Principles Of Genetic Inheritance Flashcards by Sarah Gillen

Each gene occupies a specific place, or _______

Locus

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___________ = one of two identical copies of a chromosome

Chromatid

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____________ = connects identical sister chromatids

Centromere

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_____________ = region at the end of chromosome for stability

Telomere

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Typical human diploid cell has 23 pairs of chromosomes. 22 pairs are called _______, the 23rd pair is _____ or _____

Autosomes

XX or XY

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Human ________cells are diploid and differentiated

Somatic

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________are haploid cells

Gametes

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______ Cells are undifferentiated and can divide into 2 diploid cells

Stem

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___________ chromosomes refer to pairs of chromosomes, thus there are 2 copies of each gene with the order of the 4 loci being identical

Homologous

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Entire set of patient’s chromosomes represents their ___________

Karyotype

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46 chromosomes in a karyotype are in each of the patient’s diploid cells, unless ___________ occurs, which is a condition in which patients have different genotypes

Mosaicism

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For Chr16p12.2 -

Identify chromosome, region, band, sub-band, and arm

Chr = 16
Region = 1
Band = 2
Sub-band = 0.2
Arm = p arm

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What is a natural form of mosaicism?

Lyonization - or X-inactivation. The choice of which X chromosome will be inactivated is random

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What is the genotype of Downs syndrome?

Some 46XX, some 47XX + 21

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What is the genotype of Klinefelter syndrome?

Some 46XY; some 47XXY

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What is the genotype for Turner syndrome?

Some 46XX, some 45XO

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Meiosis reduces the total number of chromosomes by half, producing four gametes. In meiosis, __________ ________ produces new combinations of genes

Homologous recombination

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______________ is the failure of one or more pairs of homologous chromosomes, or sister chromatids, to separate normally during division.

What does this cause?

Non-disjunction

Causes spontaneous abortion and mental retardation

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How does meiotic cell division produce haploid cells?

One round of DNA replication + 2 rounds nuclear divisions

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____________ are chromosomes common in both genders (one from each parent)

Autosomes

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In what 2 ways does meiosis generate genetic diversity?

Random segregation of homologs

Crossing over

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____________ refers to cells with an abnormal chromosome number

Aneuploid

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What is the most common cause of mental retardation?

Trisomy 21 (Downs)

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In 90% of trisomy 21 patients, the addition chromosome is ____________

70% occurs during __________
30% occurs during __________

Maternal

1
2

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__________ refers to cells with the normal number of chromosomes

Euploid

What type of Trisomy 21 is characterized by the genotype 47, XX + 21?

Translocation type - due to Robertsonian translocation

What is the Robertsonian Translocation?

Long q arm 21 fuses to long q arm 14, resulting in acrocentric chromosomes

What type of Trisomy 21 has the genotype 46, XX, der(14;21)(q10; q10), +21?

Mosaic type

What is the result of methylation on genes?

Downregulation

Methylated genes are considered to be __________, which can be passed on from generation to generation

Imprinted

What is the result of two chromosomes from the same parent that have parent-specific imprinting?

No gene product

Two different conditions occur with the exact same deletion on chromosome 15. What condition does the child develop if the paternal chromosome is deleted?

Prader Willi syndrome

Two different conditions occur with the exact same deletion on chromosome 15. What condition does the child develop if the maternal chromosome is deleted?

Angelman syndrome

Gregor Mendel is the 'father of modern genetics'. What 3 laws did he come up with?

Genes are discrete units Law of segregation Law of independent assortment

What are the 2 broad types of genetic diseases?

Monogenic (single-gene) Multifactorial

Dystrophin --> Duchenne Muscular Dystrophy What is the genetic mechanism?

Loss of function

Oncogene --> cancer What is the genetic mechanism?

Gain of function

B-globin --> sickle cell anemia What is the genetic mechanism?

Protein alteration

Individuals with distinct genotypes can have a single phenotype, as is the case with ________ _________ Conversely, individuals with the same genotype can have multiple phenotypes, as is the case with _________

Cystic fibrosis PKU

Why is it that PKU patients with the same genotype (PAH deficiency) have multiple phenotypes?

Some patients will be able to metabolize and excrete Phe more efficiently than others

Why is it that cystic fibrosis patients have distinct genotypes and only one phenotype?

Whether you have no CFTR proteins at all, or dysfunction of your existing CFTR proteins, you will have the same resulting symptoms

When looking at pedigrees, the ________ refers to the first diagnosed person in the pedigree.

Proband

What type of inheritance is characterized by only 1 allele needed for expression, so only one parent was affected

Autosomal dominant inheritance

With autosomal dominant inheritance, unaffected individuals do not transmit the trait. Males and females can transmit the trait to both males and females - (_______________) Trait is expected in ________ generation Recurrent risk is ________%

Autosomal Every 50

Postaxial polydactyly is an example of what type of inherited disorder?

Autosomal dominant

What type of inheritance requires 2 copies of a gene to influence the phenotype?

Autosomal recessive

Tyrosinase-negative albinism is an example of what type of inherited disorder?

Autosomal recessive

What is the recurrent risk of autosomal recessive diseases?

25%

With autosomal recessive disease, occurence is more likely among individuals who engage in ___________ mating

Consanguinous

X-linked Recessive disorders: Disease allele on X in males is termed ___________ Females can be __________ or ______________ Unaffected males do not transmit the trait Females transmit to ____% of sons and _____% of daughters

Hemizygous Heterozygous; homozygous 50; 50

If a male is a carrier of an x-linked recessive disorder, how many of his potential daughters will be heterozygous carriers?

All of them

Duchenne muscular dystrophy is an example of what type of inherited disorder?

X-linked recessive

Hypophosphatemia is what type of inherited disorder?

X-linked dominant

How do males and females compare in their ability to pass on an x-linked dominant trait?

Males with disease allele transmit the trait only to females with 100% transmission rate Females with disease allele transmit the trait to both male and female offspring with 50% transmission rate

The frequency that a gene manifests itself is called _________

Penetrance [with retinoblastoma, the phenotype occurs in 90% of individuals inheriting the gene defect, so 90% penetrance]

What type of inheritance is demonstrated by retinoblastoma?

Autosomal dominant

What is the term used to describe a range of phenotypes that vary between individuals with a specific genotype?

Variable expressivity

What is a disease example of variable expressivity?

Neurofibromatosis People develop tumor like growths called neurofibromas - cafe-au-lait spots = pigmented areas that vary in their clinical presentation

Osteogenesis imperfecta may result from a mutation in either Chr 7 or Chr 17, this is an example of what concept of mendelian inheritance

Locus heterogeneity - a single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci

What principle specifies the relationship between gene frequencies and genotype frequencies?

Hardy-Weinberg principle

What type of inheritance is characterized by vertical transmission of phenotype, lack of skipped generations, roughly equal males and females affected, and father-son transmission may occur?

Autosomal dominant

What type of inheritance is characterized by clustering of disease phenotype among siblings, but not usually seen among parents or other ancestors, equal males and females affected, consanguinity may be present

Autosomal recessive

Traits in which variation is thought to be caused by the combined effects of multiple genes = _________

Polygenic

When environmental factors cause variation in the trait, the term __________ is used

Multifactorial

For diseases that do not follow the bell-curve distribution, there is an underlying ___________distribution. For multifactorial diseases that are either present or absent, it is thought that a ________________ must be crossed before the disease is expressed. Below that, the person appears normal.

Liability Threshold of liability

Explain the concept of the threshold model as it relates to pyloric stenosis, which is 5x more common in males than females

Children of women with pyloric stenosis are more likely to be born with the condition - especially males Children of affected males with pyloric stenosis are less likely to be born with the condition

The recurrence risk is ______ if more than one family member is affected If the expression of disease in proband is more severe, the recurrence risk is ________ The recurrence risk is ______ if the proband is of the less commonly affected sex The recurrence risk is usually _____ in more remotely related areas

Higher Higher Higher Decreased