Heredity

1. Heredity

2. Heredity Benchmarks III.3.MS.1 - Describe how the characteristics of living things are passed on from generation to generation. III.3.MS.2 – Describe how heredity and environment may influence/determine characteristics of an organism.

3. Breaking down the Benchmarks • III.3.MS.1 - Describe how the characteristics of living things are passed on from generation to generation. • Chromosome • Gene • Hereditary information • Common traits controlled by a single gene pair. • Wrinkled or smooth seeds in a pea plant • Color of horse hair • Human traits such as tongue rolling

4. Breaking down the Benchmarks • III.3.MS.2 – Describe how heredity and environment may influence/determine characteristics of an organism. • Inherited Traits • Acquired Traits

5. Heredity Basics • Heredity is the passing of traits from parent to offspring (children). • The traits are controlled by genes. • The genes are the chemical code found in helical (spiral-shaped) molecules of deoxyribonucleic acid (DNA), which are packed away inside the cells of all living things.

6. Inherited Traits • Inherited traits are those present in the genetic makeup of an organism that have been passed on from one generation to the next. These may include: • Eye color • Left- or right-handedness • Butterfly wing patterns • Animal fur color

7. Acquired Traits • Acquired traits develop or occur after an organism is born. • They occur in response to environmental factors such as stress, overall health, nutritional choices, chemical exposure, and changes in land use and are not a result of the organism’s genetic code. • These include: • Straightened teeth from wearing braces • The loss of a limb in an accident

8. Chromosome • There are several lengths of DNA in a cell’s nucleus. • Each one is called a chromosome.

9. Chromosome • There are two copies of each chromosome in every cell of an organism. • One set of chromosomes comes from the mother and one comes from the father.

10. Gene • A gene is one area of a chromosome that has the instructions to make one protein. • DNA works by telling a cell how to make the many different proteins that your cells need to work.

11. Gene • Each DNA molecule forms a threadlike structure, or gene. Genes then in turn form chromosomes. • There are two copies of each chromosome--one from the father and one from the mother.

12. Hereditary Information • We are all familiar with the idea that traits can be inherited from parent to child. • For example, think of dogs: a purebred pair of Great Danes would never produce puppies with the tiny, short-legged characteristics of a dachshund -- but what does that really mean?

13. Hereditary Information • Traits are inherited because discrete units called genes are passed from parent to child when the child is conceived. • These genes are a unique blueprint for an individual organism, providing all the biological information needed for its pre-birth development and life, as well as for the characteristics that make that individual unique.

14. Hereditary Information • Just as in an engine, where the removal of one part can disrupt the entire engine's ability to run, so the removal of the influence of one gene can have a severe effect on the life of an organism.

15. Gregor Mendel • In the 1800s Gregor Mendel an Austrian monk studied how traits were passed from one generation to the next. • He experimented with plants (green peas).

16. How do we know genes exist? • He kept careful track of the traits displayed by the pea plants produced by cross-fertilization, discovering that traits of the parent plants were inherited by the progeny plants in specific patterns.

17. Gregor Mendel • Examination of the trait inheritance patterns of the pea plants suggested to Mendel that each trait resulted from two units of inheritance. • Mendel proposed that one unit came from each parent plant. • We now call these units genes.

18. Gregor Mendel • The study of how different forms of a gene affect generations of offspring is genetics. • That is why Mendel is called the father of genetics.

19. Gregor Mendel • Mendel also learned that a particular trait could have several varieties that were produced by different versions of the "units of inheritance" or genes. • For example, the pea plant flower color could be pink or white. • We use the term allele to designate a version of a gene.

20. Gregor Mendel • Mendel's experiments showed that some alleles appeared to be dominant over others. • For example, if a pea plant inherits one pink flower color gene and one white flower color gene, the resulting flowers will all be pink -- just as if the plant had two pink flower color genes. (Pink is the dominant flower color in peas; white is the recessive flower color.)

21. Gregor Mendel • If a gene was not dominant then it could be • recessive • or even a blend.

22. Genotype/Phenotype • Two other concepts that are useful in understanding genetics are… • phenotype and • genotype.

23. Genotype/Phenotype • The phenotype of an organism is its observable traits, and these traits are produced by the organism's genotype -- or genes -- for that trait. • For example, the pea plant with one pink and one white flower gene has the genotype pink/white (one pink gene and one white gene) while its phenotype is pink (only pink flowers are observed).

24. Genotype/Phenotype • Again…in simpler terms… • Genotype-What the gene says • Phenotype-What you see

25. Homozygous/Heterozygous • Homozygous pairs of chromosomes have the same gene for a given trait. • For example, if the gene for brown eyes is B, then the homozygous pair would be (BB). • Heterozygous pairs of chromosomes have different versions of a gene for a given trait. • For example, if the gene for brown eyes is B, and the gene for blue eyes is b, then the heterozygous pair would be (Bb).

26. Homozygous/Heterozygous • Homozygous gene pair- • Same • (BB) (bb) • Heterozygous gene pair- • Different • (Bb)

27. Punnet Square

28. Inference and Analysis • Genetics is an elegant and indirect science, but it is very powerful. In genetics, inference plays a critical role. • Mendel's experiments led him to infer the existence of genes, but he never actually saw them. • Similarly, analysis of mutations, or defects, in genes help scientists infer normal gene function.

29. Inference and Analysis • By seeing what happens to organisms when the function of a gene is changed, scientists can make educated guesses regarding what the normal job of the gene is in the cell.

30. What kinds of jobs do genes do? • Genes are responsible for all the functions of the cell and are used throughout the life of an organism.

31. How does Heredity affect You? • Imagine the phone ringing. Pick it up. Put it to your ear. Notice which ear you are using. • Interlock your fingers. Notice which thumb is placed on top. Pull your hands apart and repeat the process in reverse order. Notice how difficult/awkward it is to have the opposite thumb on top. • Cross and re-cross your arms. Notice which is the dominant way you cross your arms.

32. What other traits have been passed on to you? • Handedness (right vs. left) • Eye color • Rolling your tongue in a "U" shape • Free or attached ear lobes • Widow’s peak ("V" hairline on forehead) • Hair on fingers between first and second knuckle • Cleft chin

33. Let’s Chart It! • Wow!! We have inherited a lot of different traits. • Let’s collect the data and record it in a chart, so that we can better understand that our individual traits are a blend of our parents genetic information.