Interesting Facts About Genetics

byProf. Liwayway Memije-Cruz

Johann Gregor Mendel (1822-1884)Father of GeneticsAustrian monk who discovered the fundamental laws of inheritance based on his experimental work with pea plants.He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits. He recognized the mathematical patterns of inheritance from one generation to the next.

Mendel's Law of Segregation Each inherited trait is defined by a gene pair. Parental genes are randomly separated to the sex cells so that sex cells contain only one gene of the pair. Offspring therefore inherit one genetic allele from each parent when sex cells unite in fertilization.

Law of Independent Assortment:Genes for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another.

Law of DominanceAn organism with alternate forms of a gene will express the form that is dominant.

What is Genetics?

Genetics is…

the science of studying how living things pass on characteristics or traits and its variations in their cell make-up from one generation to the other. the study of how living things inherit features like eye-colour, nose shape, height and even behavior from their parents.

What are Genes?Instruction manuals in our body. They are molecules in our body that explain the information hidden in our DNA, and supervises our bodies to grow in line with that information.It is believed that each cell in our body contains over 25,000 genes, all working together. These genes carry specific biological codes or information that determine what we inherit from our parents.Supervise protein production through the Deoxyribonucleic Acid (DNA), a chemical that has a genetic code for making proteins for living cells. Proteins are the building blocks for living things and almost everything in our body, bones, blood and muscles are all made up of proteins,

How is a gene represented?

AllelesAllele - one alternative form of a given allelic pair; tall and dwarf are the alleles for the height of a pea plant; more than two alleles can exist for any specific gene, but only two of them will be found within any individual Allelic pair - the combination of two alleles which comprise the gene pair

Genotype and PhenotypeGenotype is the genetic make-up of an individual organism. Your genotype functions as a set of instructions for the growth and development of your body. The word ‘genotype’ is usually used when talking about the genetics of a particular trait(like eye colour).

Phenotype is the observable physical or biochemical characteristics of an individual organism, determined by both genetic make-up and environmental influences, for example, height, weight and skin colour.

Genotype and PhenotypeGenotype - the genes that an organism contains for a particular trait.Phenotype - the observable traits of an individual.

Homozygous and Heterozygous

Homozygous - an individual which contains two genes that the same Heterozygote - an individual which contains two genes that are different

What is DNA?

Means Deoxyribonucleic Acid. It is a hereditary molecule that is found in almost all living things (cells). It carries a code (information) that genes use to make living things grow. It is found in all cells in structures called chromosomes. DNA is located in the nucleus of cells. This is called ‘nuclear DNA. Some DNA is also located in the mitochondria of the cell and that is also called mitochondrial DNA. All the cells in that living thing carry the same DNA.

Four chemical bases that make up the code in DNA

Adenine (A), Guanine (G), Cytosine (C), Thymine (T)These chemical bases are contained in the shape of a twisted ladder called the double helix.

DNA sequenceIn humans, all the bases are the same — BUT, the combination or order, or sequence is unique to every individual. DNA can duplicate or copy itself. This is why all cells in an individual have the same DNA.The strand in the DNA is made up of Letters G A T C. These letters combine in a set way to make words. The words combine to make sentences. The sentences can be called “Gene’ It is the gene that instructs all the cells in the body to perform their functions, as specified in our DNA, including making protein.

What are chromosomes?a compact store of DNA strands folded and compacted together by The Double Helix. Chromosomes are all contained in the nucleus of the cell.

Number of ChromosomesHumans have 46 chromosomes in each of the cells of our organs. These are organized into two sets of 23 chromosomes. Each human gets 23 chromosomes from their mom, and 23 chromosomes from their dad. This is why almost everyone has some traits they got from their parents.

Sex Chromosomesthe 23rd chromosome is our sex chromosomes. Boys carry XY chromosomes and girls carry XX chromosomes.

FertilizationEach parent contributes a cell each. The female always contributes an X cell (because that all she has, XX chromosome) The male contributes either an X or a Y cell. The male has no control over this, as it is purely random. If the male releases and X chromosome, it adds to the X chromosome of the female, it forms an XX— and the gender of the baby will be a girl. If the male releases a Y chromosome and adds to the females X chromosome, it forms an XY and the gender of the baby is a boy.

Chromosomal Theory of Inheritance1. Homologous chromosome pairs are independent of other

chromosome pairs. 2. Chromosomes from each homologous pair are sorted

randomly into pre-gametes. 3. Parents synthesize gametes that contain only half of their

chromosomes; eggs and sperm have the same number of chromosomes.

4. Gametic chromosomes combine during fertilizationto produce offspring with the same chromosome number as their parents.

Noted scientists known for the Chromosomal Theory of Inheritance: chromosomes carry the unit of heredity known as genes.

a. Walter Sulton b. Theodore Boveri

Chromosome Mappinga technique used in DNA testing which allows the testee to determine which segments of DNA came from which ancestor. one should test both parents, one of their children, and a number of first to third cousins on both the maternal and paternal sides of the family.

Gene Splicing

cutting out part of the DNA in a gene and adding new DNA in its place.

Genetic Mapping: Linkage Mappingcan offer firm evidence that a disease transmitted from parent to child is linked to one or more genes. also provides clues about which chromosome contains the gene and precisely where the gene lies on that chromosome. used successfully to find the gene responsible for relatively rare, single-gene inherited disorders such as cystic fibrosis and Duchenne muscular dystrophy.also useful in guiding scientists to the many genes that are believed to play a role in the development of more common disorders such as asthma, heart disease, diabetes, cancer, and psychiatric conditions.

Gene Therapy: Biotechnologyan experimental technique that uses genes to treat or prevent disease. In the future, this technique may allow doctors to treat a disorder by inserting a gene into a patient’s cells instead of using drugs or surgery.Researchers are testing several approaches to gene therapy, including:

1. Replacing a mutated gene that causes disease with a healthy copy of the gene.

2. Inactivating, or “knocking out,” a mutated gene that is functioning improperly.

3. Introducing a new gene into the body to help fight a disease.

References:http://www.genesolutions.com/page8.htmlhttp://learn.genetics.utah.edu/content/genetherapy/gtintro/http://sciencelearn.org.nz/Contexts/Uniquely-Me/Science-Ideas-and-Concepts/Genotype-and-phenotypehttps://www.genome.gov/