GENES AND ALLELES biology document presentation.pptx

On genes and allelies

1. ANA 208 GENES AND ALLELES LECTURER IN CHARGE: DR. S.A. ADELAKUN DEPARTMENT OF ANATOMY FEDERAL UNIVERSITY OF TECHNOLOGY AKURE

2. 2 KEY CONCEPT Genes encode proteins that produce a diverse range of traits

3. Genes Genes are the basic units of heredity. They are composed of DNA and are located on chromosomes. Genes are composed of DNA sequences, which are made up of four nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). The sequence of nucleotides in a gene determines the code for a specific protein. Genes are located on chromosomes, which are thread-like structures found in the nucleus of every cell. 3

4. Genes Humans have 23 pairs of chromosomes, with each pair containing one chromosome from each parent. Genes code for proteins, which are essential for all cellular functions. Proteins are responsible for building and repairing tissues, regulating metabolism, and carrying out other essential tasks. 4

5. Genes Diagram of the gene 5

6. DNA Structure and Gene Composition DNA Structure: DNA is a double-stranded molecule that resembles a twisted ladder. The two strands are held together by hydrogen bonds between complementary nucleotides. Exons and Introns: Genes contain both coding and non-coding regions . The coding regions, called exons, are transcribed into RNA and translated into proteins. The non-coding regions, called introns, are removed during RNA processing. Exon Function: Exons contain the genetic code for proteins. This code is composed of triplets of nucleotides, called codons. Each codon corresponds to a specific amino acid. Intron Function: Introns play a role in regulating gene expression. They can also contain regulatory elements that control when and where a gene is expressed. 6

7. Inheritance of Genes Genetic inheritance is the process by which genes are passed from parents to offspring. Mendel's Laws: Mendel's laws of inheritance describe the patterns of inheritance for single genes. Law of Segregation: Alleles for a gene segregate, or separate, during meiosis. This means that each gamete (sperm or egg) receives only one allele for each gene. Law of Independent Assortment: Alleles for different genes assort independently during meiosis. This means that the inheritance of one gene is not linked to the inheritance of another gene. Inheritance of Alleles: Each parent contributes one allele for each gene to their offspring. The combination of alleles that an individual inherits determines their genotype. The genotype determines the phenotype, which is the observable expression of a trait. 7

8. Gene Expression Gene expression is the process by which genes are converted into proteins. Gene expression occurs in two steps: transcription and translation . Transcription: During transcription, the DNA sequence of a gene is copied into a molecule of RNA (messenger RNA ). Translation : During translation, the RNA sequence is converted into a sequence of amino acids, which form a protein. Importance: Gene expression is essential for all cellular functions, including growth, repair, and reproduction. 8

9. Gene Expression Diagram of gene expression 9

10. Genetic Variation and Evolution Genetic Diversity: Genetic diversity is the variety of alleles that are present in a population. Evolution : Genetic variation is the driving force of evolution. When a population has a lot of genetic diversity, it is better able to adapt to changing environments. Mechanisms of Genetic Variation: There are two main mechanisms of genetic variation: mutation and recombination. Mutation : Mutation is a change in the DNA sequence of a gene. Mutations can be caused by a variety of factors, such as environmental toxins or errors in DNA replication. Recombination : Recombination is a process in which DNA is exchanged between chromosomes during meiosis. This can lead to new combinations of alleles in offspring. 10

11. Gene Therapy Gene therapy is a technique that uses genes to treat or prevent diseases. It works by delivering a normal copy of a gene to cells in the body to replace a defective or missing gene. Gene therapy is currently being used to treat a variety of diseases, including cystic fibrosis, sickle cell anemia, and cancer. Steps of gene therapy: A normal copy of a gene is inserted into a vector, such as a virus or a liposome. The vector is delivered to the target cells in the body. The vector enters the cells and releases the gene. The gene is taken up by the cells and expressed. 11

12. Types Of Gene Therapy Somatic Cell Gene Therapy Germ Line Gene Therapy Therapeutic genes transferred into the somatic cells. E.g. Introduction of genes into bone marrow cells, blood cells, skin cells etc. Will not be inherited later generations At present all researches directed to correct genetic defects in somatic cells Therapeutic genes transferred into the germ cells. E.g. Genes introduces into eggs and sperm It is heritable and passed on to later generations. For safety, etical and technical reasons, it is not being attempted at present 12

13. Approaches In Gene Therapy In vivo gene therapy:- direct delivery of genes into the cells of a particular tissue in the body. Ex vivo gene therapy:- transfer of genes to cultured cells and reinsertion. 13

14. Advantages of Gene Therapy Gene therapy has the potential to eliminate and prevent hereditary diseases such as cystic fibrosis, ADA-SCID etc. It is a possible cure for heart disease, AIDS and cancer. It gives someone born with a genetic disease a chance to life. It can be used to eradicate diseases from the future generations. 14

15. Disadvantages of Gene Therapy Long lasting therapy is not achieved by gene therapy; Due to rapid dividing of cells benefits of gene therapy is short lived. Immune response to the transferred gene stimulates a potential risk to gene therapy. Viruses used as vectors for gene transfer may cause toxicity, immune responses and inflammatory reactions in the host Disorder caused by defects in multiple genes cannot be treated effectively using gene therapy. 15

16. What are Alleles? An allele is an alternative form of a gene . occurring at a specific locus on a chromosome. Each parent donates one allele for every gene. They can be identical or slightly different. Alleles are the source of genetic variation . Genetic variation is important because it allows populations to adapt to changing environments. Some examples of alleles for various traits: Blood type: Alleles for blood type can code for type A, type B, type AB, or type O blood. Hair color: Alleles for hair color can code for black, brown, blonde, or red hair. Eye color: Alleles for eye color can code for brown, blue, green, or hazel eyes . 16

17. Alleles and Dominance Dominant and Recessive Alleles: Some alleles are dominant, while others are recessive. A dominant allele will always be expressed , even if the individual also has a recessive allele for the same trait. A recessive allele will only be expressed if the individual has two copies of the recessive allele . Alleles can be represented using letters. Dominant alleles are represented by uppercase letters ; Recessive alleles are represented by lowercase letters. 17

18. Alleles and Dominance Example: Let's say that eye color is controlled by a single gene with two alleles: brown and blue. The brown allele(B) is dominant , while the blue allele(b) is recessive . If an individual has one brown allele and one blue allele, they will have brown eyes (because the brown allele; Bb is dominant). If an individual has two blue alleles, they will have blue eyes (because the blue allele; bb is recessive). Punnett squares: are a tool that can be used to predict the probability of different genotypes and phenotypes in offspring. Genotype : The genotype of an individual is the combination of alleles that they have for a particular trait. It consists of 2 alleles 18

19. Alleles and Dominance For example: PP, Pp , pp Phenotype: The phenotype of an individual is the observable expression of a trait. The genotype determines the phenotype. Phenotype: The appearance 19

20. Alleles and Dominance When a dominant allele always gets its way (the dominant phenotype is present no matter its partner) it is called COMPLETE DOMINANCE . Example; Pp = Purple Flower , PP = Purple Flower Some times dominant traits don’t completely get their way……the alleles compromise. This results in a phenotype that is a mix of both parents. This is called INCOMPLETE DOMINANCE. Example; Pp = light purple flower In a few instances both alleles need to be expressed. This is called Codominance . Example; A mom chicken is black and dad chicken is white, but the baby chick comes out black and white. 20

21. Homozygous vs. Heterozygous An individual is homozygous for a trait if they have two identical alleles for that trait . When both letters are the same. Example; TT , tt . An individual is heterozygous for a trait if they have two different alleles for that trait. When letters are different, always write the big letter first. Example; Tt , Xx. 21

22. Homozygous vs. Heterozygous The genotype of an individual influences their phenotype. However, the relationship between genotype and phenotype is not always straightforward. In some cases, the environment can also play a role in determining the phenotype . Example: Let's say that an individual is heterozygous for eye color. They have one brown allele and one blue allele. Their genotype is Bb. Their phenotype will be brown eyes, because the brown allele is dominant. However , if this individual is exposed to a lot of sunlight, their blue eyes may become more pronounced. This is because the sunlight can damage the melanin in their brown eyes. 22

23. Alleles in Human Blood The ABO blood group system is the most well-known example of alleles in human blood. There are three alleles for the ABO blood group system: A, B, and O. Each person has two alleles for the ABO blood group system, one from their father and one from their mother. The combination of alleles that a person has determines their blood type. There are four blood types: A, B, AB, and O. The ABO blood group system is important for blood transfusions. People with the same blood type can safely donate blood to each other 23

24. More Alleles in Human Blood In addition to the ABO blood group system, there are many other alleles in human blood. These alleles can code for different proteins that are involved in blood clotting, immunity, and other functions. For example, the Rh factor is a protein that is found on the surface of red blood cells. People who have the Rh factor are Rh-positive, while people who do not have the Rh factor are Rh-negative. The Rh factor is important for pregnant women who are Rh-negative. If an Rh-negative woman has an Rh-positive baby, her immune system may attack the baby's red blood cells . Other blood group system includes; Duffy group, Bombat group, Auberger groups.. 24

25. Genes, Alleles, and the Environment Gene-Environment Interactions: Gene-environment interactions are situations in which the environment can influence the expression of genes. Epigenetics : Epigenetics is the study of how the environment can influence gene expression without changing the DNA sequence. Examples : Here are some examples of environmental influences on gene regulation: Diet : Diet can influence the expression of genes that control metabolism and weight gain. Exercise : Exercise can influence the expression of genes that control muscle growth and cardiovascular health. Stress : Stress can influence the expression of genes that control the immune system and mental health. 25

26. Importance of Genes and Alleles Genes and alleles are essential for all life on Earth. They determine everything from our physical appearance to our susceptibility to diseases. Genes and alleles are also important for the evolution of life. Genetics is a rapidly evolving field with a wide range of applications in medicine, agriculture, and biotechnology. 26

27. Medical Importance of Gene and Alleles Disease Susceptibility: Genes and alleles play a crucial role in determining an individual's susceptibility to various diseases, including genetic disorders, chronic conditions, and infectious diseases. Targeted Therapies: Understanding specific genes and alleles allows for the development of targeted therapies and personalized medicine, increasing treatment effectiveness while minimizing side effects. Genetic Testing: Genetic information from genes and alleles is utilized in medical diagnostics and genetic testing to assess an individual's risk of developing certain diseases and to guide treatment decisions. Pharmacogenomics : Genes and alleles influence an individual's response to medications, and pharmacogenomics uses this information to tailor drug prescriptions for better patient outcomes. Disease Prevention: Knowledge of genetic variants can help identify at-risk populations and implement preventive measures and early interventions to reduce the incidence and impact of genetic and hereditary diseases. 27

28. Thank You For Listening 28