Sometimes, things don’t always follow Mendel’s Laws

I. Incomplete Dominance INTERMEDIATEThe production of a phenotype that is INTERMEDIATE to that of the two homozygous parents. Neither allele seems DOMINANT or recessive—both traits are partially expressed.

Examples Four o’clock flowers PINKFour o’clock flowers—A red flower crossed with a white flower makes a PINK flower (not red or white, as in normal dominance/recessiveness)

With incomplete dominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits. I remember Incomplete Dominance in the form of an example like so: RED Flower x WHITE Flower ---> PINK Flower

Another Similar Example… Cattle Color: partially Cattle Color: “Red” cattle and “white” cattle are both dominant and when crossed—both colors are partially expressed as in “roan”.

With codominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together. I remember codominance in the form of an example like so: red x white ---> red & white spotted

This can occur in other animals as well…

peasMendel did not observe this because it does not occur in peas. It was discovered when crossing other organisms (the four o’clock flowers) dominantIn a Punnett Square or genotype, the dominant parents are expressed with 2 capital letters (one for each dominant allele). (The letters are different) Snapdragon Example Incomplete Dominance in HumansIncomplete Dominance in Humans & Plants

II. Multiple Alleles formsSometimes, there are more than two forms a gene can take. three twomom dadExample: There are three possible alleles for blood type (A, B, and O alleles). Any person still only can inherit two, one from mom and one from dad.

Examples **Blood Type is a special example because it both demonstratesIncomplete/Co-dominance AND multiple alleles.

Examples Blood Type ABBlood Type AB dominant oBlood Types A, B are both dominant alleles recessive oThe O allele is recessive AB oIf a person gets both alleles, then both are expressed and the person has AB blood type.

Examples AA AO oIf a person has blood type A, then either they inherited two A alleles (AA) or an A and an O (AO). BBBO oIf a person has blood type B, then either they inherited two B alleles (BB) or a B and an O (BO). oIf a person has blood type O, what would be their genotype? oAB blood type would be OO AB

genotypephenotype oRemember the difference between genotype and phenotype! Multiple Alleles & Co Dominance in Blood Type

III. Multiple Genes POLYGENICMore than one gene can control a trait. This is called POLYGENIC INHERITANCE combination of alleles can produce a wide varietyThe effect of each allele by itself is small, but the combination of alleles can produce a wide variety. Example : Eye color –One allele may control pigment production and how this one interacts with the color gene will vary in individuals. That is why there is such a variety in eye colors.

VARIETY Other examplesTraits controlled in this way show much VARIETY in a population. Other examples of traits controlled by polygenic inheritance are: Fingerprints heightheight weight buildbody build shape of eyes/ears/lips There are other traits in other organisms that are controlled by mulitple genes, too.

Sometimes mutations in genes can cause an unwanted trait. There are several diseases that can be caused by mutations in the alleles controlling a particular trait. Not all mutations produce harmful results.

Recessive Genetic Disorders TWOPerson must get TWO copies of the recessive gene to get the disease.

Recessive Genetic Disorders sickle-shapedSickle Cell Anemia--red blood cells are sickle-shaped instead of disc- shaped oxygen –Can’t carry enough oxygen –Don’t moveeasily –Don’t move through blood vessels easily –Treated by transfusions of normal cells or drugs to increase oxygen capacity

Cells are sickle-shaped instead of disc-shaped.

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Cystic Fibrosisthick mucusCystic Fibrosis--thick mucus instead of thin fluid in lungs and intestines –Most common –Most common genetic disorder among Caucasians recessive allele –1 in 20 white people carry a recessive allele for the disorder everyday –Four babies born in U.S. with this disease everyday

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Cystic Fibrosis affects the lungs! People who have it tend not to live very long livesPeople who have it tend not to live very long lives.

Sex Determination determined by X YSex or gender in many organisms is determined by X and Y chromosomes differ from one another in shape and sizeThese chromosomes differ from one another in shape and size. The Y chromosome is very short. female maleTwo X chromosomes will produce a female and one X and one Y will produce a male.

23 rd Chromosome Pair Is it a boy or a girl? A girl !

Sex-linked Disorders “linked” to the X and Y chromosomeSome genetic disorders are “linked” to the X and Y chromosome and are therefore called “sex-linked” sex-linked geneAn allele inherited on a sex chromosome is called a sex-linked gene show up most often in malesTraits controlled by genes on the X chromosome show up most often in males (they inherit the trait from their mothers)

FemalesMales are not carriers for sex-linked traits…(Females are!) Colorblindness hemophiliaSome examples: Colorblindness and hemophilia

Color Blindness “tests”

The test to the left is simpler. The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots.The test to the left is simpler. The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots. The test below is simpler. The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots.

Pedigrees trace a trait through a familyA tool used to trace a trait through a family is called a pedigree a male circleIn pedigrees, a square represents a male and a female is represented by a circle.

Pedigrees filled inIf the square or circle is filled in or darkened, the person has the trait or condition. carrierIf it is half colored or half darkened, the person is a carrier (has one allele for the trait, but doesn’t show it)

Sample Pedigree: Shows how the cystic fibrosis gene (recessive) got passed in this family

Genetic Engineering changeChemical or biological methods to change the DNA sequence that makes up a gene diabetes,Already used to treat diabetes, improve crop production for different plants Genetic Engineering Clip Manipulating Genes

Types of Selective Breeding Inbreeding- have alleles that are very similar to their parents. Ex. Increases the probability that organisms may inherit alleles that lead to genetic disorders

Types of Selective Breeding (cont) Hybridization- receive the best traits form both parents Cloning- exactly like the parent. Ex. Dolly the Sheep y+the+sheep%2C+cloning+video&ei=UTF- 8&hspart=mozilla&hsimp=yhs-002https://search.yahoo.com/yhs/search?p=doll y+the+sheep%2C+cloning+video&ei=UTF- 8&hspart=mozilla&hsimp=yhs-002