Genetics

Heredity is the passing of traits from the parents to the offspring and is controlled by genes

What are genes? Made of segments of DNA Control the traits of an organism Found on the chromosomes Have different forms called alleles

Alleles are the different forms that a gene can have for a trait. What are alleles? Alleles are the different forms that a gene can have for a trait.

So, what is genetics? Genetics is the study of how traits are inherited through the actions of alleles.

determine the traits of the organisms Alleles determine the traits of the organisms

Alleles An organism with the same two alleles for a trait is homozygous. An organism with two different alleles for a trait is heterozygous.

Therefore: An organism’s genetic makeup is it’s genotype. An organism’s physical makeup is it’s phenotype.

Gregor Mendel Father of Genetics

Gregor Mendel Born in 1822 in Austria and lived in Europe. Was a monk who studied mathematics and science. Determined the basic laws of Genetics.

Mendel’s Garden As a boy, he worked in his father’s orchard and became interested in plants He experimented with peas.

Gregor Mendel Called the form of a trait that appears to dominate or mask another form of the same trait dominant.

Gregor Mendel Called the weak form of a trait that is prevented from showing up by a dominant trait recessive.

Probability The branch of mathematics that helps you predict the chance something will happen is called probability

Punnett Square The tool used to predict the probability of certain traits in offspring that show the different ways alleles can combine.

Punnett Square Dominant allele is Upper case letter =G Recessive allele is Lower case letter =g

G G g Gg Gg g Gg Gg Punnett Square

Curled Up Nose Roman Nose Traits governed by simple dominance (not an exhaustive list) Dominant Recessive Brown Eyes Blue Eyes Curled Up Nose Roman Nose Clockwise Hair Whorl Counter-clockwise hair Whorl Can Roll Tongue Can't Roll Tongue Widow's Peak No Widow's Peak Facial Dimples No Facial Dimples Able to taste PTC Unable to taste PTC Earlobe hangs Earlobe attaches at base Mid-digital hair No mid-digital hair No hitchhiker's Hitchhiker's thumb thumb Tip of pinkie bends Pinkie straight in

Genetics Since Mendel Ch. 5 section 2 Are all traits inherited only by dominant or recessive alleles?

INCOMPLETE DOMINANCE Production of a phenotype,(physical trait), that is intermediate, (blended), between the two homozygous parents. WHITE RED PINK

Incomplete Dominance Chestnut Horse Cremello Horse Palomino Horse

Multiple Alleles A trait that is controlled by more than two alleles. Examples is blood type which is controlled by three alleles, A, B, O which gives us four phenotypes: A, B, AB, or O.

Polygenic Inheritance Poly means many. Polygenic inheritance is when many gene pairs act together to produce a trait. Examples for this inheritance would be eye color, height and skin color. This is why we might not have the same shade of color of eyes or skin as our parents have. Also this is why it is hard to predict height just based on our parents height. eyes

Even though your traits are determined by your genes, environmental influences can alter how your trait is expressed. Examples: If you have a gene for skin cancer, you can limit your exposure to the sun and take care of your skin. If you have a gene for lung cancer, you can make sure you do not smoke and try to control your air quality. Himalayan rabbits have alleles for dark-colored fur. But this allele can only express itself at lower temperatures which are areas located away from the main body heat.

Mutations Mutations are changes in genes. Some mutations are harmful some are helpful. Mutations in genes can occur when the DNA is copied and something goes wrong. Chemicals can also alter genes. Examples of things that can mutate genes are radioactive material and X-rays

Chromosome Disorders Occur when mistakes in the process of meiosis results in an organism with too many or too few chromosomes. Examples: Down Syndrome- baby has 47 chromosomes instead of 46 chromsomes.

Downs Syndrome characteristic facial features, short stature; heart defects susceptibility to respiratory disease, shorter lifespan prone to developing early Alzheimer's and leukemia often sexually underdeveloped and sterile, usually some degree of mental retardation. Down Syndrome is correlated with age of mother but can also be the result of nondisjunction of the father's chromosome 21.

Patau syndrome (trisomy 13): serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. Children rarely live more than a few months.

Edward's syndrome (trisomy 18): almost every organ system affected 1:10,000 live births. Children with full Trisomy 18 generally do not live more than a few months.

Too few chromsomes Monosomy X (Turner's syndrome): 1:5000 live births; the only viable monosomy in humans - women with Turner's have only 45 chromosomes!!! XO individuals are genetically female. Have short stature, normal intelligence and are sterile. (98% of these fetuses die before birth)

Recessive Genetic Disorders When each parent has the recessive gene and their baby receives the recessive gene from both parents. Examples of this type of disorder: Cystic Fibrosis- affects for Caucasian Americans Causes thick mucus in lungs and intestinal tract Sickle Cell Anemia-affects more African Americans Causes clogging of blood vessels, organ damage, kidney failure Tay-Sachs- Buildup of lipids causes death by age 2-3.

Sex-Determination Female chromosomes are XX Male Chromosomes are XY XX

SEX LINKED DISORDERS An allele inherited on a sex chromosome, X or Y is called a sex linked disorder. Males are more likely to have sex linked disorders than females. The reason for this is that for a male to have a disorder he only has to have the allele on one chromosome, XcY. In order for the female to have the disorder she has to have the allele on both her sex chromosomes, XcXc. If she has the allele only on one of her sex chromosomes she is considered to be a carrier, XcX and can pass it on to her children.

XY Examples of sex linked disorders Color Blindness-is a recessive trait on the X chromosome A B Xc Y X Y XcX XY XcX XcY XX XY X X c X X In example A, a color blind Male has a child with a normal Female. They will have a 50% Chance of having a normal male Baby and a 50% chance of having A female baby who is a carrier for Color blindness. In example B, a normal male has a child with a carrier female. They will have a 25% chance of having a female who is a carrier, 25% chance of having a male who is colorblind, 25% chance of having a normal female and 25% chance of having a normal male.

Another example of a sex linked disorder is hemophilia Another example of a sex linked disorder is hemophilia. A person with this disorder do not make enough platelets in their blood that helps the blood to clot when they are cut. Pedigree Chart

Why would you use a Pedigree Chart? A geneticist would study a pedigree chart of someone to predict the probability that a baby would be born with a specific trait. Breeders of animals or plants can study the pedigree of these organisms for desirable physical and ability traits.

Genetic Engineering It is biological and chemical methods to change the arrangement of a gene’s DNA to improve crop production, produce large volumes of medicine, and change how cells perform their normal functions. Recombinant DNA-(helps with making insulin) Gene Therapy-(using a virus to deliver a normal allele to replace a defective allele; cystic fibrosis and cancers)

Cloning- Dolly the sheep

Genetically Engineered Tobacco Plants that are resistant to the Tobacco Mosaic Virus

Human Genome Project

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