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MCM Final > Genetic Inheritance > Flashcards

Flashcards in Genetic Inheritance Deck (54):
1

Genes

Segments of DNA in a chromosome

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Locus (Loci)

A specific place where a gene is located

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Chromatid

One of two identical copies of a chromosome

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Centromere

Connects identical sister chromatids

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Telomere

A region at the ed of a chromosome for stability

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Typical human diploid cells have ___ pairs of chromosomes - a total of ___

22 pairs are called ____

And the 23rd pair is ___ or ___

23 , 46

Autosomal

XX or XY

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Human somatic cells are _____

Diploid cells that are differentiated

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What cells are haploid?

Gametes

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_______ cells are cells that are undifferentiated and can divide into two _________ cells

Stem, diploid

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Refer to pairs of chromosomes

Homologous chromosomes

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Karyotype

Entire set of a person's chromosomes. 46 chromosomes show in the karyotype of each of the patient's cells

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Mosaicism

A condition in which cells from a patient have different genotypes (and karyotype)

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Downs Syndrome

Some 46XX, some 47XX, +21

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Klinefelter Syndrome

Some 46XY, some 47XXY

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Turner Syndrome

Some 46XX, some 45XO

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Lionization

X inactivation - the choice of which x -chromosome to be inactivated is random

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Ovaries and testes undergo ________ to produce ________ that have one of each pair of chromosomes and are called _________ cells

Meiosis ; gametes ; haploid

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Interphase

Chromosome duplication

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Cell division

One copy of each chromosome and 1/2 of the cytoplasm/organelles are distributed b/w the 2 daughter cells

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Homologous recombination

Can produce new combos of genes in meiosis; homologous chromosomes are not identical

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Non-disjunction

The failure of one or more pairs of homologous chromosomes, or SISTER CHROMATIDS to separate normally during division

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Meiosis consists of __ round(s) of DNA ________ and __ round(s) of nuclear __________

1 ; replication

2 ; divisions

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Autosomal

Chromosomes common in both genders, one from each parent

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Sex chromosomes

X, female

Y, male

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Name two ways that meiosis creates genetic diversity.

1) Random segregation of homologs

2) Cross-over exchange

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Nondisjunction

When homologs fail to separate properly

Common and increases w/ advancing maternal age

Cause of spontaneous abortions and mental retardation

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Aneuploid

Cells with abnormal chromosome number

Trisomy 21 (Down Syndrome): most common cause of mental retardation

In 90% of trisomy 21 patients, the additional chromosome is maternal
70% occur during MI
30% occur during MII

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Euploid

Cells with a normal number of chromosomes

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Genotype vs. phenotype

An individual's genetic makeup vs. what is actually observed

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Autosomal Dominant Inheritance

- Only 1 allele of a gene is needed for expression

-Affected offspring has one affected parent

- Males and females can transmit trait to both males and females

- Recurrent risk is 50%

Ex) Postaxial polydactyly

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Autosomal Recessive Inheritance

2 copies of a gene is needed to influence phenotype

Recurrent risk for heterozygous parents is 25%

Ex) tyrosinase-negative albinism

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X-linked Recessive

Because males have one X, disease Allen on X in males is termed "hemizygous"

No such thing as a male carrier - they have it or they don't

Females can be heterozygous carriers though

Ex) Duchenne Muscular Dystrophy

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X-Linked Dominant

Very rare, no carriers

Males with the disease
Males transmit the trait only to females - 100% transmission

Females with the disease transmit the trait to both males and females-50% of offspring

Ex) hypophophatemia

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The frequency a gene manifest itself is called ________

Penetrance

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Reduced Penetrance

In some cases, 100% of individuals inheriting a genetic defect show the clinical presentation (phenotype) of the disease (100?% penetrance)

In other cases penetrance is less than 100%

Ex) Retinoblastoma (autosomal dominant inheritance): phenotype occurs in 90% of individuals inheriting gene defect, so 90% penetrance

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Variable Expressivity

Term used to describe the range of phenotype that vary b/w individual w/ a specific genotype

Ex) Neurofibromatosis
Pts develop tumor-like growths called neurofibromas and develope cafe-au-lait spots

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Locus heterogeneity

Single disorder, trait or pattern of traits caused by mutations in genes at different chromosomes loci

Ex) Osteogenesis imperfecta
- brittle-bone disease
- mutations in collagen genes

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Probability

Defined as the proportion of times that a specific outcome occurs in a series of events - b/w 0 and 1

39

What is the probability of producing three girls? (THe probability of producing 1 girl is 1/2)

1/2 x 1/2 x 1/2 = 1/8

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What is the probability of producing either three girls or three boys?

1/8 + 1/8 = 1/4

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______ specify the proportions of each allele in a population

Gene frequencies

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________ specify the proportions of each genotype in a population

Genotype frequencies

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Hardy-Weinberg Principle

P^2 + q^2 + 2pq = 1


Specifies the relationship b/w gene frequencies and genotype frequencies
Useful in estimation genes frequencies from disease prevalence data and in estimating the incidence of heterozygous carriers of recessive disease genes

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Autosomal Dominant Inheritance

Characterized by vertical transmission of the disease phenotype, lack of skipped generations, and roughly equal numbers of affected males and females

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Autosomal Recessive Inheritance

Characterized by clustering of the disease phenotype among siblings,but the disease is not typically seen among parents or other ancestors. Equal numbers of males and females and consanguinity may be present

46

Consanguineous makings are more likely to produce offspring affected by rare __________ Disorders

Autosomal Recessive

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Studies show that mortality rates among the offspring of _______ matings are up to 9% higher than those of the general population

First-cousin

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Each person carries one to five ________ lethal to offspring if matched with another copy of the mutation (homozygosity)

Recessive mutations

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Traits in which variation is thought to be caused by the combined effects of multiple genes are called ________

Polygenic genes

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

Multifactorial

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Liability distribution

Seen in diseases that do not follow the bell-curve distribution

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For multifactorial diseases that are either present or absent, it is thought that a ____________ use be crossed before the disease is expressed

Threshold liability

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Pyloric Stenosis


5x more common in _______ than ________

Muscular hypertrophy b/w stomach and duodenum leading to vomiting and obstruction

Males than females

Males need less risk genes to show disease

Least affected sex has a higher risk threshold and transmits the condition more often to the most frequently affected sex

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Multifactorial disease

Caused by the simultaneous influence of multiple genetic and environmental factors