Chapter 10 & 11Chapter 10 & 11Sexual Reproduction Sexual Reproduction

and Geneticsand Genetics

I. Meiosis produces four haploid I. Meiosis produces four haploid sex cells from one original sex cells from one original diploid (2n) cell.diploid (2n) cell.

A. Eggs are gametes A. Eggs are gametes produced by the female.produced by the female.

B. Sperm are gametes produced B. Sperm are gametes produced by the male.by the male.

C. Diploid cells (C. Diploid cells (2n2n) are cells with ) are cells with two of each kind of chromosome.two of each kind of chromosome.

D. Gametes are haploid cells (D. Gametes are haploid cells (n)n)——cells with one of each kind of cells with one of each kind of

chromosome.chromosome.

E. When a sperm fertilizes and E. When a sperm fertilizes and egg,egg,

the resulting cell is called a the resulting cell is called a zygote.zygote.

II. Phases of Meiosis III. Phases of Meiosis I

A. During Prophase I, each A. During Prophase I, each pair of homologous pair of homologous

chromosomes comes together chromosomes comes together to form a to form a tetradtetrad..

B. Homologous chromosomes B. Homologous chromosomes may exchange genetic may exchange genetic

material in a process known as material in a process known as crossing overcrossing over..

III. Phases of Meiosis IIIII. Phases of Meiosis II

IV. Mendel’s GeneticsIV. Mendel’s GeneticsA. Gregor MendelA. Gregor Mendel

1. Studied 1. Studied heredityheredity (passing of (passing of characteristics from characteristics from parent to offspring)parent to offspring)

2. Father of 2. Father of geneticsgenetics(branch of biology that (branch of biology that studies heredity)studies heredity)

3. Inherited 3. Inherited characteristics are called characteristics are called traitstraits..

B. Mendel’s B. Mendel’s ExperimentsExperiments

1. Used pea plants 1. Used pea plants because:because:

a.a. Grew fastGrew fast

b. reproduced sexuallyb. reproduced sexually

(1)(1)Male gamete is Male gamete is pollenpollen

(2) Female gamete is an (2) Female gamete is an ovuleovule

2. Mendel transferred pollen 2. Mendel transferred pollen from one plant to another—from one plant to another—this was a this was a cross.cross.

a. Transfer of pollen to a. Transfer of pollen to ovule is ovule is pollinationpollination..

b. b. FertilizationFertilization occurs occurs when male and female when male and female gametes fuse.gametes fuse.

33. Characteristics or “Traits” Mendel . Characteristics or “Traits” Mendel observed:observed:

4. Phenotype and 4. Phenotype and GenotypeGenotype

a.a. Genotype Genotype is gene is gene combination (TT)combination (TT)

b. b. PhenotypePhenotype is physical is physical appearance; appearance;

expression expression of the of the genotype (tall)genotype (tall)

c. Two organisms can c. Two organisms can looklook alike but have different alike but have different underlying gene underlying gene combinations.combinations.TT=tallTT=tallTt=tallTt=tall

5. 5. HomoHomozygous-two alleles zygous-two alleles for a trait are the for a trait are the samesame (TT or tt)(TT or tt)

6. 6. HeteroHeterozygous-two zygous-two alleles for a trait are alleles for a trait are different different (Tt)(Tt)

C. Mendel’s Monohybrid C. Mendel’s Monohybrid CrossesCrosses

1. Cross between two 1. Cross between two parents that differ only parents that differ only by a single trait.by a single trait.

2. Generations2. Generationsa. P1 = parenta. P1 = parent

b. F1 = filial (daughter b. F1 = filial (daughter or or son)son)

c. F2 = 2c. F2 = 2ndnd filial filial

Heterozygote(note color)

RecessiveHomozygote(note color)

RecessiveHomozygote(note color)

genotype?

genotype?

genotype?

= monohybrid

D. Mendel’s Rule of Unit D. Mendel’s Rule of Unit FactorFactor1. Genes exist in alternative 1. Genes exist in alternative

forms called forms called alleles.alleles.

E. Mendel’s Rule of E. Mendel’s Rule of DominanceDominance

1. Only one trait is observed (phenotype) 1. Only one trait is observed (phenotype) (either TALL (either TALL oror short) short)

2. The observed trait is 2. The observed trait is dominant.dominant.

3. The trait that “disappeared” is 3. The trait that “disappeared” is recessiverecessive..

F. Mendel’s Law of F. Mendel’s Law of SegregationSegregation

A parent passes on at A parent passes on at random only one allele for random only one allele for each trait to its offspringeach trait to its offspring

RecessiveHomozygote(note color)

Heterozygote(note color)

RecessiveHomozygote

Heterozygotes

DominantHomozygote

Segregation occurs here

Dominant Homozygote

G. Punnett SquaresG. Punnett Squares Method used to establish the Method used to establish the probabilities of the results of a genetic probabilities of the results of a genetic cross.cross.

H. Uses of Punnett H. Uses of Punnett Squares in Monohybrid Squares in Monohybrid crosses.crosses.

H. Uses of Punnett Squares H. Uses of Punnett Squares in Monohybrid crosses in Monohybrid crosses 1. Example one1. Example one Show the cross between a Show the cross between a

homozygous tall pea plant and a homozygous tall pea plant and a homozygous short pea plant.homozygous short pea plant.

TT X ttTT X tt

T T

t

t

Tt

Tt

All offspring will be heterozygous Tall

Tt

Tt

Show the cross between a Show the cross between a homozygous rough coat guinea pig homozygous rough coat guinea pig and a heterozygous guinea pig. and a heterozygous guinea pig.

Rough is dominant to smoothRough is dominant to smooth

RR X RrRR X Rr

2. Example 22. Example 2

R R

R

r

RR RR

Rr Rr

Genotypic Ratio- RR 2: Rr 2 =1:1 Phenotypic ratio- 100% Rough

3. Example 33. Example 3 Show the cross between two Show the cross between two

heterozygous Black coat rabbits.heterozygous Black coat rabbits. Black is dominate to brown. Black is dominate to brown. Bb X BbBb X Bb

B b

B

b

BB Bb

Bb bb

Genotypic ratio-BB 1: Bb 2: bb 1

Phenotypic ratio- Black 3: Brown 1

I. Uses of Punnett squares I. Uses of Punnett squares to show Incomplete to show Incomplete dominance and dominance and Codominance.Codominance.

1.1. Incomplete Incomplete DominanceDominance

The phenotype of the The phenotype of the heterozygotes is a heterozygotes is a blend of the two blend of the two homozygotes.homozygotes.

Example of Japanese Four Example of Japanese Four O’clocksO’clocks

Red=RRRed=RR White=R’R’White=R’R’ Show the cross between a Show the cross between a

homozygous red and a homozygous red and a homozygous white flower.homozygous white flower.

RR X R’R’RR X R’R’R R

R’

R’

RR’ RR’

RR’ RR’

Example 2 of Japanese Four Example 2 of Japanese Four O’clocksO’clocks Show the cross between two pink Show the cross between two pink

flowered Japanese Four O’clocks.flowered Japanese Four O’clocks.R R’

R

R’

RR RR’

RR’ R’R’

2. Codominance2. Codominance

The phenotypes of both The phenotypes of both homozygotes are produced in a homozygotes are produced in a heterozygote.heterozygote.

Both alleles are expressed equally.Both alleles are expressed equally.

Example of Black and White Example of Black and White Checked ChickensChecked Chickens

BB=BlackBB=Black WW=WhiteWW=White

BW

B B

W

W BW

BW

BW

B W

B

W

BWBB

BW WW

3. Codominance in 3. Codominance in HumansHumans Example: Sickle-Cell Anemia (page Example: Sickle-Cell Anemia (page

303)303)

1.1. Test CrossTest Cross -the procedure in which an -the procedure in which an

individual of unknown genotype individual of unknown genotype is crossed with a homozygous is crossed with a homozygous recessive individual. recessive individual.

J. Uses of Punnett J. Uses of Punnett Squares with Test Squares with Test

CrossesCrosses

Bunny’s genotype: HH or Bunny’s genotype: HH or Hh?Hh?

H H H h

h

h

h

h

Hh Hh

Hh Hh

Hh hh

Hh hh

K. Uses of Punnett K. Uses of Punnett Squares in Dihybrid Squares in Dihybrid Crosses. Crosses. A dihybrid cross is a cross A dihybrid cross is a cross

involving two different traits.involving two different traits.

Example: Show the cross Example: Show the cross between two heterozygous tall between two heterozygous tall plants with round seeds. plants with round seeds.

TtRr X TtRrTtRr X TtRr

Tt

Rr

Combinations of Combinations of gametes with TtRr X TtRrgametes with TtRr X TtRr

1.1. TRTR

2.2. TrTr

3.3. tRtR

4.4. trtr

Each one of these could become a Each one of these could become a gamete. gamete.

TR Tr tR tr

TR

Tr

tR

tr

TTRR TTRr TtRR TtRr

TTRr TTrr TtRr Ttrr

TtRR TtRr ttRR ttRr

TrRr Ttrr ttRr ttrr

L. Dominant Genetic L. Dominant Genetic Disorders:Disorders: 1. Organism needs one dominate 1. Organism needs one dominate

allele for phenotype to be expressed.allele for phenotype to be expressed. 2. That means recessive 2. That means recessive

homozygotes are normalhomozygotes are normal 3. Human disorders include:3. Human disorders include:

a. Hapsburg lipa. Hapsburg lip

The above portrait is of Charles II, who was King of Spain from The above portrait is of Charles II, who was King of Spain from 1665 to 1700, and who displays this characteristic trait, a trait 1665 to 1700, and who displays this characteristic trait, a trait that was passed down through the Austro-Hungarian monarchy that was passed down through the Austro-Hungarian monarchy through successive inbreeding.  The Hapsburg lip deformity through successive inbreeding.  The Hapsburg lip deformity affected poor Charles II so badly that he could not chew his affected poor Charles II so badly that he could not chew his food.  Years of inbreeding had also taken its toll on his food.  Years of inbreeding had also taken its toll on his intelligence (he was retarded) and his powers of procreation (he intelligence (he was retarded) and his powers of procreation (he was impotent). was impotent).

b. Hitchhiker’s Thumbb. Hitchhiker’s Thumb

c. c. Huntington’Huntington’s diseases disease

Gene affects Gene affects neurological neurological functionfunction

The Huntington's disease gene was identified in 1993 and is located near the top of the fourth chromosome.

d. d. AchondroplasiaAchondroplasia

Gene affects bone Gene affects bone growth (short arms growth (short arms & legs, large head)& legs, large head)

M. Recessive Genetic M. Recessive Genetic DisordersDisorders 1. Most genetic disorders are caused 1. Most genetic disorders are caused

by recessive alleles (homozygous). by recessive alleles (homozygous). 2. Human disorders include:2. Human disorders include:

a. Cystic fibrosisa. Cystic fibrosis

b. Albinismb. Albinism

Absence of Absence of pigment pigment melanin in skin, melanin in skin, hair, eyeshair, eyes

Gene causes absence of enzyme Gene causes absence of enzyme needed to break down gangliosides needed to break down gangliosides (fatty acid) (fatty acid) gangliosides build up gangliosides build up in the brain causing deterioration.in the brain causing deterioration.

c. Tay-Sachs Diseasec. Tay-Sachs Disease

N. Pedigree-pg. 299 N. Pedigree-pg. 299 know know symbolssymbols

O. Multiple AllelesO. Multiple Alleles

1. Multiple phenotypes 1. Multiple phenotypes result from multiple result from multiple alleles.alleles.

2. Traits controlled by 2. Traits controlled by more than two allelesmore than two alleles

3. Multiple Alleles in 3. Multiple Alleles in HumansHumansa. Blood Typing—KNOW pg. 304!!a. Blood Typing—KNOW pg. 304!!

b. Know why pg. 304 is important!!b. Know why pg. 304 is important!!

P. Sex-linked InheritanceP. Sex-linked Inheritance1. Traits controlled by genes on the sex 1. Traits controlled by genes on the sex chromosomes chromosomes are are sex-linked traitssex-linked traits..22. X and Y are not homologous. . X and Y are not homologous. 3. Y has no corresponding alleles.3. Y has no corresponding alleles.4. Y-linked traits are passed only from male to 4. Y-linked traits are passed only from male to male.male.

5. Sex-linked Traits in 5. Sex-linked Traits in HumansHumans a. Red-Green Color Blindnessa. Red-Green Color Blindness

**caused by the inheritance of either of caused by the inheritance of either of two recessive alleles at two gene two recessive alleles at two gene sites on the sites on the X chromosomeX chromosome

b. Hemophiliab. Hemophilia

**Males inherit the allele from their carrier Males inherit the allele from their carrier mother. (Queen Victoria and Royal Hemophilia mother. (Queen Victoria and Royal Hemophilia pg. 308)pg. 308)

*Females need two recessive alleles.*Females need two recessive alleles.

Q. Polygenic InheritanceQ. Polygenic Inheritance

1. Trait is controlled by two or more genes1. Trait is controlled by two or more genes Examples: skin color, eye color, fingerprintExamples: skin color, eye color, fingerprint

2. May or may not be on the same 2. May or may not be on the same chromosomechromosome

3. Represented by upper and lower case 3. Represented by upper and lower case lettersletters

4. Example of Plant Stem 4. Example of Plant Stem LengthLength *3 genes A, B, and C*3 genes A, B, and C

*aabbcc = 3 cm tall*aabbcc = 3 cm tall

*AABBCC = 12 cm tall*AABBCC = 12 cm tall

*AaBbCc = 6 cm tall*AaBbCc = 6 cm tall

*each dominant allele = 2 cm*each dominant allele = 2 cm

5. Example in Humans: Skin Color 5. Example in Humans: Skin Color

3 genes A, B, & C (6 alleles)3 genes A, B, & C (6 alleles)

*aabbcc = very light*aabbcc = very light

*AABBCC = very dark*AABBCC = very dark

*AaBbCc = medium*AaBbCc = medium

*all heterozygotes are *all heterozygotes are

intermediateintermediate phenotypes phenotypes

R. NondisjunctionR. Nondisjunction 1. Sister chromatids fail to 1. Sister chromatids fail to

separate properlyseparate properly 2. Gamete with extra 2. Gamete with extra

autosomes (we have 22 autosomes (we have 22 pairs of autosomes)pairs of autosomes)

Example: Trisomy—Example: Trisomy—

three (21three (21stst type) chromosomes type) chromosomes

instead of two (gametes have instead of two (gametes have one duplicate chromosome)one duplicate chromosome)

*Down’s Syndrome*Down’s Syndrome

Polyploidy: the occurrence of one or more sets of extra chromosomes in an organism

2. Sex Chromosomes with unusual 2. Sex Chromosomes with unusual numbersnumbers

Example 1: X Example 1: X

(monosomy)(monosomy) Turner’s Turner’s

SyndromeSyndrome

Example 2Example 2 XXY XXY TrisomyTrisomy Klinefelter Klinefelter

SyndromeSyndrome

(XXY)(XXY)