Microsoft PowerPoint - 10.1 Mendel's Laws of Heredity



GeneticsMain Concepts…Sexual reproduction involves the random distribution of ________________.We have ________________ of genes.Genes determine your ______________.Genes line up on your _________________.Chromosomes are in the ___________________ of the cell. Chromosomes ________________ and ______________ in cell division.Chromosomes are typically in _______________.A ________________ cell has complete set of chromosomes.HeredityHEREDITY – ______________________________________________ from parents to offspringCharacteristics that are inherited are called _______________________Gregor Mendel1. Gregor Mendel was an Austrian monk and was the first person to successfully study ______________________, the branch of biology that studies heredityPea PlantsMendel chose to study the garden pea plant:The male gamete is __________ and fuses with the female gamete in a process called _________________Fertilized egg = _______________The transfer of male pollen to the female reproductive organ is called __________________________Pea Plant (con’t)Pea plants can reproduce by SELF-POLLINATION because each plant has both male and female gametesMendel performed a process called CROSS-POLLINATION by dusting pollen from one plant to any other plant of his choosing. This allowed him to control which plants mate with which plantsResearchMendel was a careful researcher: He studied only one _______________ at a time (e.g. Height) and analyzed the data mathematicallyMendel used ___________________________ plants for his crosses. This means the plants have the same traits for many generations (e.g. all purple flowers)_______________ExperimentWhen Mendel crossed two different _________________ for a trait he called this a ______________ When Mendel only crossed __________ trait at a time he called this a ____________________________Monohybrid Cross (Height)All pea plants are either tall (6ft) or short (2ft) 191706514160500The 1st Generation:Mendel cross-pollinated a true breeding tall pea plant with a true breeding short pea plant. The offspring were all tall pea plants181102017589500P1 -->__________________________________________________ Monohybrid Cross (Height)191706517208500The 2nd Generation: Mendel allowed the tall offspring to self-pollinate.180721018034000F1 -->_____________________________________________________________________________________________Mendel’s Experiments Review Short pea plants X Tall pea plants Q: What did he get?A: ____________________________________________Then, Tall X Tall pea plants Q: What did he get?A: ____________________________________________________________________________________________GenerationsThe original (true breeding) parents are known as the P1 generation_____= “parent”The offspring of the P1 generation are known as the F1 generation_____ = “filial” (son or daughter)Crossing two F1 plants creates the F2 generation Conclusions from Mendel’s ExperimentsFactors = ________________________Law of _______________: in any pair of genes, one may hide the appearance of the other.Dominant: ______________________Recessive: masked, hidden, ________________________________Law of _______________________: the pairs of genes (and chromosomes) separate _________________!Law of ______________________: During Meiosis chromosomes separate, and genes separate also.Rule of DominanceMendel also concluded that one allele is _________________ and one is ___________________The dominant allele is the one that shows up in the F1 generation (Tall)Capital letter -->TThe recessive allele is the trait that is hidden in the F1 generation (Short)Lowercase letter --> tCapital letter is always written before the lowercase letterDominant/Recessive TraitsA dominant trait (tall) is the result of either TT or TtTT = tallTt = tall A recessive trait (short) can ONLY be the result of tttt = short The dominant allele always overrides the recessive allele, therefore, dominant traits are more common than recessive traitsAllelesMendel concluded that each organism must have two factors that control each of its traitsWe now know that traits are controlled by _____________ and are located on ____________________.Genes exist in alternative forms called ________________________Gene --> plant heightAlleles --> tall or shortAlleles --> dominant or recessiveAllelesAlleles are located in exactly the same position on ___________________ chromosomes In a diploid organism, there are ______________ alleles for a given geneOne from ________________; one from ___________________ A plant might have:2 copies of the tall allele (TT)2 copies of the short allele (tt)1 tall and 1 short allele (Tt)Punnett SquaresReginald Punnett devised an easy system to predict genotypic outcomes of a cross called a PUNNETT SQUAREParents gametes are combined in every possible combination Monohybrid cross – one gene (height)Dihybrid cross – two genes (height and color)Fractions, Percent, RatiosOffspring outcomes can be expressed as: Fractions – ? or ? Percent – 25% or 50% or 75%Ratio – 3:1 or 1:2:1Law of SegregationThe Law of Segregation – every individual has two alleles for each gene and each gamete receives one of these allelesThe Law of Independent AssortmentThe Law of Independent Assortment – genes for different traits are inherited independently of each otherHeight does not affect flower color; they are independent of each other Independent assortment results in increased _______________ because of the shuffling of individual genesGenotype vs. Phenotype13398505778500 1. ______________________: physical appearance; what it looks like.13398504318000EX. Green pea pod, pink flower, tall stems _____________________: genetic make-up; combination of genes.Represented by ______________________.3 possible genotypes. EX. GG, Gg, ggHomozygous vs. HeterozygousHomozygous – two alleles are the _________________Homozygous dominant -->TTHomozygous recessive -->ttTrue breeding (pure bred) Heterozygous – two alleles are ____________________TtHybridsTest CrossA TEST CROSS is a cross of an individual of unknown genotype with an individual with a known genotypeTest crosses use homozygous recessive individuals because the phenotype always indicates the genotype (short = tt)Example:Tall pea plant: genotype unknown (TT or Tt)Short pea plant: known genotype (tt)Cross the tall plant with the homozygous recessive and look at the offspringIf the offspring are all tall then the unknown genotype is TTIf the offspring are 50% tall and 50% the unknown genotype is Tt ................
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