Mendelian Genetics Gregor Mendel Father of modern genetics
Objectives I can compare and contrast mitosis & meiosis. I can properly use the genetic vocabulary presented. I can differentiate and gather data from the genetic tools of karyotypes, Punnett squares and pedigrees. I can describe and apply Mendel s Laws. I can set up and utilize Punnett squares. I can describe different patterns of inheritance.
Cell Division Review mitosis produces two daughter cells genetically identical to the original parent cell (diploid) meiosis produces four daughter cells with exactly half the genetic material of the original parent cell. (haploid)
Gametogenesis-meiosis Creation of the gametes. Male meiosis generally results in the production of four sperm that are capable of producing offspring. Female meiosis generally results in the production of ONE viable oocyte plus 3 polar bodies.
allele: different forms of a gene found in the gene pool ie: A, B & O alleles for human blood type. phenotype: the physical trait in an organism ie: hitchhiker s thumb genotype: the actual genes of an organism ie: homozygous recessive (aa) dominant allele: if present, determines the phenotype of trait - ie: roll tongue recessive allele: No dominant allele present, trait will be expressed ie: no tongue roll. homozygous: the two alleles are the same (dominant AA or recessive - aa). heterozygous: the two alleles are different (one big, one small - Aa) autosomal trait: a gene located on one of the autosomes (any chromosome that is not a sex chromosome). sex-linked trait: a gene located on one of the sex chromosomes (either the X (X-linked) or Y (Y-linked) chromosome).
A karyotype is a picture of an individuals chromosomes Chromosome numbers are arranged by size. Pictures are taken when the cell is in metaphase Sex chromosomes are the last pair Karyotype of normal human male & female. 46 chromosomes (23 pair)
DNA make up your chromosomes. Chromosomes are where your genes are stored. Genes determine your traits (proteins). You inherit 1 allele from each parent for each trait. (total of 2) Traits have dominant forms and recessive forms. Your alleles will determine your genotype and phenotype.
Mendel s Laws worked with pea plants to make observations. Law of Segregation - The two forms of a gene (now known as alleles) present in each organism segregate into different cells during gamete formation. Law of Independent Assortment - The (two) alleles of the many different genes present in any given (diploid) organism segregate/assort from one another in a random fashion. Law of Dominance - alleles can be dominant or recessive. The dominant allele, if present, will always determine the trait.
Law of Dominance Laws of Segregation & Independent assortment
Karyotype Tools for Genetics Pedigrees show how a single heritable trait runs through generations. Pedigree Punnett Squares
Punnett Squares The outside of a Punnett Square represents the possible gametes that pa parent can give based on the law of segregation. gametes Aa Aa gametes Aa Aa The inside of the Punnett Square represents the possible offspring if those two gametes fertilized each other. In this example, all of the offspring would be yellow because they each have a dominant allelle.
Punnett Square Practice!! t T t Cross a male who is heterozygous for tongue rolling (Tt) with a female that is homozygous recessive (tt) Genotypic ratio: TT : Tt : tt t Phenotypic ratio: Rolling ; no rolling
Punnett Square Practice!! F F f Cross 2 parents who are heterozygous for freckles (Ff) f Genotypic ratio: FF : Ff : ff Phenotypic ratio: Freckles ; no freckles
Patterns of Human Inheritance Dominance If dominant allele is present, it is expressed. Incomplete dominance - Neither allele fully expressed in heterozygote -Aa; looks like a mixture of both (red & white = pink) Co-dominance both alleles equally expressed in heterozygote -Aa (AB blood type) Sex-linked traits on the sex chromosomes Polygenic many genes control ONE trait (height)
Pedigrees