Ch 20 Lesson 2Ch 20 Lesson 2

From Generation to GenerationFrom Generation to Generation

Things to do before we start Things to do before we start class…class…

Take out Prenatal Development WorksheetTake out Prenatal Development Worksheet

Lesson 2 Objectives:Lesson 2 Objectives:

Summarize the process of heredity.Summarize the process of heredity. Define terms associated with heredity.Define terms associated with heredity. Identify some genetic disorders.Identify some genetic disorders.

Heredity is the passing of physical Heredity is the passing of physical traits from parents to their childrentraits from parents to their children

What traits did you What traits did you inherit from your inherit from your parents? (ex. Eyes, parents? (ex. Eyes, height)height)

Inherited traits can Inherited traits can also be influenced by also be influenced by the environment (ex. the environment (ex. poor nutrition limits poor nutrition limits growth during growth during childhood)childhood)

ChromosomesChromosomes

Thread-like structures Thread-like structures within the nucleus within the nucleus (control center) of each (control center) of each cell in our bodycell in our body

They carry codes for They carry codes for inherited traitsinherited traits

Most cells in the Most cells in the human body contain human body contain 46 chromosomes 46 chromosomes arranged in pairs of 23arranged in pairs of 23

GenesGenes

Sections of chromosomes Sections of chromosomes are called genesare called genes

They are the basic units of They are the basic units of heredityheredity

They appear in pairsThey appear in pairs 1 gene from each pair is 1 gene from each pair is

inherited from each parentinherited from each parent 1000s of genes are found 1000s of genes are found

in every cell in your bodyin every cell in your body

DNADNA

DNA is the chemical unit DNA is the chemical unit that makes up that makes up chromosomeschromosomes

Deoxyribonucleic acid is Deoxyribonucleic acid is basis of all living thingsbasis of all living things

Made up of chemical Made up of chemical building blocks arranged building blocks arranged along single moleculealong single molecule

Several molecules link in a Several molecules link in a strand to form a DNA strand to form a DNA sequence called genetic sequence called genetic codecode

DNADNA

A child carries a A child carries a combination of DNA combination of DNA sequencing from both sequencing from both parentsparents

Identical twins share Identical twins share the same DNA patternthe same DNA pattern

Genetics and Fetal DevelopmentGenetics and Fetal Development

Chromosomes from a sperm and egg unite to carry the Chromosomes from a sperm and egg unite to carry the hereditary traits from parentshereditary traits from parents– A sperm and egg have 23 chromosomesA sperm and egg have 23 chromosomes– After fertilization, the zygote will have 46 chromosomes (23 from After fertilization, the zygote will have 46 chromosomes (23 from

each parent)each parent)– A zygote divides many times, ultimately producing trillions of cells A zygote divides many times, ultimately producing trillions of cells

that make up the human bodythat make up the human body– Between each cell division, each chromosome in the nucleus of the Between each cell division, each chromosome in the nucleus of the

cell copies itself, producing 2 sets of 46 chromosomescell copies itself, producing 2 sets of 46 chromosomes– The cell then divides and the 2 sets of chromosomes separateThe cell then divides and the 2 sets of chromosomes separate– Each new cells then contains one complete set of the 46 Each new cells then contains one complete set of the 46

chromosomes that are identical to the ones found in the first cell of chromosomes that are identical to the ones found in the first cell of the zygotethe zygote

2 Types of Genes2 Types of Genes

RecessiveRecessive– The traits of the The traits of the

recessive genes usually recessive genes usually appear only when the appear only when the dominant genes are not dominant genes are not presentpresent

DominantDominant– The traits of the The traits of the

dominant genes dominant genes generally appear in the generally appear in the offspring when they are offspring when they are presentpresent

Genes and GenderGenes and Gender

One pair of chromosomes determines One pair of chromosomes determines gendergender– Females have 2 x chromosomes that look alikeFemales have 2 x chromosomes that look alike– Males have a shorter y chromosome and a Males have a shorter y chromosome and a

longer x chromosome longer x chromosome – Who do you think determines the sex of a baby Who do you think determines the sex of a baby

when the sperm and egg unite? The male or when the sperm and egg unite? The male or female?female?

Genetic DisordersGenetic Disorders

Caused partly or Caused partly or completely by a defect completely by a defect in genesin genes

Common ones include:Common ones include:– Sickle-cell anemiaSickle-cell anemia– Tay-sachs diseaseTay-sachs disease– Cystic fibrosisCystic fibrosis– Down syndromeDown syndrome– HemophiliaHemophilia

Sickle-cell anemiaSickle-cell anemia– RBC’s become C-RBC’s become C-

shaped, stiff and stickyshaped, stiff and sticky– Don’t move through Don’t move through

blood easily and get blood easily and get stuck in vesselsstuck in vessels

– Block blood flow to Block blood flow to limbs and organs limbs and organs causing pain, infections, causing pain, infections, and organ damageand organ damage

Tay-Sachs diseaseTay-Sachs disease– Harmful quantities of a Harmful quantities of a

fatty acid derivative fatty acid derivative accumulate in the nerve accumulate in the nerve cells of the braincells of the brain

– Infants appear normal Infants appear normal the first months and the first months and then deteriorate in then deteriorate in mental and physical mental and physical abilitiesabilities

Cystic fibrosisCystic fibrosis– Inherited disease of the Inherited disease of the

sweat and mucus sweat and mucus glandsglands

– Causes mucus to be Causes mucus to be thick and sticky - clogs thick and sticky - clogs lungs & makes it easy lungs & makes it easy for bacteria to growfor bacteria to grow

Down syndromeDown syndrome– Extra genetic material Extra genetic material

causes delays in the causes delays in the way a child develops way a child develops often leading to mental often leading to mental retardationretardation

HemophiliaHemophilia– Rare inherited disorder Rare inherited disorder

in which blood does not in which blood does not clot normallyclot normally

– Usually occurs in malesUsually occurs in males– May bleed for a long May bleed for a long

time after injury or time after injury or accidentaccident

– May also bleed into May also bleed into joints (painful and leads joints (painful and leads to arthritis)to arthritis)

3 Methods of Identifying Health of 3 Methods of Identifying Health of the Childthe Child

1. Amniocentesis1. Amniocentesis– A syringe is inserted A syringe is inserted

into pregnant woman’s into pregnant woman’s abdomin3 and into the abdomin3 and into the amniotic fluid amniotic fluid surrounding the fetussurrounding the fetus

– Some fluid is removed Some fluid is removed to study chromosomes, to study chromosomes, body chemistry and body chemistry and determine sex of childdetermine sex of child

– Done at 16-20 weeksDone at 16-20 weeks

3 Methods of Identifying Health of 3 Methods of Identifying Health of the Childthe Child

2. Ultrasound test2. Ultrasound test– Sound waves are used Sound waves are used

to project light images to project light images on a screenon a screen

– Waves act like an echo Waves act like an echo and form image of fetusand form image of fetus

– Used to determine Used to determine position of fetus and position of fetus and number of fetusesnumber of fetuses

3 Methods of Identifying Health of 3 Methods of Identifying Health of the Childthe Child

3. Chorionic villi sampling3. Chorionic villi sampling– CVS is a procedure in which a small piece of CVS is a procedure in which a small piece of

membrane is removed from the chorion, a layer membrane is removed from the chorion, a layer of tissue that develops into the placentaof tissue that develops into the placenta

– Can be examined for genetic disorders or to Can be examined for genetic disorders or to determine the age and gender of childdetermine the age and gender of child

– Usually done around the eighth week of fetal Usually done around the eighth week of fetal developmentdevelopment

Battling Genetic DiseasesBattling Genetic Diseases

Gene therapy – process of inserting normal genes Gene therapy – process of inserting normal genes into human cells to correct genetic disordersinto human cells to correct genetic disorders– Scientists think that if defective gene is replaced with Scientists think that if defective gene is replaced with

normal gene, cells can begin producing normal genenormal gene, cells can begin producing normal gene Genetic counselingGenetic counseling

– Can guide families about risks and treatmentsCan guide families about risks and treatments Genetically engineered drugsGenetically engineered drugs

– Genes used to treat diseases are not inserted directly into Genes used to treat diseases are not inserted directly into humans but placed into other organisms causing it to humans but placed into other organisms causing it to produce the substance that can be used to treat human produce the substance that can be used to treat human diseases and disorders diseases and disorders

Genetic EngineeringGenetic Engineering

Can you speculate why this is such a Can you speculate why this is such a controversial topic and what ethical controversial topic and what ethical concerns it involves?concerns it involves?

Did you master the Ch 20 lesson 2 Did you master the Ch 20 lesson 2 objectives?objectives?

Summarize the process of heredity.Summarize the process of heredity. Define terms associated with heredity.Define terms associated with heredity. Identify some genetic disorders.Identify some genetic disorders.