Std. 10.4 In sexually reproducing organisms, each offspring contains a mix of characteristics inherited from both parents.
D 37. Use the Punnett square technique to predict the distribution of traits in mono- and di-hybrid crossings.
Learning Target: Principles of Heredity
I Can…Explain the foundation principles of Mendelian Genetics
I Will…• Briefly describe Mendel’s contribution• Describe Mendel’s experimental design• Describe Mendel’s conclusions and Law of
Segregation• Define basic hereditary terms• Distinguish between genotype and phenotype
All started with Austrian monk Gregor Mendel in the 1800s.
Mendel showed that:• Traits are inherited as discrete units.• Laid groundwork of genetics• Demonstrated patterns of
inheritance
Mendel used purebred, self-pollinating pea plants with a selection of • “either / or” traits including:• Pea shape, pea color, pod shape, pod color,
plant height, flower color, and flower position.
Mendel’s Experimental Design:• Use of self-pollinating pea plants• Can control reproduction of plants• Reproduce quickly• Self-pollination creates genetically “pure”
genetic lines• “Either / Or” Traits• Only two allele versions for each trait studied• No blending of traits• Dominant v. Recessive
• Good scientific method (controlled variables and one I.V.)
• Many trials / reproduced results (validity)_
Mendel’s Experimental Design:
Cross – mating of two organisms• P1 – Parental generation
• F1 – First Filial (first offspring) generation
• F2 – Generation produced from F1
Mendel’s Experimental Design:
Cross – mating of two organisms• P1 – Parental generation
• F1 – First Filial (first offspring) generation
• F2 – Generation produced from F1
Law of Segregation:• Organisms donate only one copy of
each gene in the gametes (haploid) to their offspring
• Genes segregate or separate during meiosis• Remember the process of meiosis
segregates only one of each chromosome into each of the gametes
Mendel’s Conclusions
Vocabulary terms:• Genetics – study of biological
inheritance patterns and variation in organisms
• Trait – distinguishing characteristic that is inherited e.g. earlobe attachment, freckles, hairline pattern
• Gene – section of DNA that codes for a protein e.g. hemoglobin for RBCs
• Allele – different versions of a gene e.g. normal or sickle hemoglobin
Genetics and HeredityCh. 6.3 pp. 177-179Ch. 6.4 pp. 180-182
Vocabulary terms:• Homozygous – two of the same allele at
the same gene locus (location on chromosome) for a trait e.g.
Gene trait = earlobe attachment
• A homozygous individual would have: • 2 unattached earlobe alleles or • 2 attached earlobe alleles
• Purebred – genetically uniform
Genetics and Heredity
Vocabulary terms:• Heterozygous – two different alleles at
the same gene locus (location on chromosome) for a trait e.g.
Gene trait = earlobe attachment
Genetics and Heredity
• A heterozygous individual would have: • 1 unattached earlobe allele and • 1 attached earlobe allele
• Hybrid - NOT genetically uniform
Vocabulary terms:• Dominant - allele that is expressed
even when 2 different alleles are present e.g. unattached allele is dominant to attached allele in earlobe attachment
Genetics and Heredity
Heterozygous E e
Homozygous E E Designated with an uppercase (capital) letter representing the trait e.g. “E” = Dominant earlobe attachment (unattached)
Vocabulary terms:• Recessive - allele that is expressed
only when 2 of the same allele are present e.g. attached allele is recessive and will only show if 2 attached alleles are present for earlobes
Genetics and Heredity
Homozygous attached e e
Designated with a lowercase (small) letter representing the trait e.g. “e” = recessive earlobe attachment (attached)
Vocabulary terms:• Genotype – Genetic makeup of an
organism; actual genes present • Homozygous unattached earlobes (E E)• Heterozygous unattached earlobes (E e)• Homozygous attached earlobes (e e)
Genetics and Heredity
Vocabulary terms:• Phenotype – physical appearance of
trait in organism from expression of allele• Unattached earlobes • Could be (EE) or (Ee) genotype• Phenotype shows • Dominate version
• Attached earlobes• Must be (ee) genotype• Phenotype of recessive only shows • When homozygous recessive
genotype
Genetics and Heredity
• Phenotype – Dominant trait• Genotype – Could be either:• Homozygous Dominant – e.g. EE• Heterozygous – e.g Ee
Genetics and Heredity
• If you know the genotype you will know the phenotype, BUT…
• If you know the phenotype you cannot know the genotype of a dominant trait without more information
• Phenotype – Reccessive trait• Genotype – Must be :• Homozygous reccessive – e.g. ee
Vocabulary terms:• Genome – all of
an organism’s genetic material• Human somatic
cells have 46 chromosomes in 23 pairs
• Estimated to contain 25,000 genes
Genetics and Heredity
Learning Check √: Principles of Heredity
Considering Ms. Brown has unattached earlobes and her son has attached earlobes and her daughter has unattached earlobes, • What is Ms. Brown’s genotype? ________________• What is Ms. Brown’s son’s genotype? ______________• How did you figure this out?
• Can you determine Ms. Brown’s daughter’s genotype? Explain Why or Why not.