzymes make an RNA copy of a portion of a DNA RNA copy of a portion of a DNA strandstrand This process is called This process is called
transcriptiontranscription Begins as enzymes unzip the Begins as enzymes unzip the
molecule of DNA in region of molecule of DNA in region of gene being transcribedgene being transcribed
RNA polymerases pair free RNA polymerases pair free nucleotides with their nucleotides with their complementary strandscomplementary strands
The mRNA strand breaks awayThe mRNA strand breaks away
RNA ProcessingRNA Processing Genes usually contain long non-coding Genes usually contain long non-coding
sequences of bases, called intronssequences of bases, called introns Regions that contain coding Regions that contain coding
sequences are called exonssequences are called exons Enzymes in the nucleus cut out the Enzymes in the nucleus cut out the
intron segments from the mRNA intron segments from the mRNA strand and then paste it back togetherstrand and then paste it back together
Genetic CodeGenetic Code A code is needed to convert the A code is needed to convert the
language of mRNA (4 letters) into the language of mRNA (4 letters) into the language of proteins (20 amino acids)language of proteins (20 amino acids) How big do the words have to be??????How big do the words have to be??????
A codon is a group of 3 nitrogenous A codon is a group of 3 nitrogenous bases in mRNA that codes for an amino bases in mRNA that codes for an amino acidacid 1st one found was UUU - coding for 1st one found was UUU - coding for
phenalyninephenalynine 64 possible codons, so some amino acids 64 possible codons, so some amino acids
correspond to multiple codonscorrespond to multiple codons
Genetic CodeGenetic Code Some codons don’t Some codons don’t
code for an amino acid code for an amino acid - they code for - they code for “instructions”“instructions” UAG - codon for “stop”UAG - codon for “stop” AUG is the “start” AUG is the “start”
codon as well as coding codon as well as coding for methionine for methionine
The code is universalThe code is universal Used in ALL organisms Used in ALL organisms
the samethe same
TranslationTranslation Translation is the Translation is the
process of converting process of converting the information in a the information in a sequence of nitrogenous sequence of nitrogenous bases in mRNA into a bases in mRNA into a sequence of amino acids sequence of amino acids in a proteinin a protein
Takes place at the Takes place at the ribosomes in the ribosomes in the cytoplasmcytoplasm
Transfer RNATransfer RNA Transfer RNA (tRNA) molecules Transfer RNA (tRNA) molecules
bring the amino acids (which bring the amino acids (which are in the cytoplasm) to the are in the cytoplasm) to the ribosome ribosome Each tRNA molecule attaches Each tRNA molecule attaches
to only one type of amino to only one type of amino acidacid
There is a sequence of 3 There is a sequence of 3 nucleotides on the opposite side nucleotides on the opposite side of the tRNA molecule from the of the tRNA molecule from the amino-acid attachment siteamino-acid attachment site It is complementary to a It is complementary to a
specific codon, thus it is specific codon, thus it is called an anti-codoncalled an anti-codon
At the Ribosome
• tRNA attaches to mRNA at the ribosome
• mRNA strand “slides along” and another tRNA attaches at second bonding site
• two amino acids bond together with a peptide bond
• mRNA “slides along” again, allowing another tRNA to come on in
• stops at certain codon and is released
Section 2 ReviewSection 2 Review How does the DNA nucleotide sequence How does the DNA nucleotide sequence
determine the amino acid sequence in a protein?determine the amino acid sequence in a protein? What is a codon, and what does it represent?What is a codon, and what does it represent? What is the role of tRNA in protein synthesis?What is the role of tRNA in protein synthesis? Compare DNA replication and transcription.Compare DNA replication and transcription. You have learned that there are stop codons that You have learned that there are stop codons that
signal the end of an amino acid chain. Why is it signal the end of an amino acid chain. Why is it important that a signal to stop translation be part important that a signal to stop translation be part of protein synthesis?of protein synthesis?
In general, sequence the steps involved in In general, sequence the steps involved in protein synthesis from the production of mRNA to protein synthesis from the production of mRNA to the final translation of the DNA code.the final translation of the DNA code.
MutationsMutations Any change in the DNA Any change in the DNA
sequence is called a mutationsequence is called a mutation Can be caused by errors in Can be caused by errors in
replication, transcription, cell replication, transcription, cell division, or by external agentsdivision, or by external agents
Most mutations are Most mutations are detrimental - create detrimental - create disfunctional proteins, etc. disfunctional proteins, etc.
Occasionally, they may have Occasionally, they may have positive effectspositive effects
MutationsMutations Mutations in reproductive cells are Mutations in reproductive cells are
passed on to offspringpassed on to offspring Happen to a sperm or eggHappen to a sperm or egg All of offspring’s cells have this traitAll of offspring’s cells have this trait Most embryos do not surviveMost embryos do not survive
Mutations in body cells effect only that Mutations in body cells effect only that individual individual Usually only one cell or a few cells at firstUsually only one cell or a few cells at first
Passed on if continue to dividePassed on if continue to divide
Point MutationsPoint Mutations A change in a single A change in a single
base pair in DNAbase pair in DNA Will change one Will change one
amino acidamino acid Affects depend on Affects depend on
which amino acid is which amino acid is changedchanged
Example Example THE DOG BIT THE CATTHE DOG BIT THE CAT THE DOG BIT THE CARTHE DOG BIT THE CAR
Frameshift MutationFrameshift Mutation A mutation in which A mutation in which
a single base is a single base is added or deleted added or deleted from the DNAfrom the DNA
Every codon after Every codon after the mutation would the mutation would be differentbe different
ExampleExample THE DOG BIT THE CATTHE DOG BIT THE CAT THE DOB ITT HEC ATTHE DOB ITT HEC AT
Chromosomal AlterationsChromosomal Alterations Structural changes in chromosomesStructural changes in chromosomes
Parts of chromosomes break offParts of chromosomes break off Parts of chromosomes switch placesParts of chromosomes switch places
Especially common in plantsEspecially common in plants Often happens in meiosisOften happens in meiosis
Most zygotes fail to growMost zygotes fail to grow Non-disjunction is an exampleNon-disjunction is an example
Chromosomal MutationsChromosomal Mutations 4 kinds4 kinds Deletion: part of a chromosome is Deletion: part of a chromosome is
left outleft out Insertion: part of a chromatid Insertion: part of a chromatid
breaks off and attaches to sister breaks off and attaches to sister chromatid (duplication of segment)chromatid (duplication of segment)
Inversion: part of a chromosome Inversion: part of a chromosome breaks off and reattaches breaks off and reattaches backwardsbackwards
Translocation: part of a chromosme Translocation: part of a chromosme breaks off and attaches to non-breaks off and attaches to non-homologous chromosomehomologous chromosome
Causes of MutationsCauses of Mutations Spontaneous mutations occur Spontaneous mutations occur
as a mistake during DNA as a mistake during DNA replication (probably - we don’t replication (probably - we don’t know for certain)know for certain)
Mutagens are environmental Mutagens are environmental agents that can cause a change agents that can cause a change in DNAin DNA X-rays, UV light, nuclear radiationX-rays, UV light, nuclear radiation Dioxins, asbestos, benzene, Dioxins, asbestos, benzene,
formaldehydeformaldehyde
Repairing DNARepairing DNA Cells have repair Cells have repair
mechanisms for fixing DNAmechanisms for fixing DNA These enzymes “proofread” These enzymes “proofread”
new DNA strands during new DNA strands during replication and replace replication and replace incorrect nucleotides with incorrect nucleotides with correct onescorrect ones Work well, but not perfectWork well, but not perfect The more exposure to a The more exposure to a
mutagen, the more likely mutagen, the more likely the mutation will not be the mutation will not be fixedfixed
Section 3 ReviewSection 3 Review What is a mutation?What is a mutation? Describe how point mutations and frameshift Describe how point mutations and frameshift
mutations affect the synthesis of proteins.mutations affect the synthesis of proteins. Explain why a mutation in a sperm or egg cell has Explain why a mutation in a sperm or egg cell has
different consequences than one in a heart cell.different consequences than one in a heart cell. How are mutations and cancer related?How are mutations and cancer related? Name and describe the four kinds of chromosomal Name and describe the four kinds of chromosomal
mutations.mutations. The chemicals in cigarette smoke are known to The chemicals in cigarette smoke are known to
cause cancer. Propose a series of steps that could cause cancer. Propose a series of steps that could lead to development of lung cancer in a smoker.lead to development of lung cancer in a smoker.