Genetics Notes Essay Sample

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Introduction of TOPIC


– Cells are basic units of what organisms are made up of

– The shape and size of cells are related to their functions

– Bacteria is a DNA that is not encapsulated by a membrane/nucleus

– Chromosomes contain information for processing the functions of cells

– Proteins (meats) are broken down into amino acids. These are very important for the body development

– Everything in the body is made up of protein

– If there is an excess of protein the body excretes it

– Proteins are used for movement and repairing memory

– Cilia are tiny hairs outside the cell that help it to move and attract food


– Genetics: The study of hereditary and the variations of characteristics

– Mendel is known as the “Father of genetics” because he was the first person to discover things which we now know as genes. He was a monk who experimented with pea plants

– True-breeding plants are plants which consistently produce offspring the same as the parents for a particular trait

– In genetics, a dominant trait is a gene that expresses its instructions whereas a recessive trait ‘masks’ itself even though it’s present

– Mendel concluded from his experiments that some dominant and recessive genes were preset in each of the F1 and F2 generation

– Genes are made from de oxy ribonucleic acid (DNA)

– Chromosomes are the structures in which genes are kept. They are long, coiled; thread-like structures found in the nucleus of your body cells and are made up of DNA and protein

– Each chromosome acts as a container for thousands of genes

– Body (somatic) cells have 46 chromosomes whereas sex cells only contain 23. When a female and male sex cell combines, they will have 46 chromosomes; this alters the characteristics of the newly made cell

– Homologous refers to chromosomes that are partly male and partly female

– Diploid cells are those that contain two chromosomes, an example can be body cells. Haploid cells, however, are those which contain one type of chromosome, an example can be sperm cells

– Mitosis: This is when each body cell reproduces and duplicates their chromosomes. This process occurs inside body cells

– Meiosis: This is when a sperm cell meets a female egg; the resulting cell will have the correct number of chromosomes. This process occurs inside sex cells

– Pea plants possess two hereditary factors for each characteristic which separate from each other and pass into gametes

– Gametes are the reproductive cells, called ova in females and sperm in males and combine to form the first cell of a new organism

– Each new organism receives one hereditary factor from each parent which do not blends with each other but instead act as independent units

– A gene is a hereditary unit that controls a particular characteristic. Each body cell contains thousands of genes

– Alleles are different forms of the same gene

– Phenotype is the physical appearance of an organism for a particular characteristic

– Genotype is the genes for a particular characteristic present in an organism

– Homozygous is an organism with the same genes for a particular characteristic

– Heterozygous is an organism with different genes for a particular characteristic

– Capital letters are used to indicate dominance

– Co-dominance is the expression of both alleles in a heterozygous individual

– Incomplete dominance is a situation where neither gene dominates the other nor both exercise an influence on the individual.

– The Rh system is controlled by two alleles; a person may be homozygous or heterozygous Rh positive or homozygous Rh negative

– The ABO blood group includes the following types of inheritance: Dominance, recessive and co-dominance with the alleles I(A), I(B) and I(O) in which A & B are dominant over O.

– Discontinuous variation involves sharply defined characteristics such as left or right handedness, whereas continuous variation is the more complex variation, involving a wide range of characteristics to be chosen such as. A continuous variation is brought about by the combined effect of many genes

– The main method of gathering human inheritance information is pedigrees that show patterns of inheritance in certain families

– Males have the genotype XY whilst females h

ave XX – Sex-linked diseases occur due to the modification

in the structure of the X chromosome which doesn’t match with the Y chromosome

– DNA is made up of the three chemicals: sugar units, phosphates and base pairs

– Complementary bases are pairs on nitrogen bases which only pair up with each other

– Replication: the process when DNA is copied exactly

– Because cells multiply they need the correct DNA, which also needs to be replicated to meet demand

– There are 20 different amino acids which combine to form thousands of types of proteins possessing a unique sequence code

– A codon is a set of three bases that make up amino acids and further create proteins

– Gene expression refers to the appearance in the organism of the characteristic that the gene codes for. Genes contain information about when and where the gene is to act

– A mutation is nay spontaneous change in a gene or chromosome that may produce and alteration in the related characteristic

– Mutagens are any agents that increase the likelihood of having a mutation such as X-rays, gamma rays and UV radiation

– An enzyme is a biological catalyst that increases the rate of a chemical reaction, without being consumed

– We know that ALL cells contain exactly the same type and quantity of DNA, but in order for us to differ between different types of cells such as blood, muscle and nerve cells, we need to look at which genes inside that cell is turned on or off. For example a blood cell has a structure of ABC where B= hemoglobin (switched on), the nerve cell also has the structure of ABC where B= hemoglobin (switched off).

– Mutations primarily cause more damage than improvements; however, due to results of mutation, there are wide varieties of animals, fruits and human characteristics

– Mutations in somatic cells are unimportant because they cannot be inherited whereas they serve of bigger value when they occur in sex cells

– Genetic engineering: A technology used to alter the genetic material of living cells in order to make them capable of producing new substances or performing new functions

– A genetically modified plant is a plant that has undergone the process of genetic engineering

– A transgenic animal is an animal that has had a new gene implanted on it

– Plasmids are found in bacteria and are cut open using an enzyme, having the foreign DNA inserted and the plasmid is rejoined

– A recombinant DNA is a mixed molecule made through the process in which DNA strands are cut and attached to plasmids

– Much of the genetic code that makes each person unique is in fact 99.9% the same for all people and that only 6% of the DNA actually codes for genes whilst the rest is referred to as “junk DNA”

– Organism that have had their gene sequence altered are referred to as genetically modified plants or animals

– Gene technology allows us to:

1. Isolate a gene

2. Alter the gene

3. Copy the gene

4. Reinsert the gene into another organism

– DNA segments are not directly inserted into bacteria; circular pieces of DNA called plasmids are used

– Altered plasmids may be put into bacteria, and the bacteria is grown to provide many copies of the introduced DNA

– A gene probe is a small piece of DNA with a base sequence identical to part of a gene which enables it to stick to a specific gene

– Gene probes are used to recognize the base sequence of genes associated with disease. Also, DNA samples from embryos can be tested with probes to determine if diseases such as sickle-cell anemia are present in the baby.

– Prenatal testing refers to the testing of cells to check if any abnormalities are present in a baby before it is born. Cells to be tested are obtained by placing a needle through the uterus in order to retrieve any cells the have ‘fallen off’ the fetus (baby). This process is known as amniocentesis. We use amniocentesis to determine the sex of the baby, to identify any chromosome abnormalities and to test for certain enzymes.

– Cloning: refers to the production of an organism from a single cell. Each body cell contains all the information needed to make a new organism. To clone an organism, you’ll require a cell from a donor and an egg cell from a female with the DNA removed. The egg cell and donor cell are then fused to create the first cell of the organism. The cell then is grown inside a glass dish for a few days and then implanted into a female host to develop and be born in the usual way.

– Therapeutic cloning: refers to the cloning of a certain cell whether it being a muscle, nerve or skin cell to repair or replace old damaged ones. To clone a cell, you need to remove a cell from a person, extract the DNA, and put the DNA into an egg. The egg will then get fertilized and grows into a blastocyst in which stem cells are found. These stem cells are special as they can grow into any type of cell given the right condition. The cell can then be put back into the donors’ body to give a desirable outcome; also the cells won’t be rejected by the body since they carry the same DNA as the donor. Therapeutic cloning can be used to repair injuries by placing new nerve muscles into a damaged spinal cord, growing skin for victims of burns, etc.

– Gene cell therapy involves removing the genetic material from some body cells, manipulating it and reinserting it into the person. This can be used to cure diseases such as cancer by removing the cancer-causing mutation.

– Human genome refers to the genetic map of the human body’s DNA, including chromosomes and genes

– Biotechnology is the use of living organisms and the substances produced by them or biological techniques developed through basic research

– There are key biotechnologies used in DNA fingerprinting and they include:

> Restriction enzymes are protein molecules that can bind to a particular sequence of base pairs in a DNA molecule and then cut the DNA into sections

> Then the DNA pieces need to be separated by using a process called electrophoresis which works by separating DNA molecules in an electric field by their differences in size

> Thanks to a process called polymerase chain reaction which copies the DNA samples many times, only a small amount of DNA is needed for the fingerprinting process

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