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ANSC 313 > Chromosomal inheritance > Flashcards

Chromosomal inheritance Flashcards

1
Q

cytogenetics and somethings we can see within it

A

the study of chromosomes
-multiple malformations
-fertility problems
-phylogeny/evolution
-sexing animals

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2
Q

when does DNA get turned into chromosomes

A

after interphase it gets condensed into chromosomes in prophase I

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3
Q

how are chromosomes packed up

A

-DNA double helix
-DNA and histones
-chromatin fiber
-super coiled DNA
-chromosome

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4
Q

types of chromosomes

A

-depends on centromere placement
-telocentric (no P arm)
-acrocentric (small P arm)
-submetacentric (bigger p arm)
-metacentric (almost equal p and q arm

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5
Q

what are the part of the chromosome

A

-centromere
-p arm (short)
-q arm (long)

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6
Q

karyotype

A

-arranges by size (depending order b-s)
-numbered
-sex chromosomes last
-short arm up (p)
-autosomes
-grouped by centromere placement
-homologous chromosomes, same size, band patterns

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7
Q

how many chromosomes do pigs have

A

38

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8
Q

how many chromosomes to humans have

A

46

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9
Q

how many chromosomes do cows have

A

60

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10
Q

sexing birds

A

-now done with DNA typically
-many chromosomes
-6-9 pairs of macrochromosomes
(including sex chromosomes)

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11
Q

how many chromosomes do dogs have

A

78

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12
Q

how many chromosomes do horses have

A

64

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13
Q

chromosomes nonenclature

A
  1. total # of chromosomes
  2. sex
  3. special findings (e.g. + or -)
    ie. 78, XX, (normal bitch)
    65, XY, +15(abnormal colt fetus)
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14
Q

origin of chromosomal anomalies

A

-many chromosomal anomalies arise “de novo” during meiosis of one of the parents
-arise through mismatching of homologues during meiosis
-also can occur through an error in cell division

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15
Q

how do chromosomes divide

A

-mitosis
-meiosis

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16
Q

mitosis

A

-exact duplication of somatic cells
-DNA replicates
-chromatids separate
-results in 2 diploid cells

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17
Q

stages of mitosis

A

-interphase (DNA replicates)
-prophase (chromosomes become visible as extended double structures)
-metaphase (nucleus is replaced by the spindle, chromosomes become aligned on the equator)
-anaphase (chromosomes pairs split and move towards opposite poles
-telophase (chromosomes reach poles)
cytokinesis (nuclei reform; each daughter cells has complete set of chromosomes, one member of each pair derived from each parent

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18
Q

meiosis

A

-(reduction division-in gametes)
-meiosis I
-DNA replicates
-homologous pair (crossing over)
-chromosomes separate
-result in 2 haploid cells

-meiosis II
-chromatids separate
-result in 4 haploid gametes

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19
Q

meiosis I

A

Prophase I - chromosomes become visible
Metaphase I - bivalents align at the equator
Anaphase I - homolog pairs move to opposite poles
Telophase I - homolog pairs enter separate cells

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20
Q

meiosis II

A

Prophase II - chromosomes re-form
Metaphase II - homologs line up at equator
Anaphase II - homologs move to opposite poles
Telophase II - four gametes each have one copy of each
chromosome

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21
Q

when does meiosis occur

A

gametogenesis

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22
Q

gametogenesis

A
  • a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes
  • Oogenesis, spermatogenesis
    ▪ Timing is different depending on if female or
    male
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23
Q

oogonum

A

immature egg cell

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24
Q

what does the oogonum turn into

A

-primary oocyte (2n)
-gains zona pellucida after puberty
-after meiosis I becomes secondary oocyte + polar body (1n)
-then because of fertilization meiosis II occurs and turns into zygote + second polar body (2n)

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25
Q

what happens to spermatogonium

A

-(2n) can become dormant for later division or active
-active undergoes mitosis
-16x (2n) primary spermatocytes
-meiosis I
- two (n) secondary spermatocytes
meiosis II
-four (n) spermatids
-turns into spermatozoa

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26
Q

what are the differences in gametogenesis

A

-female
-one ovum + two polar bodies form one primary oogonium cell
-male
-four sperm form one primary spermatogonium cell
-female
-no new oocytes during lifetime, so accumulate damage (initiated in fetus)
-males
-new sperm generated every 60 days

27
Q

different types of chromosome anomalies

A

-with phenotypic effect: numerical, structural
-w/o phenotypic effect: structural

28
Q

chromosome numerical errors

A

-called aneuploidy (loose or gain)
-cause is usually non disjunction
-usually results in multiple malformations
-risk increases with maternal age

29
Q

non disjunctional

A

-chromosomes in egg do not separate properly during meiosis I or II
-either have too many chromosomes or too little in fertilized eggs

30
Q

risks of downs and chromosomal mutations

A

-risk increases exponentially in humans at the age of 35 (less then 1 % before)
-cows after 9 years of age

31
Q

incidence of chromosomal problems

A

-~30% of human conceptuses abort
-2.5-10% of “late” spontaneous abortions have chromosomal problems/causes
-assume a high proportion of early abortions have chromosomal problems

-live birth weights with major malformations
-many chromosomal

32
Q

type of numerical errors

A

-aneuploidy
which includes:
-trisomy
-monosomy
-mosaicism
-chimera

33
Q

aneuploidy

A

one chromosome pair has the wrong number (i.e. not 2)

34
Q

trisomy

A

-3 of one chromosome
-severe, usually lethal effects

35
Q

klinefelter syndrome

A

-sex chromosome aneuploidy
-61, XXY
-infertile

36
Q

monosomy

A

-1 of one chromosome
-severe, usually lethal effects early in gestation
-59, XX, -15

37
Q

turner syndrome

A

-sex chromosome aneuploidy
-63, X0 (mare with one X missing)
-infertile
-note if X is missing in a male, lethal (i.e 63, Y0 is not viable)

38
Q

what are the deaths of the different types of numerical errors like

A

-monosomies abort earliest
-trisomies may abort later
-aneuploids of larger chromosomes abort earlier
-few survive to term
-usually the bigger the chromosome that is affected= abort earlier

39
Q

mosaicism

A

-> 1 cell type
-moderate abmornalities
-60, XX/59, XX, -?
-likely a mitotic error
-some cells normal but not all
-if less then 10% of their cells have abnormal chromosome karyotype, individuals may not exhibit symptoms

40
Q

chimera

A

-own karyotype plus other (twin)
-special type of mosaic
-> 1 cell type, derived from >1 individual
->10% of cells abnormal leads to problems
-60, XX/60, XY
-freemartin heifer is sterile and male co-twin has lower sperm count

41
Q

placenta anastomosis

A

a cross connection between cotyledons

42
Q

chimeric twins in different species

A

-~99% of cattle
-<10% of goats
-few sheep (who have the same kind of placenta)
-rare in dogs, humans, etc. none of who have this form of placenta

43
Q

implications of a numerical error

A

-cull affected individual (but they aren’t viable)
-usually retain parents unless old
-recurrence risk ~1% if “young”

44
Q

polyploidy

A

-triploidy
-tetraploidy

45
Q

triploidy

A

-3 haploid sets
-fert egg becomes 3n
-dispermy?

46
Q

tetraploidy

A

-4 haploid sets
-chickens die
-cattle mosaics live (also have normal cells)

47
Q

types of chromosome anomalies with and with out phenotypic effects

A

with phenotypic effects:
-numerical
-structural
without phenotypic effects:
-structural

48
Q

structural errors (with phenotypic effects)

A

-deletion
-duplication
-ring
(rarely reported in animals because rarely studied)

49
Q

types of chromosomal structural errors (without phenotypic effect)

A

-translocation
-inversion

50
Q

indications of structural errors with out phenotypic effect

A

-sub fertility
-25% reduced litter size
->10% of cows serviced by bull remain open
->2% spontaneous abortions
(or late conception in cows)

51
Q

robertsonian translocation

A

-2 acrocentric chromosomes fuse
-count is off by one (2n-1)

52
Q

reciprocal translocation

A

-2 chromosomes exchange pieces
-number is unchanged (2n)

53
Q

what is the most common translocation in cattle

A

robertsonian translocation t(1;29)
-normal and balanced translocation=live calf
-trisomy 1, 29 and monosomy 1,29=aborted calf

54
Q

where is translocation in cattle more commonly seen

A

10% in some continental breeds not common in british breeds

55
Q

t(14;30)

A

extremely rare but seen in some simmintals

56
Q

where is translocation testing mandatory in

A

some breeds:
-charolais
-simmental
some countries:
-australia
-brazil
-england
-newzeland
-sweden
some AI companies

57
Q

implications of robertsonian translocation

A

-cull unbalanced bulls (usually lethal but in the case they arent)
-screen relatives if economic
-cull translocation carriers?

58
Q

reciprocal translocation example

A

part of chromosome 7q exchanged with chromosome 11q

59
Q

implications of reciprocal translocations

A

-translocation carrier will have low fertility (litter size)
-may observe mummified piglets
-serious if a boar

60
Q

two kinds of translocations

A

reciprocal and robertsonian

61
Q

phylogeny evolutionary relationship

A

-acrocentric= more primitive
-fusion of chromosomes=more recent
-results in increase metacentric chromosomes
-decrease in chromosome number

62
Q

hybrid fertility

A

-if karyotype is different; both sexes are sterile,
(eg. horses have 64, donkey 62, mule 63)
-if karyotype is similar; only the heterogametic sex is sterile, increased embryo mortality
(eg. bison and domestic cattle, yak and domestic cattle)

63
Q

dogs/wolf/coyote hybrids

A

-both sexes of canid hybrids are fertile
-species or subspecies
-canis lupus
-canis latrans

64
Q

bos taurus and indicus hybrids

A

-both sexes oh hybrids are fertile
-species or sub species
-but when they are crosses with yak and bison (all have 60 chrmosomes) sterile male

ANSC 313 (25 decks)

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