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Genetics-study of heredity Heredity- transmission of traits from parents to offspring.

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Presentation on theme: "Genetics-study of heredity Heredity- transmission of traits from parents to offspring."— Presentation transcript:


2 Genetics-study of heredity Heredity- transmission of traits from parents to offspring

3 I. You are a unique individual 2 things determine this: A. Heredity examples: hair color, eye color, body build and features, diseases, blood type, etc.

4 B. Environment- your surroundings examples: family, friends, school, community, country, environmental (sun, climate), and internal factors (hormones)

5 C. Heredity and Environment work together to determine who you are.

6 !!! Heredity sets limits but environment determines if you reach those limits

7 Examples: sun (tan??) height (54 or 58)

8 II. Characteristics inherited A. Species-things that make you like others arms with fingers, hair, eyes

9 B. Individual things that make you different length, curly or straight, color

10 III. Gregor Mendel The Father of Genetics

11 A.His work with garden peas

12 B. Observed 7 different traits

13 C. Experimented by breeding plants


15 D. Plant anatomy: 1. male anther produces pollen with sperm cells

16 2. Female ovary produces the egg (ovules)

17 3. Pollination-movement of pollen from stamen to pistil a. Self-pollination -same flower b. Cross-pollination - different plants

18 E. Mendels Experiment Mendel controlled the crosses by removing the stamen

19 F. Mendels results: Tall + tall = tall Short + short = short Short + tall = ?????

20 IV. Why??? Mendels hypothesis: 1. Concept of Unit Characters - Hereditary characteristics are controlled by factors that occur in pairs

21 We call these factors genes, that are found in the homologous pairs of chromosomes in our cells

22 Alleles are different forms of a gene, often represented by capital or lowercase letters Ex: Gene = plant height - Alleles: tall or short -Allele for tall = T - Allele for short = t

23 Examples: tall or short dark hair or red hair Type A blood or Type B blood

24 2. Principle of Dominance and Recessiveness - one factor may prevent the expression of the other

25 Dominant - gene that prevents the expression of another characteristic that always appears in a cross between parents

26 Recessive- characteristic that does not appear if a dominant is present

27 V. Terms A. Pure - both genes are the same 2 dominant, or 2 recessive - Purebred - TT, tt

28 B. Hybrid - genes are different; one dominant one recessive - hybrid plants and animals - Tt

29 C. Homozygous- the same same as pure (TT, tt) D. Heterozygous- different same as hybrid (Tt)

30 F. Genotype - the genes of an organism; its genetic makeup - Use of symbols to represent genes Ex: TT tt Tt

31 G. Phenotype - the physical characteristic or trait of the organism - written in words, descriptive Ex: short or tall type A blood type

32 VI. Law of segregation - a pair of genes separate during the formation of sex cells

33 A. Punnett square- a method used to determine possible combinations of genes in offspring

34 B. Examples

35 C. Test-cross - crossing an individual with an unknown genotype but a known dominant phenotype with a recessive to determine its genotype

36 VII. Law of Independent Assortment- chromosomes with their genes separate independently of each other - Genetics cannot be predicted to an absolute, but we can determine the probability

37 Dihybrid cross-crossing organisms differing in 2 characters

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