Modern Genetics

Genetic Patterns Each chromosome pair may contain as many as 2,000 traits. Chromosome 1, the largest human Chromosome, contains between 2000 and 2100 traits. These genes carry the information or code to produce proteins. It is estimated that the 23 pairs of human chromosomes contain 20,000 to 25,000 genes. Each of these genes are a result of the processes of meiosis and fertilization.

Five theories that resulted from Mendel’s work: 1.Law of Segregation-every organism contains a pair of alleles for any particular trait and that this Organism can pass a randomly selected copy of one Of these alleles to its offspring.(meiosis) The offspring then receives its own pair of alleles for that trait by inheriting homologous chromosomes from its parents. (recombination) 2. Law of Independent Assortment- genes located On different chromosomes or nonhomologous Chromosomes will be inherited independently and Randomly. This allows for diversity and variety. Roughly 8 million combinations exist.

3. Gene linkage-genes for different traits that are found on the same chromosome are linked and will be inherited together. This is the reason why freckles and Red hair are frequently found inherited together. 4.Sex linked-genes for traits found on the X Chromosome will be inherited if the X chromosome Is passed to an offspring. 5. Law of Dominance-each allele can be classified as Dominant or recessive. If a dominant allele is in- herited it will always be seen in the phenotype of the organism, masking the recessive allele. For the recessive allele to be seen the organism must inherit both recessive alleles.

Remember how this process works: Within the nucleus there are homologous chromosomes-chromosomes carrying alleles for the same trait. One allele came from the female-the Other from the male. Because they carry the code For the same trait they are Called homologous Chromosomes.

During interphase, the chromosomes replicate, making 2 of each homologous chromosomes. The process continues through each of the phases Of meiosis.

During prophase the chromosomes are very Close together. They may exchange some Codes that are on the chromatids. This changes The code for those traits that are linked by a Gene producing a different combination of Alleles. Crossing over: Increases the Diversity of Species.

Remember, genes are segments or specific codes of DNA. These codes are a result of a specific pattern of nitrogen bases. If the pattern is changed in any way the code changes, in both DNA and RNA. C C G T A T G G C G G C A T A C C G DNA code C C G U A U G G C - RNA code C C G T A T G G C G C C A T A G C G MUTATED DNA CODE C G G U A U C G C – MUTATED RNA CODE

These changes in the pattern are called mutations – sometimes good, but most of the times harmful. Mutations are harmful because the code is changed and the function related to that code is also changed. If the code is for protein synthesis through the RNA Molecule, then the protein/enzymes will not form Or function correctly. If the code is altered where there is a dominant recessive allele and the dominant allele is not affected then the cell will continue to function properly. Mutations in somatic cells are not inherited. Mutations in gametes are inherited

Mutations can occur in several different ways: *these changes in the pattern are results of: Viruses, chemicals, radiation ** in most cases the body can heal these changes. 1.deletion-loss of all or part of the code=loss of trait 2. insertion- segment is repeated Chain becomes longer=domino effect

3. Cross over: genetic material from one chromatid Is exchanged with the genetic material from its Homologous chromatid (as seen earlier in this PPt) Few diseases result from this. Rather a greater variety or diversity is observed.

4.Translocation: similar to cross over but occurs on nonhomologous chromosomes. This means that 2 translocations occur simultaneously because 2 nonhomologous chromosomes are involved. This type of mutation is usually not observed (phenotypically) in a heterozygous individual, but will affect meiosis.

Nondisjunction: occurs during meiosis. Chromatin Fail to separate. One less chromatid To be inherited Normal gamete formation One extra chromatid In gamete

Some disorders/diseases caused by these mutations: Deletion – Cri-du-chat, DeGeorge Syndrome Insertion – Fragile X Huntingtons disease Translocation – Philadelphia gene – leukemia Nondisjunction – Down Syndrome Turner Syndrome Kleinfelter Syndrome

Sex determination: Diploid cells contain two different Types of chromosomes-alleles. Those chromosomes Controlling body traits are called autosomes 22 pairs. But one pair of chromosomes control the gender of a species, called sex chromosomes. Specifically these alleles are found on the 23 rd pair and have the combination of XX and XY. There is a 50/50 chance of inheriting the X and Y Chromosome. Female = XX Mother gives X to son Male = XY Father gives Y to son

Sex linked disorders/traits are those found on the X chromosomes. Men: will be affected by the disorder if they have Inherited the affected X :will pass the affected X to their daughters. Women: can be carriers of the disorder if they have Inherited only one affected X or affected if they have Inherited both X chromosomes. :will pass the affected X to their sons.

Genetic Engineering: term used to describe the use of specific techniques to move genetic material from one organism to another organism. One small piece of DNA from a cell is removed and added to the DNA of another cell. The new DNA that results from This process is call recombinant DNA. This recombinant DNA will continue to produce the polypeptide product that it was originally coded for giving the organism a new polypeptide. This techniques improves the functions of the Cells/organism. This can only work because the DNA is the same for all organisms.

A couple of facts to remember: a.DNA is the same for all organisms-only the pattern changes. b.Bacteria is often used as the ‘carrier’ molecule. It is called a plasmid. Think of ‘plaster’. Once this bacteria is injected into the recipient, the recipient’s cells will use the code to produce the needed protein. c.Restriction enzymes are used to cut the DNA molecule apart.

Insulin, growth hormone, interferon

 Better Crops (drought & heat resistance)  Recombinant Vaccines (ie. Hepatitis B)  Prevention and cure of sickle cell anemia  Prevention and cure of cystic fibrosis  Production of clotting factors  Production of insulin  Production of recombinant pharmaceuticals  Plants that produce their own insecticides Some uses of recombinant DNA

Cloning: an identical copy of an organism. Two organisms have the exact DNA code. identical twins are a natural form of cloning mitosis

Why clone? All DNA will be inheritable. 1.Maintain supply of diseased lab animals for testing. 2.Grow stem cells 3.Protect endangered species 4.Produce high quality livestock/plants for food 5.Produce drug carrying animals. Negatives: 1.Loss of diversity 2.Moral issues