Chapter 9 GeneticsBy Mr. “I love winter” Chapman
Intro. Genetics Genetics – a field of biology dedicated to understanding how characteristics are transmitted from parents to offspring (heredity). Student Characteristics?
Genetics Terms Allele – several alternative forms of a gene; 2 alleles for hair color (brown and black hair) Ex. Bb
Genetic Terms Pollination – occurs when pollen grains (sperm) produced by anther reach the female reproductive part (stigma).
Genetic Terms Self-pollination – when pollen reaches female part on the same plant.
Genetic Terms Cross-pollination – is the transfer of pollen between two different plants.
Genetics Gregor Mendel the father of genetics. Gregor Mendel experimented with peas: He observed different traits in peas Ex. Plant height, flower position, pod color, seed color and flower color He noticed that purple flowered pea plants produced purple and white flowered pea plants.. why?
Mendel’s Experiments Began by growing plants that were pure for a trait they always produce offspring with that trait (P1 Generation) Ex. Purple flowers purple flowers Cross pollinate two different traits their offspring is the F1 Generation Purple and white flowers F1 Generation self pollinated their offspring is the F2 Generation
Mendel’s ExperimentMendel’s Conclusions1. Dominant and Recessive Traits Dominant allele – an allele that dominates or masks the other allele Ex. When a green pod allele (G) is with a yellow pod allele (g) the green pod will result Recessive allele – an allele that has not observable effect on an organism’s appearance when paired with a dominant allele Ex. The yellow pod allele
Mendel’s Conclusions 2. The Law of Segregation paired alleles separate during the formation of reproductive cells (gametes)
Mendel’s Experiment 3. The Law of Independent Assortment the alleles for different characteristics are distributed to gametes independently A yellow pod could appear in plants with purple or white flowers
Genetic Terms Genotype – the genetic make-up of an organism. Ex. the alleles PP, Pp or pp are three different genotypes Phenotype – the appearance of an organism Ex. Purple flowers or White flowers
Example Purple allele is P White allele is p Genotype: PP or Pp and pp Phenotype: Purple or white
Genetic Terms Genotype – the genetic make-up of an organism. Ex. the alleles PP, Pp or pp are three different genotypes Phenotype – the appearance of an organism Ex. PP and Pp are purple flowers, pp is white Homozygous – the two alleles are the same Ex. PP or pp Heterozygous – the two alleles are different Ex. Pp
Genetic Terms Monohybrid cross – a cross between individuals that involves one pair of traits Ex. crossing a plant with all purple flowers with a plant with all white flowers.
Genetic Terms A Punnett Square is a handy dandy device for predicting the results of a monohybrid cross.
Sex Chromosomes Sex Determination Thomas Morgan (early 1900’s) bred fruit flies and observed the sex chromosomes Females XX Males XY
Sex Chromosomes Homologous chromosomes separate during Meiosis I Male gametes have either X or Y Female gametes have X When fertilization occurs who determines the sex of the offspring?
Sex Chromosomes What is the chance that the offspring will be female and what is the chance that the offspring will be male? Sex Linkage – the presence of a gene on the sex chromosome X-linked genes – genes on the X chromosome