Glorious Genetics with a Glorious Genetics with a Marvelous Monk Named Mendel Marvelous Monk Named Mendel

Chapter 14Chapter 14

Science as a Process Science as a Process

1. Gregor Mendel 1. Gregor Mendel – monk turned scientist, worked with garden peas monk turned scientist, worked with garden peas

to study inheritanceto study inheritance– father of modern geneticsfather of modern genetics

Science as a ProcessScience as a Process

2. Why Peas???2. Why Peas???– Come in many varieties (i.e. purple/white flowers, Come in many varieties (i.e. purple/white flowers,

round/wrinkled)round/wrinkled)– Easy to control parentageEasy to control parentage

sex organs are in flowers and each flower has both male sex organs are in flowers and each flower has both male (stamens) and female (carpals) parts(stamens) and female (carpals) parts

Science as a ProcessScience as a Process

3. How did he do it?3. How did he do it?– Mendel removed Stamens before plants could self-Mendel removed Stamens before plants could self-

fertilize. The plant now only has the female parts. fertilize. The plant now only has the female parts. – He then he put the pollen from another plant onto the He then he put the pollen from another plant onto the

now “female” flower and made offspring (seeds)now “female” flower and made offspring (seeds)– focused on either/or characters (there were only two focused on either/or characters (there were only two

varieties of each trait)varieties of each trait)– started with true-breeding plants = purple flowered started with true-breeding plants = purple flowered

plants that produced only purple flowered offspringplants that produced only purple flowered offspring

Terrific Terminology Terrific Terminology

CharacterCharacter - heritable feature (i.e. flower - heritable feature (i.e. flower color)color)

TraitTrait - variant of a character (purple, white) - variant of a character (purple, white) HybridizationHybridization - mating or crossing of two - mating or crossing of two

varietiesvarieties True-breedingTrue-breeding- after many generations of - after many generations of

self pollination, parent plant produces only self pollination, parent plant produces only the same variety of offspring (i.e. purple the same variety of offspring (i.e. purple plant makes only purple offspringplant makes only purple offspring))

Terminology - contTerminology - cont

Monohybrid crossMonohybrid cross - looks at only one trait at - looks at only one trait at a timea time

P generationP generation - parental (original cross) - parental (original cross) F1 generationF1 generation - offspring from P generation - offspring from P generation F2 generationF2 generation - results if the F1 plants are - results if the F1 plants are

allowed to self - fertilizeallowed to self - fertilize

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Mendel’s Shocking results Mendel’s Shocking results

P GenerationP Generation - Purple x White flower - Purple x White flower

ProducedProduced F1 GenerationF1 Generation - ALL PURPLE (GASP!!!) - ALL PURPLE (GASP!!!)

Let F1 self fertilize Let F1 self fertilize

F2 GenerationF2 Generation - 705 Purple, 224 White - 705 Purple, 224 White (WOW!)(WOW!)

So Who Cares???So Who Cares???

Most scientists thought that traits blended Most scientists thought that traits blended together. So after the Parents bred, the F1 together. So after the Parents bred, the F1 should have been pale purple, but Mendel’s should have been pale purple, but Mendel’s results disproved this. Even more surprising results disproved this. Even more surprising was that the white flowers showed up again was that the white flowers showed up again in the F2in the F2

Mendel continued his studies with 6 other Mendel continued his studies with 6 other characters (round/wrinkled, tall/short etc) characters (round/wrinkled, tall/short etc) and found the same results in all characters. and found the same results in all characters.

What does it all mean???What does it all mean???

Alternate versions of genes account for Alternate versions of genes account for variations in inherited charactersvariations in inherited characters

ex. There is a gene for flower color in peas. ex. There is a gene for flower color in peas. This gene exists in two forms, purple or This gene exists in two forms, purple or white.white.

alleleallele - alternate form of a gene - alternate form of a gene

How does it work???How does it work???

1.1. Alternative versions of genes account for Alternative versions of genes account for variations in inherited characteristicsvariations in inherited characteristics

Different alleles are caused by slight changes in Different alleles are caused by slight changes in nucleotide sequences for a gene on the DNA nucleotide sequences for a gene on the DNA

This change results in a slightly different protein This change results in a slightly different protein (causing the difference in appearance)(causing the difference in appearance)

The gene is in the same place on the The gene is in the same place on the chromosome, but the order of the nitrogen bases chromosome, but the order of the nitrogen bases (A, T, G, C) is different. (A, T, G, C) is different.

How does it work???How does it work???

2.2. An organism inherits two alleles for each trait, An organism inherits two alleles for each trait, one from each parent (one copy in sperm/pollen, one from each parent (one copy in sperm/pollen, the other copy from egg). the other copy from egg).

The offspring can inherit two of the same alleles, The offspring can inherit two of the same alleles, or two different allelesor two different alleles

3.3. If the two alleles differ, then the Dominant allele If the two alleles differ, then the Dominant allele determines the organisms appearance and the determines the organisms appearance and the Recessive allele is not seen in the organisms’ Recessive allele is not seen in the organisms’ appearance appearance

– (Mendel’s F1 generation looked purple because purple (Mendel’s F1 generation looked purple because purple color is dominant over white color in peas)color is dominant over white color in peas)

Why only one trait???Why only one trait???

4.4. Two alleles for each character separate Two alleles for each character separate during meiosis and only one is passed on during meiosis and only one is passed on to the next generation = to the next generation = Law of Law of SegregationSegregation

Terrific Terminology contTerrific Terminology cont

HomozygousHomozygous - organism with two of the same alleles for a - organism with two of the same alleles for a charactercharacter

Homozygous DominantHomozygous Dominant - AA Homozygous recessive - aa - AA Homozygous recessive - aa HeterozygousHeterozygous = organism with two different alleles for a = organism with two different alleles for a

character = Aacharacter = Aa GenotypeGenotype = genetic makeup (actual genes the organism = genetic makeup (actual genes the organism

has)has) PhenotypePhenotype = physical appearance = physical appearance Punnett SquarePunnett Square - box used to show all possible offspring - box used to show all possible offspring

resulting from the cross between two parentsresulting from the cross between two parents

Punnett Square review Punnett Square review

Purple flowers are dominant to white Purple flowers are dominant to white flowers. Mendel crossed a true breeding flowers. Mendel crossed a true breeding (homozygous) purple flower to a true (homozygous) purple flower to a true breeding (homozygous) white flower. What breeding (homozygous) white flower. What are the possible genotype and phenotype are the possible genotype and phenotype results of this cross?results of this cross?

The AnswerThe Answer

A = purpleA = purple a = whitea = white P gen. = AA x aaP gen. = AA x aa

Genotype resultsGenotype results 4/4 Aa4/4 Aa Phenotype resultsPhenotype results 4/4 Purple4/4 Purple

AaAa AaAa

AaAa AaAa

A A

a

a

More fun!!!More fun!!! Next, Mendel let the F1 generation self fertilize. Next, Mendel let the F1 generation self fertilize.

What are the possible results of this cross?What are the possible results of this cross? Cross Aa x AaCross Aa x Aa Genotype resultsGenotype results 1/4 AA 1/2 Aa 1/4 aa1/4 AA 1/2 Aa 1/4 aa Phenotype resultsPhenotype results 3/4 Purple, 1/4 White3/4 Purple, 1/4 White Do the results above agree with Mendel’s Do the results above agree with Mendel’s

results?results?

AAAA AaAa

AaAa aaaa

A a

A

a

How can you tell if the plant is How can you tell if the plant is Homozygous or Heterozygous???Homozygous or Heterozygous???

Do a Test-cross Do a Test-cross Cross your unknown purple plant with a Cross your unknown purple plant with a

white plant.white plant. If the offspring are all purple, you know your If the offspring are all purple, you know your

original plant is homozygous (AA).original plant is homozygous (AA). If 50% of the offspring are purple and 50% If 50% of the offspring are purple and 50%

are white, your original plant is are white, your original plant is heterozygous (Aa)heterozygous (Aa)

Do the squares if you don’t believe me!!!Do the squares if you don’t believe me!!!

Dihybrid Crosses - look at two traits Dihybrid Crosses - look at two traits at onceat once

Used to determine if traits assort Used to determine if traits assort independently of one anotherindependently of one another

Try these (remember the 16 squares!!)Try these (remember the 16 squares!!) Purple flowers are dominant to white Purple flowers are dominant to white

flowers.flowers. Round seeds are dominant to wrinkled Round seeds are dominant to wrinkled

seeds.seeds. Cross a homozygous purple round plant Cross a homozygous purple round plant

with a homozygous white wrinkled plant.with a homozygous white wrinkled plant.

How do you do it???How do you do it???

A = purpleA = purple a = whitea = white R = roundR = roundr = wrinkledr = wrinkled AARR AARR x x aarraarr First find the gametesFirst find the gametes GametesGametes ARAR arar

Dihybrid crosses (cont)Dihybrid crosses (cont)

Next – make the Next – make the square – This one’s square – This one’s easyeasy

AaRrAaRr

AR

ar

Dihybrid crosses (cont)Dihybrid crosses (cont)

Genotype resultsGenotype results

1/1 AaRr1/1 AaRr

Phenotype resultsPhenotype results

1/1 Purple, Round1/1 Purple, Round

Dihybrid crosses (cont)Dihybrid crosses (cont)

Now let the plants self-fertilizeNow let the plants self-fertilize AaRr x AaRrAaRr x AaRr What will the gametes be?What will the gametes be? ARAR ArAr aRaR arar

Yikes – 16 boxes!!!Yikes – 16 boxes!!!

AR Ar aR ar

AR

Ar

aR

ar

AARRAARR AARrAARr AaRRAaRR AaRrAaRr

AARrAARr AArrAArr AaRrAaRr AarrAarr

AaRRAaRR AaRrAaRr aaRRaaRR aaRraaRr

AaRrAaRr AarrAarr aaRraaRr aarraarr

AR Ar aR ar

AR

Ar

aR

ar

Now Count Now Count Genotype resultsGenotype results 1/16 AARR1/16 AARR 2/16 AaRR2/16 AaRR 2/16 AARr2/16 AARr 4/16 AaRr4/16 AaRr 1/16 AArr1/16 AArr 2/16 Aarr2/16 Aarr 1/16 aaRR1/16 aaRR 2/16 aaRr2/16 aaRr 1/16 aarr1/16 aarr

More countingMore counting

Phenotype resultsPhenotype results 9/16 Purple, Round9/16 Purple, Round 3/16 Purple, wrinkled3/16 Purple, wrinkled 3/16 white, Round3/16 white, Round 1/16 white, wrinkled1/16 white, wrinkled

Law of Independent AssortmentLaw of Independent Assortment

If you look at each of the characters If you look at each of the characters individually you get the correct ratiosindividually you get the correct ratios

Purple 3: White: 1Purple 3: White: 1 Round 3: Wrinkled: 1Round 3: Wrinkled: 1

Law of Independent Assortment – Alleles Law of Independent Assortment – Alleles sort independently of one another during sort independently of one another during meiosis ( traits are not linked together)meiosis ( traits are not linked together)

Laws of Probability (shortcuts we Laws of Probability (shortcuts we never learned in Biology)never learned in Biology)

Rule of Multiplication – used to determine Rule of Multiplication – used to determine the chance that two or more independent the chance that two or more independent events will occur together in some specific events will occur together in some specific combinationcombination

To figure this out – find the probability of one To figure this out – find the probability of one event occurring and multiply it by the event occurring and multiply it by the probability of the other event(s) occurringprobability of the other event(s) occurring

Try itTry it

You are crossing two plants that are You are crossing two plants that are heterozygous (Aa) for purple color. What is heterozygous (Aa) for purple color. What is the chance of getting a white (aa) offspring?the chance of getting a white (aa) offspring?

Chance of plant 1 giving a = ½Chance of plant 1 giving a = ½ Chance of plant 2 giving a = ½Chance of plant 2 giving a = ½ Chance of white offspring aa = ¼Chance of white offspring aa = ¼

Does it work??? Do the square to confirmDoes it work??? Do the square to confirm

Now try with a dihybridNow try with a dihybrid

You are crossing two plants that are You are crossing two plants that are heterozygous Purple, Round (AaRr). What heterozygous Purple, Round (AaRr). What is the chance of getting a plant that is aarr?is the chance of getting a plant that is aarr?

Chance of plant 1 being ar = ¼Chance of plant 1 being ar = ¼ Chance of plant 2 being ar = ¼Chance of plant 2 being ar = ¼ Chance of aarr = 1/4 x 1/4 = 1/16Chance of aarr = 1/4 x 1/4 = 1/16 Check the results in the dihybrid problemCheck the results in the dihybrid problem

Rule of AdditionRule of Addition

The probability of an event that can occur in two or The probability of an event that can occur in two or more different ways is the sum of the separate more different ways is the sum of the separate probabilities of those ways.probabilities of those ways.

Cross two plants that are heterozygous (Aa). Cross two plants that are heterozygous (Aa). What is the chance that the offspring will be What is the chance that the offspring will be heterozygous?heterozygous?

Chance of Aa = 1/4 (if plant 1 gives A, plant 2 Chance of Aa = 1/4 (if plant 1 gives A, plant 2 gives a)gives a)

Chance of Aa = 1/4 (if plant 2 gives A, plant 1 Chance of Aa = 1/4 (if plant 2 gives A, plant 1 gives a)gives a)

Chance of heterozygous = 1/4 + 1/4 = 1/2Chance of heterozygous = 1/4 + 1/4 = 1/2

Now for a tough oneNow for a tough one

Parents AaRrTt x AarrttParents AaRrTt x Aarrtt Looking for the chance of at least two Looking for the chance of at least two

recessivesrecessives aarrTt = aarrTt = Aarrtt = Aarrtt = aarrtt = aarrtt = aaRrtt = aaRrtt = AArrtt = AArrtt =

Solution AaRrTt x AarrttSolution AaRrTt x Aarrtt

aarrTt = 1/4 x 1/2 x 1/2 = 1/16aarrTt = 1/4 x 1/2 x 1/2 = 1/16 Aarrtt = 1/2 x 1/2 x 1/2 = 1/8 = 2/16Aarrtt = 1/2 x 1/2 x 1/2 = 1/8 = 2/16 aarrtt = 1/4 x 1/2 x 1/2 = 1/16aarrtt = 1/4 x 1/2 x 1/2 = 1/16 aaRrtt = 1/4 x 1/2 x 1/2 = 1/16aaRrtt = 1/4 x 1/2 x 1/2 = 1/16 AArrtt = 1/4 x 1/2 x 1/2 = 1/16AArrtt = 1/4 x 1/2 x 1/2 = 1/16 Total chance of at least 2 recessives = 6/16 Total chance of at least 2 recessives = 6/16

or 3/8or 3/8

Now use the rules of probability to Now use the rules of probability to determine the followingdetermine the following

PKU is an inherited disease caused by a PKU is an inherited disease caused by a recessive allele. If a woman and her recessive allele. If a woman and her husband are both carriers (Aa x Aa), what is husband are both carriers (Aa x Aa), what is the probability of each of the following:the probability of each of the following:

All three of her children will be of normal All three of her children will be of normal phenotypephenotype

3/4 x 3/4 x 3/4 = 27/643/4 x 3/4 x 3/4 = 27/64

ContCont

One or more of the three children will have the One or more of the three children will have the diseasedisease

64/64 – 27/64 = 37/6464/64 – 27/64 = 37/64

All three children will have the diseaseAll three children will have the disease 1/4 x 1/4 x 1/4 = 1/641/4 x 1/4 x 1/4 = 1/64

At least one child will be phenotypically normalAt least one child will be phenotypically normal 64/64 – 1/64 = 63/6464/64 – 1/64 = 63/64

Exceptions to Mendel’s findingsExceptions to Mendel’s findings

Mendel looked only at traits following simple Mendel looked only at traits following simple inheritance (complete dominance). inheritance (complete dominance). Mendel’s laws lay the foundation for modern Mendel’s laws lay the foundation for modern genetics and the basic principles are true, genetics and the basic principles are true, but there are exceptions to his rules.but there are exceptions to his rules.

Incomplete DominanceIncomplete Dominance

Heterozygous organisms show a blending of two Heterozygous organisms show a blending of two other traits.other traits.

Ex. – red flower x white flower = pink flowerEx. – red flower x white flower = pink flower

Try a few problemsTry a few problems Red color is incompletely dominant to white. Red color is incompletely dominant to white.

Heterozygous flowers are pink.Heterozygous flowers are pink. What would be the results of a cross between a What would be the results of a cross between a

red and white flower?red and white flower?

RR x WW RR x WW Genotype = 4/4 RWGenotype = 4/4 RW Phenotype = 4/4 pinkPhenotype = 4/4 pink

Try these twoTry these two Pink x PinkPink x Pink Red x PinkRed x Pink

RWRW RWRW

RWRW RWRW

R R

W

W

RRRR RWRW

RWRW WWWW

RRRR RRRR

RWRW RWRW

R W

R

W

R R

R

W

1/4 RR, 1/2 RW, 1/4 WW25% red, 50% pink, 25% white

1/2 RR, 1/2 RW50% red, 50% pink

CodominanceCodominance

One gene is codominant to another. One gene is codominant to another. Heterozygous organisms show both traits.Heterozygous organisms show both traits.

Ex – Normal blood x sickle blood = both Ex – Normal blood x sickle blood = both normal and sickle cellsnormal and sickle cells

Try some problems – Normal red blood cells Try some problems – Normal red blood cells are codominant to sickle cells. are codominant to sickle cells. Heterozygous individuals (carriers) have Heterozygous individuals (carriers) have both normal and sickle cells (also resistant both normal and sickle cells (also resistant to malaria – Cool!!)to malaria – Cool!!)

Normal x SickleNormal x Sickle Sickle x CarrierSickle x Carrier Carrier x CarrierCarrier x Carrier

NSNS NSNS

NSNS NSNS

NSNS NSNS

SSSS SSSS

NNNN NSNS

NSNS SSSS

N N

S

S

4/4 NS = 100% carriers

S S

N

S

2/4 = NS, 2/4 SS50% carrier, 50% sickle

N S

N

S 1/4 NN, 2/4, NS, 1/4 SS25% normal, 50% carrier, 25% sickle

Multiple AllelesMultiple Alleles

More than two alleles exist for a trait More than two alleles exist for a trait Ex – blood types – A, B, AB, OEx – blood types – A, B, AB, O

PhenotypePhenotype GenotypeGenotype AntibodiesAntibodies

AA IIAAIIAA or I or IAAii Anti – BAnti – B

BB IIBBIB or IIB or IBBii Anti – AAnti – A

ABAB IIAAIIBB NoneNone

OO iiii Anti-A,Anti - BAnti-A,Anti - B

Try some probsTry some probs

Homozygous A x OHomozygous A x O AB x OAB x O Hetero A x Hetero BHetero A x Hetero B

IIAi IIAi

IIAi IIAi

IIAAii IIBBii

IIAAii IIBBii

IIAAIIBB IIBBii

IIAAii iiii

IA IA

i

iIA IB

i

iIA i

IB

i

4/4 IAi100% Type A

2/4 IAi, 2/4 IBBi50% type A, 50% type B

1/4 IAIB, 1/4 IBi, 1/4 IAi, 1/4 ii25% AB, 25% B, 25% A, 25% O

PleiotropyPleiotropy

One gene can affect an organism in many One gene can affect an organism in many waysways

Ex – sickle cell disease causes many Ex – sickle cell disease causes many different symptoms in the patientdifferent symptoms in the patient

EpistasisEpistasis

A gene at one locus changes the expression A gene at one locus changes the expression of another geneof another gene

Ex – one gene causes pigment, the other Ex – one gene causes pigment, the other causes the actual colorcauses the actual color

Sample problemsSample problems

One dominant gene in mice causes pigment One dominant gene in mice causes pigment to appear (D). If the mouse is homozygous to appear (D). If the mouse is homozygous recessive (dd), no pigment will appear.recessive (dd), no pigment will appear.

Another gene (B) causes black color, the Another gene (B) causes black color, the recessive form (bb) causes brown color.recessive form (bb) causes brown color.

Cross DDbb x Ddbb – How many black Cross DDbb x Ddbb – How many black mice will result?mice will result?

Chance of pigment 1/1 x chance of black 0 Chance of pigment 1/1 x chance of black 0 = no black mice= no black mice

Try anotherTry another

DdBb x DdBb – How many brown mice will DdBb x DdBb – How many brown mice will resultresult

Chance of pigment 3/4 x chance of brown Chance of pigment 3/4 x chance of brown 1/4 = 3/161/4 = 3/16

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PolygenicPolygenic

More than one gene controls a traitMore than one gene controls a trait Ex – hair color, skin color in humansEx – hair color, skin color in humans Result is a range of trait in offspring - i.e not Result is a range of trait in offspring - i.e not

just black or brown hair, but many shades in just black or brown hair, but many shades in betweenbetween

Nature vs NurtureNature vs Nurture

Some phenotypes are affected by Some phenotypes are affected by environmental factorsenvironmental factors

Ex – amount of red blood cells depends not Ex – amount of red blood cells depends not only on genes, but on altitude, nutrition, only on genes, but on altitude, nutrition, physical activityphysical activity

PedigreePedigree

Used to trace traits in organisms that don’t Used to trace traits in organisms that don’t produce many offspring or have long produce many offspring or have long generation span (like humans)generation span (like humans)

Square = maleSquare = male Circle = femaleCircle = female Shaded = trait being traced – can be Shaded = trait being traced – can be

dominant or recessivedominant or recessive

Recessively inherited Disorders Recessively inherited Disorders

Caused only when organism inherits two Caused only when organism inherits two recessive alleles (aa)recessive alleles (aa)

Cystic Fibrosis Cystic Fibrosis

1/2500 whites of European descent. 1/2500 whites of European descent. Normal people can transport chloride into Normal people can transport chloride into

cells, channels are defective in disease.cells, channels are defective in disease. Causes excessive mucous build up in many Causes excessive mucous build up in many

organs organs Untreated = death by 15, treated can live Untreated = death by 15, treated can live

longerlonger

. Tay-Sachs . Tay-Sachs

Dysfunction in enzyme that doesn’t break Dysfunction in enzyme that doesn’t break down brain lipids. down brain lipids.

Causes seizures, blindness, decreased Causes seizures, blindness, decreased motor performancemotor performance

Usually death within a few years. Usually death within a few years. High incidence in Jewish peopleHigh incidence in Jewish people

Sickle-cell disease Sickle-cell disease

Most common in Africans. Most common in Africans. Caused by substitution of one amino acid in hemoglobin. Caused by substitution of one amino acid in hemoglobin. Red Blood cells abnormally shaped, can’t carry oxygen Red Blood cells abnormally shaped, can’t carry oxygen

affectively. affectively. Treated with blood transfusions, but no cure. Treated with blood transfusions, but no cure. Heterozygous individuals have Heterozygous individuals have both normal/sickle blood both normal/sickle blood

cells but show a resistance to Malaria (common in Africa).cells but show a resistance to Malaria (common in Africa). Heterozygotes have an advantage in these areas which Heterozygotes have an advantage in these areas which

may be why the gene has remained in the population.may be why the gene has remained in the population.

Dominantly inherited disorders Dominantly inherited disorders

Occur when at least one dominant gene is Occur when at least one dominant gene is present in an organism.present in an organism.

Huntington’s disease Huntington’s disease

Degenerative disease of nervous system.Degenerative disease of nervous system. Gene has remained in population because Gene has remained in population because

illness doesn’t occur until 35-40 yrs of age.illness doesn’t occur until 35-40 yrs of age. Many people with disease have children and Many people with disease have children and

pass disease to them before they even pass disease to them before they even know they have it.know they have it.

Achondroplasia Achondroplasia

Dwarfism - Aa = dwarf (.01%),Dwarfism - Aa = dwarf (.01%), aa = normal size (99.99%)aa = normal size (99.99%) AA = lethal (death before birth)AA = lethal (death before birth)

Many other dominant disease are lethal and Many other dominant disease are lethal and kill organisms before birthkill organisms before birth

_s-xclick

Genetic testingGenetic testing

Prenatal - amniocentesis - chromosome Prenatal - amniocentesis - chromosome analysis of amniotic fluid (weeks)analysis of amniotic fluid (weeks)– carrier recognition - determining whether carrier recognition - determining whether

parents are carriersparents are carriers CVS - chorionic villus sampling - fetal tissue CVS - chorionic villus sampling - fetal tissue

from placenta is used to do chromosome from placenta is used to do chromosome analysis (24 hrs)analysis (24 hrs)

Ultrasound - looks for developmental Ultrasound - looks for developmental problems in organsproblems in organs

Newborn screening Newborn screening

many tests are done before babies leave many tests are done before babies leave hospital to indicate genetic disordershospital to indicate genetic disorders

PKU - tests for phenylketonuria - if detected, PKU - tests for phenylketonuria - if detected, parents can alter diet of children to prevent parents can alter diet of children to prevent symptoms (no phenylalanine)symptoms (no phenylalanine)