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Unit 2 M2M > Unit 2 Day 1 > Flashcards

Unit 2 Day 1 Flashcards

1
Q

What does a family history consist of information wise?

A
  • Biological relationships between family members

- any medical conditions they may have

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2
Q

What can a family history reveal?

A
  • Patterns of inheritance
  • what type of inheritance may be part of a condition
  • distinguishing btw. conditions with similar presentations
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3
Q

How many generations should be included in a family history?

A

3 (if in doubt)

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4
Q

genotype

A
  • an individual’s collection of genes. The term also can refer to the two alleles inherited for a particular gene. The genotype is expressed when the information encoded in the genes’ DNA is used to make protein and RNA molecules.
  • the DNA sequence*
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5
Q

phenotype

A
  • an individual’s observable traits, such as height, eye color, and blood type. The genetic contribution to the phenotype is called the genotype. Some traits are largely determined by the genotype, while other traits are largely determined by environmental factors.
  • refers to observed traits*
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6
Q

dominance

A
  • the phenomenon whereby, in an individual containing two allelic forms of a gene, one is expressed to the exclusion of the other.
  • phenotype that is expressed in the heterozygous state*
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7
Q

recessive

A
  • relating to or denoting heritable characteristics controlled by genes that are expressed in offspring only when inherited from both parents, i.e., when not masked by a dominant characteristic inherited from one parent.
  • a phenotype that is expressed only in homozygotes or hemizygotes*
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8
Q

semidominant

A

One of a series of terms applied to the phenotypic effect of a particular allele in reference to another allele (usually the standard wild-type allele) with respect to a given trait. An allele “A” is said to be semidominant with respect to the allele “a” if the A/A homozygote has a mutant phenotype, the A/a heterozygote has a less severe phenotype, while the a/a homozygote is wild-type. An example is Pmp22(Tr-J) in mouse. Pmp22(Tr-J)/Pmp22(Tr-J) animals display a myelination defect associated with a “trembler” phenotype, while Pmp22(Tr-J)/Pmp22(+) animals are less severely affected, and Pmp22(+)/Pmp22(+) animals are wild-type.
when the heterozygous phenotype is intermediate btw the 2 homozygous phenotypes

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9
Q

single-gene disorders

A

When a certain gene is known to cause a disease, we refer to it as a single gene disorder or a Mendelian disorder. For example, you may have heard of cystic fibrosis, sickle cell disease, Fragile X syndrome, muscular dystrophy, or Huntington disease.

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10
Q

Mendel’s First Law

A

The principle of segregation (First Law): The two members of a gene pair (alleles) segregate (separate) from each other in the formation of gametes. Half the gametes carry one allele, and the other half carry the other allele.

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11
Q

Mendel’s Second Law

A

The principle of independent assortment (Second Law): Genes for different traits assort independently of one another in the formation of gametes.

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12
Q

penetrance***

A

the percentage of individuals with a given genotype who exhibit the phenotype associated with that genotype. For example, an organism may have a particular genotype but may not express the corresponding phenotype, because of modifiers, epistatic genes, or suppressors in the rest of the genome or because of a modifying effect of the environment.
the fraction of individuals with a trait genotype who show manifestations of the disease

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13
Q

expressivity***

A

measures the extent to which a given genotype is expressed at the phenotypic level. Different degrees of expression in different individuals may be due to variation in the allelic constitution of the rest of the genome or to environmental factors.
the degree to which a trait is expressed in an individual (severity)

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14
Q

pleiotropy***

A

occurs when one gene influences two or more seemingly unrelated phenotypic traits, an example being phenylketonuria, which is a human disease that affects multiple systems but is caused by one gene defect. Consequently, a mutation in a pleiotropic gene may have an effect on some or all traits simultaneously.
some mutations–>multiple and different phenotypes. different than variable expressivity

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15
Q

homozygous

A

2 identical alleles at a given locus (wt or mutant)

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16
Q

heterozygous

A

2 different alleles at a given locus

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17
Q

hemizygous

A

mostly refers to males (XY) who have just a single copy of each X-chromosomal gene

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18
Q

autosomal dominant

A

pattern of inheritance characteristic of some genetic diseases. “Autosomal” means that the gene in question is located on one of the numbered, or non-sex, chromosomes. “Dominant” means that a single copy of the disease-associated mutation is enough to cause the disease.

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19
Q

autosomal recessive

A

one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop.

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20
Q

mitochondrial inheritance

A

They are maternally inherited because they are supplied by the egg at fertilization. Mitochondria contain their own their own DNA, including 39 genes that are susceptible to mutations at a rate 10-20 times higher than nuclear DNA.

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21
Q

x-linked dominant

A

a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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22
Q

x-linked recessive

A

a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males (who are necessarily heterozygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation, see zygosity.
not male-to-male transmission

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23
Q

What are the major patterns of Mendelian inheritance?

A

autosomal dominant
autosomal recessive
sex linked/x-linked recessive

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24
Q

age dependent penetrance

A

the likelihood of manifesting the disease in mutation carriers is dependent on age

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25
Q

sex influence and sex limitations

A

the manifestation of a trait is dependent on the individual’s sex

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26
Q

environmental factors

A

some environmental factors can affect the expression of Medellian diseases

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27
Q

modifier genes

A

genetic factors that influence a phenotype

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28
Q

stochastic effects

A

random effects can influence the expression of phenotypes

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29
Q

phenocopies

A

same phenotypes (as genetic condition) due to non-genetic factors

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30
Q

human genome structure

A

3x10^9 base pairs distributed on 46 nuclear chromosomes

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31
Q

how many pairs of chromosomes are there?

A

23

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32
Q

how many autosomes?

A

22

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33
Q

how many sex chromosomes?

A

1 pair

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34
Q

What can mutations in the beta globin gene cause?

A

variety of disorders in hemoglobin

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35
Q

How many exons are in the beta globin gene?

A

3

36
Q

What are mutations in BRCA1 responsible for?

A

cases of inherited breast cancer, or breast and ovarian cancer

37
Q

What are mutations in beta-myosin responsible for?

A

inherited hypertrophic cardiomyopathy

38
Q

Globing-How are they expressed?

A

as a function of development. they are turned on or off in the gene. In Chromosome 11 they are turned on in the order they appear in the genome (unusual)

39
Q

What types of genes are retained?

A

genes that are adaptive

genotype+environment=phenotype

40
Q

What is the significance of random variation?

A

fuel of evolution
almost always a deleterious consequence
but allows for variation/evolution

41
Q

How many mutations occur in each individual?

A

~30

42
Q

When are genes shuffled/recombined?

A

Meiosis

produces somatic and germ line DNA changes

43
Q

What composes the majority of the human genome?

A

stable regions

AT rich regions (54%)

44
Q

What is clustering?

A

non-random distribution of GC rich and AT rich regions as a basis for chromosomal binding patterns
allows for G banding

45
Q

How much of the genome is translated?

A

1.5% for protein coding

46
Q

how much of the genome is made of genes?

A

20-25% (exons, introns, flanking sequences)

47
Q

What is a more relaxed region called?

A

Euchromatic

where gene sequencing is focused

48
Q

What is a more condensed region called?

A

Heterochromatic (repeat rich areas)

essentially unsequenced

49
Q

Tandem repeats

A

“satellite DNA”
used as basis for cytogenetic banding
found as part of human-specific heterochromatic regions on the long arms of Chr 1, 9, 16, Y (hotspots for evolution)

50
Q

alpha satellite repeats

A

171 bp repeat unit
near centromeres
may be important in chromosomal segregation in mitosis and meiosis

51
Q

dispersed repetitive elements

A

insert and become pseudo genes
retrotransposition may cause insertional inactivation of genes
facilitate abberant recombination events btw diff copies of dispersed repeats leading to disease

52
Q

segmental dynamic mutation

A

non-allelic homologous recombination btw blocks of segmental duplication during meiosis that leads to micro deletion/duplication of unique region bracketed by the duplication

53
Q

insertion-deletion polymorphisms

A

minisatellites (tandem repeat 10-100bp blocks, VNTR)

microsatellites (di, tri, tetra nucleotide repeats)

54
Q

single nucleotide polymorphisms

A

also known as simple nucleotide polymorphism, (SNP, pronounced snip; plural snips) is a DNA sequence variation occurring commonly within a population (e.g. 1%) in which a single nucleotide — A, T, C or G — in the genome (or other shared sequence) differs between members of a biological species or paired chromosomes.

55
Q

copy number variations

A

variation segments of genome
can range from one extra copy to many
array comparative genomic hybridization

56
Q

gene family

A

composed of genes with high sequence similarity that may carry out similar but distinct functions

57
Q

how do gene families arise?

A

through duplication. allows one copy to vary while the other carries out critical functions

58
Q

copy number variations

A

primary type structural variation
may cover 12% of genome
implicated in many diseases

59
Q

what are they types of constitutional abnormalities

A

de novo, sporadic

familial

60
Q

m phase

A

where we visualize metaphase of chromosomes

many macromolecules doubled

61
Q

kinectochore

A

protenatious complex that allows pulling apart of chromosomes into daughter cells

62
Q

How is ISCN written?

A

label arm (p, q)
then region
then band
human chromosome pairs are numbered 1022 autosomes, arranged by size and centromere position, sex chromosomes (x, y)

63
Q

metacentric

A

these are X-shaped chromosomes, with the centromere in the middle so that the two arms of the chromosomes are almost equal. A chromosome is metacentric if its two arms are roughly equal in length.

64
Q

submetacentric

A

having the centromere situated so that one chromosome arm is somewhat shorter than the other.

65
Q

acrocentric

A

having the centromere situated so that one chromosomal arm is much shorter than the other
all short arm often is is repetitive, satellite sections

66
Q

from where do you get the best chromosomes for banding study?

A

from peripheral blood-highest resolution

other types: bone marrow (smallest), amniotic (middle length)

67
Q

ploidy

A

number of homologous chromosome sets present in cell or organism

68
Q

dipoid

A

has 2 sets of chromosomes (46)

69
Q

haploid

A

has 1 set of chromosomes (23)

70
Q

euploidy

A

good ploidy-has full set of chromosomes

71
Q

polyploidy

A

many ploidy, having chromosome number that is more than double the basic or haploid number (69, etc)

72
Q

aneuploidy

A

not good aploidy-incomplete set

trisomy (47), monosomy (45)

73
Q

When can aneuploidy occur?

A

during meiosis 1 (maternal/paternal)
during meiosis 2 (maternal/paternal)
post zygotic (after fertilization, anytime)

74
Q

what are the basic steps of meiosis?

A
  1. Before meiosis begins, the chromosomes are in a threadlike form.
    Each chromosome make identical copy of itself, forming two exact halves called chromatids. The chromosomes then thicken and shorten into a form that is visible under a microscope. The nuclear membrane disappears.
  2. Each chromosome is now made up of two chromatids, the original and an exact copy. Similar chromosomes pair with one another, forming homologous chromosomes
    pairs. The pair homologous chromosomes line up at the equator of the cell.
  3. The chromosomes separate from their homologous partners and move to the opposite ends of the cell.
  4. The nuclear membrane re-forms, and the cell divides. The paired chromatids are still joined.
  5. Each cell contains one member of each homologous chromosome pair. The chromosomes are not copied again between the two cell divisions.
  6. The chromosomes line up at the equator of each cell.
  7. The chromatids pull apart and move to the opposite ends of the cell. The nuclear membrane forms around the separated chromosomes, and the cells divide.
  8. The results: four new cells have formed from the original single cell. Each new cell has half the number of chromosomes present in the original cell.
75
Q

meiotic recombination

A

2-3 cross over events (chiasma)
pair of homologous chromosomes
each event generates a physical link btw. homologues that is critical for normal disjunction

76
Q

where does genetic variability arise from?

A

recombination meiotic prophase 1

independent assortment of maternal/paternal chromosomes

77
Q

what are tolerated aneuploidies?

A

conceptions: 45X; trisomy 16, 21, 22
Births: trisomy 13, 18, 21
sex chromosome aneuploidy (gain/loss)

78
Q

trisomy 21

A

associated advanced maternal age
most common (1 in approx 800-900)
majority result of maternal meiosis 1 nondisjunction errors

79
Q

trisomy 18

A

small, abnormalities, die in first year, 1/8000 births

80
Q

turner syndrome

A

most common spontaneous abortions
1/2500 female births
only 1 x
can have mosaicism (tissues and whole person)

81
Q

kleinfelter syndrome

A 
47 xxy
1/1000 men
paternal or maternal
mosaicism in tissues, variants
more x's can mean more severe phenotypes
82
Q

triploidy

A

in karyotypes of 1-3% conceptions
mostly from 2 sperm in 1 egg
some could be 2n sperm or egg
69 chromosomes

83
Q

mosaicism

A

2 or more diff karyotypes individual/tissue
caused mostly by nondisjunction
if it occurs later it’s better

84
Q

germ line mosaicism

A

mitotic nondisjunction in germ cell precursor

85
Q

pseudomosaicism

A

occurs in laboratory, not in patient somatic cells

Unit 2 M2M (8 decks)

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