Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Pathophysiology > Genetic Influences On Disease > Flashcards

Genetic Influences On Disease Flashcards

1
Q

Traits are determined by ____ located on ____

A

Genes, chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Each person has approx __ DNA bases encoding ____ within _____ pairs

A

3.2 billion, 30,000 genes, 23 chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Each chromosome carries

A

-hundreds to thousands of genes that code for proteins that are expressed as your traits
-Everything about you are described by these genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Genes play a crucial role in determining

A

Your health status

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Maternal and paternal chromosomes in a homologous pair have..

A

-23 from each
-each have the same genes at the same locations, but possibly different variations of those genes known as alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Alleles

A

Different genes for the same trait

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Hererozygous

A

A different gene variant found on both alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Homozygous

A

The same gene variant found on both alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Genes for most sex-traits are located on

A

-The X chromosome
-X linked alleles always show up in males whether dominant or recessive because males have only one X chromosome
- = any allele on the sex chromosomes will be expressed in males

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Hemophilia

A

-Sex linked, recessive, congenital, hereditary disease
-Caused by a defective gene on the X chromosome coding for clotting factor XIII or IX
-The allele for hemophilia is recessive so two copies are needed for a female to have the disease
-Because males only have one X chromosome they only need one copy of the hemophilia allele to have the disease
-This means hemophilia is much more common in males than in females
-Females are often carriers but the disease is most often expressed in males

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Congenital

A

-Present at birth (not always genetically determined
-May be genetic like hemophilia, but may also be microbial or viral diseases
-Eg. Congenital syphilis, Zika, Toxoplasmosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Hereditary

A

-Derived from parents
-Not all hereditary genetic diseases are congenital (Eg. Huntington disease manifests in the 3rd and 4th decade of life)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Zika Virus

A

-Not hereditary
-But if mother infected during first trimester of pregnancy it may be passed onto the developing fetus
-This could cause microcephaly and the fetus would be born with a small mishapen head
-Thus it would be congenital but not hereditary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Huntington Disease

A

-Is hereditary and involved mutation of the huntington gene and is passed down as an autosomal dominant allele
-But since it takes awhile for the hungtington protein to build up to lethal levels in the brain of patients with the disease, the disease is not present at birth
-Thus hereditary not congenital

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Causes of Congenital and Hereditary Disease

A
  1. Chromosomal Abnormalities
  2. Gene Abnormalities
  3. Multifactorial Diseases
    -Intrauterine injury (Eg. Drugs, radiation, infection, environmental, etc)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Chromosomal Abnormalities

A

-Wherein large sections of chromosomes or entire chromosomes are either missing or greater than usual copy numbers
-About 50% of spontaneous abortuses have chromosomal abnormalities

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Gene Abnormalities

A

-Wherein specific genes on one or more specific chromosomes are mutated and don’t function appropriately
-Up to 20% of paediatric in patients have a genetic abnormality
-If these abnormalities are passed down parent to child they become hereditary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Multifactorial Diseases

A

-Which encompass both gene Abnormalities and environmental effects in combination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Chromosomal Abnormalities: Nondisjunction

A

-Failure of homologous chromosomes in germ cells to separate from one another during 1st or 2nd neurotic division (anaphase 1 or 2)
-Both copies of the chromosome which didnt separate correctly will be pulled into one of two new daughter cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Nondysjunction: If daughter cell has an extra chromosome

A

-Then it may be able to survive
-The cell is not lacking in DNA, it just has more than the normal amount
-This May result in some proteins being made in greater than usual quantities, which may affect development but may not be fatal to the embryo
-Eg. Trisomy (24 or 27)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Nondysjunction: If new daughter cell is missing an autosome

A

-Then this is often fatal and the embryo will likely abort
-This is because each chromosome contains many hundreds, and in some cases many thousands of genes, most crucial to the survival of the cell
-Missing a copy of a chromosome may mean the cell lacks the DNA to form required enzymes involved in metabolism, division, etc = cell will often die
-Absent chromosome: Monosomy (22 or 45)
-Rare
-Can occur in sex chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Nondysjunction: Sex chromosomes

A

-In females one X is silenced during development, so missing one when sperm and egg come together may not be fatal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Sex Linked Chromosomal Disorders X chromosome

A

-Normally in females 1 of X is inactivated
-The inactive chromosome condenses via Epigenetic regulation and is transcriptionally silent
-However the other copy of the chromosome is active and thus any genes expressed on it, dominant or recessive, will show up in the person
-Random which X is expressed and which is silent
-Results is mosaicism = Some cells in a woman expressing a particular allele and other cells expressing a different allele

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Sex Linked Chromosomal disorders

A

-Because only X chromosome and no Y chromosome are absolutely required, nondysjunction can result in many people having varying numbers of chromosomes from a single X and no Y to extra copies of both X and Y chromosomes and still surviving development
-A number of karyotypes from 45 (X0) to 49 (XXXXY) are capable of survival
-Male phenotype is encoded by Y

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Most Common Sex-linked Disorders in Females

A
  1. Turners Syndrome: absence of one X chromosome (XO)
  2. Triple X Syndrome: extra X chromosome (XXX)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Most Common Sex-linked Disorders in Males

A
  1. Klinefelters Syndrome: extra X chromosome (XXY)
  2. XYY Syndrome: extra chromosome (XYY, obviously)
27
Q

Turner Syndrome

A

-Congenital chromosomal abnormality which results from nondysjunction of an X chromosome during meiosis 1 or 2
-Primary hypogonadism in phenotypic female (XO)
-Results in a woman with only a single X chromosome
-After fertilization there is a stage in embryonic development when both X’s are active and one hasn’t yet been silenced
-Both X’s remain active during the first 100 cell divisions after fertilization
-In addition there are two active X chromosomes during ovarian development and certain of those genes appear to need to be active for normal ovarian function

28
Q

Turner Syndrome Symptoms

A

-Growth Retardation
-Short stature
-Webbing of the neck
-Low posterior hairline
-Broad chest
-Cubitus valgus (the forearm is angled away to a greater degree than normal when fully extended)
-Streak ovaries: infertility, amenorrhea, infantile genitalia, little pubic hair
-High BP due to narrowing of the aorta or kidney abnormality

29
Q

Triple X Syndrome

A

(47, XXX)
-Inactive chromosome is reactivated when meiosis begins during fetal life and remains active during the first 100 cell divisions
-During the first 100 divisions of the fertilized embryo and during ovum development all 3 X’s are expressed and thus more than usual gene products from the X chromosomes are produced
-After 100 divisions both extra ax’s are silenced and normal cell growth and development proceed

30
Q

Triple X Syndrome Symptoms

A

-Vast majority are never diagnosed and never know
-Often taller than average
-Sometimes increased distance between eyes
-poor muscle tone
-curved in 5th finger towards 4th
-below average IQ
-developmental delays
-Normal fertility = extra X not usually passed on to children
-All typically fairly mild

31
Q

Klinefelters Syndrome

A

-47 XXY
-Most common disease linked to a male sex linked chromosomal abnormality
-The Y chromosome prevents the inactivation of the X chromosome but because there are two X’s present due to nondysjunction during meiosis
-Double the amount of X chromosome gene products are produced and so male development is significantly altered
-Additional X is either paternal or maternal

32
Q

Causes of Klinefelters

A

-Nondisjunction of X chromosome due to either advanced maternal age or history of irradiation of either parents

33
Q

Klinefelters Syndrome Symptoms

A

-Causes an increase in estrogen and decrease in testosterone =
-Reduced body and facial hair
-Gynecomastia
-Testicular atrophy
-Impaired spermatogenesis = sterility (rarely fertile)
-Congenital

34
Q

XYY Syndrome

A

-Second most common disease linked to male sex linked chromosomal abnormality
-Sex chromosome nondysjunction in meiosis 2 has resulted in two copies of the Y chromosome contained in the sperm which eventually fertilizes the ovum

35
Q

XYY Syndrome Symptoms

A

-Most men with this syndrome will display normal phenotype
-May experience learning delays in particular in speech and language
-IQ normal
-Testosterone levels normal
-Behavioural problems may occur however aggression levels normal
-have no other obvious physiological differences because of the small amount of active genes located on Y
-Usually not heritable = children are usually normal XX or XY

36
Q

Autosomal Abnormalities

A

-Absence of an autosome results in the loss of a copy of several hundred/thousand genes
-Development is generally not possible and the embryo is aborted
-Deletion of a small part of an autosome May be compatible with development but usually results in multiple severe congenital abnormalities
-Trisomy at either 21, 13, or 18

37
Q

Autosomal Abnormalities Nondysjunction or Translocation

A

-Nondysjunction or translocation of chromosomes during meiosis can result in an embryo having more than the normal compliment of chromosomes
-While in most cases this is still fatal, a few specific cases the embryo is able to continue to develop
-Patients with this have a trisomy (3 copies of a chromosome)

38
Q

Down Syndrome

A

-Most common/frequent autosomal disorder
-Parents have normal karyotype
-Caused by presence of extra chromosome 21 3 instead of 2
-Many fetuses are aborted early in pregnancy (70%)

39
Q

Symptoms of Down Syndrome

A

-Substantial intellectual disability
-Physiological symptoms

40
Q

Causes of Down Syndrome

A
  1. Nondisjunction during gametogenesis (95%)
  2. Translocation (few)
  3. Nondisjunction in zygote (rare)
41
Q

Down Syndrome Nondisjunction during Gametogenesis

A

-Occurs most often
-During meiosis specifically during anaphase 1 and 2

42
Q

Down Syndrome Translocation

A

-In some cases chromosome 21 may actually fuse with chromosome 14 during a translocation event and result in an extra copy of chromosome 21 (even if it is fused to 14) being present in the cell
-While uncommon the translocation type is important because it can result in someone who is a carrier of down syndrome but who does not have it themselves

43
Q

Down syndrome Nondisjunction in zygote

A

-Occurs during zygote formation before becoming an embryo (before and during the first cell division)
-Very rate but results in the same trisomy of chromosome 21

44
Q

Down syndrome and Meiosis

A

-Since Down syndrome is caused by an extra copy of chromosome 21, an autosome, the cell without a copy of chromosome 21 dies
-However should the sperm and egg containing two copies of chromosome 21 merge with its corresponding egg or sperm, a trisomy 21 will occur

45
Q

Translocation

A

-Translocation is the “crossing over” of two chromosomes, resulting in the fusion of one chromosome with another
-No DNA is lost but now during meiosis it is physically impossible for the chromosomes to separate into the appropriate haploid cell during gametogenesis
-Thus a parent may be carrying around a fused chromosome and have no physical symptoms as the genetic material is still there but when they form sperm and egg, the resultant embryo will have the equivalent of an extra chromosome worth of DNA because two chromosomes are fused

46
Q

Translocation of chromosome 21: If normal chromosomes in cells of both parents

A

-Translocation occurred accidentally during gametogenesis in the germ cells of one of the parents

47
Q

Translocation of chromosome 21: If 14/21 carrier in one of the parents

A

-Carrier parent has only 45 chromosomes because one is the fusion of chromosome 21 with 14
-Carrier parent is capable of transmitting abnormal chromosome to his or her children resulting in translocation Down Syndrome

48
Q

Possible Outcomes of Pregnancy involving a Female Carrier (Down Syndrome)

A

-Normal
-Carrier
-Nonviable
-Down Syndrome
-Can happen with either carrier female and normal male or carrier male and normal female
-50% change fetus will be normal, 25% chance it will be non viable, 25% of trisomy 21

49
Q

Zygote Nondisjunction

A

-Rarest genetic abnormality which can result in Down syndrome
-Here both egg and sperm from parent are 100% normal but something goes wrong during the initial egg cell division after fertilization
-After sperm and egg fusion the cells begin to divide rapidly to form embryo however that initial division results in Nondisjunction
-The cell lacking an autosome dies, however rest of the cells are able to continue to develop into the fetus and eventually the person with Down syndrome
-However since only 1/3rd of this persons cells are trisomic and the other 2/3rd are normal, the symptoms of Down syndrome tend to be LESS SEVERE
-= person will have a mosaic of normal and Down syndrome cells in their body, blood cells normal, skin cells may have trisomy 21

50
Q

Genes involved in Down Syndrome

A

-When your dealing with the addition of a large chunk or all of an autosome, youre dealing with a cell that is now expressing a large number of additional copies of genes which can have lots of consequences for growth and development of any cell in the body
-This is why there are so many clinical symptoms for Down syndrome = because so many genes affected means cellular differences in almost every tissue in the body

51
Q

Clinical symptoms Down Syndrome

A

-Intellectual Disability (IQ 25-50)
-Flat face
-Neck skin folds
-Simian crease of the hand (may also occur in FAS, klinefelters and turners)
-Skeletal muscle hypotonia
-Hypermobility of joints
-Increased risk of acute leukaemia s
-Congenital heart defects
-40% mortality until 10 years of age due to cardiac complications

52
Q

Less Frequent Autosomal Trisomy

A

-Trisomy 13 (Patau syndrome)
-Trisomy 18 (Edwards syndrome)
-Both usually fatal in the neonatal period of in early infancy

53
Q

Trisomy 13 (Patau Syndrome)

A

-Result of 3 copies of chromosome 13
-May occur in the same 3 ways as Down syndrome
-manifestations are far more severe for the development of the fetus
-Of the few who do survive to childbirth, the majorly die within the first year of life

54
Q

Trisomy 13 (Patau Syndrome) Symtoms

A

-Multiple organ defects (nervous system, musculoskeletal, urogenital, etc)

55
Q

Trisomy 18 (Edwards syndrome)

A

-Occurs in same way but with chromosome 18
-Rare
-Usually rapidly fatal and very few (7.5%) of children born with it survive past 1 year of age

56
Q

Trisomy 18 (Edwards Syndrome) Clinical Symptoms

A

-Cleft lip and palate
-Abnormal development of skull, brain, and eyes
-Congenital heart defect
-Polydactyly

57
Q

Gene Abnormalities

A

-Hereditary gene abnormalities are usually transmitted on autosome, only a few on sex chromosomes
-Gene mutation can be spontaneous (random chance) or environmental (exposure to mutagen)
-Minor structural change to a protein may result in major functional abnormality

58
Q

Point Mutations and Gene Abnormality

A

-Most common gene abnormality only one gene is altered
-DNA is miscoded frequently during DNA replication or exposure to a mitogen
-If these mutations occur in the zygote or early embryo stage of development then they may be passed on via the gametes to the next generation resulting in a heritable mutation with potentially congenital effects
-Proteins made from the RNA of this mutate gene may have incorrect amino acid sequence and may not fold or function properly = the case with common genetic diseases and may be recessive or dominant based on which gene (allele) is affected

59
Q

Recessive Gene Mutations

A

-Sickle Cell Disease
-Cystic Fibrosis
-PKU

60
Q

Sickle Cell Disease

A

-Caused by an autosomal recessive gene mutation on chromosome 11
-Even though gene will be expressed in a heterozygote, they are mostly asymptomatic for it
-Only when a person is homozygous for this mutation does the disease manifest
-The glutamic acid to valine mutation results in molecules of hemoglobin which form an abnormal quaternary structure
-Rather than sticking to each-other in small groups of 4 they form long chains which distort the structure of the RBC itself = sickle like appearance
-Begin to stick to blood vessels and cause clots which can cut off blood flow to affected tissues
-Reduced oxygen begins to cause those tissues to die, causing extreme pain
-Most common in African, middle eastern, Asian, Indian, and Mediterranean descents as carriers

61
Q

Manifestations of Sickle Cell

A

-Chronic anemia and hemolysis
-Jaundice
-Pain (often occurs as crisis)
-Stroke
-Chronic organ damage (kidneys, liver, brain, spleen, lungs, bones, eyes)
-In high income counties life expectancy 40-60 years

62
Q

Symptoms of Sickle Cell Due to

A

1) rapid turnover of sickled RBC’s in comparison with normal RBC’s = what causes anemia
2) The clotting of the blood causing hypoxia in the downstream tissue (causes majority of organ damage, happens randomly as crisis)

63
Q

Heterozygous condition and sickle cell means

A

-Protects people from malaria
-Malarial parasite can not live in a sickled RBC because pathogen that causes the disease spends part of its cycle in the RBC which are rapidly removed from the circulation and limiting the infections progress, as well as sickled cell is stretched by its unusual shape = it become porous = leaks nutrients like potassium needed for parasite to survive

Pathophysiology (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions