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What is a Gene?  Gene = a segment of DNA that codes for a protein that controls a trait.  Humans have approximately 30,000 genes  We have 2 copies of.

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Presentation on theme: "What is a Gene?  Gene = a segment of DNA that codes for a protein that controls a trait.  Humans have approximately 30,000 genes  We have 2 copies of."— Presentation transcript:

1 What is a Gene?  Gene = a segment of DNA that codes for a protein that controls a trait.  Humans have approximately 30,000 genes  We have 2 copies of each gene (one on each chromosome we inherited from our parents).  Each gene has different forms...  Allele –one of the many forms of a gene.

2 Examples of Genes and Alleles in Pea Plants  Gene – Seed Shape Alleles: _____________ _____________ _____________  Gene – seed color Alleles: _____________ _____________ _____________  Gene – flower color Alleles: _____________ _____________ _____________

3 Chromosomes occur in pairs because offspring inherit one from each parent  *We have 46 Chromosomes (23 pairs of chromosomes)  Chromosomes are made of genes  Circle one gene.  What are the 2 alleles for that gene? *Each chromosome is made up of DNA that contains hundreds to thousands of GENES. *HIERARCHY: CHROMOSOMES  CONTAIN DNA  MADE OF GENES  CODE FOR A PROTEIN  MAKE TRAITS

4 Dominant vs. Recessive  NOT ALL ALLELES ARE EXPRESSED! Some alleles are dominant, while others are recessive

5 DescriptionMore InfoExamples Dominant Alleles This trait always shows up in an organism if it is present *These usually code for a protein so they are the “normal” form of a gene. -Widows Peak -free earlobes  REPRESENTED WITH CAPITAL LETTER Recessive Alleles This trait only shows up if there is no dominant allele present *These usually code for a different protein, or deactivate the “normal” protein. -No widow’s peak -attached earlobes  REPRESENTED WITH LOWERCASE LETTER


7 Don’t let this happen to you!!

8 MUTATIONS Changes in DNA that affect genetic information

9 Gene Mutations  Point Mutations – changes in one or a few nucleotides  Substitution  THE FAT CAT ATE THE RAT  THE FAT HAT ATE THE RAT  Insertion  THE FAT CAT ATE THE RAT  THE FAT CAT XLW ATE THE RAT  Deletion  THE FAT CAT ATE THE RAT  THE FAT ATE THE RAT

10 Gene Mutations  Frameshift Mutations – shifts the reading frame of the genetic message so that the protein may not be able to perform its function.  Insertion  THE FAT CAT ATE THE RAT  THE FAT HCA TAT ETH ERA T  Deletion  THE FAT CAT ATE THE RAT  TEF ATC ATA TET GER AT H H

11 Chromosome Mutations  Changes in number and structure of entire chromosomes  What do scientists use to identify these type of mutations?  Original Chromosome ABC * DEF  DeletionAC * DEF  DuplicationABBC * DEF  InversionAED * CBF  TranslocationABC * JKL GHI * DEF

12 Your body cells have 23 pairs of chromosomes. –Homologous pairs of chromosomes have the same structure. –For each homologous pair, one chromosome comes from each parent. Chromosome pairs 1-22 are autosomes. Sex chromosomes, X and Y, determine gender in mammals. Your cells have autosomes and sex chromosomes.

13 By investigating body tissue, scientists can detect problems. Genetic problems can be identified by defective proteins/enzymes or a negative affect on the bodies metabolism. Genes can be studied directly

14 Electrophoresis (DNA fingerprinting)


16 Karyotypes  a set of photographs of chromosomes grouped in order in pairs from one cell.  What are some observations we could make from this karyotype?

17 Male vs. Female  Males have XY sex chromosomes.  Females have XX sex chromosomes  The Y chromosome carries very few genes essential for life.  The X chromosome is a much longer DNA molecule and contains many, many genes that are needed for cells to function.

18 Karyotype Notation  A short-hand way to write a person’s karyotype.  Total # of chromosomes, sex chromosomes, extra or missing chromosomes  Normal Female  46XX  Normal Male  46XY

19 Karyotype Notation

20 Significance of Mutations 1. Most are neutral Eye colorEye color Birth marksBirth marks 2. Some are harmful Sickle Cell AnemiaSickle Cell Anemia Down SyndromeDown Syndrome 3. Some are beneficial Sickle Cell Anemia to MalariaSickle Cell Anemia to Malaria Immunity to HIVImmunity to HIV

21 What Causes Mutations?  There are two ways in which DNA can become mutated: 1. Mutations can be inherited.  Parent to child 2. Mutations can be acquired.  Environmental damage  Mistakes when DNA is copied  Non-disjunction-failure of chromosomes to separate properly during Meiosis.

22  What are we making during Meiosis?  In your own words what is a non-disjunction?

23 Genetic Disorders  an illness caused by one or more abnormalities in the genome, especially a condition that is present from birth.  Conditions may or may not be inherited.  Mutations occur all the time in every cell in the body.  Each cell, however, has the remarkable ability to recognize mistakes and fix them before it passes them along to its descendants.  But a cell's DNA repair mechanisms can fail, or be overwhelmed, or become less efficient with age.

24 Turners Syndrome Affects1 in 2,500 newborns 45 chromosomes; have only 1 X chromosome #23 Monosomy girls fail to go thru puberty Caused by a nondisjunction, if a pair of sex chromosomes fails to separate during the formation of an egg or sperm

25 Turners Syndrome 96-98% do not survive to birth stocky appearance short webbed neck Other medical symptoms include: lymphedema (swelling of hands and feet) heart and/or kidney defects high blood pressure infertility (inability to have children)

26 Cri-Du-Chat Syndrome Estimated 1 in 20,000-50,000 newborns Found in ALL ethnic backgrounds Not inherited Can be XY or XX #5 Deletion These children have a deleted portion of chromosome number 5.

27 Cri-Du-Chat Syndrome Cry that is high-pitched and sounds like a cat Downward slant to the eyes Low birth weight and slow growth Low-set or abnormally shaped ears Mental handicap (intellectual disability) Partial webbing or fusing of fingers or toes Slow or incomplete development of motor skills Small head (microcephaly) Small jaw (micrognathia) Wide-set eyes

28 WAGR Syndrome 1 in 500,000 children under age 15 7 in 1000 cases have Wilms Tumor 46 chromosomes XY or XX #11 Deletion of upper arm The condition results from a deletion on chromosome 11 resulting in the loss of several genes

29 Aniridia-Wilms Tumor Syndrome Predisposed to Wilms kidney tumor Mentally handicapped Severe childhood obesity Growth retardation Blindness Tumors on kidneys Short lifespan Missing the iris of the eye

30 Thirteen Q Deletion Syndrome 600 cases worldwide 1 st diagnosed 20 years ago 46 chromosomes Affects XY or XX #13 Deletion of lower arm

31 Thirteen Q Deletion Syndrome Mentally retarded Deformed face No thumbs Heart disease Short lifespan

32 Prader-Willi Syndrome 1 in 15,000 live births 46 chromosomes XY=97% XX=3% #15 Deletion of lower arm Prader-Willi syndrome is caused by a gene missing on part of chromosome 15. Normally, your parents each pass down a copy of this chromosome. Most patients with Prader-Willi syndrome are missing the genetic material on part of the father's chromosome.

33 Prader-Willi Syndrome Low muscle tone Short stature Incomplete sexual development Cognitive disabilities Problem behaviors Chronic feeling of hunger Obesity Shorter lifespan

34 Eighteen Q Deletion Syndrome 1 in 40,000 newborns Estimated 100 babies per year 46 chromosomes XY or XX #18 Deletion of lower arm

35 Eighteen Q Deletion Syndrome Symptoms correlate with the size of the deletion Mentally handicapped Heart disease Abnormal hands and feet Large eyes Large ears Normal lifespan

36 Cat-Eye Syndrome 1 in 1,000,000 births 46 chromosomes Affects XY or XX #22 Deletion of bottom arm

37 Cat-Eye Syndrome Cat-Eye Syndrome Normal to severe malformations Fused fingers and toes Mentally handicapped Small jaw Heart problems Normal lifespan

38 Four-Ring Syndrome 1 in 10,000,000 births 46 chromosomes XY or XX #4 Inversion

39 Four-Ring Syndrome Cleft palate Club feet Testes don’t descend Short lifespan

40 Down Syndrome 1 in 31,000 births 46 chromosomes XY=97% XX=3% #14/21 Translocation 1 in 850 newborns Estimated 250,000 people are affected in the US 47 chromosomes XY or XX #21 Trisomy Nondisjunction Trisomy 21 Down Syndrome

41 Short, broad hands Stubby fingers Rough skin Impotency in males Mentally handicapped Cognitive delays Small round face Protruding tongue Short lifespan Increased risk of developing Alzheimer disease

42 Patau’s Trisomy Syndrome 1 in 14,000 births 47 chromosomes XY or XX #13 Trisomy Nondisjunction

43 Patau’s Trisomy Syndrome Small head Small or missing eyes Heart defects Extra fingers Mentally handicapped Cleft palate Most die a few weeks after birth

44 Edward’s Trisomy Syndrome 1 in 4,400 births 47 chromosomes XX=80% XY=20% #18 Trisomy Nondisjunction

45 Edward’s Trisomy Syndrome Small head Mentally handicapped Internal organ abnormalities 90% die before 5 months of age

46 Jacob’s Syndrome 1 in 1,800 births 47 chromosomes XYY only #23 Trisomy Nondisjunction

47 Jacob’s Syndrome Normal physically Normal mentally Increase in testosterone More aggressive Normal lifespan ?

48 Klinefelter Syndrome 1 in 1,100 births 47 chromosomes XXY only #23 Trisomy Nondisjunction

49 Klinefelter Syndrome Klinefelter Syndrome Scarce beard Longer fingers and arms Sterile Delicate skin Low mental ability Normal lifespan

50 Triple X Syndrome 1 in 2,500 births 47 chromosomes XXX only #23 Trisomy Nondisjunction

51 Triple X Syndrome Normally physically Normal mentally Fertile Short lifespan

52 Cystic Fibrosis (CF)  Clogs the lungs and leads to life- threatening lung infections.  Obstructs the pancreas and stops natural enzymes from helping the body break down food and absorb vital nutrients  Fluid in lungs, potential respiratory failure  Common among Caucasians  1 in 20 are carriers  Therefore is it dominant or recessive?

53 Cystic Fibrosis (CF)  Monogenic  Cause: deletion of only 3 bases on chromosome 7  Estimated in 30,000 children and adults in the U.S.  70,000 people worldwide

54 Muscular Dystrophy   X-linked or autosomal genetic disorder.   Muscular dystrophy is a disease in which the muscles of the body get weaker because of a lack of a certain protein   Can be passed on by one or both parents, depending on the form of MD Symptoms: Muscle weakness that slowly gets worse Delayed development of muscle motor skills Difficulty using one or more muscle groups Eyelid drooping (ptosis) Loss of strength in a muscle or group of muscles as an adult Loss in muscle size Problems walking (delayed walking)

55 Huntington’s Disease  Huntington's disease (HD) is an inherited, degenerative brain disorder which results in an eventual loss of both mental and physical control.  The disease is also known as Huntington's chorea. Chorea means "dance-like movements" and refers to the uncontrolled motions often associated with the disease.

56 Hemophilia, the royal disease  Hemophilia is the oldest known hereditary bleeding disorder.  Caused by a recessive gene on the X chromosome.  There are about 20,000 hemophilia patients in the United States.  One can bleed to death with small cuts.  The severity of hemophilia is related to the amount of the clotting factor in the blood. About 70% of hemophilia patients have less than one percent of the normal amount and, thus, have severe hemophilia.

57 ALS (Amyotrophic Lateral Sclerosis, or Lou Gehrig’s disease)

58  the disease strikes people between the ages of 40 and 70, and as many as 30,000 Americans have the disease at any given time  This monogenic mutation is believed to make a defective protein that is toxic to motor nerve cells.  A common first symptom is a painless weakness in a hand, foot, arm or leg, other early symptoms include speech swallowing or walking difficulty

59 Designer Baby  _ html _ html _ html

60 Chromosome Mutations  Cri-du-chat  Deletion of material on 5 th chromosome  Characterized by the cat-like cry made by cri-du-chat babies  Varied levels of metal handicaps

61 Sex Chromosome Abnormalities  Klinefelter’s Syndrome  XXY, XXYY, XXXY  Male  Sterility  Small testicles  Breast enlargement

62 Sex Chromosome Abnormalities  XYY Syndrome  Normal male traits  Often tall and thin  Associated with antisocial and behavioral problems

63 Sex Chromosome Mutations  Turner’s Syndrome  X  Female  sex organs don't mature at adolescence  sterility  short stature

64 Sex Chromosome Mutations  XXX  Trisomy X  Female  Little or no visible differences  tall stature  learning disabilities  limited fertility

65 What’s an Autosome? AAAAutosome: refers to chromosomes 1-22 EEEEx: Autosomal disorders: gene for the disease is found on chromosomes 1-22 AAAAutosomal Recessive Inheritance MMMMust inherit two copies of the disorder to be affected HHHHealthy is dominant (HH or Hh) DDDDisease is recessive (hh) EEEEx: Cystic fibrosis, PKU, Albinism, Sickle cell anemia AAAAutosomal Dominance Inheritance OOOOnly need to inherit one copy of the disorder to be affected DDDDisease is dominant (HH or Hh) HHHHealthy is recessive (hh) EEEEx: Familial hypercholesterolemia (also called FH), Huntington’s disease, Neurofibromatosis

66 Autosomal Dominance Inheritance DDDDisease is dominant (FF or Ff) HHHHomozygous dominant: early death and don’t survive to reproduce HHHHeterozygous live into adulthood HHHHealthy is recessive (ff) eeeex: Paul has familial hypercholesterolemia and Stacy is healthy. The two have 3 children. After testing, the middle child is the only healthy child. Key F = FH disease f = healthy disease healthy

67 Autosomal Dominance Inheritance  Huntington’s disease is a dominant disorder found on chromosome 4. Betty and Marcus met at a support clinic they have been attending to help them cope with the knowledge of their illness with Huntington’s disease. They would like to know the risk of having a healthy child, now that Betty is pregnant. Key H = Huntington’s disease h = healthy diseasedisease diseasehealthy



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