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Foundations Exam 2 > Genetics > Flashcards

Genetics Flashcards

1
Q

What is a gene?

A

Hereditary unit of DNA transmitted from one generation to another; code for proteins.

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2
Q

Define a locus.

A

The specific location of a gene on a chromosome.

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3
Q

Define alleles.

A

Different versions of a gene; humans have 2 alleles for each autosomal gene.

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4
Q

Define chromosomes.

A

structure composed of genes located in nucleus of a cell.

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5
Q

Define homologous chromosomes.

A

Have the same genes at the same loci, one maternal and one paternal.

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6
Q

Define genome

A

The genetic information contained in the cells, on the chromosomes, for a particular species.

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7
Q

Describe the number of chromosomes in each somatic cell.

A

The same for all members of a species.
Human cells: 46 chromosomes (23 pairs, 22 autosomes and 1 allosome).
One set of chromosomes from female parent and one homologous set from male parent (similar in size, structure, and gene composition).

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8
Q

Define mutation.

A

A change in some part of the DNA code.
Can be spontaneous or induced by exposure to mutagenic chemicals/radiation.
Varying effects depending on where in the gene code the mutation occurred.
Net result of a mutation may be a change in physical appearance or other trait.

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9
Q

Define autosome

A

Any chromosome that is not a sex chromosome. Humans have 22 pairs of autosomes. (Somatic chromosomes).

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10
Q

Define allosome.

A

Sex chromosome. Humans have one pair.

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11
Q

Define somatic cells

A

Diploid

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12
Q

Define sex/reproductive cells.

A

Haploid

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13
Q

What is a karyotype?

A

When the chromosomes are lined up with homologous pairs in order and numbered.

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14
Q

What is a karyotype?

A

When the chromosomes are lined up with homologous pairs in order and numbered.

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15
Q

Describe the structure of the chromosome.

A

The chromosome is made up of two homologous pairs connected at the centromere. The short arm is labeled the p arm (petite). and the long arm is labeled the q arm (long).

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16
Q

What is a karyotype?

A

Picture of a person’s chromosomes. The chromosomes are lined up with homologous pairs in order and numbered. Each chromosome is numbered consecutively according to length beginning with longest first.

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17
Q

Describe the structure of the chromosome.

A

The chromosome is made up of two homologous pairs connected at the centromere. The short arm is labeled the p arm (petite). and the long arm is labeled the q arm (long).

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18
Q

Describe sex chromosomes in males.

A

Human males have one morphologically dissimilar pair of chromosomes- the sex chromosomes. Heteromorphic (don’t match up in size or shape).
Labeled X and Y.
Genetic factors on the Y determine maleness.

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19
Q

Describe sex chromosomes in females.

A

Human females have two morphologically similar X’s.

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20
Q

Define Mitosis.

A

The process by which all somatic cells become descendants of one original cell.
One exact copy of each chromosome is made and distributed through the division of original cell into two daughter cells.

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21
Q

Define Meiosis.

A

The process by which gamete cells are produced (egg and sperm).
Resulting gametes have 23 new chromosomes (one from each of the pairs), with new combos of the original maternal and paternal copies.
Occurs only in specialized germ cells of gonads.
2 consecutive cell divisions producing cells with half the original chromosome number (diploid 2n->haploid n).

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22
Q

Describe gametogenesis of sperm (spermatogenesis).

A

Diploid primordial cells in testes become spermatogonia. Eventually, 4 haploid sperm cells are produced (spermatozoa).

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23
Q

Describe gametogenesis of ovums (oogenesis).

A

Diploid primordial cells in ovaries become oogonia. Eventually, 1 haploid ovum is produced and polar bodies are degenerated.

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24
Q

Define genotype.

A

All of the alleles of an organism (the actual genes they have).

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25
Q

Define phenotype.

A

A measurable trait an organism has (what you see).

Result of gene products that interact in a given environment.

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26
Q

Describe the dominant allele.

A

Phenotype can be seen in both the heterozygous and the homozygote. Phenotype overpowers the recessive allele.

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27
Q

Describe what it means to be a carrier of an allele.

A

Heterozygous individual with a recessive allele that’s hidden from phenotypic view by the dominant, normal allele.

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28
Q

What does it mean to be homozygous?

A

To contain the same alleles at a single locus.

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29
Q

What does it mean to be heterozygous?

A

To contain 2 different alleles at a single locus.

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30
Q

Describe the recessive allele.

A

Produces the phenotype only when its paired allele is identical.

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31
Q

What is the purpose to study patterns of inheritance?

A

To describe how disease is transmitted in families.
The patterns help predict the risk for relatives.
Trace single gene disorders (Mendelian disorders classified by whether they are autosomal or x-linked, dominant or recessive).

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32
Q

Describe a Punnett square.

A

It illustrates a mono factorial cross- a mating in which a single gene is analyzed.

33
Q

What principle of genetics is demonstrated in a Punnett square?

A

Mendel’s principle of segregation: one parent has 2 copies of a gene for each train, but transmits only one via a gamete.

34
Q

Describe the pattern of inheritance for albinism.

A

A=dominant, pigment-producing allele.

a=recessive, albino (no pigment) allele. Only two phenotypes and three genotypes.

35
Q

Describe codominance in alleles.

A

When two alleles for a trait are equally expressed (example: AB blood type).
This happens when alleles lack complete dominant and recessive relationships and are both observed phenotypically (no blending).
Seen in chickens and cattle as well.

36
Q

Describe incomplete dominance in alleles.

A

Heterozygotes have phenotypes that have both alleles visible as a blend (one allele isn’t expressed over the other).
Makes a third phenotype thats a blending of the two.
(wavy hair, skin color)

37
Q

Define penetrance.

A

The probability that individuals in a population who have a particular gene combination will show the condition. Ex: if a mutation causes diabetes at 95% penetrance, 95% of people with the mutation will develop diabetes.

38
Q

Define genetic marker.

A

Sequence of DNA with a known location on a chromosome.

39
Q

Define expression.

A

The components of the phenotypes that are exhibited in an individual.
Ex: myotonic muscular dystrophy phenotype may include myotonia, cataracts, narcolepsy, balding, infertility. 2 people carrying this gene may express it differently.

40
Q

Define anticipation.

A

Genetic diseases that increase in severity or have earlier onset with each successive generation. Ex: Huntington, Fragile X, Myotonic muscular dystrophy.

41
Q

Describe Inversion.

A

A chromosome piece is lifted out, turned around, and reinserted.

42
Q

Describe balanced translocation.

A

Rupture of a chromosome resulting in the pieces “re-sticking” in the wrong combinations.

43
Q

Describe balanced chromosomal abnormalities.

A

No net loss or gain of chromosomal material, just reorder.

44
Q

What is the most common chromosomal abnormality?

A

Chromosomal abnormalities can be numerical or structural but the most common is Aneuploidy: abnormal number.

45
Q

Describe unbalanced chromosomal abnormalities.

A

Addition or missing information (insertion/deletion.

46
Q

Described Robertsonian translocation.

A

An unbalanced translocation that involves any 2 out of chromosomes 13, 14, 15, 21, and 22.
Results in formation of a “new” chromosome. The bigger chromosome can produce an unbalanced gamete.
Those involving chromosome 21 can produce gametes with 2 copies; upon fertilization, can produce Trisomy 21.

47
Q

Describe an unbalanced chromosomal translocation.

A

To much or too few information present because the genes are relocated.

48
Q

Why do we use three generation pedigrees?

A

Provides a concise visual tool.
Genetic testing is more available to patients.
Many diseases with genetic links have been discovered and clarified.
More clinicians are needing to understand the genetic basis of disease to effectively understand disease processes and treatments.

49
Q

What are the functions of a three-generation pedigree?

A 
Making a diagnosis. 
Deciding on testing strategies. 
Establishing the pattern of inheritance. 
Identifying people at risk. 
Educating the patient. 
Determining reproductive options.
50
Q

What is the standard pedigree symbol for a male?

A

Square.

51
Q

What is the standard pedigree symbol for a female?

A

Circle

52
Q

What is the standard pedigree designation for a person who is deceased?

A

Diagonal line through symbol.

53
Q

What does a shaded symbol represent on a pedigree?

A

Person affected with the trait.

54
Q

What does a half shaded symbol represent on a pedigree?

A

Person is a carrier of the trait.

55
Q

What does two hash marks on a line between individuals in a pedigree represent?

A

Divorced or separated (no longer having sex).

56
Q

What is used to show a relationship on a pedigree?

A

A line between individuals.

57
Q

What is used to show sibship on a pedigree?

A

Horizontal line connecting and showing siblings.

58
Q

What is used to show a line of descent in a pedigree?

A

A vertical line showing connection to offspring.

59
Q

How do you identify a new individual to a family in the pedigree? (not genetically related).

A

A line connecting the new individual to the sibship line.

60
Q

Define a consultand and how it is represented on a pedigree.

A

The person seeking genetic advice.
Represented by an arrow on pedigree.
Can be healthy or a person with a condition.

61
Q

Define a proband.

A

The affected individual in the family.

62
Q

List some pedigree tips.

A

Use abbreviations sparingly.
Draw siblings in birth order from left to right and include their age/birth year.
Each generation goes on the same horizontal plane.

63
Q

What are the differences between a research pedigree and a clinical pedigree?

A

Research pedigree: Generations are given Roman numerals. Individuals in a generation are given a number. Easier to identify and protect confidentiality.
Clinical pedigree:
Names recorded next to individuals line. Surname recorded above sibship or relationship line. Initials often used.

64
Q

Describe autosomal dominant.

A

Mutation in a single allele can cause disease.
65% of human monogenic disorders are autosomal dominant.
Vertical pattern (transmission passes from parent to offspring).
Multiple generations affected.
Variable expressivity.
Reduced penetrance. (skipped generations).
Males and females affected equally.
Male to male transmission can be seen.

65
Q

How do you tell is a pedigree is showing an autosomal dominant mutation?

A

It shows up in at least one individual per generation in a family. (about 50% of offspring).
Males and females affected equally.
Male to male transmission can be seen.
Reduced penetrance.

66
Q

Describe autosomal recessive.

A

Two copies of diseased allele required for expressing the phenotype.
Tends to involve enzymes or receptors.
Rare.
Males and females equally affected.
Horizontal inheritance (multiple offspring affected in one generation).
Heterozygous carries of a defective allele are usually clinically normal.
Inheritance is from both parents, each being a carrier.

67
Q

How do you spot an autosomal recessive trait on a pedigree?

A

Horizontal pattern. It shows up in multiple offspring but only a single generation affected.
Generally parents don’t have it but they can.
Males and females equally affected.

68
Q

What is the chance the offspring will inherit an autosomal recessive trait?

A

25% of being affected.

50% of being a carrier.

69
Q

Describe X-linked mutation differences between sexes.

A

Risk of developing disease differs between sexes.
Males are hemizygous (heterozygous) for a mutant allele on the X: more likely to develop a mutant phenotype regardless if the mutation is dominant or recessive.
The terms x-linked dominant and recessive only apply to females.
Heterozygous females usually normal or mild.

70
Q

How do you spot a X-linked trait on a pedigree?

A

Usually only in males because they inherit only one X.
No male to male transmission possible.
Unaffected males do not transmit the phenotype.
All daughters of an affected male are heterozygous.

71
Q

What are some examples of X-linked dominant disease?

A

Alport’s syndrome

Fragile X syndrome

72
Q

What are some examples of x-linked recessive disease?

A

Wiskott-Aldrich syndrome

Duchenne muscular dystrophy

73
Q

What is an example of autosomal recessive disease?

A

Cystic fibrosis

74
Q

What is an example of autosomal dominant disease?

A

Huntington’s disease

75
Q

Which type of mutation increases with consanguinity?

A

Autosomal recessive disease.

76
Q

Describe multifactorial/complex disease.

A

Caused by interactions of variations in multiple genes and environmental factors.
Involves genetic susceptibility genes that make a person more susceptible to a disorder.

77
Q

What are some multifactorial/complex diseases people can be susceptible to?

A 
Cancer
Diabetes
Asthma
Heart disease
Mental illness
Cleft lip/cleft palate.
78
Q

Define aneuploidy.

A

The presence of an abnormal number of chromosomes in a cell.

Foundations Exam 2 (4 decks)

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