Exam 1: Ch 6 Flashcards Preview

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Flashcards in Exam 1: Ch 6 Deck (84):
1

__ pairs of autosomes

22

2

__ pairs of sex chromosomes

1 pair

3

genetic diseases are caused by...

mutations in DNA sequence

chromosome-level abnormalities

4

gene

DNA that codes for a protein

5

locus

gene location on a chromosome

6

allele

alternate version of a gene

7

homozygoes

2 identical alleles for a gene

8

heterozygous

2 different alleles for a gene

9

genotype

genetic composition

dictates phenotype

10

phenotype

observable trait/characteristic

11

dominant traits

traits that are expressed in heterozygous

only need one dominant allele to be expressed

12

recessive traits

traits expressed only in the homozygote with 2 recessive alleles

13

co-dominant

both alleles are expressed in the heterozygote

ex. blood type... A,B are codominant

14

how many alleles for blood type?

3

A, B, O

15

blood type genotypes and phenotypes

AA, AO = type A

BB, BO = type B

OO = type O

AB = type AB

16

single gene disorder

mutation in 1 gene

autosomal or sex-linked

17

sex-linked disorder

almost always on X chromosome and generally recessive

18

Punnett square mom/dad

mom's alleles are horizontal

dad's alleles are vertical

19

can you use the term carrier to describe dominant traits?

no, b/c 1 dominant allele gives you the trait

20

examples of autosomal dom. disorders

achondroplasia

adult polycystic kidney disease

huntington chorea

familial hypercholesterolemia

marfan syndrome

neurofibromatosis (NF)

21

examples of autosomal recessive disorders

cystic fibrosis

oculocutaneous albanism

phenylketonuria (PKU)

sickle cell disease

tay sachs disease

22

examples of x-linked recessive disorders

hemophilia A

R/G colorblindness

Fragile X

Bruton type hypogammaglobulinemia

Duchenne dystrophy

23

autosomal dominant disorders

single mutant allele inherited from either parent --> disease

commonly involve abnormal structural or developmental proteins

transmission equally likely to male/female children

24

variable penetrance

not everyone who gets the gene expresses it

25

variable expressivity

variation in how severely a trait is expressed

26

new mutations can arise...

affected person does not have an affected parent

27

Marfan's syndome

autosomal dom. connective tissue disorder (defect in structural protein)

mutation of FBNI gene that codes for fibrillin I, a component of elastin fibers

many different mutations possible... no genetic diagnosis

28

symptoms of Marfan's syndrome

long thin fingers (arachnodactyly)

spinal deformities (kyphoscoliosis)

lens dislocation from weakness is suspensory ligaments

pectus excavatum

dilation and aneurysm of the aorta (life threatening)

29

neurofibromatosis

autosomal dom. mutation of gene that regulates cell growth

can also appear as a new mutation

neurogenic tumors from Schwann cells and elsewhere in PNS

NF-1 or NF-2

30

NF-1

chromosome 17, more common

cutaneous and subQ neurofibromas on trunk and elsewhere

skeletal lesions (scoliosis)

neuro-endocrine tumors (polychromocytoma)

31

NF-2

chromosome 22

tumors of acoustic nerve (vestibulocochlear) VIII

headache, hearing loss, tinnitus

32

do autosomal dom. or rec. skip generations?

recessive

33

homozygous recessive disorders

often involve enzyme deficiencies

if both parents are carriers, 1/4 kids have disease, 1/2 are carriers

incest increases risk

heterozygotes may or may not be abnormal but will not have the disease

34

phenylketonuria (PKU)

autosomal recessive deficiency is hepatic enzyme phenylalanine hydroxylase (phenylalanine to tyrosine)

phenylalanine builds up in the blood

multiple defects possible, some only cause mild disease

35

diagnosis, symptoms, and treatment of PKU

measure serum phenylalanine

mental retardation if untreated

restrict phenylalanine in infants/pregnant women

36

Tay-Sachs disease

autosomal recessive lysosomal storage disease

caused by absense of enzyme that metabolizes gangliosides in cell membrane

lipids (gangliosides) accumulate in cells of the brain

causes deterioration in mental function and death by 4 years of age

37

X-linked traits

on x chromosome and often recessive

if recessive more common in males than females

males transmit gene only to daughters

females transmit gene equally to sons and daughters

38

hemizygous

males, x-linked trait term

39

p arm is long or short?

short

40

q arm is long or short?

long

41

genomic imprinting

some genes inherited from both parents but only the allele from 1 parent is expressed

non-expressed alleles can be passed on and expressed in later generations

DNA is modified by methylation --> causes gene to not be expressed

42

paternal imprinting

allele from father is not expressed due to methylation

43

maternal imprinting

allele from mother is not expressed due to methylation

44

Angelman syndrome

paternal imprinting

Del 15q12 --> loss of ubiquitin path gene

hyperactivity, autism, seizures

45

Prader-Willi

maternal imprinting

46

triplet repeat mutation example

fragile X syndrome (also Huntington)

mental retardation and distinct facial features (prominant jaws, large ears)

mutation of RNA binding protein found on X chromosome

expansion of CGG repeats

more common and severe in males

47

triplet repeat explanation

DNA has areas of repeat sequence

chromosomes don't line up correctly

if you get too many repeats, you get the disease

48

mitochondrial gene disorders

mitochondria contain genes for oxidative phosphorylation

inherited from mother (most mitochondria in egg, not sperm) only to 100% of offspring

mostly impacts tissues with high metabolic rate

49

multifactorial genetic disorders

caused by more than 1 gene and environmental factors

inheritance patterns are less clear cut, and it's hard to predict phenotypes

risk greater if a close relative has the disorder

the closer the relative the greater the risk

50

cleft lip/palate

multifactorial genetic disorder

varies greatly in severity of expression -- could have just lip or palate

commonly produces speech and feeding problems

51

during meiosis, diploid chromosome number is reduced to _____

haploid

fertilization reestablishes the diploid genome

52

mosaic

errors early in mitotic development

some daughter cells are normal and some are not

how harmful depends on the activity of the cell (less than 5% is not bad, 75% could be bad)

53

aneuploidy

abnormal chromosome number

gametes may lack a chromosome or have 2 copies

caused by nondisjunction (chromatids do not separate in meiosis II)

54

monosomy

1 copy of a chromosome post-fertilization

55

triosmy

3 copies of a chromosome post-fertilization

56

breaks in chromosomes can produce

structural abnormalities

parts either deleted or rearranged

causes are x-rays, chemicals, viruses

57

deletion

part of a chromosome is lost

58

translocation

material moves from 1 chromosome to another

balanced: no material lost

Robertsonian: short arms lost... 14 & 21 can --> DownS 5%

59

isochromosomal translocation

during meiosis 1, two chromatids connect

short and long arms fuse

2 chromatids separate in meiosis 2

60

inversion

part of chromosome inverted

61

ring formation

single chromatid's ends unite to form a ring

62

consequences of chromosomal abnormalities

depends on how much genetic material is affected

cells may undergo apoptosis

can contribute to cancer

in gametes can produce congenital defects

63

down syndrome causes & risk factors

trisomy 21 (95%)

robertsonian translocation of 14 & 21 (5%)

older maternal age (oogenesis arrest in diplotene phase)

64

down syndrome symptoms

variable level of MR

characteristic facial features, poor growth, protruding tongue, hypotonia

heart & GI defects

80% of dementia in aduthood

65

down syndrome screening and definitive test

screening: low alpha-fetoprotein, high HCG, low unconjugated estriol

tests: aminocentesis, chorionic villus sampling, umbilical cord blood sampling

66

what causes dementia in down syndrome

beta-amyloid plaques -- breakdown of APP on chromo 21

3 copies so can't make more APP + more broken down

67

turner syndrome

x-chromosome monosomy 45, X most common

mosaicism also possible (45, X or 46, XX)

short stature female without secondary sex characteristics or menstruation

congenital cardiac and renal abnormalities

68

turner syndrome treatment

growth hormone and estrogen therapy in early childhood

69

Klinefelter's syndrome

47, XXY or 48, XXXY

male phenotype with deficient secondary sexual development and infertility

tall

androgen therapy

70

each ____ _____ is vulnerable at different times during development

organ system

71

teratogenic agents

environmental agents that cause abnormal embryonic development

radiation: skeletal/neruo abnormalities

chemicals: Hg, ETON, cocaine, anti-cancer meds, thalidomide

folic acid deficiency --> neural tube defect

infectious agents: toxoplasmosis (protozoa in cat litter), rubella, other viruses

72

fetal alcohol syndrome

drug induced developmental abnormality caused by EtOH consumption during pregnancy

physical, cognitive, and behavioral abnormalities

growth retardation, developmental delay, characteristic facial features

severity determined by amount of EtOH consumed, and at what time during pregnancy

73

goals of prenatal screening

detect fetal abnormalities

provide pt info needed to make informed decisions

provide reassurance to members of high-risk groups

74

methods of prenatal screening

ultrasound

maternal blood screen

aminocentesis


chorionic villus sample

fetal blood sample

75

it is now possible to detect ____ ____ or ___ ___ in maternal circulation

fetal cells or nucleic acids

noninvasive of fetus, early application, paternal DNA easiest to assay

76

ultrasound

finds NTD, spina bifida, hydrocephalus, heart defects

77

maternal blood screen

AFP (fetal protein) increase in maternal blood in NTD, also HCG for Downs

78

aminocentesis

amniotic fluid contains fetal cells

finds chromosomal abnormalities (Downs)

79

chorionic villus sampling

fetal tissue for chromosomal and genetic analysis

80

fetal blood sample

finds fetal blood abnormalities and infections

81

think mitochondrial disease when ___+ organ systems are involved

3+

myoclonic epilepsy with RRFs

82

SRY gene on Y chromosome

if nonfunctioning, can be XY and female phenotypically

83

Periods of vulnerability

CNS 2-5 wks

Heart 3-6 wks

Extremities/eyes 4-7 wks

External genitalia 6-10 wks

84

Periods of vulnerability

CNS 2-5 wks

Heart 3-6 wks

Extremities/eyes 4-7 wks

External genitalia 6-10 wks