Genetics

1. Genetics

2. Vocabulary Background INHERITANCE or HEREDITY- The genetic transmission of characteristics from parent to offspring, such as hair, eye, and skin color.

3. Vocabulary Background GENOTYPE- the genes present in the DNA of an organism.  There are always 2 letters in the genotype because (as a result of sexual reproduction) 1 gene from MOM + 1 gene from DAD = 2 genes (2 letters) foroffspring

4. Vocabulary Background • HOMOZYGOUS: GENOTYPE has 2 capital or 2 lowercase letters (ex: TT or tt) ("homo" means "the same") • Sometimes the term "PUREBRED" is used instead of homozygous.

5. Vocabulary Background • HETEROZYGOUS:GENOTYPE has 1 capital letter & 1 lowercase letter (ex: Tt) ("hetero" means "other") • A heterozygous genotype can also be referred to as HYBRID.

6. Vocabulary Background • PHENOTYPE- how the trait physically shows-up in the organism; it is the observable traits present in an organism What the organism LOOKS like • Examples of phenotypes: blue eyes, brown fur, striped fruit, yellow flowers

7. Vocabulary Background • ALLELES- alternative forms of the same gene.  Alleles for a trait are located at corresponding positions on homologous chromosomes called loci. ALLELES Chromosome from MOM A b C d e Chromosome from DAD A B c d E

8. Vocabulary Background • When 1 allele masks (hides) the effect of another, that allele is called DOMINANT and the hidden allele is called RECESSIVE. • Dominant alleles are represented by a CAPITAL letter • Recessive alleles are represented by a LOWERCASE letter

9. Knowledge Check • Vocabulary Review: • Define • Genotype:Phenotype: • Allele: • Genes: • Homozygous: • Heterozygous

10. Work of Gregor Mendel Genetics is the scientific study of heredity. Gregor Mendel was an Austrian monk. His work was important to the understanding of heredity. Mendel carried out his work with ordinary garden peas.

11. Work of Gregor Mendel • Mendel knew that • the male part of each flower produces pollen, (containing sperm). • the female part of the flower produces egg cells.

12. Work of Gregor Mendel During sexual reproduction, sperm and egg cells join in a process called fertilization. Fertilization produces a new cell. Pea flowers are self-pollinating.

13. Work of Gregor Mendel Cross-pollination Mendel was able to produce seeds that had two different parents. Mendel had true-breeding pea plants that, if allowed to self-pollinate, would produce offspring identical to themselves.

14. Work of Gregor Mendel • Genes and Dominance • A trait is a specific characteristic that varies from one individual to another. • Mendel studied seven pea plant traits, each with two contrasting characters. • He crossed plants with each of the seven contrasting characters and studied their offspring.

15. Mendel’s F1 Crosses on Pea Plants Each original pair of plants is the P (parental) generation. The offspring are called the F1, or “first filial,” generation. The offspring of crosses between parents with different traits are called hybrids.

16. Work of Gregor Mendel • Mendel's first conclusion • biological inheritance is determined by factors that are passed from one generation to the next • Today, scientists call the factors that determine traits genes.

17. Work of Gregor Mendel • Each of the traits Mendel studied was controlled by one gene that occurred in two contrasting forms that produced different characters for each trait. • The different forms of a gene are called alleles. • Mendel’s second conclusion • principle of dominance • some alleles are dominant and others are recessive

18. Work of Gregor Mendel • Segregation • Mendel crossed the F1 generation with itself to produce the F2 (second filial) generation. • The traits controlled by recessive alleles reappeared in one fourth of the F2 plants.

19. Work of Gregor Mendel The reappearance of the trait controlled by the recessive allele indicated that at some point the allele for shortness had been separated, or segregated, from the allele for tallness.

20. Work of Gregor Mendel Mendel suggested that the alleles for tallness and shortness in the F1 plants segregated from each other during the formation of the sex cells, or gametes.

21. Summary of Mendel’s Laws (there is one more to go) Genes are passed from parents to their offspring. If two or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive. In most sexually reproducing organisms, each adult has two copies of each gene. These genes are segregated from each other when gametes are formed.

22. Genetics and Probability The likelihood that a particular event will occur is called probability. The principles of probability can be used to predict the outcomes of genetic crosses.

23. Punnett Squares The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a Punnett square. Punnett squares can be used to predict and compare the genetic variations that will result from a cross.

24. A capital letter represents the dominant allele for tall. • A lowercase letter represents the recessive allele for short. • In this example, • T = tall • t = short

25. Organisms that have two identical alleles for a particular trait are said to be homozygous. Organisms that have two different alleles for the same trait are heterozygous. Homozygous organisms are true-breeding for a particular trait. Heterozygous organisms are hybrid for a particular trait.

26. All of the tall plants have the same phenotype, or physical characteristics. The tall plants do not have the same genotype, or genetic makeup. One third of the tall plants are TT, while two thirds of the tall plants are Tt.

27. The plants have different genotypes (TT and Tt), but they have the same phenotype (tall).

28. Now, it’s time for you to practice!!!