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chromosomes Flashcards

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1
Q

chromosome structure explained

A

consists of two identical strands called chromatids joined at the centromere

centromere divides the chromatids into short p and long q arms

telomeres at the tip

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2
Q

two different types of chromosome + definition

A

acrocentric- centromere is on one side

metacentric- centromere is in the middle

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3
Q

telomere function

A

maintain the structural integrity of chromosomes formed of highly conserved tandem repeat sequences

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4
Q

how is structure integrity maintained?

A

telomerase enzyme ensures replication, preventing the shortening of the DNA strand

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5
Q

what happens in cancers?

A

telomeres are over produced, preventing cell senesence

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6
Q

karyotype definition

A

a picture of a person’s chromosomes

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7
Q

G-banding explained

A

denature the proteins in the chromosome using trypsin, stain with Giemsa, a DNA binding dye which gives the chromosome a stripy pattern

active areas stain light

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8
Q

Other genetic techniques used to view chromosomes

A

FISH, Chromosome painting, CGH and array CGH

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9
Q

explain FISH

A

Uses DNA probe to anneal to its complementary target sequence where it is located on a metaphase spread

Used to detect chromosome abnormalities, such as Down’s syndrome

Three red dots shows that three probes bound to three chromosomes which signify Down’s syndrome

used when scientists are looking for a known sequence

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10
Q

explain chromosome painting

A

used when sequence is unknown

a mixture of probes specific for each chromosome are used, able to view translocations and identify which chromosomes they came from

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11
Q

CGH stands for

A

comparative genome hybridisation

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12
Q

explain CGH use

A

used when people do not look normal. try to detect regions of gene amplification or gene loss

Test DNA is labelled with green paint, normal DNA is labelled with red paint. Too much green shows gene amplification, too much red shows gene loss

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13
Q

Determination of the male sex

A

presence of Y chromosome leads to maleness regardless of the number of X chromosomes present

presence of SRY region on Y, the sex determining region, which encodes a transcription regulator

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14
Q

what happens if SRY gene is mutated?

A

XY female

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15
Q

SRY function

A

unregulated the gene transcription of genes involved in testis production from Wolffian ducts

testis Sertoli cells produce mullein inhibitory Factor, inhibiting female genitalia production

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16
Q

what happens if there is androgen insensitivity?

A

body does not react to testosterone, leading to an XY female despite SRY

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17
Q

Explain X-linked inactivation

A

Early in embryonic life, structurally abnormal X is preferentially inactivated, otherwise it is random.

Inactivation is not complete, some genes are known to escape inactivation

Inactivation is not permanent, reversed in development of germ cells

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18
Q

Barr body definition

A

inactivated X chromosome =, if an individual had 4 X chromosomes they would have 3 Barr bodies

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19
Q

abnormalities linked to X and Y

A

more Xs, more intellectually impaired

extra Y, more aggressive, increased criminal tendencies

20
Q

2 different syndromes linked to sex chromosomes

A

Turner syndrome X

Klinefelter’s syndrome XXY

21
Q

Explain Turner syndrome

A

intellectually normal, infertility, primary amenorrhoea, cardiac abnormalities and webbed neck

22
Q

explain klinefelter’s

A

feminised male, moobs, fat around his and thighs, impaired IQ

23
Q

three trisomies

A

Trisomy 21- Down’s

18- Edward’s

Patau- 13

24
Q

explain nondisjunction of chromosomes

A

failure of separation of chromosomes during meiosis in gametes which results in cells with extra or less copies of a particular chromosome

25
Q

explain down’s syndrome

A

tongue too big for their mouth, low muscle tone, single palmar crease, wide sandal gap, intellectual disability, septal defects, more prone to Alzheimers

26
Q

explain Edward’s syndrome

A

clenched fingers they cannot release, rocker bottom feet, protuberant back of head, severe intellectual disability

27
Q

explain patau syndrome

A

extra digits, propensity to develop cleft lip and cleft palate, severe intellectual disability, cyclopia

problem with Shh, responsible for mediating midline patterning

28
Q

examples of chromosomal micro deletion syndromes

A

DiGeorge, WAGR, Williams

29
Q

explain DiGeorge syndrome

A

deletion on the long arm q of chromosome 22 leading to cardiac abnormalities, immunodeficient, cleft palate, short stature

30
Q

WAGR explained

A

Wilms Tumour Aniridia Genital Abnormalties Retardation

Renal tumour that occurs in children under 5, absence of iris, short arm of chromosome 11 deleted

31
Q

Williams syndrome explained

A

intellectual disability, unable to form ideas of a conversation, raised calcium level, cardiac abnormalities, short stature, full cheeks, long arm of chromosome 7 deletion

32
Q

chromosomal translocation definition

A

transfer of genetic material from one chromosome to another

33
Q

two types of chromosomal translocation + definition

A

robertsonian - break points are close to centromeres of 2 acrocentric chromosomes, form of reciprocal

reciprocal- break in two chromosomes and their segments are exchanged

34
Q

example of reciprocal translocation

A

Bcr-Abl

Abl is an oncogene, Bcr upstream of All prevents oncogene regulation leading to leukaemia

35
Q

two types of robertsonian translocation

A

homologous acrocentric- both long ends join together from the same chromosome

non homologous afrocentric- both long ends from two different chromosomes join and short parts are lost

36
Q

two different chromosome structures + definition

A

isochromosome- mirror image chromosome, loss of one arm, duplication of another arm

37
Q

ring chromosome

A

delete the ends of one chromosome, forming a ring, normally removes telomeres

38
Q

5 other chromosomal mutations

A

inversion, insertion, duplication, mosaicism, chimerism

39
Q

two types of inversion + definition

A

pericentric- swapping of segment involving p and q arm and centromere

paracentirc- involves one arm

two breaks in one chromosome, fragments generated rotate 180 degrees and reinsert into the chromosome

40
Q

mosaicism definition

A

presence in an individual of a tissue of 2 or more cell lines that differ in their genetic constitution but are derived from a single zygote

tends to result from non disjunction in an early mitotic division

41
Q

chimerism definition

A

the presence of 2 or more genetically distinct cell lines derived from more than one zygote

42
Q

two examples of chimeras

A

dispermic, 2 sperm, 2 eggs one embryo

blood- exchange of cells between non identical twins via placenta

43
Q

normal chromosome complement defnition

A

22 pairs of autosomes

2 sex chromosomes

44
Q

three numerical chromosome mutations

A

aneuploidy, monosomy, trisomy

45
Q

aneuploidy definition

A

presence of an abnormal number of chromosomes in a cell

46
Q

example of a monosomy

A

turners

genetics (6 decks)

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