Unit 4 Study Guide - Karyotype
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Shane Tang © 2008
Unit Four Study Guide Test Format: 10 Multiple Choice 10 True or False 8 Short Answers Karyotypes Y Chromosome in Males •
It basically determines whether one is a male or female. A Y chromosome makes one a male. For a while during development, everyone is hermaphroditic. Around the 7th week, presence or absence of the Y determines what hormones create one and degenerate the other. SRY gene on Y chromosome encodes Testis Determining Factor (TDF).
Difference in polyploidy and aneuploidy •
Polyploidy – It is when one person has extra complete sets of chromosomes (triploidy = 3N, Tetraploidy = 4N). Not compatible at all with human life, but common among plants.
•
Aneuploidy – One or more missing or extra chromosomes. It is almost always incompatible with human life, although some types of human aneuploids are viable.
Writing genetic mutations in karyotypes •
Syndrome, Number of Chromosomes, Sex Chromosomes o (Ex: Klinefelters 47,XXY)
Cri du Chat (Cry of the Cat) •
Caused by the deletion of the short arm of one chromosome #5 and leads to mental retardation, characteristic facial appearance, and gastrointestinal problems. When the baby cries, it sounds like a cat. The eyes are bent inward also.
Connection between Fragile X and Huntington’s disease •
The connection is the repetition of the gene sequence.
Clinical info of Karyotype – sex, # of chromosomes •
There are normally 46 Chromosomes, 44 being autosomes and 2 being sex chromosomes.
Shane Tang © 2008 Chromosomal Address •
Example: 22q11.2 o o o o
Chromosome 22 Q arm (Bigger…because it comes after P in the alphabet) Region 11 Band 2
Types of Karyotypical Analysis – Banding, Coloring, etc. •
The traditional type is called G-band staining. In the classic karyotype, the dye that is used is called Giesma or less frequently Quinacrine. Giemsa is specific for the phosphate groups of DNA. Quinacrine binds to the adenine-thymine-rich regions. Each chromosome has a characteristic banding pattern that helps to identify them; both chromosomes in a pair will have the same banding pattern.
•
Chromosome painting using fluorescent dyes is also a way to visualize chromosomes. o DNA sequences are isolated from different chromosomes and are labeled with different fluorescent dyes. o The labeled sequences are then used to pair with the chromosome from which they were obtained and “paint” those regions. o Using several different DNA sequences and fluorescent dyes produces a unique pattern for each of the 24 types of human chromosomes. o It is easier to detect the labeled regions of the chromosomes this way than with Giesma staining. o Even single genes can be detected using this approach.
•
FISH (Fluorescent In Situ Hybridization) o Specially individually prepared fluorescent “paints” can be applied to each chromosome and if part of it is missing (deleted) or moved (translocated) to another chromosome, its new position can be identified. SKY (Spectral) o Basically the same thing as FISH but with the light spectrum colors.
•
Look over Patau’s Syndrome – aneuploidy condition •
Trisomy 13. Average survival time is 6 months and only 1 in 15,000 live births involve this trisomy.
Nondisjunction causes Aneuploidy •
Failure of chromosome separation (nondisjuntion) in Meiosis 1 or of chromosome separation in Meiosis 2 produces gametes with 22 or 24 chromosomes. Only one chromosome pair is usually involved.
Shane Tang © 2008
•
o Monosomy – 2N – 1 – All Monosomy Autosomal are Lethal o Trisomy – 2N + 1 – Trisomy 13, 18, 21, are ok while rest are lethal. Aneuploidy can occur for almost any chromosome pair. Most aneuploids are spontaneously aborted. Seven types occur in live births, 3 autosomal, and 4 involving the sex chromosomes.
CVS and Amniocentesis •
CVS – CVS or Chorionic villus sampling is a method of sampling fetal chorionic cells by inserting a catheter through the vagina or abdominal wall into the uterus. Used in diagnosing biochemical and cytogenetic defects in the embryo. Usually performed in the eighth or ninth week of pregnancy.
•
Amniocentesis – A method of sampling the fluid surrounding the developing fetus by inserting a hollow needle and withdrawing suspended fetal cells and fluid; used in diagnosing fetal genetic and developmental disorders; usually performed in the sixteenth week of pregnancy.
Differences between pericentric and paracentric •
A pericentric inversion is an inversion of the chromosome that includes the centromere. Ex. -------o--, when the inversion of the last four occurs it is --------o-.
•
A paracentric inversion is an inversion of the chromosome that excludes the centromere. Ex. ----o-----, when the inversion of the last four occurs it is ----o-----.
Shane Tang © 2008 Robertsonian Translocation vs. other types of translocation (Two main types) •
Reciprocal Translocation – It is when two nonhomologous chromosomes exchange parts. No genetic information is gained or lost except for the possibility that a pair of genes affected at the breakpoints. Genes are moved to new chromosomal locations.
•
Robertsonian Translocation – It is individuals with a translocation between chromosome 14 and 21. It produces six sorts of gametes/zygotes (offspring). 1. 2. 3. 4. 5. 6. o
Translocational carrier, chromosome number (45) Normal, chromosome number (46) Translocation Down syndrome, chromosome number (46) Monosomy 21 Lethal, chromosome number (45) Trisomy 14 Lethal, chromosome number (47) Monosomy 14 Lethal, chromosome number (45) Extra info: 5% of all cases of Down syndrome involve this translocation. Chromosomal material is lost from short arms.
Family Situation – become a genetic counselor Dosage Compensation • • •
Dosage compensation through X inactivation. The inactivated X chromosomes are called Barr Bodies. Barr Bodies are only in female nuclei. The female has too much X, so she shuts one down. Lyon’s Hypothesis o One of 2 X chromosomes becomes randomly and irreversibly inactivated during early development and stably inherited to daughter cells. Ex. Consider a cat heterozygous for alleles of X-linked gene o. Genotype = Oo. o O = black coat, o = orange coat (recessive) o When X-inactivation occurs, either O or o allele is on the inactivated X patches of orange and black fur.
Shane Tang © 2008 Go over specific gene that makes you male •
Y chromosome makes a person male.
5 Conditions to Test for Genetic Disorder 1. 2. 3. 4. 5.
Maternal age is over 35 A previous chromosomally abnormal child – recurrence risk is 1 to 2% One parent that carries the chromosomal translocation The woman is heterozygous for a sex-linked recessive gene Both parents are heterozygous for an autosomal recessive mutation in a known location
Know Downs, Klinefelters, Turner, Trisomy •
Down Syndrome – Trisomy 21 or Translocation of 14 and 21. Occurs in 1/900 live births.
•
Klinefelters Syndrome – XXY, Trisomy of 23rd Chromosome.
•
Turners Syndrome – X, Monosomy 23.
•
Trisomy o 13 – Patau’s Syndrome o 18 – Edward’s Syndrome o 23 – XYY Syndrome … Above average in height. Minor effects on mental function and social behavior o 23 – XXX Syndrome … Normal, 1/1000 female births.
Major diseases (chromosome it’s on and major characteristics) •
Huntington’s o Chromosome 4 o Mental Deterioration
•
Rett’s o X Chromosome o Occurs only in females (X lethal) o Holds and grasps their hands a lot
•
Williams o Chromosome 7, deletion on the big arm o Elf like o Overly friendly, and develops phobia
Shane Tang © 2008
•
Zellweger’s o Chromosome 12 o Usually die within first 6 months o Brain damage caused by Iron and Copper o No eyebrows, and Low Muscle Tone
•
Trisomy 18 (Edward’s) o Chromosome 18 o Clenched Hands, Rocker Bottom Feet, Heart Defects, Excess Amniotic Fluid
•
Angelman’s o Chromosome 15, deletion on the big arm o Always happy o Mental Retardation
•
Von-hipper o Chromosome 3 o Tumors from Blood Vessels o Dizziness
•
Tourette’s o Chromosome 13 o Eye Blinking, Clicking Feet, Throat Clearing o Shouting Random Profanity
•
Fragile X o X Chromosome o Long face, Ears that Stick o Mental Retardation and Autism
•
Prader-Willi o Chromosome 15 o Obese, Low Muscle Tone o Mental Disabilities
•
Marfan o Chromosome 15 – FBN1 Gene o Autosomal Dominant o Scoliosis, Really Tall, Average life span is 72
•
Klippel Feil o Chromosome 20, small arm
Shane Tang © 2008 o Short neck, fusion of neck vertebrae •
Maple Syrup Urine Disorder o Chromosome 7, big arm o Mental Retardation, and the Urine smells like Maple Sugar o Autosomal Recessive
Unit Four Study Guide Test Format: 10 Multiple Choice 10 True or False 8 Short Answers Karyotypes Y Chromosome in Males •
It basically determines whether one is a male or female. A Y chromosome makes one a male. For a while during development, everyone is hermaphroditic. Around the 7th week, presence or absence of the Y determines what hormones create one and degenerate the other. SRY gene on Y chromosome encodes Testis Determining Factor (TDF).
Difference in polyploidy and aneuploidy •
Polyploidy – It is when one person has extra complete sets of chromosomes (triploidy = 3N, Tetraploidy = 4N). Not compatible at all with human life, but common among plants.
•
Aneuploidy – One or more missing or extra chromosomes. It is almost always incompatible with human life, although some types of human aneuploids are viable.
Writing genetic mutations in karyotypes •
Syndrome, Number of Chromosomes, Sex Chromosomes o (Ex: Klinefelters 47,XXY)
Cri du Chat (Cry of the Cat) •
Caused by the deletion of the short arm of one chromosome #5 and leads to mental retardation, characteristic facial appearance, and gastrointestinal problems. When the baby cries, it sounds like a cat. The eyes are bent inward also.
Connection between Fragile X and Huntington’s disease •
The connection is the repetition of the gene sequence.
Clinical info of Karyotype – sex, # of chromosomes •
There are normally 46 Chromosomes, 44 being autosomes and 2 being sex chromosomes.
Shane Tang © 2008 Chromosomal Address •
Example: 22q11.2 o o o o
Chromosome 22 Q arm (Bigger…because it comes after P in the alphabet) Region 11 Band 2
Types of Karyotypical Analysis – Banding, Coloring, etc. •
The traditional type is called G-band staining. In the classic karyotype, the dye that is used is called Giesma or less frequently Quinacrine. Giemsa is specific for the phosphate groups of DNA. Quinacrine binds to the adenine-thymine-rich regions. Each chromosome has a characteristic banding pattern that helps to identify them; both chromosomes in a pair will have the same banding pattern.
•
Chromosome painting using fluorescent dyes is also a way to visualize chromosomes. o DNA sequences are isolated from different chromosomes and are labeled with different fluorescent dyes. o The labeled sequences are then used to pair with the chromosome from which they were obtained and “paint” those regions. o Using several different DNA sequences and fluorescent dyes produces a unique pattern for each of the 24 types of human chromosomes. o It is easier to detect the labeled regions of the chromosomes this way than with Giesma staining. o Even single genes can be detected using this approach.
•
FISH (Fluorescent In Situ Hybridization) o Specially individually prepared fluorescent “paints” can be applied to each chromosome and if part of it is missing (deleted) or moved (translocated) to another chromosome, its new position can be identified. SKY (Spectral) o Basically the same thing as FISH but with the light spectrum colors.
•
Look over Patau’s Syndrome – aneuploidy condition •
Trisomy 13. Average survival time is 6 months and only 1 in 15,000 live births involve this trisomy.
Nondisjunction causes Aneuploidy •
Failure of chromosome separation (nondisjuntion) in Meiosis 1 or of chromosome separation in Meiosis 2 produces gametes with 22 or 24 chromosomes. Only one chromosome pair is usually involved.
Shane Tang © 2008
•
o Monosomy – 2N – 1 – All Monosomy Autosomal are Lethal o Trisomy – 2N + 1 – Trisomy 13, 18, 21, are ok while rest are lethal. Aneuploidy can occur for almost any chromosome pair. Most aneuploids are spontaneously aborted. Seven types occur in live births, 3 autosomal, and 4 involving the sex chromosomes.
CVS and Amniocentesis •
CVS – CVS or Chorionic villus sampling is a method of sampling fetal chorionic cells by inserting a catheter through the vagina or abdominal wall into the uterus. Used in diagnosing biochemical and cytogenetic defects in the embryo. Usually performed in the eighth or ninth week of pregnancy.
•
Amniocentesis – A method of sampling the fluid surrounding the developing fetus by inserting a hollow needle and withdrawing suspended fetal cells and fluid; used in diagnosing fetal genetic and developmental disorders; usually performed in the sixteenth week of pregnancy.
Differences between pericentric and paracentric •
A pericentric inversion is an inversion of the chromosome that includes the centromere. Ex. -------o--, when the inversion of the last four occurs it is --------o-.
•
A paracentric inversion is an inversion of the chromosome that excludes the centromere. Ex. ----o-----, when the inversion of the last four occurs it is ----o-----.
Shane Tang © 2008 Robertsonian Translocation vs. other types of translocation (Two main types) •
Reciprocal Translocation – It is when two nonhomologous chromosomes exchange parts. No genetic information is gained or lost except for the possibility that a pair of genes affected at the breakpoints. Genes are moved to new chromosomal locations.
•
Robertsonian Translocation – It is individuals with a translocation between chromosome 14 and 21. It produces six sorts of gametes/zygotes (offspring). 1. 2. 3. 4. 5. 6. o
Translocational carrier, chromosome number (45) Normal, chromosome number (46) Translocation Down syndrome, chromosome number (46) Monosomy 21 Lethal, chromosome number (45) Trisomy 14 Lethal, chromosome number (47) Monosomy 14 Lethal, chromosome number (45) Extra info: 5% of all cases of Down syndrome involve this translocation. Chromosomal material is lost from short arms.
Family Situation – become a genetic counselor Dosage Compensation • • •
Dosage compensation through X inactivation. The inactivated X chromosomes are called Barr Bodies. Barr Bodies are only in female nuclei. The female has too much X, so she shuts one down. Lyon’s Hypothesis o One of 2 X chromosomes becomes randomly and irreversibly inactivated during early development and stably inherited to daughter cells. Ex. Consider a cat heterozygous for alleles of X-linked gene o. Genotype = Oo. o O = black coat, o = orange coat (recessive) o When X-inactivation occurs, either O or o allele is on the inactivated X patches of orange and black fur.
Shane Tang © 2008 Go over specific gene that makes you male •
Y chromosome makes a person male.
5 Conditions to Test for Genetic Disorder 1. 2. 3. 4. 5.
Maternal age is over 35 A previous chromosomally abnormal child – recurrence risk is 1 to 2% One parent that carries the chromosomal translocation The woman is heterozygous for a sex-linked recessive gene Both parents are heterozygous for an autosomal recessive mutation in a known location
Know Downs, Klinefelters, Turner, Trisomy •
Down Syndrome – Trisomy 21 or Translocation of 14 and 21. Occurs in 1/900 live births.
•
Klinefelters Syndrome – XXY, Trisomy of 23rd Chromosome.
•
Turners Syndrome – X, Monosomy 23.
•
Trisomy o 13 – Patau’s Syndrome o 18 – Edward’s Syndrome o 23 – XYY Syndrome … Above average in height. Minor effects on mental function and social behavior o 23 – XXX Syndrome … Normal, 1/1000 female births.
Major diseases (chromosome it’s on and major characteristics) •
Huntington’s o Chromosome 4 o Mental Deterioration
•
Rett’s o X Chromosome o Occurs only in females (X lethal) o Holds and grasps their hands a lot
•
Williams o Chromosome 7, deletion on the big arm o Elf like o Overly friendly, and develops phobia
Shane Tang © 2008
•
Zellweger’s o Chromosome 12 o Usually die within first 6 months o Brain damage caused by Iron and Copper o No eyebrows, and Low Muscle Tone
•
Trisomy 18 (Edward’s) o Chromosome 18 o Clenched Hands, Rocker Bottom Feet, Heart Defects, Excess Amniotic Fluid
•
Angelman’s o Chromosome 15, deletion on the big arm o Always happy o Mental Retardation
•
Von-hipper o Chromosome 3 o Tumors from Blood Vessels o Dizziness
•
Tourette’s o Chromosome 13 o Eye Blinking, Clicking Feet, Throat Clearing o Shouting Random Profanity
•
Fragile X o X Chromosome o Long face, Ears that Stick o Mental Retardation and Autism
•
Prader-Willi o Chromosome 15 o Obese, Low Muscle Tone o Mental Disabilities
•
Marfan o Chromosome 15 – FBN1 Gene o Autosomal Dominant o Scoliosis, Really Tall, Average life span is 72
•
Klippel Feil o Chromosome 20, small arm
Shane Tang © 2008 o Short neck, fusion of neck vertebrae •
Maple Syrup Urine Disorder o Chromosome 7, big arm o Mental Retardation, and the Urine smells like Maple Sugar o Autosomal Recessive
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