Pedigree Mendelian Genome Trouble Flashcards

0
Q

Which pedigree type can skip generations?

A

Autosomal recessive

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1
Q

Outsider rules for autosomal dominant and recessive

A

Dominant: unknown parents are assumed to be heterozygous
Recessive: unknown parents are assumed to be homozygous normal

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2
Q

Are males and females equally affected for autosomal recessive disorders? X-linked recessive?

A

Autosomal recessive: yes

Xlinked recessive: females more likely to be carriers than displayers of phenotype

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3
Q

What cell cycle stage does the Mendel’s two laws take place in?

A

Meiosis for both

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4
Q

What is Mendel’s first law of segregation state?

A

At meiosis, alleles separate from eachother so that each gamete receives 1 copy of each allele

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5
Q

What does Mendel’s second law state?

A

Segregation of each set of alleles in meiosis is independent of segregation of other alleles

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6
Q

2 principal factors that determine the inheritance patterns seen in single gene disorders

A
  1. Quality of phenotype

2. Location of gene locus

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7
Q

Penetrance

A

Probability that a gene will have phenotypic expression at all.

“All or nothing”

Gene is expressed or it isn’t.

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8
Q

What is a threat to Penetrance?

A

Age dependent mechanism.

Likelihood manifesting trait dep on age

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9
Q

5 threats to expressivity

A

PMSES

  1. Phenocopies
  2. Modifier genes
  3. Stochastic effects
  4. Environmental factors
  5. Sex influenced/ limitations
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10
Q

Allelic heterogeneity

A

Different Mutations of same gene/locus can similar phenotype

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11
Q

Pleiotropy

A

1 gene mutation/defect can cause multiple phenotypes

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12
Q

What two factors produce phenotype?

A

Genotype and environment

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13
Q

SNP error frequency

A

1 SNP every 1000 bp = each individual ~ 3 mil bp different

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14
Q

Is random variation in genome beneficial/harmful?

A

Almost always harmful

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16
Q

Minisatellite (indel)

A

Type of variation in genome

VNTR (variable # tandem repeats)
Randomly repeated 10-100 bp
Imp for fingerprinting

17
Q

Copy number variation (CNV)

A

Type of variation in genome

Variation in segments of genome from 200bp-2Mbp
Can range from 1 additional copy to many (Ie: A-B-C-C-D)
Primary type of structural variation

17
Q

Categories of genomic DNA sequencing and frequencies

A
  1. Single copy sequences (50%)
  2. Repetitive DNA (40-50%)
  3. Genes (introns, exons, flanking seq) (20-25%)
  4. Translated/protein coding seq (1.5%)
18
Q

Microsatellite (indel)

A

Type of variation in genome

STRP (short tandem repeat polymorphisms)
Di, tri, tetra nucleotide repeats
5x10^4 per genome

19
Q

Types of repetitive DNA that exist in hu genome

A
  1. Tandem repeats

2. Dispersed repetitive elements

20
Q

Types of Dispersed repetitive elements

A
  1. Alu family
    • ie: short interspersed repetitive elements (SINES)
  2. L1 family
21
Q

Tandem repeats

A

aka “Satellite DNA”
Spread throughout the genome
Found on heterochromatic regions on ch 1, 9, 16, y

Ie: alpha satellites

22
Q

Describe estimated number of genes

A

25,000-30,000

23
Q

Retrotransposition

A

These repeats may cause insertional inactivation of genes and may facilitate aberrant recombination events btwn diff copies of dispersed repeats, leading to disease

Ie: nonallelic homologous recombination (NAHR)

24
List diff types of hu genes
1. Protein coding 2. RNA coding 3. Pseudogenes
25
1q21.1 duplication and deletions result in what?
Dup: macrocephaly, autism Del: microcephaly, schizophrenia
26
DUF1220
a protein domain that cause evolutionary advantage (inc in brain size) -> inc 1q21.1instability -> inc in DUF1220
27
Prior to meiosis, cells complete how many rounds of replication?
One (s phase)
28
After initiation of meiosis, cells then undergo how many rounds of chromosome segregation?
2 successive rounds
29
Synapsis
Homologous ch. align along their lengths and pair at corresponding DNA seq.
30
Bivalents
Pair of homologous chromosomes (during Synapsis)
31
Synaptonemal complex does what?
Promotes inter homolog intxn
32
Chiasmata
Physical links btwn homologs during reciprocal recombination
33
Random segregation of homologous ch gives rise to how many diff possible combinations?
8x10^6 or 2^23 (2 homologs of each 23 ch)
34
Nondisjunction
Pairs of ch fail to segregate properly
35
Nondisjunction events are related to what two factors?
Position and numbers of Chiasmata
36
What happens if recombination occurs too close to centromere? Too far?
1. Cause Spindle attachments, segregation during meiosis 1 -> crossing over less effective -> inc risk of ND 2. Homologs become entangled -> reduced/absent recombination and inc risk of ND
37
What happens to gametes when ND occurs in meiosis I? Meiosis II?
l. All gametes abnormal | II. Half gametes normal, half abnormal
38
Triploidy
Extra ch in all 23 pairs ( ie, 69, XXX)