What is a Gene? What is a Gene? Gene = Gene = a segment of DNA that codes a segment of DNA that codes for a protein that controls a trait. for a protein that controls a trait. Humans have approximately 30,000 Humans have approximately 30,000 genes genes We have 2 copies of We have 2 copies of each gene (one on each chromosome each gene (one on each chromosome we inherited from our parents). we inherited from our parents). Each gene has different forms . . . Each gene has different forms . . . Allele –one of the many forms of a Allele –one of the many forms of a gene. gene.
Transcript
What is a Gene?What is a Gene? Gene = Gene = a segment of DNA that codes for a a segment of DNA that codes for a
protein that controls a trait.protein that controls a trait. Humans have approximately 30,000 genesHumans have approximately 30,000 genes We have 2 copies of We have 2 copies of
each gene (one on each chromosome each gene (one on each chromosome
we inherited from our parents).we inherited from our parents).
Each gene has different forms . . . Each gene has different forms . . . Allele –one of the many forms of a gene.Allele –one of the many forms of a gene.
Examples of Genes and Alleles in Pea Examples of Genes and Alleles in Pea PlantsPlants
Chromosomes occur in pairs Chromosomes occur in pairs because offspring inherit because offspring inherit one from each parentone from each parent
*We have 46 Chromosomes *We have 46 Chromosomes (23 pairs of chromosomes)(23 pairs of chromosomes)
Chromosomes are made of genesChromosomes are made of genes Circle one gene.Circle one gene.
What are the 2 alleles for that gene?What are the 2 alleles for that gene?
*Each chromosome is made up of DNA that contains hundreds to *Each chromosome is made up of DNA that contains hundreds to thousands of GENES.thousands of GENES.
*HIERARCHY: CHROMOSOMES *HIERARCHY: CHROMOSOMES CONTAIN DNA CONTAIN DNA MADE MADE OF GENES OF GENES CODE FOR A PROTEIN CODE FOR A PROTEIN MAKE TRAITS MAKE TRAITS
Dominant vs. RecessiveDominant vs. Recessive NOT ALL ALLELES ARE EXPRESSED! NOT ALL ALLELES ARE EXPRESSED!
Some alleles are dominant, while others Some alleles are dominant, while others are recessiveare recessive
Description More Info Examples
DominantAlleles
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
WHAT HAPPENS IF WE WHAT HAPPENS IF WE CHANGE OUR DNA?CHANGE OUR DNA?
Don’t let this happen to you!!
MUTATIONSMUTATIONS
Changes in Changes in DNADNA that affect genetic that affect genetic informationinformation
Gene MutationsGene Mutations
Point Mutations – changes Point Mutations – changes in in one or a fewone or a few nucleotides nucleotides SubstitutionSubstitution
THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT HAT ATE THE RATTHE FAT HAT ATE THE RAT
InsertionInsertion THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT CAT XLW ATE THE RATTHE FAT CAT XLW ATE THE RAT
DeletionDeletion THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT ATE THE RATTHE FAT ATE THE RAT
the the reading framereading frame of the genetic of the genetic message so that the message so that the protein protein may not be able to perform its may not be able to perform its function.function. InsertionInsertion
THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT HCA TAT ETH ERA TTHE FAT HCA TAT ETH ERA T
DeletionDeletion THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT TEF ATC ATA TET GER ATTEF ATC ATA TET GER AT
H
H
Chromosome MutationsChromosome Mutations Changes in number and structure of entire Changes in number and structure of entire
chromosomes chromosomes What do scientists use to identify these What do scientists use to identify these
KaryotypesKaryotypes a set of photographs of chromosomes grouped a set of photographs of chromosomes grouped
in order in pairs from one cell. in order in pairs from one cell.
What are some observations we could make What are some observations we could make from this karyotype?from this karyotype?
Male vs. FemaleMale vs. Female
Males have Males have XYXY sex chromosomes. sex chromosomes. Females have Females have XXXX sex chromosomes sex chromosomes The Y chromosome carries very few genes The Y chromosome carries very few genes
essential for life. essential for life. The X chromosome is a much longer DNA The X chromosome is a much longer DNA
molecule and contains many, many genes molecule and contains many, many genes that are needed for cells to function. that are needed for cells to function.
Karyotype NotationKaryotype Notation A A short-handshort-hand way to write a person’s way to write a person’s
karyotype.karyotype. Total # of chromosomes, sex chromosomes, Total # of chromosomes, sex chromosomes,
extra or missing chromosomesextra or missing chromosomes Normal FemaleNormal Female 46XX46XX Normal MaleNormal Male 46XY46XY
Karyotype NotationKaryotype Notation
Significance of MutationsSignificance of Mutations1. Most are neutral1. Most are neutral
• Eye colorEye color• Birth marksBirth marks
2. Some are harmful2. Some are harmful• Sickle Cell AnemiaSickle Cell Anemia• Down SyndromeDown Syndrome
3. Some are beneficial3. Some are beneficial• Sickle Cell Anemia to MalariaSickle Cell Anemia to Malaria• Immunity to HIVImmunity to HIV
What Causes Mutations?What Causes Mutations? There are two ways in which DNA can There are two ways in which DNA can
become mutated:become mutated:1. Mutations can be inherited. 1. Mutations can be inherited.
Parent to childParent to child
2. Mutations can be acquired.2. Mutations can be acquired. Environmental damageEnvironmental damage Mistakes when DNA is copiedMistakes when DNA is copied
Non-disjunctionNon-disjunction-failure of chromosomes to separate -failure of chromosomes to separate properly during Meiosis. properly during Meiosis.
What are we making during Meiosis?What are we making during Meiosis? In your own words what is a non-disjunction?In your own words what is a non-disjunction?
Genetic DisordersGenetic Disorders an illness caused by one or more abnormalities in an illness caused by one or more abnormalities in
the genome, especially a condition that is present the genome, especially a condition that is present from birth.from birth.
Conditions may or may not be inherited.Conditions may or may not be inherited.
Mutations occur all the time in every cell in the body. Mutations occur all the time in every cell in the body. Each cell, however, has the remarkable ability to recognize Each cell, however, has the remarkable ability to recognize
mistakes and fix them before it passes them along to its mistakes and fix them before it passes them along to its descendants. descendants.
But a cell's DNA repair mechanisms can fail, or be overwhelmed, But a cell's DNA repair mechanisms can fail, or be overwhelmed, or become less efficient with age.or become less efficient with age.
Turners Turners SyndromeSyndrome
• 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
Turners SyndromeTurners Syndrome
•96-98% do not survive to birth•stocky appearance•short webbed neckOther medical symptoms include: •lymphedema (swelling of hands and feet) •heart and/or kidney defects •high blood pressure•infertility (inability to have children)
Cri-Du-Chat Cri-Du-Chat SyndromeSyndrome
•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.
Cri-Du-Chat SyndromeCri-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
WAGR SyndromeWAGR Syndrome
1 in 500,000 children under age 15
7 in 1000 cases have Wilms Tumor46 chromosomesXY or XX
#11 Deletion of upper arm
•The condition results from a deletion on chromosome 11 resulting in the loss of several genes
•Predisposed to Wilms kidney tumor•Mentally handicapped•Severe childhood obesity•Growth retardation•Blindness•Tumors on kidneys•Short lifespan•Missing the iris of the eye
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.
Prader-Willi SyndromePrader-Willi Syndrome
Low muscle toneShort statureIncomplete sexual developmentCognitive disabilitiesProblem behaviorsChronic feeling of hungerObesityShorter lifespan
Eighteen Q Deletion SyndromeEighteen Q Deletion SyndromeSymptoms correlate with the size of the deletionMentally handicappedHeart diseaseAbnormal hands and feetLarge eyesLarge earsNormal lifespan
Cat-Eye SyndromeCat-Eye Syndrome
1 in 1,000,000 births
46 chromosomes
Affects XY or XX
#22 Deletion of bottom arm
Cat-Eye SyndromeCat-Eye Syndrome•Normal to severe malformations•Fused fingers and toes•Mentally handicapped•Small jaw•Heart problems•Normal lifespan
Small headMentally handicappedInternal organ abnormalities90% die before 5 months of age
Jacob’s SyndromeJacob’s Syndrome
1 in 1,800 births
47 chromosomesXYY only
#23 Trisomy Nondisjunction
Jacob’s SyndromeJacob’s Syndrome
Normal physicallyNormal mentallyIncrease in testosteroneMore aggressiveNormal lifespan
?
Klinefelter SyndromeKlinefelter Syndrome
1 in 1,100 births
47 chromosomesXXY only
#23 Trisomy Nondisjunction
Klinefelter SyndromeKlinefelter Syndrome
Scarce beardLonger fingers and armsSterileDelicate skinLow mental abilityNormal lifespan
Triple X SyndromeTriple X Syndrome
1 in 2,500 births
47 chromosomesXXX only
#23 TrisomyNondisjunction
Triple X SyndromeTriple X Syndrome
Normally physically Normal mentallyFertileShort lifespan
Cystic Fibrosis (CF)Cystic Fibrosis (CF)
Clogs the lungs and leads to life-threatening Clogs the lungs and leads to life-threatening lung infections.lung infections.
Obstructs the pancreas and stops natural Obstructs the pancreas and stops natural enzymes from helping the body break down enzymes from helping the body break down food and absorb vital nutrientsfood and absorb vital nutrients
Fluid in lungs, potential respiratory failureFluid in lungs, potential respiratory failure Common among CaucasiansCommon among Caucasians 1 in 20 are carriers1 in 20 are carriers
Therefore is it dominant or recessive?Therefore is it dominant or recessive?
Cystic Fibrosis (CF)Cystic Fibrosis (CF)
MonogenicMonogenic Cause: Cause: deletion of only 3 deletion of only 3
bases on chromosome 7bases on chromosome 7 Estimated in 30,000 Estimated in 30,000
children and adults in children and adults in the U.S.the U.S.
70,000 people 70,000 people worldwideworldwide
Muscular DystrophyMuscular 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)
Huntington’s DiseaseHuntington’s Disease
Huntington's disease Huntington's disease (HD) is an inherited, (HD) is an inherited, degenerative brain degenerative brain disorder which results in disorder which results in an eventual loss of both an eventual loss of both mental and physical mental and physical control. control.
The disease is also The disease is also known as Huntington's known as Huntington's chorea. Chorea means chorea. Chorea means "dance-like movements" "dance-like movements" and refers to the and refers to the uncontrolled motions uncontrolled motions often associated with often associated with the disease. the disease.
Hemophilia, the royal Hemophilia, the royal diseasedisease Hemophilia is the oldest Hemophilia is the oldest
known hereditary known hereditary bleeding disorder.bleeding disorder.
Caused by a recessive Caused by a recessive gene on the X gene on the X chromosome.chromosome.
There are about 20,000 There are about 20,000 hemophilia patients in hemophilia patients in the United States.the United States.
One can bleed to death One can bleed to death with small cuts.with small cuts.
The severity of The severity of hemophilia is related to hemophilia is related to the amount of the the amount of the clotting factor in the clotting factor in the blood. About 70% of blood. About 70% of hemophilia patients hemophilia patients have less than one have less than one percent of the normal percent of the normal amount and, thus, have amount and, thus, have severe hemophilia. severe hemophilia.
ALS ALS (Amyotrophic Lateral (Amyotrophic Lateral Sclerosis, or Lou Gehrig’s Sclerosis, or Lou Gehrig’s disease)disease)
the disease strikes people between the the disease strikes people between the ages of 40 and 70, and as many as ages of 40 and 70, and as many as 30,000 Americans have the disease at 30,000 Americans have the disease at any given time any given time
This monogenic mutation is believed to This monogenic mutation is believed to make a defective protein that is toxic to make a defective protein that is toxic to motor nerve cells. motor nerve cells.
A common first symptom is a painless A common first symptom is a painless weakness in a hand, foot, arm or leg, weakness in a hand, foot, arm or leg, other early symptoms include speech other early symptoms include speech swallowing or walking difficulty swallowing or walking difficulty
Cri-du-chatCri-du-chat Deletion of material on 5Deletion of material on 5thth
chromosomechromosome Characterized by the cat-like Characterized by the cat-like
cry made by cri-du-chat cry made by cri-du-chat babiesbabies
Varied levels of metal Varied levels of metal handicapshandicaps
Sex Chromosome Sex Chromosome AbnormalitiesAbnormalities Klinefelter’s Klinefelter’s
SyndromeSyndrome XXY, XXYY, XXXYXXY, XXYY, XXXY MaleMale SterilitySterility Small testiclesSmall testicles Breast enlargementBreast enlargement
Sex Chromosome Sex Chromosome AbnormalitiesAbnormalities
XYY SyndromeXYY Syndrome Normal male traitsNormal male traits Often tall and thinOften tall and thin Associated with antisocial and behavioral Associated with antisocial and behavioral
problemsproblems
Sex Chromosome Sex Chromosome MutationsMutations
Turner’s SyndromeTurner’s Syndrome XX FemaleFemale sex organs don't sex organs don't
mature at mature at adolescenceadolescence
sterilitysterility short stature short stature
Sex Chromosome Sex Chromosome MutationsMutations
XXXXXX Trisomy XTrisomy X FemaleFemale Little or no visible differencesLittle or no visible differences tall staturetall stature learning disabilitieslearning disabilities limited fertility limited fertility
What’s an Autosome?What’s an Autosome? Autosome: refers to chromosomes 1-22Autosome: refers to chromosomes 1-22
Ex: Autosomal disorders: gene for the disease is found on Ex: Autosomal disorders: gene for the disease is found on chromosomes 1-22chromosomes 1-22
Autosomal Recessive InheritanceAutosomal Recessive Inheritance Must inherit two copies of the disorder to be affectedMust inherit two copies of the disorder to be affected Healthy is dominant (HH or Hh)Healthy is dominant (HH or Hh) Disease is recessive (hh)Disease is recessive (hh) Ex: Cystic fibrosis, PKU, Albinism, Sickle cell anemiaEx: Cystic fibrosis, PKU, Albinism, Sickle cell anemia
Autosomal Dominance InheritanceAutosomal Dominance Inheritance Only need to inherit one copy of the disorder to be affectedOnly need to inherit one copy of the disorder to be affected Disease is dominant (HH or Hh)Disease is dominant (HH or Hh) Healthy is recessive (hh)Healthy is recessive (hh) Ex: Familial hypercholesterolemia (also called FH), Ex: Familial hypercholesterolemia (also called FH),
Disease is dominant (FF or Ff)Disease is dominant (FF or Ff) Homozygous dominant: early death and don’t survive to reproduceHomozygous dominant: early death and don’t survive to reproduce Heterozygous live into adulthoodHeterozygous live into adulthood
Healthy is recessive (ff)Healthy is recessive (ff) ex: Paul has familial hypercholesterolemia and Stacy is healthy. ex: Paul has familial hypercholesterolemia and Stacy is healthy.
The two have 3 children. After testing, the middle child is the The two have 3 children. After testing, the middle child is the only healthy child.only healthy child.
Huntington’s disease is a dominant disorder found on Huntington’s disease is a dominant disorder found on chromosome 4. Betty and Marcus met at a support clinic they chromosome 4. Betty and Marcus met at a support clinic they have been attending to help them cope with the knowledge of have been attending to help them cope with the knowledge of their illness with Huntington’s disease. They would like to know their illness with Huntington’s disease. They would like to know the risk of having a healthy child, now that Betty is pregnant.the risk of having a healthy child, now that Betty is pregnant.
