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MCP UNIT 7 > Intro to Cytogenetics > Flashcards

Intro to Cytogenetics Flashcards

1
Q

What is the most important phase of mitosis in cytogenetics?

A

metaphase

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2
Q

What are the two critical phases in meiosis?

A
  • recombination which occurs in prophase I

- reduction division (anaphase I)

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3
Q

what is reduction division?

A

reduction by 1/2 of the original number of chromosomes

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4
Q

what is crossover?

A

exchange between homologous chromosomes resulting in a reassortment of the genes/alleles present on each chromosome

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5
Q

During meiosis II how many chromosomes does each daughter cell get? are there pairs?

A

23; no

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6
Q

What is the net result of nondisjunction that occurs in meiosis I and not in meiosis II?

A

4 cells with a chromosomal imbalance

-2 disomic gametes and 2 nullsomic gametes

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7
Q

What is nullsomic?

A

cells that are missing chromosomes

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8
Q

gametogenesis (includes spermatogenesis and oogenesis ) are a combination of

A

mitosis and meiosis

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9
Q

How many functional gametes are produced at the end of spermatogenesis?

A

primary germ cells–>spermatocytes via mitosis

4 per spermatocyte

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10
Q

How many functional gametes are produced at the end of oogenesis?

A

primary germ cells–>oocytes via mitosis

1 per oogonia

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11
Q

Why don’t oocytes become ovum until ovulation?

A

primary oocytes are formed by 3rd month of gestation, reach prophase I and pause until ovulation

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12
Q

Why is there only one functional oocyte formed?

A

at the completion of meiosis I, two daughter cells are produced one secondary oocyte and one polar body

after meiosis 2, you get one ovum and one polar body

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13
Q

What is the difference between a secondary oocyte and a polar body?

A

secondary oocyte received most of the cytoplasm and will go on to become an ovum

polar body didn’t get much cytoplasm and will go on to degenerate or produce 2 more polar bodies

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14
Q

When is meiosis completed in the female?

A

during fertilization

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15
Q

What prompts the fusion of the male and female pronuclei?

A

penetration of sperm head and release of second polar body

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16
Q

Describe the differences in the frequency of gamete production in males and females.

A

Males: primary spermatocytes produced throughout life; gametes produced continuously
4 equal gametes per gametocyte

females: all primary oocytes present at birth
gametes made once a month
1 gamete per gametocyte

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17
Q

Which sex is homogametic and which is heterogametic?

A

females; males

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18
Q

What is the TDF?

A

testis determining factor

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19
Q

What is SRY

A

sex determining region og Y

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20
Q

What is the pseudoautosomal region of Y?

A

region on the short arms of the X and Y chromosomes that engages in recombination

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21
Q

What is the default sexual development? what triggers it?

A

female; absence of TDF/SRY

22
Q

What does presence of TDF/SRY do?

A

leads to differentiation of gametocytes to testes and inhibition of Mullerian ducts–>degeneration of Mullerian ducts

proliferation of Wolffian ducts

23
Q

Are the protein produced by TDF initiates the male developmental pathway the only factors determining sex?

A

No

24
Q

Is it possible to have functional TDF/SRY with a female genotype?

A

yes; there are also males with XX and females with XY;

25
Q

Why are females not at a deficit because they have no Y chromosome?

A

The genes present on the Y chromosome seem to be primarily involved with male characters, so females are not negatively impacted

26
Q

Why are males not at a deficit because they only have one X chromosome?

A

males and females get the same enzyme production from X linked genes because of X inactivation.

27
Q

What is the Lyon hypothesis?

A
  • for determination of a normal female, there must be 2 active X chromosomes
  • they inactivate 3-7 days after fertilization
  • inactivation is random, but irreversible in somatic tissues
28
Q

What is the result of X-inactivation?

A

dosage compensation

29
Q

What is dosage compensation

A

equalization of the amount of active genetic material

30
Q

somatic mosaicism

A

heterozygous females have subpopulations of cells within their bodies. some of the x chromosomes will be the mother’s and some will be the father’s

31
Q

non-random X inactivation

A

deletion or damage to one of the X chromosomes can lead to a change in the inactivation patterns

32
Q

How can non-random X inactivation cause clinical problems?

A

If a female is a carrier for X linked disease and her normal chromosome is damaged, then the abnormal chromosome will be expressed and she may manifest some disease symptoms

33
Q

Describe the mechanism of X inactivation

A

-epigenetic (no gene mutations occur)

34
Q

Where does methylation of X begin?

A

-methylation initiated at XIST

35
Q

What sites escape inactivation?

A

pseudoautosomal and others

36
Q

Is methylation reversible?

A

No; inactive X must be reactivated at meiosis so that all gametes will have an active X

37
Q

How often do conceptuses have chromosomal abnormality? How often are born alive?

A

1/13; 6/1000

38
Q

T or F: the body recognizes most errors in chromosomes and they are spontaneously eliminated

A

true

39
Q

What should you do if an infant presents with the signs or symptoms of a defined syndrome?

A

karyotype analysis may confirm chromosomal anomaly.

40
Q

What are the two major types of chromosomal anomalies? Describe them.

A

Numerical: change in the total number of chromosomes of the set
Structural: change in the size or shape of one or more chromosomes

41
Q

How do we identify chromosomal abnormalities?

A

look during metaphase for:

  • size
  • position of centromere
  • banding pattern
42
Q

What is the most common specimen used for karyotyping? What are others?

A

blood; bone marrow–>oncology; amniotic fluid and chorionic villi

43
Q

p arm

A

shorter of two arms of a chromosome

44
Q

q arm

A

longer of two arms of a chromosome

45
Q

metacentric

A

centromere is equidistant from both ends

46
Q

submetacentric

A

closer to one end than the other

47
Q

acrocentric

A

modified short arms containing a stalk with copies of rRNA

48
Q

How is the total loss of telomeres thought to be partially responsible for aging?

A

mechanics of DNA replication are such that not all the telomere DNA can be replicated at each division so there is a shortening of telomeres over time

49
Q

ideogram

A

representation of each pair of chromosomes that has a unique band pattern

50
Q

chromosome polymorphism

A

presence of two or more alternative structural forms for a chromosome within a population

mendelian characters can be traced through pedigrees

MCP UNIT 7 (4 decks)

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