A dominant allele is expressed even if it is paired with a recessive allele.
A recessive allele is only visible when paired with another recessive allele.
One Locus Inheritance heterozygote homozygote 2 1 A | A a | a A | a 3 4 a | a A | a 5 6 a | a Male Female
Mendel’s 1 st Law Two members of a gene pair segregate from each other into the gametes, so half the gametes carry one member of the pair and the other half carry the other member of the pair. Y / y y / y ½ y/y ½ Y/y ½ y ½ Y all y Gamete production Gamete production
We want to predict patterns of inheritance of traits and diseases in pedigrees.
E.g., we want to know the likelihood that a dog chosen at random from the study population will have blue eyes.
X-linked Inheritance Different results obtained from reciprocal crosses between red-eyed and white-eyed Drosophila. Explanation : The gene responsible for eye-color is X-linked . Females have 2 X-chromosomes, while males have 1 X-chromosome and 1 Y-chromosome.
Cystic fibrosis – disease affecting the mucus lining of the lungs, leading to breathing problems and other difficulties
Huntington disease - or Huntington's chorea is an inherited disorder characterized by abnormal body movements called chorea, and loss of memory. There also is evidence that doctors as far back as the Middle Ages knew of this devastating disease. The incidence is 5 to 8 per 100,000. It takes its name from the New York physician George Huntington who first described it precisely in 1872.
Hemophilia- illness that impair the body's ability to control bleeding.
Fragile X syndrome - is a genetic condition that causes a range of developmental problems including learning disabilities and mental retardation. Usually males are more severely affected by this disorder than females. In addition to learning difficulties, affected males tend to be restless, fidgety, and inattentive. Affected males also have characteristic physical features that become more apparent with age.
DNA - a pair of molecules joined by hydrogen bonds: it is organized as two complementary strands, head-to-toe, with the hydrogen bonds between them. Each strand of DNA is a chain of chemical "building blocks", called nucleotides, of which there are four types:adenide (abbreviated A), cytozyne (C), guanine (G) and thymine (T).
Mitochondria , which are structures in each cell that convert molecules into energy, each contain a small amount of DNA.
A chromatid forms one part of a chromosome after it has coalesced for the process of mitosis or meiosis. During either process, the word "chromosome" indicates a pair of two exactly identical (" sister ") chromatids joined at the central point of each chromatid, called the centromere.
Mitosis is the process by which a cell separates its duplicated genome into two identical halves
Meiosis is the process that transforms one diploid into four haploid cells.
Reciprocal cross a cross, with the phenotype of each sex reversed as compared with the original cross, to test the role of parental sex on inheritance pattern. A pair of crosses of the type genotype A(female) X genotype B(male) and genotype B(female) X genotype A(male).