Chapter 11: Complex Chapter 11: Complex Inheritance and Human Inheritance and Human

HeredityHeredity

Section 11.1: Basic Patterns of Human InheritanceSection 11.1: Basic Patterns of Human InheritanceSection 11.2: Complex Patterns of InheritanceSection 11.2: Complex Patterns of InheritanceSection 11.3: Chromosomes and Human HereditySection 11.3: Chromosomes and Human Heredity

Section 11.1: Basic Patterns of Human Section 11.1: Basic Patterns of Human InheritanceInheritance

Main idea: The inheritance of a trait over several Main idea: The inheritance of a trait over several generations can be shown in a pedigreegenerations can be shown in a pedigree

ObjectivesObjectives– Analyze generic patterns to determine dominant or Analyze generic patterns to determine dominant or

recessive inheritance patternsrecessive inheritance patterns– Summarize examples of dominant and recessive Summarize examples of dominant and recessive

disordersdisorders– Construct human pedigrees from generic informationConstruct human pedigrees from generic information

Review VocabularyReview Vocabulary– Genes: segments of DNA that control the production of Genes: segments of DNA that control the production of

proteinsproteins New VocabularyNew Vocabulary

– CarrierCarrier– PedigreePedigree

Recessive Genetic DisordersRecessive Genetic Disorders Mendel’s work was ignored for more than 30 years During the early 1900’s scientists began to take an

interest in heredity and Mendel’s work was rediscovered Dr. Archibald Garrod, an English physician, became

interested in a disorder linked to an enzyme deficiency called alkaptonuria, which results in black urine and runs in families.

A recessive trait is expressed when the individual is homozygous recessive for the trait.

Therefore, those with at least one dominant allele will not express the recessive trait.

An individual who is heterozygous for a recessive disorder is called a carrier

Recessive Genetic DisordersRecessive Genetic Disorders

Cystic FibrosisCystic Fibrosis

Affects the mucus-producing glands, Affects the mucus-producing glands, digestive enzymes, and sweat glandsdigestive enzymes, and sweat glands

Chloride ions are not absorbed into Chloride ions are not absorbed into the cells of a person with cystic the cells of a person with cystic fibrosis but are excreted in the fibrosis but are excreted in the sweat.sweat.

Without sufficient chloride ions in the Without sufficient chloride ions in the cells, a thick mucous is secreted.cells, a thick mucous is secreted.

AlbinismAlbinism

Caused by altered genes, resulting in Caused by altered genes, resulting in the absence of the skin pigment the absence of the skin pigment melanin in hair and eyesmelanin in hair and eyes

White hairWhite hair Very pale skinVery pale skin Pink pupilsPink pupils

Tay-Sachs DiseaseTay-Sachs Disease

Caused by the absence of the Caused by the absence of the enzymes responsible for breaking enzymes responsible for breaking down fatty acids called gangliosides.down fatty acids called gangliosides.

Gangliosides accumulate in the Gangliosides accumulate in the brain, inflating brain nerve cells and brain, inflating brain nerve cells and causing mental deterioration.causing mental deterioration.

GalactosemiaGalactosemia

Recessive genetic disorder Recessive genetic disorder characterized by the inability of the characterized by the inability of the body to digest galactose.body to digest galactose.

Severity of condition varies.Severity of condition varies.

Dominant Genetic DisordersDominant Genetic Disorders

Caused by dominant allelesCaused by dominant alleles Those who do not have the disorder Those who do not have the disorder

are homozygous recessive.are homozygous recessive. Huntington’s disease affects the Huntington’s disease affects the

nervous system.nervous system. Achondroplasia is a genetic condition Achondroplasia is a genetic condition

that causes small body size and that causes small body size and limbs that are comparatively shortlimbs that are comparatively short

Dominant Genetic DisordersDominant Genetic Disorders

PedigreesPedigrees

A diagram that traces the inheritance of a A diagram that traces the inheritance of a particular trait through several particular trait through several generations.generations.

PedigreesPedigrees

Inferring GenotypesInferring Genotypes– Knowing physical traits can determine Knowing physical traits can determine

what genes an individual is most likely what genes an individual is most likely to have.to have.

Predicting DisordersPredicting Disorders– Record keeping helps scientists use Record keeping helps scientists use

pedigree analysis to study inheritance pedigree analysis to study inheritance patterns, determine phenotypes, and patterns, determine phenotypes, and ascertain genotypes.ascertain genotypes.

11.2 Complex Patterns of 11.2 Complex Patterns of InheritanceInheritance

Main idea-Complex inheritance of traits does not Main idea-Complex inheritance of traits does not follow inheritance patterns described by Mendelfollow inheritance patterns described by Mendel

ObjectivesObjectives– Distinguish between various complex inheritance Distinguish between various complex inheritance

patternspatterns– Analyze sex-linked and sex-limited inheritance patternsAnalyze sex-linked and sex-limited inheritance patterns– Explain how the environment can influence the Explain how the environment can influence the

phenotype of an organismphenotype of an organism Review VocabularyReview Vocabulary

– Gamete: a mature sex cell (sperm or egg) with a haploid Gamete: a mature sex cell (sperm or egg) with a haploid number of chromosomesnumber of chromosomes

New VocabularyNew Vocabulary– Incomplete dominanceIncomplete dominance - Codominance- Codominance– Multiple allelesMultiple alleles - Epistasis- Epistasis– Sex chromosomeSex chromosome - Autosome- Autosome– Sex-linked traitSex-linked trait - Polygenic trait- Polygenic trait

Incomplete DominanceIncomplete Dominance

The heterozygous phenotype is an The heterozygous phenotype is an intermediate phenotype between the two intermediate phenotype between the two homozygous phenotypes.homozygous phenotypes.

CodominanceCodominance

Both alleles are Both alleles are expressed in the expressed in the heterozygous heterozygous conditioncondition

ExampleExample– Sickle-cell DiseaseSickle-cell Disease

Changes in hemoglobin Changes in hemoglobin cause red blood cells cause red blood cells to change to a sickle to change to a sickle shapeshape

People who are People who are heterozygous for the heterozygous for the trait have both normal trait have both normal and sickle-shaped cellsand sickle-shaped cells

Multiple AllelesMultiple Alleles

Blood groups in Blood groups in humanshumans

ABO blood groups ABO blood groups have three forms have three forms of allelesof alleles

Multiple AllelesMultiple Alleles

Coat Color of Coat Color of RabbitsRabbits– Multiple Multiple

alleles can alleles can demonstrate demonstrate a hierarchy a hierarchy of of dominancedominance

– In rabbits, In rabbits, four alleles four alleles code for code for color: C, ccolor: C, cchch, , cccc, and c., and c.

EpistasisEpistasis

Variety is the result of one allele hiding the Variety is the result of one allele hiding the effects of another allele.effects of another allele.eebbeebb eeB_eeB_ E_bbE_bb E_B_E_B_No dark pigment presentNo dark pigment present Dark pigment Dark pigment presentpresent

Sex DeterminationSex Determination

Sex chromosomes Sex chromosomes determine an determine an individual’s individual’s gendergender

Dosage CompensationDosage Compensation

The X chromosome carries a variety The X chromosome carries a variety of genes that are necessary for the of genes that are necessary for the development of both females and development of both females and malesmales

The Y chromosome mainly has genes The Y chromosome mainly has genes that relate to the development of that relate to the development of male characteristicsmale characteristics

Chromosome inactivationChromosome inactivation Barr bodiesBarr bodies

Sex-linked TraitsSex-linked Traits

Genes located on the X chromosomeGenes located on the X chromosome Since males have only one Since males have only one

chromosome, they are affected by chromosome, they are affected by recessive X-linked traits more often recessive X-linked traits more often than are femalesthan are females

Red-green color blindnessRed-green color blindness HemophiliaHemophilia

Polygenic TraitsPolygenic Traits

Polygenic traits arise from the interaction of Polygenic traits arise from the interaction of multiple pairs of genesmultiple pairs of genes

Skin color, height, eye color, and fingerprint Skin color, height, eye color, and fingerprint pattern pattern

Environmental InfluencesEnvironmental Influences

Environmental factors affect Environmental factors affect phenotypephenotype– Diet and exerciseDiet and exercise– Sunlight and waterSunlight and water– TemperatureTemperature

Twin StudiesTwin Studies

Helps scientists separate genetic Helps scientists separate genetic contributions from environmental contributions from environmental contributions.contributions.

Traits that appear frequently in Traits that appear frequently in identical twins are at least partially identical twins are at least partially controlled by heredity.controlled by heredity.

Traits expressed differently in Traits expressed differently in identical twins are strongly identical twins are strongly influenced by environmentinfluenced by environment

11.3 Chromosomes and Human 11.3 Chromosomes and Human HeredityHeredity

Main idea – Chromosomes can be studied using karyotypes.Main idea – Chromosomes can be studied using karyotypes. ObjectivesObjectives

– Distinguish normal karyotypes from those with abnormal Distinguish normal karyotypes from those with abnormal numbers of chromosomes.numbers of chromosomes.

– Define and describe the role of telomeres.Define and describe the role of telomeres.– Relate the effect of nondisjunction to Down syndrome and Relate the effect of nondisjunction to Down syndrome and

other abnormal chromosome numbers.other abnormal chromosome numbers.– Assess the benefits and risks of diagnostic fetal testingAssess the benefits and risks of diagnostic fetal testing

Review VocabularyReview Vocabulary– Mitosis- a process in the nucleus of a dividing cell, including Mitosis- a process in the nucleus of a dividing cell, including

prophase, metaphase, anaphase, and telophaseprophase, metaphase, anaphase, and telophase New VocabularyNew Vocabulary

– KaryotypeKaryotype– TelomereTelomere– NondisjunctionNondisjunction

Karyotype StudiesKaryotype Studies

Karyotype-micrograph in which the pairs Karyotype-micrograph in which the pairs of homologous chromosomes are arranged of homologous chromosomes are arranged in decreasing sizein decreasing size

Images of chromosomes stained during Images of chromosomes stained during metaphasemetaphase

Chromosomes are arranged in decreasing Chromosomes are arranged in decreasing size to produce a micrographsize to produce a micrograph

22 autosomes are matched together with 22 autosomes are matched together with one pair of nonmatching sex one pair of nonmatching sex chromosomeschromosomes

TelomeresTelomeres

Protective caps consist of DNA Protective caps consist of DNA associated with proteinsassociated with proteins

Serves a protective function for the Serves a protective function for the sttructure of the chromosomesttructure of the chromosome

Might be involved in both aging and Might be involved in both aging and cancercancer

NondisjunctionNondisjunction

Cell division during which sister Cell division during which sister chromatids fail to separate properlychromatids fail to separate properly

Results in extra copy of chromosome or Results in extra copy of chromosome or only one copy of a chromosomeonly one copy of a chromosome

Having a set of three chromosomes of one Having a set of three chromosomes of one kind is trisomykind is trisomy

Having only one copy of a chromosome is Having only one copy of a chromosome is monosomymonosomy

Down Syndrome – Trisomy 21Down Syndrome – Trisomy 21– Distinctive facial features, short stature, heart Distinctive facial features, short stature, heart

defects, and mental disabilitydefects, and mental disability

NondisjunctionNondisjunction

Sex Chromosomes Sex Chromosomes – XX – Normal femaleXX – Normal female– XO – Female with Turner’s SyndromeXO – Female with Turner’s Syndrome– XXX – Nearly normal femaleXXX – Nearly normal female– XY – Normal maleXY – Normal male– XXY – Male with Klinefelter’s SyndromeXXY – Male with Klinefelter’s Syndrome– XYY – Normal or nearly normal maleXYY – Normal or nearly normal male– OY – Results in death OY – Results in death

Fetal TestingFetal Testing Used to diagnosis genetic disorders before birthUsed to diagnosis genetic disorders before birth AmniocentesisAmniocentesis

– Benefits-diagnosis of chromosome abnormalities and other Benefits-diagnosis of chromosome abnormalities and other defectsdefects

– Risks-discomfort for expectant mother, slight risk of Risks-discomfort for expectant mother, slight risk of infection, and risk of miscarriageinfection, and risk of miscarriage

Chorionic villus samplingChorionic villus sampling– Benefits-diagnosis of chromosome abnormalities and certain Benefits-diagnosis of chromosome abnormalities and certain

genetic defectsgenetic defects– Risks-miscarriage, infection, and newborn limb defectsRisks-miscarriage, infection, and newborn limb defects

Fetal blood samplingFetal blood sampling– Benefits-diagnosis of genetic or chromosomal abnormality, Benefits-diagnosis of genetic or chromosomal abnormality,

checks for fetal problems and oxygen levels, and checks for fetal problems and oxygen levels, and medications can be given to the fetus before birthmedications can be given to the fetus before birth

– Risks-bleeding from sample site, infection, amniotic fluid Risks-bleeding from sample site, infection, amniotic fluid might leak, and fetal deathmight leak, and fetal death