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Could you please insert ‘Genes and Diseases’ intro slide here?

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Presentation on theme: "Could you please insert ‘Genes and Diseases’ intro slide here?"— Presentation transcript:

1 Could you please insert ‘Genes and Diseases’ intro slide here?

2 What is DNA Day? SLIDE 1: What is DNA Day? DNA Day is April 25th because: Watson and Crick determined structure of DNA on April 25, 1953 Human Genome Project completed in April, 2003 On April 25, 1953 Drs. James Watson and Francis Crick determined the structure of DNA In April 2003, Human Genome Project determined the entire DNA sequence of a human (3 billion letters) 2

3 Information is stored in DNA
Genes contain instructions to make proteins Information is stored in DNA RNA copy Gene = segment of DNA that tells the cell how to make a certain protein. Proteins work together to form the functional machinery that makes up a cell. The central dogma of molecular biology was established by Francis Crick in 1958. The Central Dogma states that DNA provides the instructions for making RNA, and RNA then provides the instructions for making protein. The overall concept of protein synthesis is basic, but the details of this process are quite complex and we wont go into those today. Basically DNA information is copied into messenger RNA (mRNA) by the process known as transcription and proteins are synthesized using the information in the mRNA as a template in a process known as translation. Can anyone tell me one of the differences between DNA and RNA? Bases: Thymine (DNA) and Uracil (RNA) Here are all the ways they differ: ・They differ in composition: 1.The sugar in RNA is ribose, not the deoxyribose in DNA. 2.The base uracil is in RNA instead of thymine. ・They also differ in size and structure: 1.RNA molecules are smaller (shorter) than DNA molecules, 2.RNA is single-stranded, not double-stranded like DNA. ・Another difference between RNA and DNA is in function. DNA has only one function-STORING GENETIC INFORMATION in its sequence of nucleotide bases. But there are three main kinds of ribonucleic acid, each of which has a specific job to do. 1.Ribosomal RNAs-exist outside the nucleus in the cytoplasm of a cell in structures called ribosomes. Ribosomes are small, granular structures where protein synthesis takes place. Each ribosome is a complex consisting of about 60% ribosomal RNA (rRNA) and 40% protein. 2.Messenger RNAs-are the nucleic acids that "record" information from DNA in the cell nucleus and carry it to the ribosomes and are known as messenger RNAs (mRNA). 3.Transfer RNAs-The function of transfer RNAs (tRNA) is to deliver amino acids one by one to protein chains growing at ribosomes. Proteins do most of the work in a cell and provide much of its structure. Protein

4 A change in gene result in a change in protein
Change in DNA is called a mutation ACT|CCT|GAG|GAG|AAG|CTG SAM AND TOM ATE THE HAM Thr Pro Glu Lys Leu Possible Change: SAM AND TOM ATE THE HIM ACT|CCT|GAG|GAG|AAG|CGG Result: Changed meaning or function SLIDE 11: How does an Altered Gene Result in an Altered Protein? Each 3-letter codon is translated into an amino acid. Example: SAM AND TOM ATE THE HAM – if we change A to I, does not make sense. If we change one letter in DNA, can change one letter in amino acid, and protein may not work properly Changes in DNA are called mutations. There are many types of mutations. Thr Pro Glu Lys Met Variations in the DNA of different individuals can cause phenotypic changes in individuals 4 4

5 Variations in the DNA of different individuals can cause visible changes in individuals
Just by looking around the room, we can see many examples of genetic variation. Some genetic traits, such as skin color and eye color, are controlled by multiple genes Others are controlled by only one gene We are going to look at 7 traits that are each determined by one gene with two possible alleles.

6 Single-gene Traits Laugh dimples ll no dimples (homozygous recessive)
L dimples (heterozygous or homozygous dominant) Tongue roll tt can’t roll tongue into “U” shape (homozygous recessive) T can roll tongue into “U” shape (heterozygous or homozygous dominant )

7 Single-gene Traits Crossing Thumbs
cc right thumb on top of clasped hands (homozygous recessive) C left thumb on top of clasped hands (heterozygous or homozygous dominant ) Pinkies pp pinkies are straight when pressed side by side (homozygous recessive) P pinkies bend away from each other, toward the ring fingers, when pressed side by side (heterozygous or homozygous dominant)

8 Single-gene Traits Ear lobes
ee attached ear lobe (homozygous recessive) E free ear lobe (heterozygous or homozygous dominant) Widow’s peak ww no widow’s peak (homozygous recessive) W has a widow’s peak (heterozygous or homozygous dominant)

9 Single-gene Traits Bending thumbs (Hitch-hiker’s thumb)
bb thumb bends at 90 degree angle (homozygous recessive) B thumb is straight (heterozygous or homozygous dominant)


11 99 Genetic wheel with one person’s information

12 99 Genetic wheel with two people’s information filled in 79

13 Genetic Wheel Results There are 128 possible combinations from the 7 traits illustrated on the genetic wheel. Are you the same as anyone else? If this much genetic variation exists in traits that are visible, imagine how different we all are in ways that we can’t see! I think it would be neat to go through the numbers, and ask the students to raise their hands if they have a result between numbers 1 and 10; 11 and 20; etc. If more than one student raises their hand for a set of numbers, investigate further and see if they have the same numbers. Everything has a genotype, and knowledge about genetic traits allows us to create a new phenotype. See next slide for examples.

14 Variations in the DNA of different individuals can cause varying traits in individuals

15 These traits can be inherited!
SLIDE 14: How are Genetic Traits Inherited? Next we’ll talk about how DNA is inherited. Child’s traits are combination of mother’s and father’s traits. Before disease, first we’ll talk about inheritance of traits in general.

16 Traits are inherited through genes
Genes are on chromosomes One chromosome inherited from each parent We have two copies of each gene SLIDE 15: Traits are inherited through genes Traits are inherited through our genes. Genes are carried on chromosomes. We inherit one chromosome from each parent. Each person has 2 copies of each gene. 16

17 Different versions of genes are alleles
For each gene, you might have… Combinations of alleles determine what traits you have OR SLIDE 16: Allele = A Version of a Gene We can have different versions of genes. Each version is called an “allele.” You can have two different alleles of a gene; or you could have two of the same alleles. 2 different alleles 2 of same allele

18 Can you roll your tongue?
Yes! You carry a copy of the dominant allele. No! You have two copies of the recessive allele. If you inherit both alleles, the dominant one is expressed. or Dominant does NOT mean more common! SLIDE 17: Can You Roll Your Tongue? The ability to roll your tongue is an example of a trait. Who can roll your tongue? You carry a dominant allele. Who cannot? You have two copies of the recessive “no roll” allele. Dominant does NOT mean more common. Dominant means that if you inherit 1 dominant and 1 recessive allele, the dominant one is expressed. 18

19 Inheriting Traits- Tongue Rolling
R = Roll allele (Dominant) Mother’s alleles Disease alleles can be inherited just like a “tongue rolling” allele... R r r = No-roll allele (Recessive) r r R r r Father’s alleles SLIDE 18: Inheriting Traits – Tongue-Rolling For a dominant trait, if you have one copy of the allele, you express the trait (e.g. mother). Two copies of a recessive allele (no-roll), means that person, the father, will not be able to roll their tongue. Punnett Squares: mother’s eggs & father’s sperm carry 1 chromosome; one chromosome from each parent is passed on to child. 50% chance of child having trait. This is the probability are for each child. Disease alleles can be inherited just like a “tongue rolling” allele. Each parent contributes 1 allele to offspring r r R r r 19

20 Some diseases are caused by genetic factors and can be inherited
A good example of genetically inherited disease is Cystic Fibrosis

21 Symptoms of Cystic Fibrosis
Thick mucus in airways and lungs Chronic Lung infections can cause permanent lung-cell damage. Digestive problems Lack of nutrient absorption Diseases are mostly defined by the symptoms a patient experiences. …… You can tell them how antibiotics became the common treatment for CF, but lead them to thinking about genetics.

22 What is the cause of Cystic Fibrosis?

23 The lungs are lined with specialized cells.
Cilia Out to mouth Dust Dirt Dust Mucus gland Mucus gland So now that we know what are the symptoms of CF, what is wrong with the cells in the lungs? Lets first look at how the lungs work (point to picture in upper right corner of slide): At first glance, some people might think that the lungs are just big hollow bags. In reality they are more like sponges, which increases the area inside the lungs that is available for blood to meet with the air. Did you know that the surface area inside your lungs is big enough to cover the floor of your classroom? That's how much area your lungs need to get all of the oxygen into your body! Your lungs need to be clean in order to function properly. The air you breathe is not always clean. For this reason, your lungs have a cleaning system. Dust, dirt, and germs are trapped in the mucus that lines your nose, trachea and lungs. The glands that make the mucus are called mucus glands. The dirty mucus is them pushed out of your lungs and into your throat by tiny hairs called cilia. This system is called the mucociliary escalator. Without it, we would have no way to get rid of germs from our lungs and we would be sick all the time!! Lower right image is an image (scanning EM) ofwhat human respiratory epithelial cells actually look like! Reference: Dust Mucus

24 These special cells clear mucus
Cilia Mucous

25 Cystic Fibrosis patients’ airways are dehydrated and cannot clear mucus.
Healthy Airway CF Airway Normal mucus Thick, dry mucus In Cystic Fibrosis, the outside of the lung cells (airway) is dehydrated. Instead of being able to move freely like in the healthy airway, the cilia in a CF airway are trapped in thick mucus (think GAK!) and cannot move. The thick mucus gets stuck in the lungs and becomes a breeding ground for all sorts of infectious bacteria. How does water move in and out of cells? Answer: osmosis/water follows concentration gradient of solute

26 As a result, CF airways accumulate bacteria and inflammatory cells.
Pseudomonas aeruginosa Too many inflammatory cells can cause permanent lung-cell damage.

27 CFTR protein hydrates and allows mucus clearance
= In healthy lung epithelial cells, the CFTR protein is at the cell surface and lets chloride ions leave the cell. Water follows the chloride ions into the airways.The reason why water needs to go into the airways is that the cillia, also at the cell surface, need it to work properly. When a person has CF, the the CFTR protein is missing from the cell surface. Consequently, chloride ions are trapped inside the lung epithelial cells and have no way of getting out into the airway. Without a way to move chloride ions, the cells cannot create an imbalance in the concentration of chloride ions and get water to follow the chloride. This means that water cannot move out of the cells. With no water moving out into the airway, the layer of mucus secreted by the mucus glands becomes very thick. The cilia get stuck in the thick mucus and can no longer move the mucus out to the mouth properly. Why does the CFTR protein not get to the plasma membrane in CF cells? Answer- Because it is not made properly/there is a mutation in the CFTR gene

28 The CFTR in Lung Cells Cilia CFTR protein Cell nuclei

29 Cystic Fibrosis Transmembrane Regulator
(CFTR) Chromosome 7 DNA DNA transcription RNA RNA translation CFTR protein Protein

30 Mutations in the CFTR gene blocks CFTR protein function
Healthy cell CFTR Cystic fibrosis cell For the most common mutation, delta F508, the CFTR does not fold properly and so it gets degraded before ever reaching the plasma membrane. Changes in the DNA sequence lead to a protein that cannot reach the plasma membrane. Mutant CFTR

31 Cystic Fibrosis Activity
You be the investigator… Find a cystic fibrosis patient

32 Investigate the BALF Do not open the tubes!!
Analyze the contents of each tube for: Mucus consistency Presence of inflammatory cells Evidence of infection with Pseudomonas aeruginosa (bacterial cells) A Record your findings on the worksheet provided. = inflammatory cell (macrophage) = bacterium (Pseudomonas)

33 Who do think has Cystic Fibrosis?
What would you do next to confirm the diagnosis?

34 Sequence the DNA and look for mutations in the cftr gene.
There are ~900 different mutations that have been found in the cftr gene. To save time, we have printed the DNA sequences from the sequencing reactions for you. Remember the Central Dogma? DNA RNA Protein

35 How do mutations in the DNA sequence lead to defective proteins?
DNA RNA Protein AGG TCG GGT CAA CAA TGC DNA UCC AGC CCA GUU GUU ACG RNA *Convert the DNA sequence into the RNA intermediate. DNA A T C G RNA U A G C

36 Now convert the mRNA message to a protein.
DNA RNA Protein UCC AGC CCA GUU GUU ACG mRNA Ser Ser Pro Val Val Thr Protein

37 Which patient has the defective CFTR protein?
Now you know that mutations in the genes (or DNA) can lead to changes in the protein. Refer to lesson plan for running the activity. Keep the students in groups after the activity for the ELSI discussion.

38 Genes & environment can work together to cause disease
Will you have the disease? Disease gene yes gene “family history” Cancer Disease maybe SLIDE 32: Genes & Environment Work Together Some diseases are caused only by genetic factors. Many diseases are complex and are caused by both genetic and environmental factors. Genetic factors (i.e. family history) and environmental factors can increase your risk, or “predispose” you to getting a complex disease like heart disease. What other diseases have both genetic & environmental component? environment smoking environment bad diet environment lack of exercise What diseases have both a genetic and an environmental component? 38 38 38

39 Cancer Your own cells dividing out of control
tumor cells behave abnormally, invade tissues Why? mutations in DNA tumor SLIDE 34: Cancer Cancer arises from uncontrolled cell division. Masses of cancer cells are called tumors. Tumors can invade tissues or move to other parts of the body. A major cause of cancer is mutations. More than one mutation has to occur for cancer to arise. mutation many mutations 39

40 What causes these mutations?
Environment (carcinogens) Can inherit mutations in certain genes SLIDE 35: What Causes these Mutations? Environmental factors that increase cancer risk are called carcinogens. Many carcinogens act by creating mutations in DNA. Examples: tobacco products, certain chemicals, x-rays, and UV light. Mutations can be inherited. Inherited mutations can increase your cancer risk (predisposition). Cancer is unique because the mutations in your genes are often caused by the environment. 40

41 How does knowing the genetics of diseases help us?
Does this mean we can cure everything? No Better understanding of disease can lead to better or safer treatments: Better, more specific drugs Gene replacement therapy Personalized medicine SLIDE 37: How does Knowing the Genetics of Diseases Help Us? How does knowing the genetics of a disease help us? Does it mean we can cure everything? No, but better and safer treatments: target drugs better, gene therapy, personalized medicine. 41


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