Introduction to Genetics Biology 1-2

Genetics Genetics is the study of heredity and inheritable traits. Genetics is the study of heredity and inheritable traits. Gene-a discreet unit of hereditary information consisting of a DNA sequence. Gene-a discreet unit of hereditary information consisting of a DNA sequence.

Law of Segregation The law of segregation explains how traits are passed to offspring and which traits will show. The law of segregation explains how traits are passed to offspring and which traits will show. 1. There are alternate forms of genes. 1. There are alternate forms of genes. Alternate forms of genes are called alleles. Alternate forms of genes are called alleles. Alleles create variation in a trait. Alleles create variation in a trait. 2. For each inherited characteristic, an organism has two genes, one from each parent. 2. For each inherited characteristic, an organism has two genes, one from each parent.

Law of Segregation cont’d 3. If the two alleles differ, one is fully expressed in the organism’s appearance. The other allele has no noticeable effect on the organism’s appearance. 3. If the two alleles differ, one is fully expressed in the organism’s appearance. The other allele has no noticeable effect on the organism’s appearance. The dominant allele is the one that is fully expressed. The dominant allele is the one that is fully expressed. There is no intermediate form or mixing when the alleles are different. There is no intermediate form or mixing when the alleles are different. The recessive allele is covered up by the dominant allele. The recessive allele is covered up by the dominant allele. Only shows when there are two recessive alleles together. Only shows when there are two recessive alleles together.

Law of Segregation cont’d 4. Each sperm or egg carries only one allele for each inherited trait. 4. Each sperm or egg carries only one allele for each inherited trait. When the sperm or egg form, each gets one allele for each trait. When the sperm or egg form, each gets one allele for each trait. When the sperm an egg meet, the resulting offspring ends up with two alleles for each trait. When the sperm an egg meet, the resulting offspring ends up with two alleles for each trait. Homozygous dominant-two dominant alleles. Homozygous dominant-two dominant alleles. Homozygous recessive-two recessive alleles. Homozygous recessive-two recessive alleles. Heterozygous-one dominant and one recessive allele. Heterozygous-one dominant and one recessive allele. The dominant trait shows, hiding the recessive trait. The dominant trait shows, hiding the recessive trait.

Law of Segregation cont’d Genotype-the genetic makeup of an organism. Genotype-the genetic makeup of an organism. What genes the organism has. What genes the organism has. Phenotype-the expressed traits of an organism. Phenotype-the expressed traits of an organism. The physical appearance of an organism. The physical appearance of an organism. Genotype creates the phenotype. Genotype creates the phenotype.