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Anatomy & Anatomy & Physiology IPhysiology I
Unit FiveUnit Five
The Characteristics The Characteristics and Functions of and Functions of
MeiosisMeiosisProduction of Production of gametesgametes
Creates new Creates new combinations of genescombinations of genes
Assures correct Assures correct chromosome numbers chromosome numbers in offspringin offspringBegins with a diploid Begins with a diploid sex cell & ends with sex cell & ends with non-identical haploid non-identical haploid gametesgametes
MeiosisMeiosis
Meiosis is the cell division Meiosis is the cell division process by which gametes are process by which gametes are producedproducedIt occurs only in sex cells that It occurs only in sex cells that are found in the gonadsare found in the gonads
MeiosisMeiosis
The process goes The process goes through two through two meiotic divisions meiotic divisions – meiosis I and – meiosis I and meiosis IImeiosis II
MeiosisMeiosisHomologous chromosomesHomologous chromosomes
MeiosisMeiosis
MeiosisMeiosis
Meiosis Meiosis
Meiosis Meiosis vs. vs.
MitosisMitosis
GeneticGeneticss Genetics – the study of Genetics – the study of
heredityheredityHeredity – the passing of Heredity – the passing of traits from one generation traits from one generation to the nextto the nextTrait – a physical or Trait – a physical or physiological characteristic physiological characteristic coded for by a genecoded for by a geneGene – a portion of a Gene – a portion of a chromosome that codes for chromosome that codes for a particular proteina particular proteinAllele – a form of a geneAllele – a form of a gene
GeneticGeneticss
Dominant allele – an allele Dominant allele – an allele that masks the effects of the that masks the effects of the other other Recessive allele – an allele Recessive allele – an allele that can be masked by a that can be masked by a dominant alleledominant alleleLocus – the position of a gene Locus – the position of a gene on a chromosomeon a chromosome
GeneticGeneticss
Homologous chromosomes – Homologous chromosomes – a pair of chromosomes, one a pair of chromosomes, one each from the female & male each from the female & male parent, that have identical parent, that have identical structure and gene locistructure and gene loci
Homologous chromosome
s
Mom (female)
Dad (male)
Dominant allele
Recessive allele
GeneticGeneticss
GeneticGeneticss
Genotype – the set of genes Genotype – the set of genes an organism hasan organism hasHomozygous – alleles are the Homozygous – alleles are the same typesame typeHeterozygous – alleles are Heterozygous – alleles are differentdifferent
GeneticGeneticss
Phenotype – the expression Phenotype – the expression of the genotypeof the genotypePurebred – having a Purebred – having a homozygous genotypehomozygous genotypeHybrid – having a Hybrid – having a heterozygous genotypeheterozygous genotype
GeneticGeneticss
Codominance – the two Codominance – the two alleles at a locus are equally alleles at a locus are equally expressedexpressedKaryotype – a chart of the Karyotype – a chart of the chromosomes of an chromosomes of an organism, arranged in order organism, arranged in order by size and structureby size and structure
GeneticGeneticss
D D d d
D d
Punnett SquarePunnett Square
D DD D
dd
dd
DdDd DdDd
DdDd DdDd
D D dd
dD
D D Dd d d
Monohybrid CrossMonohybrid Cross
D dD d
DD
dd
DDDD DdDd
DdDd dddd
Genotypic Ratio – Genotypic Ratio – 1:2:11:2:1Phenotypic Ratio – Phenotypic Ratio – 3:13:1
Complete Complete DominanceDominance
Complete Complete DominancDominanc
ee
Monohybrid CrossMonohybrid Cross
D dD d
dd
dd
DdDd dddd
DdDd dddd
Genotypic Ratio – Genotypic Ratio – 2:22:2Phenotypic Ratio – Phenotypic Ratio – 2:22:2
Complete Complete DominancDominanc
ee
Codominance
A O
B
O
AB BO
AO OO
Genotypic Ratio – 1:1:1:1Phenotypic Ratio – 1:1:1:1
Autosomal vs. Sex Autosomal vs. Sex LinkedLinked
Autosomes – all Autosomes – all chromosomes except for the chromosomes except for the ones that determine sexones that determine sexSex chromosomes – Sex chromosomes – chromosomes that determine chromosomes that determine sexsexSex linked traits – traits Sex linked traits – traits controlled by genes on the controlled by genes on the sex chromosomessex chromosomes
Sex Linked CrossSex Linked Cross
XXBB X Xbb
XXbb
YY
XXBBXXbb XXbbXXbb
XXBBYY XXbbYY
Human Sex Human Sex ChromosomesChromosomes
♀♀ ♂♂
XX XX XX YY
Human Sex Human Sex ChromosomesChromosomes
♀♀ ♂♂
MutationsMutations
A mutation is any change in A mutation is any change in the DNA of an organismthe DNA of an organismMutations occur due to:Mutations occur due to: - pathogen infection- pathogen infection - exposure to radiation- exposure to radiation - introduction of chemicals - introduction of chemicals - nondisjunction- nondisjunction
MutationsMutations
Mutations involve:Mutations involve: - base pair substitutions- base pair substitutions - base pair insertions or - base pair insertions or deletionsdeletions - DNA segments- DNA segments
MutationsMutations
Genes, Genetic Code & Genes, Genetic Code & Genetic DiseaseGenetic Disease
Remember, genes are portions Remember, genes are portions of DNA that code for a of DNA that code for a particular proteinparticular proteinIn order for the protein to be In order for the protein to be functional, the DNA nitrogen functional, the DNA nitrogen base sequence must be correctbase sequence must be correct
Genes, Genetic Code & Genes, Genetic Code & Genetic DiseaseGenetic Disease
Any variance of that sequence Any variance of that sequence can cause the wrong amino can cause the wrong amino acid to be inserted into the acid to be inserted into the polypeptide which could result polypeptide which could result in:in: - a non-functioning protein - a non-functioning protein - a protein that changes the - a protein that changes the outcome of a processoutcome of a process
NondisjunctionNondisjunction
Nondisjunction is the failure of Nondisjunction is the failure of chromosomes to separate chromosomes to separate during anaphase I of meiosisduring anaphase I of meiosisThe normal separation, The normal separation, disjunction, produces daughter disjunction, produces daughter cells with 23 chromosomes cells with 23 chromosomes eacheach
NondisjunctionNondisjunction
Nondisjunction results in one Nondisjunction results in one daughter cell with 24 daughter cell with 24 chromosomes and the other chromosomes and the other with 22 chromosomeswith 22 chromosomes
NondisjunctionNondisjunction
Monosomy is the result of the Monosomy is the result of the fertilization of a normal fertilization of a normal gamete and one that has only gamete and one that has only 22 chromosomes22 chromosomesTrisomy is the product of the Trisomy is the product of the fertilization of a normal fertilization of a normal gamete and one that has 24 gamete and one that has 24 chromosomeschromosomes
NondisjunctionNondisjunctionDisjunctionDisjunction
Genetic DisordersGenetic Disorders
Several genetic disorders are Several genetic disorders are sex linked and found sex linked and found predominantly in men, but predominantly in men, but can also be present in womencan also be present in womenThe shorter Y chromosome The shorter Y chromosome means there is only one allele means there is only one allele that determines these traits that determines these traits
Genetic DisordersGenetic Disorders
Male pattern baldness and Male pattern baldness and color blindness are two color blindness are two examples that are examples that are inconvenient, but non-life inconvenient, but non-life threateningthreateningHemophilia, a condition in Hemophilia, a condition in which the blood does not clot which the blood does not clot correctly, can be deadlycorrectly, can be deadly
Genetic DisordersGenetic DisordersRemember:Remember:Any variance of the DNA base Any variance of the DNA base sequence can cause the sequence can cause the wrong amino acid to be wrong amino acid to be inserted into the polypeptide inserted into the polypeptide which could result in:which could result in: - a non-functioning protein - a non-functioning protein - a protein that changes the - a protein that changes the outcome of a processoutcome of a process
Genetic DisordersGenetic Disorders
These mutations can lead to a These mutations can lead to a number of human health number of human health disordersdisordersSome of these abnormalities Some of these abnormalities are inconvenient, while others are inconvenient, while others can be lethalcan be lethal
Genetic DisordersGenetic Disorders
Albinism is a condition in Albinism is a condition in which the body does not which the body does not produce the pigment melaninproduce the pigment melaninThe phenotypic results are The phenotypic results are white hair, pale skin and pink white hair, pale skin and pink colored eyescolored eyes
Genetic DisordersGenetic Disorders
Albinism is the result of a Albinism is the result of a homozygous recessive homozygous recessive genotype that produces a genotype that produces a nonfunctional tyrosinase nonfunctional tyrosinase enzyme enzyme Melanin is synthesized from Melanin is synthesized from tyrosine by way of the tyrosine by way of the enzyme tyrosinaseenzyme tyrosinase
Genetic DisordersGenetic Disorders
Sickle cell Sickle cell disease is a disease is a condition in condition in which red blood which red blood cells are cells are deformed due to deformed due to the substitution the substitution of one amino of one amino acid in a acid in a hemoglobin hemoglobin chainchain
Genetic DisordersGenetic Disorders
The deformation of the RBCs The deformation of the RBCs inhibits the binding of inhibits the binding of oxygen, causing anemia oxygen, causing anemia The deformation also causes The deformation also causes the sickled RBCs to be sticky the sickled RBCs to be sticky and agglutinateand agglutinate
Genetic DisordersGenetic Disorders
Without treatment a child will Without treatment a child will usually die before age two usually die before age two Even with treatment most Even with treatment most affected people die before the affected people die before the age of fiftyage of fifty
Genetic DisordersGenetic Disorders
The substitution of one amino The substitution of one amino acid is caused by a recessive acid is caused by a recessive allele allele Sickle cell is the result of a Sickle cell is the result of a homozygous recessive homozygous recessive genotype that produces the genotype that produces the malformed hemoglobin malformed hemoglobin
Genetic DisordersGenetic Disorders
Approximately 8.5% of people Approximately 8.5% of people of central and southern African of central and southern African descent are carriers of the descent are carriers of the alleleallele
Genetic DisordersGenetic Disorders
Phenylketonuria (PKU Phenylketonuria (PKU disease) is a disorder in which disease) is a disorder in which the amino acid phenylalanine the amino acid phenylalanine is not metabolized due to the is not metabolized due to the lack of an enzymelack of an enzyme
Genetic DisordersGenetic Disorders
PKU disease is the result of a PKU disease is the result of a homozygous recessive homozygous recessive genotype that does not genotype that does not produce the enzyme that produce the enzyme that converts phenylalanine into converts phenylalanine into tyrosine tyrosine
Genetic DisordersGenetic Disorders
Phenylalanine accumulates in Phenylalanine accumulates in the blood and acts as a the blood and acts as a neurotoxin, causing brain neurotoxin, causing brain damage and retardationdamage and retardationRequired tests on newborns Required tests on newborns now identify those affected, now identify those affected, which will be put on a low which will be put on a low phenylalanine dietphenylalanine diet
Genetic DisordersGenetic Disorders
Remember:Remember:Nondisjunction in gametes Nondisjunction in gametes causes a change in causes a change in chromosome numbers that chromosome numbers that affects the development of an affects the development of an embryoembryoApproximately 90% of Approximately 90% of nondisjunction events are nondisjunction events are maternal in originmaternal in origin
Genetic DisordersGenetic Disorders
The presence of an extra The presence of an extra chromosome (trisomy) or lack chromosome (trisomy) or lack of one (monosomy) accounts of one (monosomy) accounts for approximately 50% of all for approximately 50% of all spontaneous abortionsspontaneous abortions
Genetic DisordersGenetic Disorders
Only three autosomal trisomies Only three autosomal trisomies are survivable:are survivable: * trisomy 13 – Patau * trisomy 13 – Patau syndromesyndrome * trisomy 18 – Edward * trisomy 18 – Edward syndromesyndrome * trisomy 21 – Down * trisomy 21 – Down syndromesyndrome
Genetic DisordersGenetic Disorders
Most fetuses with Patau or Most fetuses with Patau or Edward syndrome will die Edward syndrome will die before birthbefore birthThe few that are born are The few that are born are severely deformed and usually severely deformed and usually die within their first yeardie within their first year
Genetic DisordersGenetic Disorders
Karyotype Karyotype of Down of Down syndrome syndrome (trisomy (trisomy 21)21)
Genetic DisordersGenetic Disorders
Down syndrome is the most Down syndrome is the most survivable of the trisomies, but survivable of the trisomies, but approximately 75% die before approximately 75% die before birth and 20% of those born birth and 20% of those born will die before the age of tenwill die before the age of ten
Genetic DisordersGenetic Disorders
Down syndrome effects:Down syndrome effects: * short stature* short stature * a flat face with almond * a flat face with almond shaped shaped eyeseyes * enlarged protruding tongue* enlarged protruding tongue * broad hands with short * broad hands with short fingersfingers * varying degrees of mental * varying degrees of mental retardationretardation
Genetic DisordersGenetic Disorders
Of those that survive past the Of those that survive past the age of ten, life expectancy has age of ten, life expectancy has been extended to sixty yearsbeen extended to sixty yearsHowever, after the age of forty However, after the age of forty many develop early onset many develop early onset Alzheimer diseaseAlzheimer disease
Genetic DisordersGenetic Disorders
Nondisjunction also occurs Nondisjunction also occurs with the sex chromosomes:with the sex chromosomes: * trisomy 23 – Klinefelter * trisomy 23 – Klinefelter syndrome (XXY)syndrome (XXY) * trisomy 23 – Triplo-X * trisomy 23 – Triplo-X syndromesyndrome (XXX)(XXX) * monosomy 23 – Turner * monosomy 23 – Turner syndrome syndrome (XO)(XO)
Genetic DisordersGenetic Disorders
Triplo-X syndrome (XXX) Triplo-X syndrome (XXX) results in a female phenotype results in a female phenotype that is usually infertile and that is usually infertile and may exhibit some intellectual may exhibit some intellectual impairmentimpairment
Genetic DisordersGenetic Disorders
Klinefelter syndrome (XXY) Klinefelter syndrome (XXY) results in a sterile male results in a sterile male phenotype that is of normal phenotype that is of normal intelligence and upon the intelligence and upon the onset of puberty exhibits onset of puberty exhibits unusually long arms, sparse unusually long arms, sparse body hair, undeveloped testes body hair, undeveloped testes and enlarged breastsand enlarged breasts
Genetic DisordersGenetic Disorders
Turner syndrome (XO) results Turner syndrome (XO) results in a sterile female phenotype in a sterile female phenotype that fails to develop secondary that fails to develop secondary sex characteristics at puberty sex characteristics at puberty and is usually short in statureand is usually short in statureApproximately 97% of all (XO) Approximately 97% of all (XO) fetuses die before birthfetuses die before birth