CHAPTER 11/14CHAPTER 11/14

I.I. MendelMendel

A. Gregor MendelA. Gregor Mendel

1. Austrian monk-carried out impt 1. Austrian monk-carried out impt studies of heredity studies of heredity

(passing on (passing on chars. from chars. from parents to offspring)parents to offspring)

a. traits are inheriteda. traits are inherited

2. Father of Genetics2. Father of Genetics

a. branch of bio that studies a. branch of bio that studies heredityheredity

3. Used garden pea due to several good 3. Used garden pea due to several good traits/easy to growtraits/easy to grow

a. cross pollinationa. cross pollination

b. true breeding plants (P1-parents)b. true breeding plants (P1-parents)

* F1- 1* F1- 1stst gen gen

* F2- 2* F2- 2ndnd gen gen

4. Laws of Heredity4. Laws of Heredity

a. Law of Segregationa. Law of Segregation

b. Law of Independent Assortmentb. Law of Independent Assortment

II. CrossesII. Crosses

A. Genes exist in alternative forms = A. Genes exist in alternative forms = allelesalleles

1. Dominant allele1. Dominant allele

a. written 1a. written 1stst

b. b. capitalcapital letter (J) letter (J)

c. usually use letter of the domc. usually use letter of the dom

traittrait

* black hair = B* black hair = B

2. Recessive allele2. Recessive allele

a. a. lower caselower case (j) letter of dom trait. (j) letter of dom trait.

B. Phenotypes & GenotypesB. Phenotypes & Genotypes

1. Phenotype = way an org looks 1. Phenotype = way an org looks (descriptions)(descriptions)

a. blue eyesa. blue eyes

2. Genotype = allele/gene combi an org2. Genotype = allele/gene combi an org

has (letters)has (letters)

a. BBa. BB

b. Heterozygous genotypeb. Heterozygous genotype* Tt* Tt

c. Homozygous genotypec. Homozygous genotype* TT (homoz dom)* TT (homoz dom)* tt (homoz rec)* tt (homoz rec)

C. Punnett SquaresC. Punnett Squares1. Diagram that shows the outcome of 1. Diagram that shows the outcome of genetic combis (checkerboard)genetic combis (checkerboard)

a. genes of parents written on the TOP a. genes of parents written on the TOP & LEFT side of Punnett & LEFT side of Punnett

2. Determine geno & pheno of offspring2. Determine geno & pheno of offspringa. Ratios/ percentages/fractionsa. Ratios/ percentages/fractions

3. Monohybrid Crosses3. Monohybrid Crosses

a. cross between inds involving one pair a. cross between inds involving one pair of contrasting traits (HH x hh)of contrasting traits (HH x hh)

* * 44 boxes boxes

4 Dihybrid Crosses4 Dihybrid Crosses

a. cross between inds involving 2 pairs of a. cross between inds involving 2 pairs of contrasting traits (HhFf x HhFf)contrasting traits (HhFf x HhFf)

* * 1616 boxes boxes

* pheno ratio-9:3:3:1* pheno ratio-9:3:3:1

* geno ratio-4:1:1:1:1:2:2:2:2* geno ratio-4:1:1:1:1:2:2:2:2

III. ProbabilityIII. ProbabilityA. In reality you do not get the exact ratio A. In reality you do not get the exact ratio

of results shown in the square of results shown in the square (chance plays a role)(chance plays a role)

1. like flipping a coin1. like flipping a coin

2. probability of getting a 2. probability of getting a TT vs. a vs. a tt

is is 50:5050:50

IV. Incomplete dominanceIV. Incomplete dominance

A. alleles neither dominant nor recessive (use A. alleles neither dominant nor recessive (use 2 different letters-CAPITAL)2 different letters-CAPITAL)

1. 4 boxes1. 4 boxes B. traits are inherited in an B. traits are inherited in an incomplete incomplete dominancedominance pattern, the phenotype of pattern, the phenotype of heterozygous individuals is heterozygous individuals is intermediate intermediate between those of the 2 homozygotesbetween those of the 2 homozygotes

1. blending1. blending

C. Example: C. Example:

Homozygous Homozygous Red-flowered snapdragon plant plant ((RRRR)) crossed w/ homozygous crossed w/ homozygous White-flowered White-flowered snapdragon plantsnapdragon plant (WW): (WW):

ALL of the FALL of the F11 offspring will be offspring will be PINKPINK ( (RWRW))

Incomplete dominanceIncomplete dominance

Red White

All pink

Red (RR)

White

WW

Pink (RW)

Pink RW

All pink flowers 1/4 red: 2/4 pink: 1/4white

V. CodominanceV. Codominance

A.A. Codominant alleles Codominant alleles cause the phenotypes cause the phenotypes of both homozygotes to be produced in of both homozygotes to be produced in heterozygous individuals. heterozygous individuals.

1. both alleles are expressed equally1. both alleles are expressed equally

a. cattle-red hair codominant with a. cattle-red hair codominant with white hair = white hair = ROANROAN color color

2. Sickle Cell Disorder=defective hemoglobin 2. Sickle Cell Disorder=defective hemoglobin forms crystal-like structures that change shape forms crystal-like structures that change shape of the RBC’sof the RBC’s

a. Normal (NN) red blood cells are a. Normal (NN) red blood cells are disc-disc-shapedshaped, but abnormal red blood , but abnormal red blood

cells cells are shaped like a are shaped like a sickle sickle (half-moon).(half-moon).

b. homozygote for trait (SS) =sickle cellb. homozygote for trait (SS) =sickle cell

c. heterozygotes (SN) have both normal & c. heterozygotes (SN) have both normal & sickle blood cells, but more normalsickle blood cells, but more normal

change in shape occurs in the body’s narrow change in shape occurs in the body’s narrow capillaries after the hemoglobin delivers oxygen capillaries after the hemoglobin delivers oxygen to the cellsto the cells

Sickle-cell disease

Normal red blood cell

Sickle cell

VI. Multiple Alleles VI. Multiple Alleles

A. common for more than 2 alleles to control A. common for more than 2 alleles to control a trait in a populationa trait in a population

1. traits controlled by more than 2 alleles 1. traits controlled by more than 2 alleles have have Multiple AllelesMultiple Alleles

B. B. ABOABO blood group is a classic example of a blood group is a classic example of a single gene that has single gene that has multiple allelesmultiple alleles in in humans.humans.

Multiple Alleles Govern Blood Multiple Alleles Govern Blood TypeType

Human Blood Types

lA lA or lAilB lB or lBilA lB

ii

Genotypes Surface Molecules Phenotypes

AB

A and BNone

ABABO

1. Determining blood type is necessary before a 1. Determining blood type is necessary before a person can receive a blood transfusion person can receive a blood transfusion because the RBC’s of incompatible blood types because the RBC’s of incompatible blood types could clump together, causing death could clump together, causing death (immune (immune system will attack).system will attack).

2. Gene for blood type, 2. Gene for blood type, gene gene l,l, codes for a codes for a molecule that attaches to a membrane protein molecule that attaches to a membrane protein found on the surface of RBC’s.found on the surface of RBC’s.

a. a. llA A & & llBB alleles each code for a alleles each code for a different different moleculemolecule

* * llAA allele is dominant to allele is dominant to ii, so inheriting either , so inheriting either the the llAAii alleles or alleles or llA A llAA alleles from both alleles from both parents will give you parents will give you type A blood.type A blood.

b. Phenotype A Surface molecule A

llBB allele is also allele is also dominant to dominant to ii

c. Phenotype c. Phenotype BB

B blood: must inherit the B blood: must inherit the llBB allele from one parent allele from one parent & either another& either another llBB allele allele or theor the ii allele from the allele from the otherother

Surface molecule B

llA A and and llBB alleles are alleles are codominantcodominant

Universal receiverUniversal receiver

d. Phenotype AB Surface molecule B

Surface molecule A

e. Phenotype O

Homozygous Homozygous iiii

Universal donorUniversal donor

A. Humans = 23 pairsA. Humans = 23 pairs

1. 22 pairs of homolog. chrms 1. 22 pairs of homolog. chrms (autosomes)(autosomes)

2. 232. 23rdrd pair differs in males & females pair differs in males & females (sex chrms)(sex chrms)

a. a. XXXX = girl= girl

b. b. XYXY = boy = boy

3. X chroms larger3. X chroms larger

a. Barr bodya. Barr body

VII. Sex DeterminationVII. Sex Determination

Sex determinationSex determination

XX Female

XY Male

X

X

X Y

XX Female

XY Male

XX Female

XY Male

1. Traits controlled by genes located on 1. Traits controlled by genes located on sex chromosomes = sex chromosomes = sex-linked sex-linked

traitstraits a. alleles for sex-linked traits are a. alleles for sex-linked traits are written as written as superscriptssuperscripts of the of the X or X or

Y chromosomesY chromosomes

b. many found on the “X”b. many found on the “X”

* males just one “X” thus all “X-linked” * males just one “X” thus all “X-linked” alleles are expressed even if alleles are expressed even if

recessive (from ma) recessive (from ma)

B. Sex-linked inheritanceB. Sex-linked inheritance

Females:

Males:1/2 red eyed1/2 white eyed

all red eyed

White-eyed male (XrY)

Red-eyed female (XRXR)

F1 All red eyed

F2

Sex-linked inheritanceSex-linked inheritance

c. Females, who are XX, pass one of their X c. Females, who are XX, pass one of their X chromosomes to each child.chromosomes to each child.

Male Female

Sperm Eggs

FemaleFemale MaleMale

Female Male

MaleMaleFemale Female

Eggs Sperm

d. sex-linked traits in humansd. sex-linked traits in humans 2 traits that are governed by X-linked 2 traits that are governed by X-linked

recessive inheritance in humans = recessive inheritance in humans = red-green red-green color blindness & hemophiliacolor blindness & hemophilia

People who have red-People who have red-green color blindness green color blindness can’t differentiate these can’t differentiate these two colors. Color two colors. Color blindness is caused by blindness is caused by the inheritance of a the inheritance of a recessive allele at either recessive allele at either of two gene sites on the of two gene sites on the X chromosome.X chromosome.

Red-Green Color BlindnessRed-Green Color Blindness

b. Determining gamete letters for parentsb. Determining gamete letters for parents* HhJj (heterozygous for both traits)* HhJj (heterozygous for both traits)

HJHJHjHjhJhJhjhj

A. A. MetaphaseMetaphase chromosomes are chromosomes are photographed; the chromosome pictures photographed; the chromosome pictures are enlarged & arranged in pairs by a are enlarged & arranged in pairs by a computer according to length & location of computer according to length & location of centromere.centromere.

XIXI. Karyotype. Karyotype

1.1. Chart of chromosome pairs =Chart of chromosome pairs =karyotypekaryotype (it’s (it’s valuable in identifying unusual chromosome valuable in identifying unusual chromosome numbers in cells)numbers in cells)

a. longest pair #1a. longest pair #1

b. pairs match (banding, length, traits)b. pairs match (banding, length, traits)

c. 23c. 23rdrd pair = X, Y(smaller chroms) pair = X, Y(smaller chroms)

*1-22 pairs = autosomes*1-22 pairs = autosomes

d. Normal=23 pairs or 46 chrmsd. Normal=23 pairs or 46 chrms

Sex determinationSex determination If you are female, If you are female,

your 23your 23rd rd pair of pair of chromosomes are chromosomes are homologous, homologous, XX.XX.

If you are male, your If you are male, your 2323rd rd pair of pair of chromosomes chromosomes XYXY, , look different. look different.

X X

Female

YX

Male

B. B. NondisjunctionNondisjunction

1. failure of homologous chroms to 1. failure of homologous chroms to separate properly during meiosis-separate properly during meiosis-AnaphaseAnaphase

a. monosomy 2N - 1a. monosomy 2N - 1

b. trisomy 2N + 1b. trisomy 2N + 1

C. Sex Chromo. Anomalies C. Sex Chromo. Anomalies

1. Klinefelter’ Syndrome-XXY (47)1. Klinefelter’ Syndrome-XXY (47)

2. Turner’s Syndrome-X?(45)2. Turner’s Syndrome-X?(45)

3. XYY(47)3. XYY(47)

4. Downs-three 21(47)4. Downs-three 21(47)

Down syndrome Down syndrome is is caused by caused by autosomal autosomal

trisomy trisomy (#21)(#21)

Trisomy (3’s)Trisomy (3’s)

B. B. PedigreePedigree is a graphic representation of is a graphic representation of genetic inheritance.genetic inheritance.

1. made up of a set of symbols that 1. made up of a set of symbols that identify males/females, identify males/females, individuals affected by the trait individuals affected by the trait being studied, & family being studied, & family relationshipsrelationships

X. Pedigree

A. Family tree that traces family thru successive generations

Pedigrees illustrate

inheritance

Pedigrees illustrate

inheritance

Male

Female

Affected male

Affected female

Mating

Parents

Siblings

Known heterozygotes for recessive allele

Death

2. 2. Circle Circle represents a represents a female; a female; a square square represents a represents a malemale

Female Male

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3. Highlighted 3. Highlighted circles/squares circles/squares represent represent individuals individuals showing the trait showing the trait being studied.being studied.

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4. Circles & squares 4. Circles & squares that are not that are not highlighted highlighted designate designate individuals that individuals that do do notnot show the trait. show the trait.

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5. A half-shaded 5. A half-shaded circle or square circle or square represents a represents a carriercarrier, a , a heterozygous heterozygous individual.individual.

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6. 6. HorizontalHorizontal line line connecting a circle & connecting a circle & a square indicates a square indicates that the individuals that the individuals are are parents(marriage), & parents(marriage), & verticalvertical line connects line connects parents with their parents with their offspring.offspring.

7. Ea. horizontal 7. Ea. horizontal row of circles & row of circles & squares in a squares in a pedigree pedigree designates a designates a generationgeneration, with , with the most recent the most recent generation shown generation shown at the at the bottombottom..

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8. The generations 8. The generations are identified in are identified in sequence by sequence by Roman Roman numerals, & ea. numerals, & ea. individual is individual is given an Arabic given an Arabic number.number.

a. oldest kid: a. oldest kid: leftleft

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XI. Disorders

A. Cystic fibrosis

XI. Disorders

A. Cystic fibrosis1. Due to a defective protein in the 1. Due to a defective protein in the

plasma membrane, cystic plasma membrane, cystic fibrosis results in the formation fibrosis results in the formation /accumulation of thick mucus in /accumulation of thick mucus in lungs/digestive tract.lungs/digestive tract.

B. Tay-Sachs diseaseB. Tay-Sachs disease

1.1. Tay-SachsTay-Sachs disease is a recessive disorder disease is a recessive disorder of the CNS.of the CNS.

a. recessive allele results in the absence a. recessive allele results in the absence of an enzyme that normally breaks of an enzyme that normally breaks down a lipid produced & stored in down a lipid produced & stored in issues of the CNSissues of the CNS

b. lipid fails to break down properly, it b. lipid fails to break down properly, it accumulates in the cellsaccumulates in the cells

1.1. Phenylketonuria Phenylketonuria (PKU), is a recessive (PKU), is a recessive disorder that results from the absence of an disorder that results from the absence of an enzyme that converts 1 aa, phenylalanine, to enzyme that converts 1 aa, phenylalanine, to a a different aa-tyrosine.different aa-tyrosine.

a. phenylalanine cannot be broken a. phenylalanine cannot be broken down, down, it & its by-products accumulate in it & its by-products accumulate in the the body & result in severe damage body & result in severe damage to the to the CNS CNS

C. PhenylketonuriaC. Phenylketonuria

b. Infants affected by PKU are given a diet that is b. Infants affected by PKU are given a diet that is low in phenylalanine until their brains are fully low in phenylalanine until their brains are fully developed.developed.

PhenylketonuriaPhenylketonuria

Phenylketonurics: Contains Phenylalanine

D. Huntington’s diseaseD. Huntington’s disease

1.Huntington’s disease is a lethal genetic 1.Huntington’s disease is a lethal genetic disorder caused by a rare dominant allele.disorder caused by a rare dominant allele.

a. It results in a breakdown of certain a. It results in a breakdown of certain areas of the brain. areas of the brain.

The end