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BIOL-2301 Final Exam > Chapter 8: Human Karyotyping and Chromosomal Behavior > Flashcards

Chapter 8: Human Karyotyping and Chromosomal Behavior Flashcards

1
Q

What is a Giesma Stain?

A

a stain that produces bands along a chromosome for karyotyping purposes

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2
Q

G bands vs R bands, when do the corresponding genes replicate?

A

G bands do not containing as many genes, often appear darker. the genes in the G bands replicate in LATE S PHASE

R bands on the karyotype contain many genes and appear lighter. the genes in the R band replicate in EARLY S PHASE

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3
Q

p vs q arm of a chromosome

A

p arm is the short arm

q arm is the long bottom arms

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4
Q

What’re the alphabetical groups of a human karyotype?

A 
A; 1-3
B; 4-5
C; 6-12
D; 13-15
E; 16-18
F; 19-20
G; 21-22

and the sex chromosomes XY

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5
Q

pter?

A

terminal position in the p arm

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6
Q

qter?

A

terminal position in the y arm

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7
Q

What does a positive symbol on a karyotype indicate?

A

that there is an extra chromosome of a paritcular number

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8
Q

What does a negative symbol on a karyotype indicate?

A

that they are missing a chromosome of a particular number

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9
Q

What is a metacentric centromere

A

a centromere in the middle of the chromosome, the length of the p arms thus equal the length of the q bottom arms.

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10
Q

What classes of chromosomes on a karyotype would you expect to see a metacentric centromere?

A

on A; 1-3, and maybe C (6-12) and F (19-20)

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11
Q

What classes of chromosomes on a karyotype would you expect to see a submetacentric/subterminal centromere?

A

in chromosome groups B (4-5), some C(6-12), E (16-18) and X chromosomes.

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12
Q

What is an acrocentric centromere?

A

a centromere that is almost at the end. Found in D (13-15) G (21-22) and the Y chromosome.

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13
Q

What does dosage compensation do? What would happen if this did not occur?

A

Dosage compensation is the regulation of protein is corrected by increasing the activity of the X Chromosome in males or limiting the activity in females. If this did not happen, boys would have a serioud deficiency in protein because structural proteins would be less available.

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14
Q

What kind of dosage compensation occurs in mammals?

A

X-inactivation, where only one X chromosome in females are expressed.

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15
Q

What is X mosaicism?

A

The presence in different X activations differing between cells in the same individual. Can be seen phenotypically, like in a calico cat. Different cells have different X chromosomes that are activated, thus resulting in patches of either orange or black.

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16
Q

What’re the genes that still remain active on both X chromosomes in females even though the rest of one chromosome is inactivated?

A

PARp and PARq- the PSEUDOAUTOSOMAL REGIONS

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17
Q

What parts of an inactive X chromosome can undergo recombination with the Y chromosome?

A

PARp and PARq have HOMOLOGUES on the Y chromosome, enabling it to exchange genetic information.

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18
Q

What is the region in the Y chromosome that does not have a homologue in the X chromosome?

A

the SRY region- produces proteins that are involved in male development and fertility.

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19
Q

What is TDF on the Y chromosome? What region is it foud in?

A

TDF is the testis determining factor. found in the SRY region.

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20
Q

What is holohandric inheritance?

A

Inheritance of genes on the Y chromosome. Because only males normally have Y chromosomes, Y-linked genes can only be transmitted from father to son.

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21
Q

What is a transcription factor?

A

Transcription factors are proteins involved in the process of converting, or transcribing, DNA into RNA.

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22
Q

What is euploidy?

A

gain of one or more complete sets of chromosomes. Involves balanced translocations, inversions, triploidy, tetra ploidy etc.

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23
Q

What is aneuploidy?

A

more or less of ONE CHROMOSOME or part of a chromosome. ex/ trisomy, monosomy, duplications etc.

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24
Q

Balanced Translocations

A

A euploid condition in which nonhomologous chromosomes have a change of part, but all parts and genes are still present.

25
Q

T/F you will lose genetic content if a balanced translocation occurs

A

false. genes will be on different chromosomes that are non homologous, but all the genes will be there regardless

26
Q

Unbalanced Translocation

A

an aneuploid condition in which some part of the genome is missing

27
Q

Monosomy

A

an aneoploid condition where the entire chromosome is missing. Results from a nondisjunction

28
Q

What kind of aneuploidy events contributes to loss of genetic material?

A

Monosomy and Unbalanced Translocation

29
Q

What is nondisjunction

A

failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division (improper segregation)

30
Q

Usually, monosomy in humans results in death. What is the one chromosomal exception

A

You can have an X chromosome monosomy, results in turner syndrom (X,O)

31
Q

How do individuals with Turners syndrome survive?

A

due to X chromosome inactivation, the missing X chromosome was the one to be inactivated, so their remaining chromosome is still active. However, there are no PARp and PARq sites on the inactivated chromosome since it wasn’t there to begin with, still leading to a loss of genetic material.

32
Q

A person with turners syndrom is phenotypically ____

A

female

33
Q

What is a trisomy?

A

an aneoploid condition when a diploid organism has an extra copy of an INDIVIDUAL chromosome.

34
Q

In males and females, the inactive X chromosomes form _____

A

Barr bodies

35
Q

What is the sex chromosome genotype for someone with Klinefelter’s Syndrome? What sex is a person with klinefelters?

A

47, XXY- male

36
Q

How could you determine a guy has Klinefelters?

A

his karyotype will show the presence of a bar body in addition to the normal XY chromosomes, indicating an extra X chromosome.

37
Q

Characteristics of a person with Klinefelters?

A

male with breast development and small testis

38
Q

What is triplo X syndrome?

A

47, XXX a female with three X chromosomes instead of 2

39
Q

Characteristics of Jacobs syndrome?

A

47, XYY- affects males. They end up very tall and still fertile.

40
Q

What is Down Syndrome?

A

47, +21- extra 21 chromosome, the homologous chromosomes remain synapsed after meiosis. Characteristically flat face and mental retardation.

41
Q

What is Edwards Syndrome

A

47, +18. extremely deformed and clubbed feet, hands clenched. cardiac problems.

42
Q

What is Patau’s Syndrome

A
  1. +13, extra 13th chromosome, suffer from severe facial abnormalities, cleft lip and cleft palette, small eyes and rocker bottom feet
43
Q

What is intragenic deletion

A

loss of small amount of DNA within a gene. single gene’s activity loses function.

44
Q

Cri du Chat

A

5p deletion syndrome, 5p− syndrome (pronounced “Five P Minus”) or Lejeune’s syndrome, is a rare genetic disorder due to chromosome deletion on chromosome 5.

45
Q

What is a multigenic deletion? What kind of disease is caused by a multigenic deletion?

A

a larger deletion that can be actually seen on you a karyotype diagram. causes severe gene expression imbalances. Cri du Chat syndrome is a multigenic deletion in the 5th chromosome

46
Q

What is a tandem duplication?

A

a duplication that occurs in a chromosome in genes side by side

47
Q

What is an insertional duplication?

A

extra copy else where in the genome. duplications are less detrimental and limited to phenotype.

48
Q

T/F an inversion results in a loss of genetic material

A

false, all the genetic material is present, just reorganized.

49
Q

When will you see an inversion loop? Why?

A

you would see an inversion loop in a heterozygous-inversion person (ie, someone with one chromosome thats inverted and its homologue is normal), the loops occur so that homologous chromosomes can still pair and cross over.

50
Q

T/F an intragenic deletion can lead to recessive alleles being shown.

A

true. if an intragenic deletion occurs that removes the dominant allele from a gene, then the homologous recessive allele for the same gene will be shown.

51
Q

Paracentric vs Pericentric inversion

A

Paracentric is an inversion that takes place beside a centromere and does not involve the centromere itself

Pericentric is an inversion that takes place AROUND the centromere, and the centromere ends up getting inverted too.

Para and Pericentric inversion shave different crossing over products.

52
Q

What’re the events and results of a crossing over event in a paracentric region?

A

will form a DICENTRIC bridge; a fragment will get attached to both centromeres, and an ACENTRIC fragment, a fragment with no centromere. It gets lost.

53
Q

What is the viability of gametes that stem from inversions?

A

only gametes that did not undergo crossing over (parental gametes) will be viable. therefore, one meiotic event may lead to (in a heterozygous inversion):

1 normal chromosome
1 Inverted chromosome
2 deleted products (recombinants that were non viable)

the gamete production is reduced to half. leads to decreased fertility.

54
Q

What’re the main diagnostic features for someone with inversions?

A

1) inversion loops during MEIOSIS 1 (when crossing over occurs)
2) reduction of recombination frequencies in linked genes (0%)
3) reduced fertility from unbalanced or deleted meiotic products
4) some inversions may be directly observed as an inverted arrangement of chromosomal landmarks.

55
Q

What is a translocation?

A

the interchange of genes between non homologous chromosomes.

56
Q

What is reciprocal translocation? How does this affect the appearance of chromosomes? What is the biggest effect of this type of translocation?

A

reciprocal translocation: when 2 non-homologous chromosomes exchange pieces. You begin with 4 chromosomes and 2 homologous pairs, and end up with 4 chromosomes and no homologous pairs. the centromere position and chromosome length may change after translocation.

this affects fertility more than anything. it does not decrease genetic amount, because the genes are just rearranged; not lost. it may result in activation or inactivation of particular genes, like inversions.

57
Q

What is an important indicator that translocation has occurred?

A

the viability of gametes is exactly half.

58
Q

What is robertsonian translocation?

A

type of non reciprocal translocation. Recall that in reciprocal translocation, two non homologous chromosomes exchange genes, but in robertsonian, two chromosomes that are ACROCENTRIC fuse together. q

59
Q

What disease is caused by a robertsonian translocatioN?

A

Familial down syndrome. a carrier with a robertsonian translocation is phenotypically normal but has 45 chromosomes instead of 46 because two are fused together.

BIOL-2301 Final Exam (6 decks)

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