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105 Cards in this Set
- Front
- Back
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Diploid
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all cells except gametes “somatic cells” = 46 chromosomes or 23 pairs
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Haploid
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Gametes – 23 chromosomes from sperm or egg
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Somatic Cell
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All cells except gametes
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Gametes
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Sex cells
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Mitosis
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Cell division - somatic cell replicates itself into two daughter cells w/ 46 chromosomes
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Meiosis
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Parents cell into 4 daughter cells with 23 chromosomes
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Homologous Chromosomes
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Corresponding Chromosomes, one from each parent which contain the same linear genes
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Autosomes
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The first 22 pairs of homologous chromosomes
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Sex chromosomes
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The 23rd pair of chromosomes, XX or XY unless abnormal
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Karyotype
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The ordered display of chromosomes, showing all autosomes and sex chromosomes
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Male or female?
XXXY |
Male
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Male or female?
XXXX |
Female
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What gene on what chromosome determines gender?
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The SRY gene on the Y chromosome
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What is the name for this abnormal chromosome number? (69 or 92)
Abnormal chromosome # |
Polyploidy
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The specific name for this number of chromosomes?
69 |
Triploidy
* on all 23 |
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The specific name for this number of chromosomes?
92 |
Tetraploidy
* on all 23 |
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A somatic cell (non-gamete) that does not contain a multiple of 23 chromosomes (i.e., has one or two missing or extra chromosomes)
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Aneuploidy
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Three chromosomes instead of two in one place EX: Downs Syndrome
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Trisomy
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One chromosome instead of two
Ex: Turners Syndrome |
Monosomy
XO |
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What causes aneuploidy?
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Nondisjunction during Meiosis I or II:
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Among the autosomes, Monosomy of any chromosome=
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Lethal
ie., stillborn or spontaneously aborted |
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Monosomy among the sex chromosomes =
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Survival if X
No Survival if Y |
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Trisomy of the autosomes=
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Life if on 21 = Downs Syndrome
Non-survival otherwise |
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Triploidy of the autosomes=
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Non Survival
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Triploidy of sex chromosomes =
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XXX, XXY, or XYY
Survival, possibility of developmental issues or mosaicism |
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Tetraploidy of autosomes=
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No survival
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Tetraploidy of sex chromosomes=
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Survival
Ex: the Super Female XXXX |
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What is the genotype of persons living with Down’s syndrome?
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Trisomy 21
or 47,XY,+21 |
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What is the phenotype of persons living with Down’s syndrome?
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Usually smaller in stature, slanted eyes, depressed nasal bridge, smaller ears, mouth, hands and feet
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What are the major health concerns with Down’s syndrome?
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*congenital heart disease (septal)
*Intestinal abnormalities *Hypothyroidism *Atlanto-Axial Instability *High risk of early onset Alzeheimers *Inferior cardiopulmonary strength/fx |
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Is Down’s syndrome an example of autosomal aneuploidy or sex chromosome aneuploidy?
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Autosomal aneuploidy of the twenty first chromosome
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What does this mean?
47,XX,+21 |
The genotype of a female person with Trisomy 21
Or Down’s syndrome |
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What is the most common kind of chromosomal mosaicism?
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Trisomy mosaicism
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How does Trisomy mosaicism differ from a person with complete DS in terms of # of chromosomes in each cell of the body & symptom/severity
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A. Normal/Abnormal cells found in most tissues
B. Normal/Abnormal cells confined to specific tissues *Mosaic DS usually less severe of a conditon!! |
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At what age does the risk of having a child with DS increase exponentially?
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35
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What age is considered the threshold for a screening test for DS?
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35
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Are the number of babies born with DS greater for women below or above 35?
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Below b/c most women have children before 35
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Which of the following female chromosomal aneuploidy would have the most severe mental and physical disabilities?
XXX, XXXX, XXXXX |
XXXXX : more often mentally retardation and various physical defects.
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In Turners syndrome, why do the ovaries not develop?
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Because there is only one X chromosome leaving out the emphasis on female reproductive development
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What affect does no ovary development from Turners have on puberty?
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Do not produce adequate amounts of estrogen and progesterone = delayed or absent puberty
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What affect does no ovary development from Turners have on stature?
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Small in stature
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Turners Syndrome affects on Uterus and vagina?
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Uterus and vagina are normal
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Turners syndrome affects on Mental capacity?
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Normal mental capacity
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What is usually the treatment for Turners syndrome when a girl nears 10yrs?
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Low dose growth hormones
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What is the usual treatment for Turners when a girl reaches 13-14?
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Estrogen
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Usual treatment throughout life for Turners syndrome women?
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Continue with estrogen to maintain feminization and to prevent osteoporosis
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When considering XYY, what effect does this male aneuploidy have on IQ?
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May have a learning disability, delayed speech, language skills and developmental milestones
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What effect does SYY have on inclination to commit violent crimes?
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None, bad science
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What effect does XYY have on Behavioral disorders?
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May be hyperactive or ADHD but with good nurturing environment = fine
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What is the genotype of Klinefelter’s syndrome?
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47,XXY
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What is meant by “eunuchoid body” proportions and what causes it in Klinefelter’s?
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*Eunuchoid body – Male and female body patterns b/c of mosaicism.
*Extra X causes it |
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What treatement of Kleinfelter’s will improve the physical and 2ndary sex characteristics?
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Regular injections of testosterone
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What treatment of Kleinfelter’s will improve developmental disabilities?
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Early childhood intervention
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What can and cannot be diagnosed with ultrasound?
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Can determine visual abnormalities only such as spina bifida and malformations of face, head, body and limbs
Cannot determine biochemical or chromosomal alterations |
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What can and cannot be diagnosed with amniocentesis?
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Can determine spina bifida, anencephaly, lung maturity, enzyme activity, toxoplasmosis and chromosome abnormalities including markers for genes and diseases
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What can and cannot be diagnosed with chronic villus biopsy?
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Can determine spina bifida, anencephaly, enzyme activity, toxoplasmosis and chromosome abnormalities at a much earlier time than amniocentesis but…
Cannot find neural tube defects or lung maturity |
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What can be measured or diagnosed with the supernatant fluid?
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Levels of alfa-fetal protein to test for spina bifida or anencephaly and levels of surfactant to determine lung maturity
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What does high levels of alpha-fetoprotein indicate?
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Neural tube defects such as spina bifida or anencephaly
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What are the two advantages of chronic villus sampling over amniocentesis?
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*Results available in hours
*preformed in 1st trimester instead of later *early = more acceptable decisions of termination *early termination = safer for mother |
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What are the risks of chronic villus sampling over amniocentesis?
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*Cannot determine neural tube defects
*Cannot determine lung maturity *High risk of miscarriage or digital or limb deficiency caused by test |
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How can crossing over cause deletions and additions of genetic material within the homologous chromosomes?
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Crossing over can be even or uneven. If even they exchange evenly, if uneven, one set has extra while the other has deletions of important genetic material
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Compare crossing over to translation.
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Crossing over is between two homologous pairs of chromosomes and translocation is between two non-homologous pairs
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What is reciprocal translocation and how can it produce deletions and additions of genetic material in gametes?
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Crossing over can be even or uneven. If even translocation they exchange evenly, if uneven, one set has extra while the other has deletions of important genetic material
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The extent of chromosome breakage is increased in the presence of clastogens. What are clastogens and give examples.
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Clastogens are substances that increase the # of breaks in chromosomes that result in the gain, loss, or rearrangement of chromosome segments.
Ex: Ionizing radiation, extreme heat, and certain chemicals (tobacco, benzene, etc) |
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What would be more lethal, a child born with additional chromosome material or minus the normal amount?
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a child born with less than the normal amount of chromosome material is more lethal
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Explain cri-du-chat syndrome(ie., cause and symptoms)
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Cause – deletion of chromosome 5 caused by point mutations
Symptoms – cries sound like a cat, delayed motor development, small head |
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Using the genes for the condition of phenylketonuria, explain dominant and recessive alleles
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P= dominant (produces enzyme)
p = recessive, does not produce enzyme PP – functional PAH enzyme Pp – functional PAH enzyme pp – non-fx PAH = disease genotype |
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Show the homozygous genotype for phenylketonuria?
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pp or PP
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What is the relation of environment to phenotype in phnylketonuria?
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A child born with PKU can be spared the disease condition (phenotype) by proper diet
The environment directly effects the phenotype but not genotype |
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Explain Dominance, Recessiveness and co-dominance in terms of the ABO blood type
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Blood types A & B are dominant over O, whereas A and B are co-dominant.
Therefore O is recessive to A&B blood types |
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A couple both have an Autosomal dominant disease (both heterozygous), what is the risk of their first child having the disease?
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75%
see Pg 96 Lecture notes |
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A couple both have an Autosomal dominant disease (both heterozygous), what is the risk of their second child NOT having the disease?
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25%
see Pg 96 Lecture notes |
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For a couple, the husband has an Autosomal dominate disease (heterozygous) but the wife does not. If their first child is male, what is the risk that he will have the disease?
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50%
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For a couple, the husband has an Autosomal dominate disease (heterozygous) but the wife does not. If their second child is female, what is the risk that she will have the disease?
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50%
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Explain how the following conditions allow Autosomal dominant diseases to stay within the gene pool of a population and give an example of each: delayed age of onset; penetrance; and expressivity
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Because males and females are equally affected and effected parent could have been masked by delayed onset (huntingtons disease), penetrance (having but not expressing the disease)and expressivity (the variation of the severity of the disease) like Type 1 neurofibromatosis
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An Autosomal dominant disease has 90% penetrance, What does that mean?
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That 90% of the individuals whom have the disease show the phenotype of the disease but the other 10% that have it don’t express it and may think that they don’t have it or can’t spread it
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For an Autosomal recessive disease, the husband is a carrier and the wife is homozygous normal. If they have a child, what is the chance of that child to be normal?
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100%
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For an Autosomal recessive disease, the husband is a carrier and the wife is homozygous normal. If they have a child, what is the chance of that child to be born with the disease?
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0%
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For an Autosomal recessive disease, the husband is a carrier and the wife is homozygous normal. If they have a child, what is the chance of that child to be a carrier?
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100%
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For an Autosomal recessive disease, both husband and wife are carriers. If the first child is a girl, what is her risk of having the disease?
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25%
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For an Autosomal recessive disease, both husband and wife are carriers. If the first child is a girl, what is her risk of being a carrier?
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50%
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For an Autosomal recessive disease, both husband and wife are carriers. If the first child is a girl, what is her risk of being homozygous normal?
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25%
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For an X linked recessive disease, the husband is normal and the wife is a carrier. What is the risk of a male child with the disease?
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50%
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For an X linked recessive disease, the husband is normal and the wife is a carrier. What is the risk of a female child with the disease?
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0%
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For an X linked recessive disease, the husband is normal and the wife is a carrier. What is the risk of a male child without the disease?
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50%
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For an X linked recessive disease, the husband is normal and the wife is a carrier. What is the risk of a female child without the disease?
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100%
*although she has 50% chance of being a carrier |
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For an x-linked recessive disease, the husband has the disease (he is red-green color blind) and the wife is a carrier. What is the risk of a male child with the disease?
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50%
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For an x-linked recessive disease, the husband has the disease (he is red-green color blind) and the wife is a carrier. What is the risk of a female child with the disease?
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50%
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For an x-linked recessive disease, the husband has the disease (he is red-green color blind) and the wife is a carrier. What is the risk of a male child without the disease?
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50%
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For an x-linked recessive disease, the husband has the disease (he is red-green color blind) and the wife is a carrier. What is the risk of a female child without the disease?
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50%
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For X linked inheritance, explain the term “hemizygous”?
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Hemizygous for X-linked diseases means that males (having only one X) are more susceptible to x linked diseases because they have no “back up” to offset it. If it is dominant or recessive and X linked and they get it, it is expressed.
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Is the Fragile X syndrome a dominant or recessive condition?
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X linked dominant but mosaic is possible for females
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The absence of the fragile-X (FMR1) gene has what result?
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Mental retardation
*bc the lack of it shuts off production of protein needed for normal cognitive development |
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For Fragile-X, what is the genotype of a female permutation carrier for the FMR1 gene?
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x-50 x-300
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For Fragile-X, what is the genotype of a full mutation carrier for the FMR1 gene?
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x-500 x-500
x-50 x-500 - mosaic female x-500 Y |
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What is the root cause of the fragile X syndrome?
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Over 200 repeats = Methylation = turns off the gene and production of FMR1 for normal mental capabilities= intellectual disabilities
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Fragile X syndrome, the husband has 10 copies and the wife has one x with 35 copies and the other with 400 copies of the repeat. What is the chance of having a male child with the condition?
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50%
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Fragile X syndrome, the husband has 10 copies and the wife has one x with 35 copies and the other with 400 copies of the repeat. What is the chance of having a female child with the condition?
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50%
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What are the two main factors of Multifactoral inheritance?
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1.The majority of human diseases cannot be explained by Medelian genetics (dominant vs recessive)
2. The majority of human genetic disorders are the result of multifactorial inheritance. |
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Compare Medelian genetic diseases to polygenic diseases
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Medelian diseases = diseases caused by single genes
Polygenetic diseases = many sets of genes (alleles) contributing to disease by an additive nature and influenced by environmental factors |
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Define Multifactorial inheritance.
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Multifactorial inheritance – polygenic inheritance, additive in nature not dominant vs recessive and influeced by environmental factors
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Using the polygenic alleles for diabetes as given in the syllabus, differentiate between “bad” alleles and “good” alleles.
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Good Genes:
D-2, D-1, D0 = decreases the risk or does not increase the risk for DM Bad Genes: D+1, D+2 – increases the risk for DM by +1 or +2 |
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What is the main environmental factor that influences the development of DM2?
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Lifestyle factors:
1. Obesity (BMI>30 2. Sedentary lifestyle |
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What are the two factors that together are considered a single entity known as liability for DM2?
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Reaching The genetic and environmental threshold:
1. Genetic threshold: +2 total increments on the 4 alleles 2. BMI >30 |
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How do the Pima Indians exemplify multifactorial inheritance?
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They already meet the genetic threshold so when they reach the lifestyle threshold as many do = high prevalence of DM
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