Transcript genetics
GENETICS -The branch of biology that studies the ways in which hereditary information is passed on from parents to offspring - Explains factors that contribute to hereditary similarities and differences HEREDITY • The transmission of genetic characteristics (chemical instructions) from the reproductive cells of the parent to offspring Mendelian Genetics • Gregor Mendel “the father of genetics” • A monk who developed basic principles of heredity through experiments with pea plants • Why Pea Plants? 1- Easy to grow 2- Mature quickly 3- Contrasting traits • Why Pea Plants? 1- Easy to grow 2- Mature quickly 3- Have contrasting traits Mendelian GeneticsVocabulary • Dominant- the inherited characteristic that appears in an organism • Recessive- the inherited characteristic often masked by the dominant characteristic and not seen in an organism • Alleles- the different forms of the gene for a particular trait (factors) • Heterozygous- two different alleles for a particular trait (hybrid) • Homozygous- two identical alleles for a particular trait (pure bred) Mendelian Genetics The Law of Dominance • When an organism is hybrid for a pair of contrasting traits, only the dominant trait can be seen Law of Segregation • Factors (alleles, genes) that occur in pairs are separated from each other during gamete formation (meiosis) and recombined at fertilization Gene-Chromosome Theory • Modern explanation of genetics • Chromosomes- rod-like structures in cell nucleus that contain hereditary information (DNA) • Genes- a unit of hereditary material found in chromosomes, segment of DNA that controls a specific trait or function • Loci (locus)- particular point where a certain gene is found on a chromosome • Homologous Chromosomes- a pair of chromosomes having the same size and shape and carrying alleles for the same trait, genes at the same loci Genotype • The genetic make-up of an organism • Alleles represented with letters • Capitol letter represents the allele for a dominant trait (T- tallness) • Lower case letter represents the allele for a recessive trait (t- shortness) • Heterozygous- Tt • Homozygous- TT or tt Phenotype • The physical trait that an organism develops as the result of its genotype • Can have same phenotype but different genotype • Ex. Tt and TT Tall Punnett Square • A diagram used in genetics to predict the possible genotypes resulting from the cross between two organisms • Alleles of possible female gametes on one side and the alleles of the possible male gametes on the other side Punnett Squares Punnett Square for Pea Color • Y- dominant gamete for green peas • y- recessive gamete for yellow peas Genotype Ratio: 25% Homozygous dominant 50% Heterozygous 25% Homozygous recessive 1:2:1 Phenotype Ratio: 75% green 25% yellow 3:1 YOU TRY• Genotype Ratio: • Phenotype Ratio: Incomplete Dominance • Type of inheritance in which two contrasting alleles contribute to the individual a trait not exactly like either parent • Blending inheritance, neither is dominant or recessive Codominance • A type of inheritance in which two dominant alleles are expressed at the same time without blending traits • Ex. Roan Cattle- Red coat crossed with white coat= red and white hairs Multiple Alleles • Traits controlled by three or more different alleles • An individual only has 2 of the multiple alleles • Each produces a different phenotype • Ex- Human Blood TypeABO Blood Group You Try • Ex- A man with genotype IAi and a woman with genotype IBi have children. What are the possible blood types of the children? Try Again • A woman has blood type A and her baby has blood type AB. She accuses a man with blood type O of being the baby’s father. Is this possible?