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Ch 9. Patterns in Inheritance. Gregor Mendel. 1860’s Crossed pea plants Character vs trait. Purple. Flower color. White. Terminal. Axial. Flower position. Green. Yellow. Seed color. Seed shape. Round. Wrinkled. Pod shape. Inflated. Constricted. Green. Yellow. Pod color.

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Presentation Transcript
slide1

Ch 9

Patterns in Inheritance

gregor mendel

Gregor Mendel

1860’s

Crossed pea plants

Character vs trait

genes

Purple

Flower color

White

Terminal

Axial

Flower position

Green

Yellow

Seed color

Seed shape

Round

Wrinkled

Pod shape

Inflated

Constricted

Green

Yellow

Pod color

Tall

Stem length

Dwarf

Genes
  • Mendel hypothesized that there are alternative forms of genes the units that determine heritable traits
    • Self-fertilization
    • Cross fertilization
terms
Terms
      • True-breeding
  • Hybrid
    • Mono-hybrid
    • Dihybrid
  • Cross
  • P generation
  • F1 Generation
  • F2 Generation
  • Phenotype
  • Genotype
mendel
Mendel

Mendel’s Observations of Inheritance Patterns

  • 2 alleles inherited
  • Mendel’s law of segregation
  • If the 2 alleles of an inherited pair differ
    • Heterozygous
    • Dominant allele
    • Recessive allele
  • If the 2 alleles are the same, no conflict
    • Homozygous
homologous chromosomes
Homologous chromosomes
  • Two alleles for each characteristic.
  • Alternative forms of a gene reside at the same locus
dominance
Dominance
  • Dominant
    • Gene that determines phenotype
  • Recessive
    • Gene that has no noticeable effect
disorders
Disorders
  • Recessive
    • Carriers
  • Dominant
    • Some cases, homozygous dominant is lethal
slide10

Fetal Testing

    • Amniocentesis and chorionic villus sampling (CVS)
      • Allow doctors to remove fetal cells that can be tested for genetic abnormalities

Amniocentesis

Chorionic villus sampling (CVS)

Needle inserted

through abdomen to

extract amniotic fluid

Ultrasound

monitor

Ultrasound

monitor

Suction tube inserted

through cervix to extract

tissue from chorionic villi

Fetus

Fetus

Placenta

Placenta

Chorionic

villi

Uterus

Cervix

Cervix

Uterus

Amniotic

fluid

Centrifugation

Fetal

cells

Fetal

cells

Biochemical

tests

Several

weeks

Several

hours

Karyotyping

Figure 9.10 A

slide11

Fetal Imaging

    • Ultrasound imaging
      • Uses sound waves to produce a picture of the fetus

Figure 9.10 B

incomplete dominance
Incomplete Dominance

Intermediate phenotypes

multiple alleles codominance
Multiple Alleles/Codominance
  • ABO blood type in humans
  • Alleles for A and B blood types are codominant
pleiotropy
Pleiotropy
  • A single gene which affects many phenotypic characteristics
polygenic
Polygenic

A single characteristic that is influenced by many genes

sex determination

(male)

(female)

Parents’

diploid

cells

44

+

XX

44

+

XY

22

+

X

22

+

Y

22

+

X

Egg

Sperm

Offspring

(diploid)

44

+

XX

44

+

XY

Sex Determination
slide18

22

+

X

22

+

XX

76

+

ZW

76

+

ZZ

32

16

Other systems of sex determination exist in other animals and plants

Figure 9.22 B

Figure 9.22 C

Figure 9.22 D

independent assortment
Independent Assortment
  • Mendels Law of Independent Assortment
    • Each pair of alleles segregates independently of other pairs during gamete formation

****Not entirely true

punnett squares
Punnett Squares
  • A diagram that is used to predict an outcome of a particular cross or breeding experiment
  • Determine the probability of an offspring having a particular genotype
fig 9 3b

Genetic makeup (alleles)

P plants

pp

PP

Gametes

All

All

p

P

Fig. 9-3b

F1 plants

(hybrids)

All Pp

p

P

1

2

1

2

Gametes

Sperm

p

P

P

PP

Pp

F2 plants

Phenotypic ratio

3 purple : 1 white

Eggs

Genotypic ratio

1 PP : 2 Pp : 1 pp

Pp

pp

p

practice problems
Practice problems
  • Monohybrid cross
    • Blue eyes b, Brown eyes B
    • B is dominant
    • Both parents heterozygous brown eyed (Bb)
  • Homozygous for trait P
    • Mom is PP, dad is pp
linked genes

Experiment

Purple flower

PpLI PpLI

Long pollen

  • Observed Prediction
  • Phenotypes offspring (9:3:3:1)

Purple long

Purple round

Red long

Red round

215

71

71

24

284

21

21

55

Explanation: linked genes

P L

Parental

diploid cell

PpLI

P I

Meiosis

Most

gametes

P L

P I

Fertilization

Sperm

P I

P L

P L

P L

P L

Most

offspring

P L

P I

Eggs

P I

P I

P I

P I

P L

3 purple long : 1 red round

Not accounted for: purple round and red long

Linked Genes
  • Linked genes are close to each other on the same chromosome and tend to be inherited together
sex linked genes
Sex Linked Genes
  • Genes carried on sex chromosomes
  • XrX, XrY
  • Fruit Fly eye color- carried on X
    • R=dominant red eye (R)
    • R=recessive white eye (r)

What proportion of offspring will have white eyes is mom is heterozygous red eyed and dad is homozygous red eyed?

fig 9 21c

Female

Male

XR Xr

XR Y

Fig. 9-21c

Sperm

Y

XR

XR

XR XR

XR Y

Eggs

Xr Y

Xr

Xr XR

sex linked
Sex Linked
  • Affect mostly males