Anatomy & Physiology I Unit Five

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

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 - nondisjunctionnondisjunction

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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


Karyotype Karyotype of Down of Down syndrome syndrome (trisomy (trisomy 21)21)


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


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


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


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)


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


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


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

Anatomy & Physiology I Unit Five

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