Quiz 4 Flashcards by Liliane Ernst

Which stage of meiosis is oogenesis arrested at?

prophase 1

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Where during menstrual cycle does first meiotic division?

after ovulation

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What is a gene?

inherent properties of a species

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what is an allele

inherent property within a species

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what is rate of SNPs in terms of basepairs

1/1250

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What percentage of genome is single copy sequences?

45%

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What percentage of genome is repetitive DNA

55%

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of repetitive DNA what percentage is dispersed,

what percentage is staellite

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How long does it take to go from spermatogonia to sperm?

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what stage of sperm precursor undergoes meiotic divisions?

spermatocytes

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When does 2nd meiotic division of oocyte occur?

after sperm penetration

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human genome is how many megabases long?

3000

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4 classifications of genetic disorders

single gene/ monogenic
Chromosomal
Mitochondrial
Somatic

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dwarfism/ achondroplasia is caused by a mutation in which gene?

fibroblast growth factor receptor

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What percentage of patients with achondraplasia have new mutations

80%

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testing strategy for cystic fibrosis?

standard screening for panel of 25 mutations

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testing strategy for achondroplasia

sequencing of exon 10 using genomic DNA

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Hardy-Weinberg equation

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

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what is it called when multiple organs/tissues affected by a genetic disorder b/c gene product of mutated gene is present in multiple tissues/organs

pleitropy

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What alters gene frequency/ makes HW inaccurate

small populations/non-random mating
selection
mutation
migration and gene flow
consanguinity

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t/f all genes on the inactivated X chromosome are inactive

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What percentage of mutations in ducennes are deletions

what percentage are duplications

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6 classifications for singe gene/ monogeneic genetic disorders

Autosomal Dominant
Autosomal Recessive
X-linked Dominant
X-linked Recessive
Y-linked
Mitochondrial

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are males or females affected more for X-linked dominant disorders?

females

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What is heteroplasmy?

fraction of mitochondria that are affected

What is the main way to tell b/w germline and new mutations?

in new mutation, one egg or sperm was mutated, so only one offspring would be affected --in germline you would have multiple off spring affected because multiple germ cells are mutated

What is penetrance

percentage of people with mutation that have disease phenotype

What is variable expressivity

variable manifestations and severity

What is locus heterogeneity

mutations in different genes result in same disease phenotype

What is allelic heterogeneity?

Different mutations in the same gene result in different phenotypes

example of alleleic hetergeneity

Cystic Fibrosis

example of locus heterogeneity

Deafness caused by mutations in different genes

example of reduced penetrance

retinoblastoma

Example of delayed age of onset

huntingtons

example of non-traditional inheritance

Fragile X

two types of genetic heterogeneity

locus and allelic

In Fragile -X does expansion occur in males or females

females

what is rate of chromasomal abnormalites

1/150

what is an ideaogram

Schematic representation of chromosomes with their banding patterns

which arm of chromosome is the smallest in submetantric, acrocentric

alphoid repeat probes in FISH is useful for what?

interphase FISH...faster results, don't need to have cells go to metaphase

alphoid repeat probes are specific for which structure on chromosome?

centromere--each chromosome has specific centromere region

2 groups of chromosome abnormalities

numerical and structural

difference b/w aneuploidy and polyploidy

aneuploidy--abnormal # of chromosomes due to extra/missing | polyploidy--multiple of haploid #

95% of down syndrome cases are caused by nondisjunction from which parent and which part of meiosis

maternal | meisos 1

what happens in robertsonian translocation

long arms of 2 acrocentric chromosomes are fused at the centromere

recurrence risk for regular trisomy | roberstsonian

1 | 15

robertsonian translocation balanced/unbalanced

balanced

Reciprocal translocation balanced/unbalanced

balanced

What features/abnormalities in a patient would indicate that genetic testing should be done

1. mental retardation 2. growth retardation 3. facial features 4. major abnormalities 5. abnormal sex characteristics

what are two types of deletions

terminal deletions | interstitial deletions

what causes the difference b/w Prader-Willi and Anglemen

Imprinting PW--Paternal copy of 15q is deleted AS- Maternal copy of 15q is deleted

Advantage of array based comparative genomic hybridization | 2

- can detect very small (50kb) deletions | - Detects all known microdeletion and microduplication syndromes

Disadvantage of array based comparative genomic hybridization 2

- balanced translocations | - Can't tell where duplications are (ie next to each other/ or on another chromosome)

Turner Syndrome - karyotype - males/females

45,X --missing second X, or second X is messed up | females

Klinefelter - karyotype - males/females

47, XXY | males

XXX caused by maternal/paternal disjunction

maternal

What are the strategies for identifying disease genes 5

1. Positional mapping 2. Linkage analysis 3. functional cloning 4. Testing candidate genes 5. analysis of chromosomal abnormalities

3 Commonly used genetic markers used for linkage analysis

1. Highly polymorphic satellite repeats 2. SNPs 3. RFLP

Linkage analysis is best used under what 4 conditions

1. single gene disorders 2. Mendelian inheritance 3. highly penetrant 4. rare in population

For linkage analysis variants are often located within/ outside coding region

within

Which strategy for identifying disease genes is useful for confirming locus heterogeneity

linkage analysis

Association studies are often employed for | 4 traits

- complex disease - involving multiple genes - modest penetrance - high prevalence

genetic variants for association studies are often within/ outside of coding region

outside

what is linkage disequilibrium

nonrandom association of alleles at linked loci

(linkage analysis/ association study) is conducted using family data, while (linkage analysis/ associaton study) is performed using populations

link analysis | association study

Link analysis determines the ___ ___ b/w loci while association stud assess the ____ b/w traits

genetic distance | relationship

What is positional mapping

narrowing down area in the genome where disease genes may reside

chromosome recombination/crossing over occurs primarily at

prophase of meiosis I

3 features of suitable genetic markers for linkage analysis

highly polymorphic Mendelian inhertiance Easy genotyping

Sensitivity is ability of a test to correctly identify

affected persons

Specificity is ability of a test to correctly identify

non-affected persons

biochemical genetic testin analyzes

metabolic and enzymatic activity

DNA sequencing is good for detecting

small nucleotide changes

DNA sequencing does not detect

large deletions/duplications

Multiplex PCR analysis is good for

detecting large deletions

Allele- specific oligonucleotide analysis is sensitive/ specific

sensitive

advantage of indirect genetic testing

knowledge of mutation or disese gene is not necessary

What is indirect genetic testing

using gene markers to determine whether the chromosome with the genetic markers

disadvantage of indirect genetic testing

need to genotype multiple family members to determine linkage phase and possibility of recombination

Chromosome arrays / comparitive genomic hybridization cannot detect 3

balanced rearrangements, polyploidy, or low levels of mosaicism

Quiz 4 Flashcards

(81 cards)