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Block 6: Cell Structure & Function > Mendelian Inheritance/Pedigree/Population Genetics > Flashcards

Mendelian Inheritance/Pedigree/Population Genetics Flashcards

1
Q

What does compound heterozygote mean?

A

Two mutant alleles for a gene. Both different mutants, and both defective.

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2
Q

Achondroplasia shows what kind of inheritance?
Outcomes of DD?
dd?
Dd?

A

Incomplete dominance.
DD= lethal
Dd= affected
dd= normal

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3
Q

Big example of De novo mutation?
What is this disease, and what makes it different in inheritance compared to most de novo?
dominant or recessive?

A

Achondrogenesis type II.
Type of dwarfism where collagen type II is messed up.
Considered autosomal dominant, although since affected individual dies by puberty, it isn’t passed on.
Considered autosomal dominant.

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4
Q

What is a De novo mutation?

Chance of passing it on?

A

A spontaneous mutation in offspring that parents do not have, so low recurrence rate.
Offspring has 50% chance of passing it on.

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5
Q
  1. What is germline mosaicism?

2. Example? what is the problem? Lethal type?

A
  1. Mutation in gametes only. Despite no family history of a disease, two or more children are affected.
  2. Osteogenesis Imperfecta. Collagen type I problem. Lethal type is type II.
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6
Q

What are two genetic diseases that show delayed age of onset?

A

Huntington’s and breast cancer.

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7
Q

What is the difference between the two types of penetrance?

A

All or nothing- everyone with the gene has the trait.
Reduced penetrance- For some reason even with the gene you might not show the phenotype.
(reduced penetrance of 60% means that 60% show phenotype). you can pass it on regardless of type.

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8
Q

HNPCC shows what kind of phenotype?

A

Reduced penetrance. Colon cancer.

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9
Q

Split-hand deformity shows what kind of phenotype?

A

Reduced penetrance

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10
Q

What is variable expression?

Example?

A

With the same genotype, you show the mutation but some show it worse than others.
Ex: Neurofibromatosis

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11
Q

What is pleiotropy?

Example?

A

One gene affects multiple phenotypes.

Marfan syndrome.

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12
Q

What is locus heterogeneity?

Example?

A

A mutation can be caused by different mutations at different loci.
Hereditary breast cancer.

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13
Q

What is allelic heterogeneity?

Example?

A

Same disorder caused by different mutations all in the same gene/locus
Ex: cystic fibrosis.

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14
Q

What is phenotypic heterogeneity?

Example? Gene?

A 
Different phenotypes from different mutations all in the same gene/locus. 
craniosynostosis syndromes (FGFR2 gene)
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15
Q

What happens with trinucleotide repeat disorders from generation to generation?

A

You get more and more repeats each generation.

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16
Q

What are the 3 influencing factors in trinucleotide repeat disorders?

A
  1. Size of repeat- larger means worse
  2. Parent of origin
  3. Anticipation- You get more and more repeats each generation, disease gets worse, and can even have an earlier onset.
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17
Q
  1. What is a long expansion trinucleotide repeat disorder?
  2. Where do these repeats occur? Low yield: What is the repeat?
  3. What can go along with these?
A
  1. Ten times expansion
  2. occur outside protein coding region Low yield: CCG, CGG, or CTG.
  3. Some have fragile sites, which is a specific site where breaks tend to occur.
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18
Q
  1. Mutation of myotonic dystrophy?
  2. Symptoms of it? 3
  3. Genetics? Does it show anticipation? When?
  4. What happens if you have thousands of repeats?
A
  1. Long expansion trinucleotide
  2. hypotonia, club feet, cardiac arrhythmia
  3. Autosomal dominant. Shows anticipation, especially if inherited maternally.
  4. Congenital myotonic dystrophy (congenital DM)
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19
Q
  1. FMR-1 disorders are what kind of mutation?
  2. What exactly is the issue, compared to normal?
  3. If this expansion is methylated, what happens?
  4. Expansion of these repeats can only happen where?
A
  1. Long expansion trinucleotide repeat disorder.
  2. CGG repeats are normal, although they have ACC triplets every 10 repeats that serve as anchors against expansion. These disorders lack the ACC anchors, so you get more CGG repeats.
  3. If methylated, the protein stops being made at all.
  4. Can only happen in oogenesis.
20
Q
  1. What gene is mutated in Fragile X syndrome?
  2. Symptoms?
  3. Which parent is the expansion from?
A
  1. FMR1 full-mutation
  2. elongated face, large ears, low muscle tone, mental retardation (slighter in females)
  3. Expansion in mother
21
Q

What is the definition of short expansion trinucleotide repeats?

A

100 or less repeats IN the protein coding region.

22
Q
  1. What are the genetics/mutation in Huntington’s disease?
  2. what is expanded?
  3. Anticipation and penetrance?
  4. Symptoms?
A
  1. Autosomal dominant, short expansion trinucleotide repeat.
  2. HTT gene.
  3. Shows anticipation when pass on PATERNALLY. Some individuals show non penetrance, when they should have the disease.
  4. Neurodegenerate
23
Q
  1. What are the genetics/mutation in Friedreich’s Ataxia?
  2. Symptoms? Onset?
  3. Does it show premutation?
A
  1. Autosomal recessive, short expansion trinuc repeat in FXN.
  2. Slow, progressive ataxia before the age of 25. Dysarthria, muscle weakness, lower limb problems.
  3. Yes
24
Q

What equation do you use for x-linked recessive diseases for males?

A

p+q=1
p= unaffected hemizygotes
q= affected hemizygotes

25
Q

What equation do you use for x-linked recessive diseases for females?

A

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

26
Q

What does coefficient of relationship (R) mean?

A

Degree of consanguinity (proportion of genes shared) between two individuals.

27
Q

What is the coefficient of relationship for:

  1. Parent-child?
  2. Sibling-sibling?
  3. first cousins?
  4. second cousins?
A
  1. 1/2
  2. 1/2
  3. 1/8
  4. 1/32
28
Q

What is coefficient of inbreeding (F) mean? How does it relate to R?

A

Probability that an individual has two identical alleles for a given gene from a common ancestor. its value is always half of R.

29
Q

What does acrocentric mean? What chromosomes can be acrocentric?
How many telomeres do acrocentric chromosomes have?
What kind of translocations happen here?

A

Centromere at one extreme end of chromosome. 13, 14, 15, 21, 22
1 telomere.
Robertsonian translocations

30
Q

What does submetacentric and metacentric mean?
How many telomeres?
What are the short arms and long arms called?

A

Sumetacentric means the centromere is closer to one end.
Metacentric means its right in the center.
both have two telomeres.
short arm=p
long arm=q

31
Q

What cells can be harvested prenatally to check for problems?

A

fibroblasts and lymphocytes.

32
Q

what is mosaicism, and how does it occur?

A

Mitosis errors. Not all cells match. Some could be monosomic, while others are triploid.

33
Q

45, XY, der (15;21), (q10;q10)

What type of translocation?

A

Robertsonian translocation

34
Q

46, XX, t(7;12), (p15;q22)

What type of translocation?

A

Balanced translocation

35
Q

46, XX, der (7) t(7;12), (p15;q22)

What type of translocation?

A

Unbalanced translocation

Although unbalanced, remains diploid.

36
Q

Compare trisomy 18 to trisomy 21.
When does the error happen?
Which is more common?
Symptoms and name of both?

A

Trisomy 21- Down syndrome. Facial gestalt. 30% congenital heart. Hypotonia. Meiosis I, more commonly female meiosis I.

Trisomy 18- Edwards Syndrome. More severe than down syndrome. Dysmorphism, malformations. rocker-bottom feet, low set ears, fist clenching. Few survive past a few months.

37
Q

What is trisomy 13 called?
Commonality compared to other trisomies?
Symptoms?
Outlook?

A

Patau syndrome.
Least common of all 3.
Growth retardation, microphthalmia, clefting, polydactyl.
Very poor survival.

38
Q

What is monosomy X also known as?
Karyotype?
Symptoms?

A

Turner syndrome.
45,X
Infertility, short webbed neck, short stature, lymphedema of hands and feet.

39
Q

What is 47,XXY?

Symptoms?

A

Kleinfelter syndrome

Tall stature, delayed puberty, infertility, learning disabilities

40
Q

Symptoms of 47,XYY?

A

Tall stature, questionable increased risk of learning disability. Other than that, totally normal and fertile

41
Q

Symptoms of 47,XXX?

A

Reduced IQ, risk of learning abilities, stresses easy.

42
Q

Pericentric v. Paracentric inversions?

A

Paracentric is within same arm (avoids centromere)

Pericentric is between different arms (includes centromere)

43
Q

segregation in robertsonian translocation leads to what?

What about in balanced translocation?

A

Leads to trisomy or monosomy.

In balanced, it can lead to unbalanced.

44
Q 
FISH
Chromosomes
Microarray
Which is for dividing cells? 
Which is quick, and good for mosaicism?
A

Chromosome analysis for dividing cells.

FISH is fast and good for mos.

45
Q

Symptoms of premutation fragile x?

Inheritance?

A

Males- ataxia

females- premature ovarian failure

46
Q

What is premutation?

A

No symptoms but increased risk for expansion

Block 6: Cell Structure & Function (3 decks)

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