Presentation on theme: "Chapter 9 Genetics. 9.1 The Work of Gregor Mendel Mendel – crossed pea plants to study and understand genetics –Most pea plants self pollinate (true breeding)"— Presentation transcript:
Chapter 9 Genetics
9.1 The Work of Gregor Mendel Mendel – crossed pea plants to study and understand genetics –Most pea plants self pollinate (true breeding) –Mendel forced plants to cross pollinate (have 2 plants)
–Studied 7 traits of pea plants pg 176. –Took the plants that had different traits and crossbreds them (hybrids)
The F1 Cross First Filial (parent cross, produce the F1, then cross the F1 making an F2) –Law of segregation: Segregation of alleles occurs during the formation of gametes, sex cells. –Pg 177 –Law of Independent Assortment – factors for individual characteristics are not connected. Assort independently of each other.
Came to 2 conclusions after the breeding 1.Genes, segment of DNA, occurs in pairs, controll heredity. Visual form called alleles. (noted as “factors”) 2.Found that some of the alleles are dominant and some are recessive. 1.Dominant trait always uppercase (TT, Tt) 2.Recessive always lowercase (tt)
9.2 Probability and Punnett Squares Punnett square – table representation of crossing alleles –TT or tt – homozygous – same alleles –Tt – heterozygous – different alleles –Phenotype – physical look, all tall (TT, Tt) have same phenotype. –Genotype – based on alleles. (TT, and Tt) are different now.
Probability Penny = ½ =.50 A cross results in 787 pink flowers and 277 white flowers. If we cross the same P generation, the probability will be the same)
Dominant Recessive Curled Up Nose Roman Nose Clockwise Hair Whorl Counter-clockwise Hair Whorl Can Roll TongueCan't Roll Tongue Widow's PeakNo Widow's Peak Facial DimplesNo Facial Dimples Able to taste PTCUnable to taste PTC Earlobe hangsEarlobe attaches at base Middigital hair (fingers)No middigital hair No hitchhiker's thumbHitchhiker's thumb Tip of pinkie bends inPinkie straight Oval faceSquare face Cleft chinno cleft chin Broad eyebrowSlender eyebrow Separated eyebrowsJoined eyebrows Long eyelashesShort eyelashes Almond eyesRound eyes FrecklesNo freckles Wet-type earwax Dry-type earwax Left thumb on top of interlocking fingersRight thumb on top of interlocking fingers
Punnett Squares pg 182
Homozygous x homozygous
Homozygous x heterozygous AA x Aa
Hetero x hetero
Summary of Mendel’s Principles pg 272 Some alleles are neither dominant nor recessive, and many traits are controlled by multiples alleles or multiple genes. Incomplete Dominance – when one allele is not necessarily dominant (red and white flowers produce pink)Incomplete Dominance Codominance – both alleles contribute to the phenotype. Multiple alleles – within the population of the species there are more than just 2 types of alleles. Coloration in Rabbits Polygenic Traits – having many genes, traits controlled by 2 or more genes. Skin color in humans.
We'll use "F" for the flower color allele. FR = allele for red flowers FW = allele for white flowers red x white > red & white spotted flowers FRFR x FWFW ----> 100% FRFW