Human Heredity Chapter 14. Chromosomal Inheritance 2 Human Genetic Disorders Autosome - Any...

Human Heredity

Chapter 14

Chromosomal Chromosomal InheritanceInheritance 2

Human Genetic DisordersHuman Genetic Disorders

Autosome - Any chromosome other than a sex Autosome - Any chromosome other than a sex chromosomechromosome

Genetic disorders caused by genes on autosomes Genetic disorders caused by genes on autosomes are called autosomal disorders are called autosomal disorders Some genetic disorders are autosomal dominantSome genetic disorders are autosomal dominant An individual with AA has the disorderAn individual with AA has the disorder An individual with Aa has the disorderAn individual with Aa has the disorder An individual with aa does NOT have disorderAn individual with aa does NOT have disorder

Other genetic disorders are autosomal recessiveOther genetic disorders are autosomal recessive An individual with AA does NOT have disorderAn individual with AA does NOT have disorder An individual with Aa does NOT have disorder, but is a An individual with Aa does NOT have disorder, but is a

carriercarrier An individual with aa DOES have the disorderAn individual with aa DOES have the disorder


Autosomal Recessive Pedigree Autosomal Recessive Pedigree ChartChart


Autosomal Dominant Pedigree Autosomal Dominant Pedigree ChartChart


Autosomal Recessive DisordersAutosomal Recessive Disorders

Tay-Sachs DiseaseTay-Sachs Disease

Progressive deterioration of psychomotor Progressive deterioration of psychomotor functionsfunctions

Cystic FibrosisCystic Fibrosis

Mucus in bronchial tubes and pancreatic Mucus in bronchial tubes and pancreatic ducts is particularly thick and viscousducts is particularly thick and viscous

Phenylketonuria (PKU)Phenylketonuria (PKU)

Lack enzyme for normal metabolism of Lack enzyme for normal metabolism of phenylalaninephenylalanine


Cystic Fibrosis Cystic Fibrosis TherapyTherapy


Autosomal Dominant DisordersAutosomal Dominant Disorders

NeurofibromatosisNeurofibromatosis

Tan or dark spots develop on skin and darken Tan or dark spots develop on skin and darken

Small, benign tumors may arise from fibrous Small, benign tumors may arise from fibrous nerve coveringsnerve coverings

Huntington DiseaseHuntington Disease

Neurological disorderNeurological disorder

Progressive degeneration of brain cellsProgressive degeneration of brain cells

Severe muscle spasmsSevere muscle spasms

Personality disordersPersonality disorders


A Victim of Huntington A Victim of Huntington DiseaseDisease


Huntington Disease:Huntington Disease:Normal and Diseased Normal and Diseased BrainBrain


Multiple Allelic Traits and CodominanceMultiple Allelic Traits and Codominance

Some traits controlled by multiple allelesSome traits controlled by multiple alleles

The gene exists in several allelic forms (but each individual The gene exists in several allelic forms (but each individual only has two)only has two)

ABO blood typesABO blood types

The alleles:The alleles: IIAA = A antigen on red cells, anti-B antibody in plasma = A antigen on red cells, anti-B antibody in plasma IIBB = B antigen on red cells, anti-AB antibody in plasma = B antigen on red cells, anti-AB antibody in plasma II = Neither A nor B antigens, both antibodies = Neither A nor B antigens, both antibodies

PhenotypePhenotype(Blood Type)(Blood Type) GenotypeGenotype

A (actually AA or AO)A (actually AA or AO) IIAAIIAA or I or IAAiiB (actually BB or BO)B (actually BB or BO) IIBBIIBB or I or IBBii

ABAB IIAAIIBB

O (actually OO)O (actually OO) iiii


Inheritance of Blood Inheritance of Blood TypeType

Chromosomal Chromosomal InheritanceInheritance 13Human X-Linked Disorders:Human X-Linked Disorders:

Red-Green Color BlindnessRed-Green Color Blindness

Color vision In humans:Color vision In humans:Depends three different classes of cone cells Depends three different classes of cone cells in the retinain the retina

Only one type of pigment is present in each Only one type of pigment is present in each class of cone cellclass of cone cell The gene for blue-sensitive is autosomalThe gene for blue-sensitive is autosomal The red-sensitive and green-sensitive genes are The red-sensitive and green-sensitive genes are on the X chromosomeon the X chromosomeMutations in X-linked genes cause RG color Mutations in X-linked genes cause RG color blindness:blindness: All males with mutation (XAll males with mutation (XbbY) are colorblindY) are colorblind Only homozygous mutant females (XOnly homozygous mutant females (XbbXXbb) are ) are

colorblindcolorblind Heterozygous females (XHeterozygous females (XBBXXbb) are asymptomatic ) are asymptomatic

carrierscarriers


X-Linked Recessive X-Linked Recessive PedigreePedigree

Chromosomal Chromosomal InheritanceInheritance

• What is a karyotype?What is a karyotype?

• What patterns of inheritance do human traits follow?What patterns of inheritance do human traits follow? Dominant and Recessive AllelesDominant and Recessive Alleles

Codominant and Multiple AllelesCodominant and Multiple Alleles

• How can pedigrees be used to analyze human inheritance?How can pedigrees be used to analyze human inheritance?

• How do small changes in DNA molecules affect human traits?How do small changes in DNA molecules affect human traits?

• What are the effects of errors in meiosis?What are the effects of errors in meiosis? nondisjunctionnondisjunction

15


http://www.dnalc.org/resources/3d/17-sickle-http://www.dnalc.org/resources/3d/17-sickle-cell.htmlcell.html

16


What is Sickle Cell Anemia?What is Sickle Cell Anemia?

A serious condition in which red A serious condition in which red blood cells can become sickle-blood cells can become sickle-shapedshaped

Normal red blood cells are smooth Normal red blood cells are smooth and round. They move easily through and round. They move easily through blood vessels to carry oxygen to all blood vessels to carry oxygen to all parts of the body.parts of the body.

Sickle-shaped cells don’t move easily Sickle-shaped cells don’t move easily through blood. They’re stiff and sticky through blood. They’re stiff and sticky and tend to form clumps and get and tend to form clumps and get stuck in blood vessels.stuck in blood vessels.

The clumps of sickle cell block blood The clumps of sickle cell block blood flow in the blood vessels that lead to flow in the blood vessels that lead to the limbs and organs. Blocked blood the limbs and organs. Blocked blood vessel can cause pain, serious vessel can cause pain, serious infection, and organ damage.infection, and organ damage.

Chromosomal Chromosomal InheritanceInheritanceNormal and Sickled Red Blood Cells Normal and Sickled Red Blood Cells

in Blood Vesselsin Blood Vessels

Figure A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-

section of a normal red blood cell with normal hemoglobin.

Figure B shows abnormal, sickled red blood cells clumping and blocking the blood flow in a blood

vessel. The inset image shows a cross-section of a sickled red blood cell with abnormal strands of

hemoglobin.

Source from http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_WhatIs.html


http://www.youtube.com/watch?http://www.youtube.com/watch?v=5n29ZCvtCI8v=5n29ZCvtCI8

What is cystic fibrosis (CF)?What is cystic fibrosis (CF)?



Inherited monogenic disorder presenting as a Inherited monogenic disorder presenting as a multisystem disease.multisystem disease.

Typically presents in childhoodTypically presents in childhood

7% of CF patients diagnosed as adults7% of CF patients diagnosed as adults

Most common life limiting recessive trait Most common life limiting recessive trait among whitesamong whites



Prognosis improvingPrognosis improving

>38% of CF patients are older than 18>38% of CF patients are older than 18

13% of CF patients are older than 3013% of CF patients are older than 30

Median survivalMedian survival

Males: 32 yearsMales: 32 years

Females: 29 yearsFemales: 29 years

22Nondisjunction

23Trisomy 21

Chromosomal Chromosomal InheritanceInheritance 24Chromosome Number:Chromosome Number:

Abnormal Sex Chromosome NumberAbnormal Sex Chromosome Number

Result of inheriting too many or too few X or Result of inheriting too many or too few X or Y chromosomesY chromosomes

Caused by nondisjunction during oogenesis Caused by nondisjunction during oogenesis or spermatogenesisor spermatogenesis

Turner Syndrome (XO)Turner Syndrome (XO)

Female with single X chromosomeFemale with single X chromosome

Short, with broad chest and widely spaced Short, with broad chest and widely spaced nipplesnipples

Can be of normal intelligence and function Can be of normal intelligence and function with hormone therapywith hormone therapy



Klinefelter Syndrome (XXY)Klinefelter Syndrome (XXY)

Male with underdeveloped testes and Male with underdeveloped testes and prostate; some breast overdevelopmentprostate; some breast overdevelopment

Long arms and legs; large handsLong arms and legs; large hands

Near normal intelligence unless XXXY, XXXXY, Near normal intelligence unless XXXY, XXXXY, etc.etc.

No matter how many X chromosomes, No matter how many X chromosomes, presence of Y renders individual malepresence of Y renders individual male

26Turner and Klinefelter Syndromes



Ploy-X femalesPloy-X females

XXX simply taller & thinner than usualXXX simply taller & thinner than usual

Some learning difficultiesSome learning difficulties

Many menstruate regularly and are fertileMany menstruate regularly and are fertile

More than 3 Xs renders severe mental More than 3 Xs renders severe mental retardationretardation

Jacob’s syndrome (XYY)Jacob’s syndrome (XYY)

Tall, persistent acne, speech & reading Tall, persistent acne, speech & reading problemsproblems


Abnormal Chromosome StructureAbnormal Chromosome Structure

DeletionDeletion

Missing segment of chromosomeMissing segment of chromosome

Lost during breakageLost during breakage

TranslocationTranslocation

A segment from one chromosome moves to a A segment from one chromosome moves to a non-homologous chromosomenon-homologous chromosome

Follows breakage of two nonhomologous Follows breakage of two nonhomologous chromosomes and improper re-assemblychromosomes and improper re-assembly

Human Heredity Chapter 14. Chromosomal Inheritance 2 Human Genetic Disorders Autosome - Any...

Documents

Transcript of Human Heredity Chapter 14. Chromosomal Inheritance 2 Human Genetic Disorders Autosome - Any...