Lecture 16 Flashcards Preview

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Flashcards in Lecture 16 Deck (50):
1

how can karyotype be abnormal? (two ways)

1) in chromosome number
2) in chromosome structure

-abnormal chromosome account for at least 50% of spontaneous abortions

2

polyploidy

extra chromosome sets

3

polyploid - tripoloid (3N)

cells have three sets of chromosomes
-accounts for 17% of all spontaneous abortions and 3% of stillbirths and newborn deaths

4

how are triploids produced (2 ways)

-fertilization of one egg by two sperm
-fusion of haploid and diploid gametes

5

euploid

a normal chromosome number

6

aneuploidy

cells with extra (trisomy) or missing chromosomes (monosomy)

-most autosomal aneuploids are spontaneously aborted

7

nondisjunction

-the failure of chromosomes to separate normally during meiosis
-produces gamete with an extra chromosome and another with one missing chromosome

8

nondisjunction during meiosis I

results in copies of both homolog in one gamete

9

nondisjunction during meiosis II

results in both sister chromatids in one gamete

10

what happens when aneuploidy arises during mitosis?

Aneupoidy produces groups of somatic cells with the extra or missing chromosomes

11

mosaic

an individual with two chomosomally-distinct cell populations

12

mitotic nondisjunction event

event that occurs early in development can have serious effects on the health of the individual

13

trisomies

most autosomal aneuploids cease developing as embryos or fetuses
-seen in newborns = chromosomes 21, 18 13
-carry fewer genes than other autosomes

14

trisomy 21

-down syndrome
-most common among newborns
-distinctive facial and physical problems
-more likely to develop leukemia
-like with one form of AD

15

turner syndrome

XO syndrome
-1 in 2,500 female births
-99% of affected fetuses die in utero
-features: short stature, webbing at back of neck, incomplete sexual development (infertile), impaired hearing
-individuals who are mosaics may have children

16

triplo-X

XXX syndrome
-1 in 1,000 female births
-few modest effects on phenotype include tallness, menstrual irregularities, a slight impact on intelligence
-X-inactivation of two X chromosomes occurs and cells have two barr bodies
-may compensate for presence of extra X

17

Klineffelter Syndome

XXY syndrome (most common cause of male infertility)
-1 in 500 male births
phenotype include:
-incomplete sexual development
-rudimentary testes and prostate
-long limbs, large hands and feet
-breast tissue development

18

XYY syndrome

Jacobs syndrome
-1 in 1,000 male births
-96% are phenotypically normal
-modest phenotypes may include great height, acne, speech and reading disabilities

19

what is the most common cause of male infertility?

XXY or Klineffelter Syndrome

20

Deletions

-A deletion refers to a missing genetic segment from a chromosome
-Larger deletions increase the likelihood that there will be an associated phenotype
-Cri-du-chat (cat cry) syndrome - Deletion 5pā€“

21

Are deletions and dublications inherited?

no. Rather they arise de novo

22

duplications

-refers to the presence of an extra genetic segment on a chromsome
-The effect of duplications on the
phenotype is generally dependent on their size
- Larger duplications tend to have an effect, while smaller ones do not

23

duplications in chromosome 15

poor muscle tone
epicanthal folds
small size
mental retardations
seizures
developmental delay
curved spine
learning disabilities
autistic features

24

what is translocations and what is the two major types

two nonhomologous chromosome exchange segments
1) Robertsonian translocation
2) reciprocal translocation

25

Robertsonian Translocations

two nonhomologous acrocentric chromosome break at the centromere and their long arms fuse
-the short arms are often lost
-affects 1 in 1,000 people

26

translocation carriers (robertsonian translocations)

produce unbalanced gametes
-have 45 chromosomes

27

translocation down syndrome

About 5% of Down syndrome results from Robertsonian translocation between chromosomes 21 and 14

-more risk of spontaneous abortion

28

what happens when one of the parents is a translocation carrier?

-they may have no symptoms
-however, the distribution of the unusual chromosome leads to various imbalances

29

reciprocal translocations

two nonhomologous chromosomes exchange parts
-about 1 in 500 people are carriers. Are usually healthy because they have the normal amount of genetic material (but it is rearranged)
-However, if the translocation breakpoint interrupts a gene, there may be an associated phenotype

30

Inversions

an inversion is a chromosome segment that is flipped in orientation
-5-10% cause health problems probably due to disruption of genes at the breakpoints
1) paracentric inversion
2) pericentric inversion

-inversions may impact meiotic segregations

31

paracentric inversion

inverted region does NOT include centromere

32

pericentric inversion

inverted region includes centromere

33

isochromosomes

chromosomes with identical arms
-form when centromeres divide along the incorrect plane during meiosis

34

ring chromosomes

-occur in 1 in 25,000 conceptions
-may arise when telomeres are lost and sticky chromosome ends fuse
-genes can be lost or disrupted causing symptoms

35

uniparental disomy

inheritance of two chromosomes or chromosome parts from the same parent

36

what two rare events do unmiparental disomy (UPD) require?

the simultaneous occurrence of:
1) nondisjunction of the same chromosome in both sperm and egg
2) trisomy followed by chromosome loss

37

pathogens

protection from harmful organisms
-based upon the ability to identify foreign molecules as "nonself"

38

Foreign

bacteria, viruses, fungi, tumor, or transplanted cells

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antigens

molecules recognized by the immune system
-usually protein fragments or carbohydrates

40

how do genes affect immunity

by conferring susceptibility or resistance to infection

41

genetic control of immunity

a few types of single genes encode antibodies and cytokines that directly attack foreign antigens

genes also specify the cell surface antigens that mark the body's cells as "self"

42

what do mutations that impair immunity cause?

immune deficiencies
autoimmune disorders
allergies
cancer

43

where is major histocompatibility complex found?

found on short arm of chromosome 6
-includes about 70 genes
-code for cell protein surface features

44

major histocompatibility complex functional groups (3)

-Class III genes - encode plasma proteins that carry out non-specific immune functions
-Class I and II genes - encode human leukocyte antigens (HLA)

45

Human leukocyte antigens (HLA)

link sugars to form branched glycoproteins that extend form cell surfaces

46

antigen processing

process where human leukocyte antigens (HLA) glycoproteins can recognize bacterial and viral proteins, marking them fro immune system to target

47

which classes of major histocompatibility functional groups encode human leukocyte antigens?

Class I and II:
-Class I - found on all cell types. Class I HLA encode antigens defining "self"
-Class 2: found mostly on antigen-presenting cells

48

antigen-presenting cells

cells that bind antigens with HLA glycoporteins

49

what are the two main types of antigen-presenting cells?

machrophages
t cells (or T-lymphocytes)

50

steps of antigen-presenting cells

1. phagocytosis of the microbial invader
2. antigens from the dismantled invader are attached to MHC self proteins
3. MHC proteins and their attached antigens are displayed on machrophage surface
4. helper T cells recognize antigens and MHC proteins and bind to the macrophage, initiating a series of immune events