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Foundations Exam 1 > Genetics and Genomics > Flashcards

Genetics and Genomics Flashcards

1
Q

What is a haplotype?

A

=an individuals set of alleles at a locus or cluster or loci on a chromosome

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2
Q

What are single gene disorders?

A
  • these disorders are determined primarily by the alleles at a SINGLE locus
  • recurrence risk describes the likelihood of passing on the gene
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3
Q

Mendelian Genetics… what is it concerned with?

A

-monogenetic traits aka single gene traits

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4
Q

Independent assortment

A

is one gene locus is independently transmitted from a gene on a different locus

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5
Q

Autosomal dominant disease

A

seen in every generation
M=F
-structural genes are often seen in this inheritance pattern
-no skipping generations unless new mutation!
-probability to inherit=50%

ex. achondroplasia

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6
Q

Achondroplastics are…

A

rizomyere???

their limbs (humerus and femur) are short but their tib/fib and radius/ulna are normal length

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7
Q

What is the danger with 2 people who have an AD disease mating?

A

-they have more problems in those who will become homozygotes much more severe issues

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8
Q

Autosomal Recessive

A

-rare
-often seen in metabolic disorders
-this is sometimes seen in those who are relatives who mate CONSANGUINITY
-those that are heterozygotes may have reduced enzyme activity and then combine to make no activity
M=F
-probability to inherit from heterozygote parents 25%

Ex.
-Hurler/Hunter

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9
Q

What is hurler syndrome?

A
  • AR disease
  • skeletal abnormalities
  • similar to hunter
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10
Q

Cystic fibrosis

A
  • mutation to CTFR gene
  • Cl transporter mutation
  • pleiotropic: effects more than one organ
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11
Q

Remember that dominant and recessive refer to ___ not ___

A

traits not genes!

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12
Q

Sex linked inheritance

A

types:
X linked dominant
X linked recessive
Y linked

x chromosome: larger so more mutations
-common in men

y linked: much smaller contains less genes

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13
Q

X linked recessive

A

M > F–bc males usually only ones affected

-SONS of heterozygote mothers have 50% chance of being affected

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14
Q

X linked dominant

A

M and F can be affected

-all female offspring of affected father will be affected

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15
Q

Y linked

A

only father to son transmission

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16
Q

Mitochondrial Inheritance

A
  • only given from mother
  • all offspring of affected females show signs of disease
  • not all mitochondria congregate in specific organs… so they effect organs different =heteroplasmy
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17
Q

New mutations

A
  • this can complicate the “normal” pattern of inheritance

- the gene transmitted undergoes a mutation from the normal allele

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18
Q

Achondroplasia and risks and what they have!

A
  • most cases are due to new mutations
  • only 1/8 are transmitted from dwarf parents
  • distinguish this by taking a family hx

remember they are: Rhizomelic—> refers to either a disproportion of the length of the proximal limb, such as the shortened limbs of achondroplasia, or some other disorder of the hip or shoulder.

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19
Q

What is gremlin mosaicism?

A
  • when 2 or more offspring present with an AD disease with no familial hx
  • this is when all parts of the germline cells are affected by the same mutation
  • mutation occurs during the parents embryonic development of the germ cells
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20
Q

Age Dependent Penetrance

A

aka delayed age onset

  • ex. of this is BRCA gene
  • this is when the disease does not present until AFTER patients reach reproductive age or adulthood
  • this can cause a difficulty in detecting the mode of inheritance

other ex.
huntingtons
polycystic kidney disease
alzheimers

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21
Q

Reduced penetrance

A

-this is when those that have the genotype fail to express the appropriate phenotype although they pass it to the next generation

penetrance is the general idea that a phenotype expression is dependent upon the predisposing genotype

ex. retinoblastoma

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22
Q

Variable expression

A

a trait in which the same genotype can produce phenotypes of varying severity or expression

  • penetrance=complete
  • severity is what varies
  • a parent with midl expression may pass on the disease

ex. neurofibroblastoma

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23
Q

What are some causes for variable expression?

A
  1. environmental factors
  2. modifier genes
  3. allelic heterogeneity
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24
Q

What is pleiotropy?

A

-genes that affect multiple aspects of physio or anatomy

ex. sickle cell
OI
CF

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25
Q

Marfan syndrome

A
  • mutation to fibrillar

ex. of pleiotropy

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26
Q

Locus heterogeneity

A

=single disease phenotype caused by mutations at different loci in different families

a risk of this is testing for the wrong mutation
-ex. OI

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27
Q

Genomic Imprinting… ex. of this

A

=process by which genetic material is expressed differently when inherited from the mother than when inherited from the father

  • methylation
    ex. prader will an anglemans

Prader willi is inherited from the PATERNAL side
Anglemans is MATERNAL (heavy retardation)

28
Q

Anticipation

A

=progressivle earlier onset and increased severity of certain diseases in successive generations of a family

ex. myotonic dystrophy

29
Q

Population genetics: what factors determines it?

A

the branch of genetics dealing with genetic variation and genetic evolution of population
-it looks at how these frequencies change or are maintained in different populations

a. genetic factors
b. environmental and societal factors

30
Q

What is the multiplication rule?

A

probability that BOTH event 1 and 2 will occur together

multiply probabilities together

31
Q

What is the addition rule?

A

probability that EITHER event 1 or 2 will occur together

add the probabilities together

32
Q

hardy weinberg

A

states that population frequencies will stay at a constant from generation to generation

p=normal
q=mutant
p+q=1
*calculates genotype frequencies

p^2 +2pq + q^2=1
p^2=homozygous normal

33
Q

what are the assumptions for hardy weinberg to be true? 4

A
  1. large population
  2. no mutation
  3. no selection
  4. no migration
34
Q

when is hardy weinberg used in the clinical setting?

A

often used for autosomal recessive conditions

35
Q

what is the 2/3 rule?

A

2/3 for heterozygotes who are carriers and do not have disease. 1/4 chance for child who does not have the disease and multiple these by the population frequency

36
Q

What are some causes in population change frequencies?

A
  1. natural selection
  2. genetic drift
  3. founder effect
  4. gene flow
37
Q

natural selection… ex. of some diseases

A

-sickle cell: protects from malaria
-CF: protects against diarrhea
leiden V: entourage coagulation

38
Q

What are some examples of the founder effect?

A
  • the founder effect is a large shift in frequencies in a small population containing little genetic variation
  • often subsets of populations
    a. islands
    b. small towns
    c. ashkenazi jews
39
Q

Why is knowing the ethnic population of your patient important for genetic testing?

A
  • if you know the ethnic population you can order more specific genetic testing
  • this can ultimately save cost
40
Q

What is cytogenetics?

A

=the study of chromosomes and their abnormalities

-uses cytology and genetics

41
Q

What is a karyotype? What criteria are they numbered by?

A
  • chromosomes are extracted from nucleus, stained, and matched according to
    a. size
    b. banding patterns
    c. location of centromere
42
Q

nomenclature for chromosomes

A

p=petitie small arm
q=long arm

metacentric: equal on each side of centromere
submetacentric: longer on once side
acrocentric: very small p arm

43
Q

What is the problem with acrocentric chromosomes?

A

they often can have robertsonian translocations

44
Q

What is euploid?

A

a multiple of a haploid number (N=23)

45
Q

What is aneuploid?

A

trisomy or monosomy
=extra or missing chromosomes
-it is the state of not having euploidy
most common cause is nondisjunction

46
Q

When does nondisjunction occur?

A

it can occur during meiosis 1 or 2.

  • Often occurs during meiosis 1 in female gametes
  • it can occur in men but much later in life at about ~60 years old
47
Q

What is polyploidy?

A

=more than 2 sets of homologous chromosomes
ex.
2 sperm–1 egg
1 sperm–diploid egg

48
Q

Down syndrome… what is its MAIN cause?

A

47 chromosomes (21)

  • retardation
  • heart problems
  • early onset alzheimers

main cause: maternal meiosis I

49
Q

Kleinfelter syndrome

A

XXY

47

50
Q

XYY syndrome

A

XYY 47
-very tall
-severe acne
lots in prison population?

51
Q

Turner Syndrome

A

45 XO
-monosomy X
“webbed neck”
infertile
-could also have mosaic turners which are fertile therefore it is important to know where its full turners or not
-this is the SINGLE MOST COMMON ABNORMALITY IN ABORTIONS

52
Q

Edward Syndrome

A 
47
trisomy 18
-mental retardation 
-overlap of middle and index fingers
-only 5% survive to 1 year
53
Q

Patau Syndrome

A

47
trisomy 13
-microcephaly
polydactyl

54
Q

Prader Willi

A
  • paternal chromosome
  • 15 mutation
  • fat
  • short stature
55
Q

Angelmans Syndrome

A
  • From maternal side
  • severe
  • absence of speech
56
Q

Whats the difference between genetics and genomics?

A

genetics: study of traits
genomics: is the study of genes

57
Q

Inactivating changes in genes

A
  • these are more common that activating changes
  • mutations which reduce expression
  • reduce activity of protein
  • can alter splicing balance
58
Q

What are reasons for gaps in the genome?

A
  1. chromosomes are not continuous
  2. some sequences are hard to read high GC
  3. some sequence is hard to align–repeats

human genome is the ARTIFICIAL reconstruction of chromatin

59
Q

What is some evidence for a genetic contribution to a disease?

A
  1. congenital disorders
  2. family hx
  3. cross cultural
  4. multigenerational
  5. GWAS
  6. identical twins separated at birth ideal
  7. expression analysis
60
Q

what is missing heritability?

A

-we know its heritable but we do not know the gene for it

61
Q

Lamina A mutations

A

C–> T conversion

  • mutation is absent in both parents
  • usually acquired from a gremlin mutation
  • it is what causes progeria
62
Q

What is the difference between family Hx and Genetic status?

A

They are often used interchangeably but they are 2 different things

Family hx: stress, diet, exercise, infections, drugs/alcohol, exposure level to various things

genetic statusL shuffling, mutation to germ line, donor egg, adoption

where do they overlap? SNPs, most disease risks

63
Q

What are PROBLEMS with family hx?

A
  • time consuming
  • not recorded in a usable format
  • mistakes in recalling cause of death
  • many know little about health hx due to secrecy, and low privacy rates
  • adoption or donor eggs
  • false paternity
  • health records die with people
64
Q

What are some advantages to multi-generational pedigree analysis?

A

-families have low genetic noise (they are very similar)
-example ashkenazi jews
mormons

65
Q

gene–disease replationships

A
  1. gene is perfectly associated with disease
    * high penetrance- typical of monogenic
  2. gene is poorly associated with disease
    * low penetrance- typical of multi genic diseases
  3. gene is strongly associated with disease but at variable levels
    * high penetrant but variable EXPRESSIVITY
66
Q

What are the steps to test pre-implantation embryos for IVF?

A
  • induct the F to produce multiple oocytes
  • harvest the embryos by transvaginal aspiration with US
  • IVF with fathers sperm
  • Harvest one of the 8 cells
  • test cells for known mutations that you are looking for
  • only implant the unaffected embryos

Foundations Exam 1 (7 decks)

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