Genetics Vocabulary Background INHERITANCE or HEREDITY The genetic

Genetics

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

Vocabulary Background GENOTYPE- the genes present in the DNA of an organism. There 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) for offspring

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.

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.

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

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 A B c d E Chromosome from DAD

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

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

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.

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.

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.

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

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.

�Each original pair of plants is the P (parental) generation. �The offspring are called the F 1, or “first filial, ” generation. �The offspring of crosses between parents with different traits are called hybrids. Mendel’s F 1 Crosses on Pea Plants

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.

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

Work of Gregor Mendel �Segregation • Mendel crossed the F 1 generation with itself to produce the F 2 (second filial) generation. • The traits controlled by recessive alleles reappeared in one fourth of the F 2 plants.

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.

Work of Gregor Mendel �Mendel suggested that the alleles for tallness and shortness in the F 1 plants segregated from each other during the formation of the sex cells, or gametes.

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.

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.

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.

�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

�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.

�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.

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

Now, it’s time for you to practice!!!