2 Heredity: the passing of genetic traits from parent to offspring Characteristics:Hair ColorEarlobesFingersTraits:Type of hair color- brown, blonde, redAttached/unattachedLonger index or ring fingerA feature that has different forms in a populationDifferent forms of a characteristic governed by genes
3 How traits are passed on…. Traits are determined by genes. Genes are the instruction manuals for our body. They provide directions for building all the proteins that make our bodies function.DNA is found within a gene. Genes are carried in chromosomes.
4 How traits are passed on… Chromosomes are found in the nuclei of our cells.Everybody has 46 chromosomes (23 pairs)
5 How traits are passed on… When a zygote (baby) is formed, it too has 46 chromosomes. It receives a copy of one of each of Mom’s chromosomes and a copy of each of Dad’s chromosomes for a total of 23 pairs of chromosomes.Not all living things have 23 pairs of chromosomes.our/
6 Genes are made up of two parts… These parts are called alleles. An allele is one of the alternative forms of a gene that governs a characteristic.Alleles are represented by lettersCapital letters represent dominant traitsLower case letter represent recessive traitsA = dominanta = recessive
7 Traits are either dominant or recessive… Dominant trait- the trait that always appears when a dominant allele is present in geneThe trait observed in F1 when parents that have different traits are bredRecessive trait- the trait that does not appear unless there are 2 recessive alleles present in geneThe trait that reappears in the F2 after disappearing in the F1 when parents with different traits are bredEx) Brown hair is dominant over blonde hair, so if one brown allele is passed on from the parent the offspring will have brown hairEx) In order for someone to have blonde hair both parents must have passed on a recessive gene, resulting in 2 recessive alleles
8 Traits and Inheritance Phenotype: An organism’s appearanceDetectable physical characteristicsWhat an organism looks likeGenotype: The entire genetic makeup of an organismthe combination of genes for one or more specific traitsHomozygous- 2 of the same type of allele (2 dominant or 2 recessive)Heterozygous- 2 different alleles, one dominant and one recessive (purebred)Ex. Yellow or green seed colorEx. For a recessive trait to show up the offspring must receive 2 recessive alleles, making it homozygous
9 Punnett SquaresUsed to organize all the possible combinations of offspring from particular parents
10 Gregor Mendel Born 1822 in Heinzendorf, Austria Worked in Monastery gardenPatterns of inheritance not always clear, sometimes a trait appeared in one generation (parents) and not in the next generation (F1, offspring), but then it reappears again in the generation after that (F2).Began investigating with pea plantsGrow quicklyself-pollination create true-breedparts of a flowercross-pollination
11 Mendel studied one characteristic at a time… CharacteristicsMendel's Experiments with peas
12 Genetic InstructionsMendel realized that each parent must have 2 “sets of instructions” for each traitWhen parents reproduced they each gave their offspring one set of each of their instructions (the child will then end up with 2 “sets of instructions” for each traitMendel published his work in 1865 and not until 30 years later was his work rediscovered and understoodA Gene is one set of instructions for an inherited traitAn Allele is one of the alternative forms of a gene that governs a trait (ex. If earlobes are attached or unattached)
13 Punnett SquaresUsed to organize all the possible combinations of offspring from particular parentsCross of homozygous purple flower and homozygous white flowerP = Purple (dominant) , p = white (recessive)Parent 1Parent 2PhenotypePurplewhiteGenotypePPppP PPpF1 Generation:Genotype:PpPhenotype:Purplep
14 Mendel’s 2nd Experiment Like Mendel’s 2nd experiment, we will self pollinate the F1 generationParent 1Parent 2GenotypePpPhenotypePurplepurpleF2 Generation:Genotype:1PP, 2Pp, 1ppPhenotype:3purple, 1whiteGenotype Ratio:1:2:1Phenotype Ratio (dominant:recessive):3:1P pPPPpppPp
15 t tTtTtTt2 Tt : 2 tt or 1:1tttt2 Tt : 2 tt or 1:1
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