2What is genetics?The scientific study of heredity
3Gregor Mendel Born in 1822 in Czechoslovakia. Became a monk at a monastery in 1843.Taught biology and had interests in statistics.Also studied at the University of Vienna
4Mendel continuedAfter returning to the monastery he continued to teach and worked in the garden.Between 1856 and 1863 he grew and tested over 28,000 pea plants
5Mendel’s Peas Easy to grow. Easily identifiable traits Can work with large numbers of samples
6Mendel’s experimentsThe first thing Mendel did was create a “pure” generation or true-breeding generation.He made sure that certain pea plants were only able to self pollinate, eliminating unwanted traits.He did this by cutting away the stamen, or male part of each flower
7Genes and dominance Trait : a characteristic Mendel studied seven of these traitsAfter Mendel ensured that his true-breeding generation was pure, he then crossed plants showing contrasting traits.He called the offspring the F1 generation or first filial.
8What will happen when pure yellow peas are crossed with pure green peas? All of the offspring were yellow.Hybrids = the offspring of crosses between parents with contrasting traits
9What did Mendel conclude? Inheritance is determined by factors passed on from one generation to another.Mendel knew nothing about chromosomes, genes, or DNA. Why?These terms hadn’t yet been defined.
10What were Mendel’s “factors” The ‘factors” that Mendel mentioned were the genes.Each gene has different forms called allelesMendel’s second principle stated that some alleles are dominant and some are recessive.
11Mendel’s second crossHe allowed the F1 generation to self-pollinate thus producing the F2 generation.Did the recessive allele completely disappear?What happened when he crossed two yellow pea hybrid (F1) plants?
12Results: ¾ of the peas were yellow, ¼ of the peas were green. During the formation of the sex cells or gametes, the alleles separated or segregated to different gametes. (pollen and egg)
13Probability The likelihood of a particular event occurring. Chance Can be expressed as a fraction or a percent.Example: coin flip.
14Punnett Square Developed by Reginald Punnett. A diagram used to show the probability or chances of a certain trait being passed from one generation to another.
15Reading Punnett squares Gametes are placed above and to the left of the squareOffspring are placed in the square.Capital letters (Y) represent dominant alleles.Lower case letters (y) represent recessive alleles.
17genotypesHomozygous = when an organism possesses two identical alleles. ex.YY or yyHeterozygous = when an organism possesses different alleles. ex.Yy
18Phenotype vs genotype Genotype The genetic makeup Symbolized with lettersTt or TTPhenotypePhysical appearance of the organismExpression of the traitShort, tall, yellow, smooth, etc.
19Probability and statistics No one event has a greater chance of occurring than another.You cannot predict the precise outcome of an individual event.The more trials performed, the closer the actual results to the expected outcomes.
22Independent Assortment The two factor cross. Example: color and shape of peas.F1 cross to produce the F2 generationEx RRYY x rryyRound yellow mated with wrinkled greenOffspring would all be hybrid for both traits (RrYy)
23What is independent assortment? Alleles separate independently during the formation of gametes.
25Mendel’s death Mendel published his paper on heredity in 1866. The scientific community saw little if any importance in his work.Mendel died in 1884 with no recognition for his contributions to genetics.
26Some exceptions to Mendel’s principles: Some alleles are neither dominant nor recessive.Many traits are controlled by more than one gene (polygenic traits)
27Incomplete dominance A situation in which neither allele is dominant. When both alleles are present a “new” phenotype appears that is a blend of each allele.Alleles will be represented by capital letters only.
29What happens when a red flower is crossed with a white flower? According to Mendel either some white and some red or all offspring either red or white.All are pink
30Codominance When two alleles both appear in the phenotype. Usually signified using superscripts.example: color of hair coat in cattle.crcr = red hairscwcw = white hairscrcw = roan coat (mixture of both colors)
51Net result: Spermatogensis 4 mature sperm Each sperm has exactly half the number of chromosomes as the father.Oogensis1 mature ova or egg.Each egg has exactly half the number of chromosomes as the mother.
52Gene Linkage Are genes “linked” to each other on chromosomes? Morgan found that many genes are linked together.It was determined that chromosomes, not genes, assort independently during meiosis.
53Gene Maps First developed by Sturtevant in 1911. The farther apart two genes are, the more likely they will be separated in meiosis.