2 Vocabulary Trait Hybrid Gene Specific characteristic Offspring of parents with different traitsGeneFactors that determine traits
3 AlleleThe different forms of a geneSegregationSeparation of alleles
4 Probability Punnett square Homozygous The likelihood an event will happenPunnett squareA diagram to show the results of a genetic crossHomozygousHave 2 identical alleles
5 P = Parental generation F1 = First offspring producedF2 = Second offspring produced
6 Heterozygous Phenotype Genotype 2 different alleles Physical characteristicsGenotypeGenetic makeup
7 Independent assortment CarrierCarries a trait but doesn’t exhibit itIndependent assortmentGenes do not influence each other’s inheritanceIncomplete dominanceWhen one allele is not completely dominate over another
8 Codominance Multiple alleles Polygenic traits Both alleles contribute to the phenotypeMultiple allelesWhen genes have more than 2 allelesPolygenic traitsTraits controlled by two or more genes
9 Gregor Mendel Known as the “Father of Genetics” Genetics = the study of heredityCarried out his work with ordinary garden peas.
10 Mendel summarized his findings into 2 Laws: 1) Law of segregation2) Law of independent assortment
11 Law of SegregationStates that every individual possesses a pair of alleles (assuming diploidy) for any traitEach parent passes a randomly selected copy (allele) of only one of these to its offspringThe offspring then receives its own pair of alleles for that trait.Whichever of the two alleles in the offspring is dominant determines how the offspring expresses that trait (e.g. the color of a plant, the color of an animal's fur, the color of a person's eyes).
12 Law of Segregation Proven by meiosis The paternal and maternal chromosomes get separated and the alleles with the traits of a character are segregated into two different gametes.
13 Law of Independent Assortment States that separate genes for separate traits are passed independently of one another from parents to offspringOccurs during Metaphase I of MeiosisThe “double-file” line + crossing over
14 Punnett Squares A capital letter represents the dominant allele A lowercase letter represents the recessive alleleUse the first letter of the dominant traitHomozygous Dominant = BBHomozygous Recessive = bbHeterozygous = Bb
16 Probability & Segregation One fourth (1/4) of the F2 plants have two alleles for tallness (TT).2/4 or 1/2 have one allele for tall (T), and one for short (t).One fourth (1/4) of the F2 have two alleles for short (tt)
17 Using Punnett Square to Prove Independent Assortment Mendel performed a two-factor crossMendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy).All of the F1 offspring produced round yellow peas (RrYy)The alleles for round (R) and yellow (Y) are dominant over the alleles for wrinkled (r) and green (y).
22 Human HeredityKaryotypeA picture of the arrangement of chromosomes
23 Sex Chromosomes Autosomes X & Y Males = XY Females = XX Males determine the sex of the offspringAutosomesThe other 22 pair of chromosomes
24 A pedigree chart shows the relationships within a family.
25 Human Traits A square represents A circle represents a male. a female.A vertical line and a bracket connect the parents to their children.A horizontal line connecting a male and a female represents a marriage.A shaded circle or square indicates that a person expresses the trait.A circle or square that is not shaded indicates that a person does not express the trait.This drawing shows what the symbols in a pedigree represent.Copyright Pearson Prentice Hall
26 Recessive AllelesThe presence of a normal, functioning gene is revealed only when an abnormal or nonfunctioning allele affects the phenotype.Many disorders are caused by autosomal recessive alleles
28 Dominant AllelesThe effects of a dominant allele are expressed even when the recessive allele is present.Two examples of genetic disorders caused by autosomal dominant alleles are achondroplasia and Huntington disease.
30 Codominant AllelesSickle cell disease is a serious disorder caused by a codominant allele.Sickle cell is found in about 1 out of 500 African Americans.
31 People who are heterozygous for the sickle cell allele are generally healthy and they are resistant to malaria.An individual with both normal and sickle cell alleles has a different phenotype—resistance to malaria—from someone with only normal alleles
32 If two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with three copies of a chromosome.Down syndrome involves three copies of chromosome 21.
34 Sex-Linked Genes The X chromosome and the Y chromosomes determine sex. Genes located on these chromosomes are called sex-linked genes.More than 100 sex-linked genetic disorders have now been mapped to the X chromosome
35 For a recessive allele to be expressed in females, there must be two copies of the allele, one on each of the two X chromosomes.Males have just one X chromosome. Thus, all X-linked alleles are expressed in males, even if they are recessive.