GENETICS NAREEFA N. BACCHUS

WHAT IS GENETICS? GENETICS/ GENES control an organism’s form and funtion. The different forms of a trait that a gene may have are called alleles.

GREGORY MENDEL: The Father of Genetics.

MENDEL He studied Mathematics and Science but then decided to become a gardener. As a gardener, he was fascinated with plants so he decided to cross breed them and look at the results. So he did this. Then he applied his knowledge of mathematics to predict what the possible offspring would look like. So he crossed Purple and Purple and got Purple. Which made sense to him. Then he crossed Purple and purple and he got white. So this baffled him. How was this possible?

P AND F1 P= Parental Generation F1= First/ Filial Generation.

DOMINANT VS. RECESSIVE. Dominant traits are overpowering and black out the recessive ones. Recessive traits are not very powerful and as a result you need 2 recessive traits in order to get that outcome. (EX. bb)

HOMOZYGOUS VS. HETEROZYGOUS HOMOZYGOUS: An organism with 2 alleles that are the same for a particular trait. HETEROZYGOUS: An organism that has two different alleles for a particular trait.

PHENOTPYE VS. GENOTYPE Phenotype is the physical appearance of an organism. Genotypes is the DNA of an organism/ appearance of DNA/ the alleles you inherited from your parents.

PUNNETT SQUARES Punnett Squares are a way of determining the possible genotype and phenotype of an organism. The Punnett Squares illustrates the probability of the way the offspring will look.

INCOMPLETE DOMINANCE-BLEND Incomblend- So you’ll remember that incomplete dominance always results in a blended phenotype. Incomplete Dominance is when the offspring of 2 HOMOZYGOUS parents result in a HETEROZYGOUS OFFSPRING that is a mixture of their parents’ phenotype.

CODOMINANCE-NOT BLEND, BOTH Codominance is a form of dominance wherein the alleles of a gene pair in a heterozygote are fully expressed.

PURE/ COMPLETE DOMINANCE So, for example, If you have genotype Rr. The phenotype will be completely red. So this is regular dominance, also known as, COMPLETE or PURE DOMINANCE.

So, Quick Recap: If an organism is heterozygous, there are generally, 3 possible outcomes: For example, in the case of Rr: 1. Incomplete Dominance: Red + white = Pink flower. 2. Codominance: Red + White = Red flower with white spots. 3. Pure Dominance: Pure Red flower (because red is the dominant allele).

HUMAN GENES AND MUTATIONS A gene has two alleles and are used to determine a trait. In other words, genes code for traits.

DISORDERS: The PATTERNS OF INHERITANCE of disorders. 1. AUTOSOMAL DISORDERS: (Recessive and Dominant). 2. SEX-LINKED DISORDERS: (Women have an advantage in this case, as they have a back-up X chromosome. On the other hand, men are at a disadvantage as they have no back-up chromosomes, only. A single copy of each (x and y).

AUTOSOMAL RECESSIVE GENETIC DISORDER In order to get an autosomal recessive genetic disorders, both of your alleles have to be the recessive form, and they both must be mutated.

AUTOSOMAL DOMINANT GENETIC DISORDER In order to get this disorder, only the dominant allele has to be mutated or affected, and the person will have the disease EXCEPT in the case where a person is homozygous dominant but only ONE of their allele is mutated or defected. Then, they will just be a carrier. For example: 1. if a person is heterozygous, and the dominant allele is affected, then the person will have the disease. 2. If the person is homozygous dominant and only one of the allele is affected then they won’t get the disease, because there is another dominant allele to back up or compensate for the mutated one. 3. If the person is homozygous dominant and both of their alleles are mutated, then the person will definitely have the disorder.

SEX DETERMINATION The sex/ gender of a person is determined by the 23 chromosome. In men, the 23rd chromosome is XY while in women the 23rd chromosome is XX.

SEX-LINKED DISORDERS If there is a mutation on the Y chromosomes, then all of the sons of the man will inherit his disorder. The woman would have to have both of her X chromosomes be mutated before she gets the disease. If only one is mutated and the other one is fine, then the woman will just be a carrier. Colorblindless is a mutation on the X chromosome. That’s why, more men are likely to be colorblind than women because once their x chromosome has the colorblindness mutation, they have no back up. Women on the other hand still have a chance because of their abck-up x chromosome.

PEDIGREES

PEDIGREES

PEDIGREES: Used to trace back disorders or diseases that happened throughout your family’s lifetime, and it also give insight as to how likely you are to get any disease or mutations. In pedigrees, the circle represents the female and the square represents the male. The fully shaded shapes represents that the person has the disorder or disease. The partially shaded shapes represents that the person has the allele for the disorder or disease, but its being overpowered by something else. These people are known as carriers. Shapes with a line through it means that the person is deceased.

WHAT IS GENETIC ENGINEERING? Genetic engineering is the process whereby scientists attempts to use technology to change the arrangement of DNA. However, this is easier said than done. It is through genetic engineering that manufacturing companies are able to modify the food they sell. Hence, on some items that you purchase, you may see the abbreviation GMO (Genetically Modified Organism).

GENETIC CLONING Clones are organisms that are exact genetic copies. Every single bit of their DNA is identical. Clones can happen naturally—identical twins are just one of many examples. Or they can be made in the lab.

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