GENETICS

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CHAPTER 7

• GENETICS INHERITANCE

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Gregor Mendel

• Genetics the scientific study of heredity
• Heredity transmission of genetic info from
  parent to offspring

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• Gregor Mendel Father of Genetics
• worked in Austria
• worked in 1860s
• worked in a monastery
• worked with garden peas (Pisum sativum)
• -small
• -easy to grow
• -produce lots of offspring
• -mature fast
• -self-fertilization
• -cross- fertilization
• used quantitative methods measuring,
  counting, numbers)

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Mendels Experiments

• STEP 1 produce pure strains an organism that
  produces 1 form of a trait
• parental generation P1

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• STEP 2 cross the pure strains (purple x white)
• found only purple flowers
• first filial generation F1

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• STEP 3 allowed the F1 generation plants to
  self-fertilize
• second filial generation F2
• found both purple and white flowers
  (31)
• Other traits Mendel used in table 7-1, Pg. 119

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Mendels Results

• 1. parents transmit info (factors) to offspring
• 2. two factors for each trait
• Homozygous have the same info
• Heterozygous have different info
• 3. forms of factors alleles
• Genotype genetic make-up
• Phenotype physical appearance

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• 4. two alleles for each trait
• one from female parent
• one from male parent
• 5. Dominant alleles are expressed
• Recessive alleles are unexpressed

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Visualizing Mendels Work with Punnett Squares

• Trait flower color
• Factor purple
• Factor white
• P1 TT X tt

T T
t
Tt
Tt
Tt
Tt
t
Genotypic ratio 0 TT 4 Tt 0 tt Penotypic
ratio 4 Purple 0 white
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Mendels conclusions

• Mendel and other scientists developed four Laws
  of genetics.

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Law of Unit characters

• States traits are controlled by factors
  (genes), and these factors occur in pairs

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Law of Dominant and Recessiveness

• States one allele will dominate the other allele.
• The dominant allele is represented by a capital
  letter.
• The recessive allele is represented by a lower
  case letter.

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Law of Segregation

• States the of each pair of alleles separate
  when gametes are formed
• A gamete will receive only one allele or the
  other

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Law of Independent Assortment

• States that 2 or more pairs of alleles segregate
  independently of one another during gamete
  formation

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PATTERNS OF INHERITANCE
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Incomplete Dominance

• a genotype that is an intermediate form of
  the traits expressed by the parents
• Example Snapdragons
• red X white yields pink offspring
• The heterozygous condition will not appear red
  (dominant), but rather a different phenotype

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Codominance

• both genes of a heterozygote (Tt) are equally
  expressed
• Example Horse coat color
• Homozygous red horse X homozygous white horse
• Offspring are equal mix of two parents colors
  which is called roan

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Multiple Alleles

• traits that are controlled by genes having more
  than 2 alleles within the population
• Example Blood groups
• alleles IA, IB, i
• Phenotype Genotype
• A IAIA IAi
• B IBIB IBi
• AB IAIB
• O ii

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Polygenic Traits

• traits that are controlled by more than one
  pair of genes
• Example hair color/eye color/skin color

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• GENE EXPRESSION MAY BE AFFECTED BY ENVIRONMENT
• Read p. 126
• Fig. 7-10 a, b

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HUMAN GENETIC DISORDERS

• Mutation a change in a gene caused by
• damage to the gene
• incorrect copying
• most are harmful or neutralRARELY HELPFUL
• most are recessive

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GENETIC DISORDERS
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Cystic fibrosis

• mutation in the gene coding for transportation
  of
• chloride ions
• Symptoms mucus build up in lungs pancreas
• difficulty breathing
• difficulty digesting food

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Sickle Cell Anemia

• mutation in the gene coding for hemoglogin
• Symptoms fatigue
• headaches
• muscle cramps
• kidney failure, heart failure

Protein in blood that carries O2
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Hemophilia

• mutation is on the X chromosome and the body
  makes a defective form of a protein needed to
  clot blood
• Symptoms wounds do not heal
• difficult to stop bleeding
• internal bleeding
• arthritis

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Down Syndrome

• an extra 21st chromosome ( have a total of 3
  instead of 2)
• Symptoms extra folds in upper eye lids
• broad/flat face
• short stature
• varying degrees of mental retardation
• (1/1000 births)
• (1/16 births to women over 45)