Sex-Linked Traits and Sex-Linked Traits and KaryotypesKaryotypes
Pre APPre AP
HemophiliaHemophilia
Read the passage about hemophilia in Read the passage about hemophilia in dogsdogs
Answer the following questions in your Answer the following questions in your Bell Ringer journalBell Ringer journal– Do sex-linked disorders happen in humans Do sex-linked disorders happen in humans
only?only?– Is it important to know if a trait is sex-linked Is it important to know if a trait is sex-linked
or not? Why or why not?or not? Why or why not?– Does it surprise you to find that there are Does it surprise you to find that there are
similar genetic disorders in dogs as humans? similar genetic disorders in dogs as humans? Explain.Explain.
There are traits that are controlled by There are traits that are controlled by one gene with 2 alleles. Often, one is one gene with 2 alleles. Often, one is dominantdominant and the other is and the other is recessiverecessive
Example:Example:
widow’s peaks and dimples.widow’s peaks and dimples.
Some traits are controlled by a gene Some traits are controlled by a gene with with multiple allelesmultiple alleles – 3 or more for – 3 or more for
a single trait. a single trait.
For example: blood types and skin For example: blood types and skin color in humans.color in humans.
There are 44 chromosomes that we There are 44 chromosomes that we call call autosomal chromosomesautosomal chromosomes..
However, there are 2 chromosomes However, there are 2 chromosomes that determine our sex and we call that determine our sex and we call them them sex chromosomes. sex chromosomes.
These 46 chromosomes all carrier These 46 chromosomes all carrier genes on them that determine our genes on them that determine our traits.traits.
Out of our 23 pairs of chromosomes, Out of our 23 pairs of chromosomes, 1 pair is the sex chromosomes (X 1 pair is the sex chromosomes (X and Y).and Y).
Female = XXFemale = XX Male = XYMale = XY
Each egg produced by an ovary contains Each egg produced by an ovary contains one X chromosomeone X chromosome
Each sperm produced by a testicle Each sperm produced by a testicle contains either one X chromosome OR contains either one X chromosome OR one Y chromosomeone Y chromosome
The X chromosome is larger than the Y The X chromosome is larger than the Y chromosome and holds more geneschromosome and holds more genes
Each animal has its own sex Each animal has its own sex chromosomes and sex determination chromosomes and sex determination based on those chromosomesbased on those chromosomes
QuestionQuestion: What is the : What is the probability that your parents probability that your parents will have a boy or girl?will have a boy or girl?
XY (dad) x XX (mom)XY (dad) x XX (mom)
X Y
X
X
XX XY
XX XY
Phenotype:
50% boy
50% girl
Genotype:
50% XX
50% XY
Question?Question?
If my parents have 5 boys in a row, If my parents have 5 boys in a row, what is the chance they will have a what is the chance they will have a girl the next time?girl the next time?
50%
Sex-linked gene:Sex-linked gene:
Some traits are carried on the Some traits are carried on the sex sex chromosomeschromosomes. Genes on the X or Y . Genes on the X or Y chromosomes are chromosomes are sex-linked genessex-linked genes. .
This term is historically used to describe This term is historically used to describe traits housed on the X chromosome traits housed on the X chromosome
These traits are These traits are passes on from parent passes on from parent to childto child. Sex- linked genes can be . Sex- linked genes can be recessive or dominant. recessive or dominant.
MALESMALES are more likely to have a are more likely to have a sex-sex-linked traitlinked trait because they only have because they only have ONE X and YONE X and Y. The allele is . The allele is USUALLYUSUALLY on on the the X chromosomeX chromosome..
Fathers pass on to daughters only; Fathers pass on to daughters only; mothers pass to sons and daughtersmothers pass to sons and daughters
Ex. colorblindness, hemophilia, hairy Ex. colorblindness, hemophilia, hairy ears, muscular dystrophyears, muscular dystrophy
Are you colorblind?
What numbers do you see?
Sex linked Punnett Squares:Sex linked Punnett Squares:Question:Question: What is the probability that a carrier female What is the probability that a carrier female
and a colorblind male will have a girl who is and a colorblind male will have a girl who is colorblind (b = colorblind, B = normal)?colorblind (b = colorblind, B = normal)?
YXb
XB
Xb
XBXb
XbXb XbY
XBY
Phenotype:
25% normal boy
25% colorblind boy
25% normal girl
25% colorblind girl
Try this one on your ownTry this one on your own
Question:Question:
What is the probability that a homozygous What is the probability that a homozygous (normal vision) female and a colorblind (normal vision) female and a colorblind male will have a girl who is colorblind (b = male will have a girl who is colorblind (b = colorblind, B = normal)? colorblind, B = normal)?
XB
XB
XBXb
XBXb XBY
XBY
Xb YPhenotype:
50% normal girls
50% normal boys
Parents: XBXB x XbY
X-InactivationX-Inactivation
Since females have 2 X chromosomes, Since females have 2 X chromosomes, one is inactivatedone is inactivated
During development, each cell of the During development, each cell of the embryo randomly inactivates oneembryo randomly inactivates one
Every cell may have a different X Every cell may have a different X inactivated (ex. Tortoiseshell Cat)inactivated (ex. Tortoiseshell Cat)
Barr-bodies - inactive X chromosomes Barr-bodies - inactive X chromosomes lies along the inside of the nuclear lies along the inside of the nuclear envelopeenvelope
CarrierCarrier – person who has one recessive – person who has one recessive allele and one dominant allele for a allele and one dominant allele for a trait or trait or heterozygousheterozygous for that trait for that trait (only women can be carriers). (only women can be carriers).
Example Example
Hemophiliac carrier XHemophiliac carrier XHHXXhh
Colorblind carrier XColorblind carrier XBBXXbb
Carriers do not show that particular Carriers do not show that particular trait phenotypically but have a chance trait phenotypically but have a chance to pass the trait on to their child.to pass the trait on to their child.
Carrier – half colored
Reading a Pedigree
Task 2:
Go to the lab tables.
Each person should have one answer sheet.
Lets do the first one together.
As a group, finish analyzing the pedigrees. If you have extra time, work on conclusion questions (homework if not completed in class).
Task 1: Genotyping a pedigree chart
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Ticket OutTicket Out
Obtain a paper with a problem that Obtain a paper with a problem that asks you to create your own asks you to create your own pedigree… due on your way out of pedigree… due on your way out of the classroom.the classroom.
What is a karyotype?What is a karyotype? Picture of your Picture of your
chromosomeschromosomes Arranged from largest Arranged from largest
to smallestto smallest quickly identify quickly identify
chromosomal changeschromosomal changes http://http://
www.biology.arizona.ewww.biology.arizona.edu/human_Bio/du/human_Bio/activities/karyotyping/activities/karyotyping/karyotyping2.htmlkaryotyping2.html
Diagnose the karyotypes in the back of the room at your table. Make sure to include:
• Case number
• Boy or girl
• Number of chromosomes
• Normal or abnormal
(if abnormal, what is the problem?)
Genetics Disorders Genetics Disorders and Mutationsand Mutations
Mutations …Mutations …
are changes in the are changes in the genetic materialgenetic material
can be good or badcan be good or bad can be on a single can be on a single
gene or the whole gene or the whole chromosomechromosome
Genetic DisorderGenetic Disorder – – abnormal condition that a person abnormal condition that a person
inherits through genes or inherits through genes or chromosomes. chromosomes.
They are caused by mutations or They are caused by mutations or changes in a person’s DNA.changes in a person’s DNA.
Write down 3 disorders that have affected someone you know.
Cystic FibrosisCystic Fibrosis Recessive genetic disorder where the body produces Recessive genetic disorder where the body produces
abnormally thick mucus in the lungs and intestines making abnormally thick mucus in the lungs and intestines making respiration and digestion difficultrespiration and digestion difficult
Caused by a mutation in a gene. Body produces mucus Caused by a mutation in a gene. Body produces mucus which builds up in the breathing passages of lungs and which builds up in the breathing passages of lungs and pancreas (the organ that helps to break down and absorb pancreas (the organ that helps to break down and absorb food) food)
One in four babies are born with cystic fibrosisOne in four babies are born with cystic fibrosis Most common among Northern European descentMost common among Northern European descent
Sickle Cell AnemiaSickle Cell Anemia Sickle cell is a recessive genetic disorder that Sickle cell is a recessive genetic disorder that
affects the blood’s hemoglobin. Hemoglobin is affects the blood’s hemoglobin. Hemoglobin is the protein in your blood that carries oxygen.the protein in your blood that carries oxygen.
Sickle-cell anemia is caused by a point mutation Sickle-cell anemia is caused by a point mutation in protein chain of hemoglobin, replacing the in protein chain of hemoglobin, replacing the amino acid glutamic acid with the amino acid amino acid glutamic acid with the amino acid valinevaline
The ‘sickle shape’ of the cell causes it to form The ‘sickle shape’ of the cell causes it to form clots easily and the protein doesn’t allow the red clots easily and the protein doesn’t allow the red blood cell to carry very much oxygen.blood cell to carry very much oxygen.
Most common among African American descentMost common among African American descentFamous People with Sickle Cell Disease
Miles Davis, jazz musician. Paul Williams, singer (The Temptations)
Georgeanna Tillman, singer (The Marvelettes) Tionne "T-Boz" Watkins, singer (TLC)
HemophiliaHemophilia Hemophilia is a genetic disorder in which a Hemophilia is a genetic disorder in which a
person’s blood clots VERY slowly or not at all. person’s blood clots VERY slowly or not at all. A person with hemophilia can bleed to death A person with hemophilia can bleed to death
from a paper cut or scrape. from a paper cut or scrape. This is a recessive sex-linked disorder on the X This is a recessive sex-linked disorder on the X
chromosome.chromosome.– Queen Elizabeth suffered from this disorder.Queen Elizabeth suffered from this disorder.
This man received a vaccine. This is what having hemophilia did to is body.
Down SyndromeDown Syndrome Down Syndrome is a genetic disorder Down Syndrome is a genetic disorder
that occurs when an individual receives that occurs when an individual receives an extra copy of a chromosome. an extra copy of a chromosome.
A mistake occurs during Meiosis I: the A mistake occurs during Meiosis I: the chromosomes failed to separate correctly chromosomes failed to separate correctly (non-disjunction) therefore leaving an (non-disjunction) therefore leaving an extra copy of chromosome #21. extra copy of chromosome #21.
Doctor’s use tools like Doctor’s use tools like amniocentesisamniocentesis and and karyotypeskaryotypes to to helphelp detect detect most diseases.most diseases.
4 Types of Genetic 4 Types of Genetic DisordersDisorders
1. Single gene1. Single gene – Change in the DNA sequenceChange in the DNA sequence– More than 6000 known disordersMore than 6000 known disorders– Autosomal or sex linkedAutosomal or sex linked– 1 in 200 births1 in 200 births
Examples:Examples: cystic fibrosis, sickle cell anemia, cystic fibrosis, sickle cell anemia,
Marfan syndrome, Huntington’s disease Marfan syndrome, Huntington’s disease
Types of Genetic DisordersTypes of Genetic Disorders
2. Multi-factoral2. Multi-factoral– combination of environmental factors combination of environmental factors
and mutations in multiple genes and mutations in multiple genes – more complicated more complicated
Examples:Examples:
heart disease, high blood pressure, heart disease, high blood pressure, Alzheimer’s disease, arthritis, diabetes, Alzheimer’s disease, arthritis, diabetes, cancer, and obesity cancer, and obesity
Types of Genetic DisordersTypes of Genetic Disorders
3. Chromosomal3. Chromosomal– abnormalities in chromosome structure abnormalities in chromosome structure
as missing or extra copies or gross as missing or extra copies or gross breaks and rejoining breaks and rejoining
Example:Example:
Down SyndromeDown Syndrome
Types of Genetic DisordersTypes of Genetic Disorders
4. Mitochondrial4. Mitochondrial– rare type of genetic disorder rare type of genetic disorder – caused by mutations in the non-caused by mutations in the non-
chromosomal DNA of mitochondria chromosomal DNA of mitochondria
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Here are some genetics disorders, some you have heard about and some you haven’t.
Turners SyndromeTurners Syndrome
1 in 5,000 births
45 chromosomesX only #23 MonosomyNondisjunction
Turners SyndromeTurners Syndrome
96-98% do not survive to birthNo menstruationNo breast developmentNo hipsBroad shoulders and neck
Cri-Du-Chat Cri-Du-Chat SyndromeSyndrome
1 in 216,000 births
46 chromosomesXY or XX
#5 Deletion of lower arm
Cri-Du-Chat SyndromeCri-Du-Chat Syndrome
Moon-shaped faceHeart diseaseMentally retardedMalformed larynxNormal lifespan
Aniridia-Wilms Tumor Aniridia-Wilms Tumor SyndromeSyndrome
1 in 50,000,000 births
46 chromosomesXY or XX
#11 Deletion of upper arm
Aniridia-Wilms Tumor SyndromeAniridia-Wilms Tumor Syndrome
Mentally retardedGrowth retardedBlindnessTumors on kidneysShort lifespan
Thirteen Q Deletion Thirteen Q Deletion SyndromeSyndrome
1 in 500,000 births
46 chromosomesXY or XX
#13 Deletion of lower arm
Thirteen Q Deletion SyndromeThirteen Q Deletion Syndrome
Mentally retardedDeformed faceNo thumbsHeart diseaseShort lifespan
Prader-Willi Prader-Willi SyndromeSyndrome
1 in 5,000,000 births
46 chromosomesXY=97% XX=3%
#15 Deletion of lower arm
Prader-Willi SyndromePrader-Willi Syndrome
Small bird-like headMentally retardedRespiratory problemsObesityShort lifespan
Eighteen Q Deletion Eighteen Q Deletion SyndromeSyndrome
1 in 10,000,000 births
46 chromosomesXY or XX
#18 Deletion of lower arm
Eighteen Q Deletion SyndromeEighteen Q Deletion Syndrome
Mentally retardedHeart diseaseAbnormal hands and feetLarge eyesLarge earsNormal lifespan
Cat-Eye SyndromeCat-Eye Syndrome
1 in 1,000,000 births
46 chromosomesXY or XX
#22 Deletion of bottom arm
Cat-Eye SyndromeCat-Eye Syndrome
Fused fingers and toesMentally retardedSmall jawHeart problemsNormal lifespan
Four-Ring SyndromeFour-Ring Syndrome
1 in 10,000,000 births
46 chromosomesXY or XX
#4 Inversion
Four-Ring SyndromeFour-Ring Syndrome
Cleft palateClub feetTestes don’t descendShort lifespan
1 in 1,250 births
47 chromosomesXY or XX
#21 Trisomy Nondisjunction
Down Syndrome Trisomy
Down SyndromeDown Syndrome
Short, broad hands Stubby fingersRough skinImpotency in malesMentally retardedSmall round faceProtruding tongueShort lifespan
Patau’s Trisomy Patau’s Trisomy SyndromeSyndrome
1 in 14,000 births
47 chromosomesXY or XX
#13 Trisomy Nondisjunction
Patau’s Trisomy SyndromePatau’s Trisomy Syndrome
Small headSmall or missing eyesHeart defectsExtra fingersAbnormal genitaliaMentally retardedCleft palateMost die a few weeks after birth
Edward’s Trisomy Edward’s Trisomy SyndromeSyndrome
1 in 4,400 births
47 chromosomesXX=80%
XY=20%
#18 Trisomy Nondisjunction
Edward’s Trisomy SyndromeEdward’s Trisomy Syndrome
Small headMentally retardedInternal 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
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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 mentallyFertile
Huntington’s DiseaseHuntington’s Disease Caused by a lethal dominant gene in Caused by a lethal dominant gene in
which a section of DNA on chromosome which a section of DNA on chromosome #4 is repeated more than usual#4 is repeated more than usual
Nerve cells in the brain waste away, or Nerve cells in the brain waste away, or degeneratedegenerate
Two forms – most common is adult onset Two forms – most common is adult onset in which those affected show no signs in which those affected show no signs until 35 or 40; other is early onsetuntil 35 or 40; other is early onset
Huntington’s DiseaseHuntington’s Disease Abnormal and unusual movements Abnormal and unusual movements Behavior changes Behavior changes Dementia that slowly gets worse, including Dementia that slowly gets worse, including Additional symptoms that may be associated Additional symptoms that may be associated
with this disease:with this disease:– Anxiety, stress, and tension Anxiety, stress, and tension – Difficulty swallowing Difficulty swallowing – Speech impairmentSpeech impairment
In children:In children:– Rigidity Rigidity – Slow movements Slow movements – TremorTremor
Color-BlindnessColor-Blindness Have trouble seeing red, green, or blue or Have trouble seeing red, green, or blue or
a mix of these colors a mix of these colors Caused by a recessive sex-linked alleleCaused by a recessive sex-linked allele The cone cells in your eyes do not The cone cells in your eyes do not
function properly or are absentfunction properly or are absent You may not see red, blue, or green, or You may not see red, blue, or green, or
you may see a different shade of that you may see a different shade of that color or a different colorcolor or a different color
Doesn't change over time. Doesn't change over time.
Color-BlindnessColor-Blindness
Tay-sachsTay-sachs
Autosomal recessive disorder because of Autosomal recessive disorder because of mutation on chromosome 15mutation on chromosome 15
Infants typically appear normal until 3 to Infants typically appear normal until 3 to 6 months:6 months:
Other forms of Tay-Sachs disease are Other forms of Tay-Sachs disease are very rare.very rare.
Tay-sachs DiseaseTay-sachs Disease– development slows and muscles used for movement development slows and muscles used for movement
weakenweaken– lose motor skills such as turning over, sitting, and crawlinglose motor skills such as turning over, sitting, and crawling– develop an exaggerated startle reaction to loud noisesdevelop an exaggerated startle reaction to loud noises– Eventually experience seizures, vision and hearing loss, Eventually experience seizures, vision and hearing loss,
intellectual disability, and paralysisintellectual disability, and paralysis– eye abnormality called a cherry-red spot, which can be eye abnormality called a cherry-red spot, which can be
identified with an eye examination, is characteristic of this identified with an eye examination, is characteristic of this disorder. disorder.
– Children with this severe infantile form of Tay-Sachs Children with this severe infantile form of Tay-Sachs disease usually live only into early childhood.disease usually live only into early childhood.
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Diagnose the karyotypes cont. You have already described what is abnormal (if applicable) about the karyotypes, now you must identify what genetic disorder (if any) is portrayed using the knowledge you just received.