Ch. 26 - Genomics

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who are genetic counselors

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Biology

10th

100 Terms

1

who are genetic counselors

people that help individuals understand modes of inheritance and medical consequences of genetic disorders

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2

what is karyotyping

a visual display of someone’s chromosomes

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3

what is amniocentesis

a prenatal test

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4

what occurs in amniocentesis?

a sample of amniotic fluid is collected so fetal cells can be isolated and analyzed

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5

what is the chance of spontaneous abortion in amniocentesis

0.25 - 0.5%

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6

how does chromosome numbers change

nondisjunction

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7

what is a trisomy

an extra chromosome is carried by an egg or sperm

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8

what is a monosomy

an egg or sperm that lacks a chromosome

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9

what does an extra copy of chromosome 21 account for

down syndrome

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10

extra copies of gart genes = ?

more purines in the body

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11

what are characteristics of down syndrome

short stature, enlarged tongue, distinct palm crease

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12

what can cause chromosomes to break apart

radiation, certain chemicals, and some viruses

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13

what is williams syndrome

a chromosome deletion where chromosome 7 loses an end piece

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14

what are the symptoms of williams syndrome

individuals have a turned up nose and a wide mouth with small chin with poor academic skills but amazing verbal and musical skills

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15

what is cri du chat syndrome

a chromosome deletion where chromosome 5 loses an end piece

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16

what are the symptoms of cri du chat syndrome

small head, mental disabilites, cat-like cry

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17

what is chromosomal duplication

when chromosome segment is repeated in same or nonhomologous chromosome

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18

what can also occur to a duplicated chromosome

it can be in an inverted direction - inversion

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19

what is inversion

segment is turned 180 degrees

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20

what does inversion lead to

altered gene activity in crossing-over

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21

what can inversion result in

duplication and deletion when inverted segments loop in crossing-over

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22

what is chromosomal translocation

the exchange of chromosomal segments between two nonhomologous segments

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23

what is alagille syndrome

translocation between chromosomes 2 and 20

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24

what are family pedigrees

chart of family’s history

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25

what are males indicated on pedigrees

squares

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26

what are females indicated on pedigrees

circles

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27

what does shaded shapes mean in pedigrees

individual is affected by disorder

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28

how can we tell if a pedigree is autosomal recessive?

  • most affected children have unaffected parents

  • heterozygotes (Aa) have an unaffected phenotype

  • two affected parents will always have affected children

  • affected individuals with homozygous unaffected mates will have unaffected children

  • close relatives who reproduce are more likely to have affected children

  • both males and females affected with equal frequency

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29

how can we tell if a pedigree is autosomal dominant

  • affected children will usually have an affected parent

  • heterozygotes (Aa) are usually affected

  • two affected parents can produce an unaffected child

  • two unaffected parents will not have affected children

  • both males and females affected with same frequency

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30

in pedigrees for x-linked disorders, how can a daughter be affected?

must inherit it from both parents

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31

in pedigrees for x-linked disorders, how can sons be affected?

only inherit it from mother, therefore more males affected than females

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32

in y-linked disorders, how can sons be affected

fathers pass trait to all sons (present in only males)

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33

how can we tell if a x-linked pedigree is recessive

  • more males than females affected

  • affected son can have parents who have normal phenotype

  • for a female to have the characteristic, father must have it and mother must have it or carrier

  • the characteristic often skips a generation from the grandfather to the grandson

  • if a woman has characteristic, all sons will have it

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34

what are 4 autosomal recessive disorders

  • tay-sachs disease

  • cystic fibrosis

  • phenylketonuria

  • sickle-cell disease

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35

what is tay-sachs disease

lack of hex A enzyme and symptoms appear in the first year of life

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36

what does tay-sachs disease cause

defective lysosomes (especially in the brain)

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37

what is cystic fibrosis

defect in chloride channel proteins in cells (most common genetic disorder for caucasian males in the us)

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38

what does cystic fibrosis cause

thick, abnormal mucus production in lungs, bronchial tubes, and pancreatic ducts

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39

what is phenylketonuria

lack enzymes for phenylanine (1 of 20 amino acids) metabolism

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40

what does phenylketonuria affect

nervous system development (can be controlled with diet)

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41

what is sickle-cell anemia

irregular red blood cells caused by abnormal hemoglobin

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42

what does sickle-cell anemia cause/do

clog vessels - poor circulation and internal hemorrhaging

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43

heterozygous individuals are normal until?

dehydrated or experience mild oxygen deprivation

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44

what are 2 autosomal dominant disorders

marfan syndrome and huntington disease

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45

what is marfan syndrome

a defect in fibrillin-protein in elastic connective tisuse

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46

what does marfan syndrome

long limbs and fingers, weakened arteries, dislocated lenses in the eyes

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47

what is huntington syndrome

progressive degeneration of brain cells

gene for defective protein called huntington

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48

what does huntington syndrome

too many copies of the amino acid glutamine in the protein causes it to change shape and clump in neurons

encourages other proteins to clump

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49

what is familial hypercholesterolemia

incompletely dominant disorder that affects the number of LDL (low-density lipoproteins)-cholesterol receptors on cells

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50

what does familial hypercholesterolemia lead to

high cholesterol and cardiovascular

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51

what would being homozygous for defective gene mean (familial hypercholesterolemia)

have no LDL-cholesterol receptors and develops cardiovascular disease and die as a child or in teenage years

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52

what would being heterozygous for defective gene mean (familial hypercholesterolemia)

would have half the normal amount of LDL-cholesterol receptors and live longer

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53

what would being homozygous for normal gene mean (familial hypercholesterolemia)

normal number of receptors

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54

what percentage of caucasian males have red-green colourblindness

8%

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55

what is duchene’s muscular dystrophy

x-linked recessive disorder that has the absence of a protein called dystrophin

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56

what does duchene’s muscular dystrophy cause

causes calcium to leak into muscle cells which activates enzymes that break down the cells

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57

what is hemophilia A

a lack of clotting factor VIII

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58

what is hemophilia B

a lack of clotting factor IX

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59

what does hemophilia cause

blood clotting to go slow or not at all - can bleed externally or internally leading to hemorrhaging or death (clotting factors are now available)

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60

how do mutations lead to disorders

caused by a missing enzymes

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61

what does tay-sachs disease test for

quantity of hex A enzyme present in a sample of cells

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62

what can a tay-sachs disease test determine

if individual is homozygous normal, a carrier, or has Tay-sachs

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63

what is the PKU test

test done on newborns to determine the presence of phenyalanine

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64

what are 3 ways to test DNA for genetic disorders

genetic markers, dna probes, dna chip

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65

how do we test DNA with genetic markers

in genetic markers, restriction enzymes cleave DNA

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66

what disorder does genetic markers test for

huntington disease

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67

how do we test DNA with dna probes

a DNA probe (single stranded piece of DNA) binds to complementary DNA

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68

in genetic testing, what do dna probes typically have

mutation of interest

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69

how do we test DNA with dna chip

tagging person’s DNA with fluorescent dye and convrted to single stranded DNA before being applied to the chip

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70

what occurs on the dna chip during testing

mutated genes bind if present and are detected by laser scanner

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71

how do we test a fetus

ultrasound

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72

what is an ultrasound

high frequency sound waves used to produce an image

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73

when are fetal cells tested for in amniocentesis

15 weeks of gestation (process or period of development inside womb between contraception and birth)

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74

what can amniocentesis also test for

alpha fetoprotein which can indicate neural tube defects

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75

when can fetal cells be tested during chorionic villi sampling

earlier than amniocentesis (no amniotic fluid taken so cannot test for afp

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76

how can fetal cells in mothers blood be tested

when a small number of fetal cells enters the mother’s blood

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77

how can an embryo be tested

at the 8-cell stage following in vitro fertilization

  • only “normal” embryos are tested

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78

how are eggs tested

by testing the polar bodies of women who are heterozygous prior to in vitro fertilization

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79

if a polar body is defected, what occurs to the ovum

ovum is normal

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80

what is genomics

study of genomes

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81

what is a genome

complete set of DNA in an organism

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82

how many genomes do humans have

20,000 - 25,000

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83

what is the human genome project

a project that wanted to sequence all of the base pairs in all of the DNA of human chromosomes

  • also revealed that humans probably have 20,000 - 25,000 genomes

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84

what was the objective of the hapmap project

to catalog common sequence differences that occur in humans so scientists can link haplotypes to the risk of specific illnesses

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85

what are haplotypes

patterns of sequence differences

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86

what are proteomics

study of structure, function, and interaction of cellular proteins

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87

what is a proteome

translation of all human genes resulting in a collection of proteins

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88

how does the info computer modeling provide about the shape of proteins help

allows for greater understanding of how they work and increased efficiency of drugs

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89

what is bioinformatics

application of computer technologies to the study of genome

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90

what occurs in bioinformatics

an analysis of data produced by genomics and proteomics

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91

what is the human genome described as

three-dimensional

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92

what is the first dimension of the human genome

the sections of DNA that codes for proteins (accounts for less than 2% of DNA)

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93

what is the second dimension of the human genome

“junk DNA” that may code for RNA

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94

what is the third dimension of the human genome

outside layer that surrounds DNA and consists of proteins and other chemicals

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95

what is gene therapy

insertion of genetic material into human cells for treatment of a disorder

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96

what is vivo gene therapy

when cells are removed from the patient and those cells are treated outside the body then returned back

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97

what is an example of vivo gene therapy

SCID (severe combined immunodeficiency) and cystic fibrosis

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98

what occurs in vivo gene therapy

patient is given a foreign gene directly through viruses or lipoprotein vesicles

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99

where is the foreign gene of vivo gene therapy incorporated within

the genome within the body

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100
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