11.1- Monohybrid cross Mendels pea observation- · Variant or alternative forms (phenotype) occur because if variations (alleles) of genes on autosomes · Autosomes are chromosomes that are not involved in wed determination Dominant phenotype- . Are expresses if individuals array at least one allele for a dominant trait Recessive trait- · Expresses only if individual carry 2 alleles for a recessive trait Autosomal dominant inheritance- · A trait that is passed off to offspring via autosomal gene True breeding- · Parents with particular phenotypes produce offspring only with the same phenotype Example- YY x YY = YY or ww x ww = ww Punter square- X B Genotypes = BB- 1/4 Bb- 1/2 bb- 1/4 Phenotype= brown eyes= 3/4 blue eyes= 1/4 Ratio- brown to blue = 3:1 = 75%-25%l B B BB Bb PARENTAL GENERATION (P) FIRST FILIAL GENERATION (F1) Purple White x PP pp Purple Pp SECOND FILIAL (F2) GENERATION PP Pp Pp pp 3 Purple: 1 White B Bb bb F1 generation- Hybridization: · 2 true-breeding parents with 2 different traits and are crossed Hybrids- offspring · Two true breeding stains can be crossed to produce an F1 generation X W W Ww w Ww w Ww Ww The phenotype resulting from the genotype is red eyes Red eves are dominant F2 generation- · F2 generations are the result of crossing the individuals from the F1 generation · 3 possible alleles: - WW - Ww - WW
Autosomal Co-dominance- · 2 alleles are expressed to varying alleles are expressed to varying degrees in the phenotype of heterozygous individuals Example- snapdragon; the individual heterozygous for this trait, neither allele is completely expressed and the result is a blending effect of the 2 phenotype R = Red color R = White color · Parental generation: R R x R R F1 = R R and R R F2 = genotype X R R Genotype: 1R R : 2 R R Phenotype: 1 white: 2 pink : 1 red R RR RR R RR RR Autosomal co-dominant crosses Pedigrees wil show 3 phenotypes Crossing a homozygous dominant with a homozygous recessive leads to heterozygous offspring with the intemitodiate trait Crossing 2 heterozygous individuals leads to offspring which could show any of the three phenotypes Genotype Phenotype I I or I I A I I or I I B i i Blood type- · Three different alleles of the ABO gene · Possible genotypes : A, B, AB , O · AB= co-dominance O AB I i I i I i I The F1 generation in this example would be either blood type A or B but all would be heterozygous i I i I i Sex- linked inheritance: · Phenotype inherited through genes on sex-chromosomes are said to be sex linked . It is important to remember that sex chromosomes also carry genes which are not related to sex determination X-linked recessive inheritance- · Condition in which an alternation in one gene on the X chromosome causes the condition in