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BIO 226 > Topic 2 > Flashcards

Topic 2 Flashcards

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Biology 101 flashcards
1
Q

First Law

A

Alleles of a single gene segregates independently from each other

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2
Q

Second Law

A

Alleles of different genes segregate independently from each other

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3
Q

Chromatid

A

one leg of a homolog

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4
Q

Homolog

A

The 2 legs of a chromosome

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5
Q

Products of segregation of a pair of homologs after meiosis

A

4 chromatids, all different

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6
Q

What does segregation generate?

A

variability

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7
Q

What does the random orientation of a bivalent on the metaphase plate produce?

A

2 daughter cells with a different set of chromosomes

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8
Q

Bivalent

A

1 pair of chromosomes in a tetrad (a pair of homologous chromosomes physically held by at least 1 DNA crossover)

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9
Q

Phenotypic ratio of alternative orientations of bivalents

A

Same as Mendelian F2 phenotypic ratios

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10
Q

What does 2n=46 mean?

A

a diploid cell containing 2 copies of each chromosome (contains 46 chromosomes)

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11
Q

of possible random segregation combinations

A

8,388,608

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12
Q

Meiotic shuffling of chromosomes

A

cellular mechanism that dictates inheritance patterns

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13
Q

Drosophila

A

canonical genetic model organism

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14
Q

Thomas Hunt Morgan

A

Basically gave us the understanding of all genetic inheritance with his fruit flies

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15
Q

What first happened with the flies that started the first experiements?

A

A fly mutated to have a white eye

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16
Q

What did they discover about the segregation of the white eye mutation?

A

Sex linked

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17
Q

Morgan’s conclusions

A

Eye colour co-segregates with sex which doesn’t match 2nd law
Some traits must be stored on the stored on the same unit of segregation (can’t segregate indepenently)

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18
Q

What are chromosomes in regards to segregation?

A

carriers of genes and the actual unit of segregation

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19
Q

The chromosome theory of inheritance

A

The pattern of gene transmission reflects the chromosome’s behavior during meiosis
Genes are not inherited in isolation but as a part of a larger structural units shared with other genes with which they segregate

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20
Q

SRY gene

A

is the determinant factor for the male productive system (its presence makes the embryo develop testes)

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21
Q

What gender would an XX embryo that has a piece of Y the includes SYR?

A

Male

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22
Q

What gender is an individual that has XY but has a SYR deletion? What is this coondition called?

A

Female. Sawyer syndrome

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23
Q

How is sex determined n drosophila?

A

Determined by the ratio of sex (X) to autosomal chromosomes

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24
Q

What are the ratios determining sex in drosophila?

A

Female - 1
Male - 0.5
Metamale - less than 0.5
Metafemale - more than 1
Intersex - inbetween 0.5 to 1

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25
Q

Non-disjunction events

A

mechanistc defects in cell division that leads to an abnormal # of chromosomes(ex: failure to correctly separate during anaphase resulting in an abnormal # of chromosomes)

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26
Q

What does non-disjunction lead to in flies?

A

Aneuploid flies (some are viable but most are lethal), and aberrant inheritance of sex linked traits

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27
Q

X linked recessive in humans

A

Nearly all affected are males
Carrier female typically is phenotypically normal
All sons of an affected female are affected
Affected male never transmits the trait to male son

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28
Q

X linked dominant in humans

A

Affected males transfers trait to all daughters but none of their sons
Because females can be heterozygous or homozygous, more females are affected than males

29
Q

Cytogenetics

A

Geneticists use stains to identify specific chromosomes and to analyze their structures

30
Q

Karyotype

A

A collection of all chromosomes of a species/individual in a condensed state

31
Q

Monoploidy

A

The haploid set of chromosomes of a species (n)

32
Q

Euploidy

A

A chromosome number that is exactly the multiple of the monoploid set of chromosomes

33
Q

Polyploidy

A

A change in the number of copies of an entire set of chromosomes

34
Q

Aneuploidy

A

An uneven change of ploidy, when 1 or more chromosomes are missing or in excess

35
Q

Euploids

A

Monoploid n
Diploid 2n
Triploid 3n
Tetraploid 4n

36
Q

Aneuploids

A

Monosomic 2n-1
Trisomic 2n+1

37
Q

Natural occurring changes in ploidy

A

Polyploid - normal development of certain tissues and organisms
Monoploid - part of normal development in some insects (males are 1n, females are 2n)
Monosomy - required for sex determination in some organisms

38
Q

Plant with higher ploidy level

A

Look the same as normal ploidy plant, but bigger in size

39
Q

Autopolyploid

A

All the chromosomes originated from the same organism

40
Q

Allopolyploid

A

1 set of chromosomes originated from one organism and the other from another. The parent organisms need to be related to produce viable progeny

41
Q

Alloploidy agricultural advantages

A

Can create new phenotype and eventually new species (ex:brassica)

42
Q

Autopolyploidy agricultural advantages

A

Generates new traits valued by customer (ex: bigger, sterile/no seeds)

43
Q

How are autopolyploids generated?

A

Mistakes in meiosis that lead to failure in one of meiotic division producing a gamete with twice as many chromosomes as normal
Or
Gametes paused in labs in the metephase stage

44
Q

How are allopolyploid generated?

A

Formed by hybridization: crosses between 2 related species

45
Q

Polyploid tissue in organs (liver, heart, skin, etc.)

A

Replicate DNA in S phase but do not divide, leading to formation of polyploid tissue. Can help increase cell volume or cell metabolism

46
Q

Aneuploidy in humans

A

Defects can typically trace back to defects in meiosis 1. Don’t often carry genetic predisposition or predictable inheritance

47
Q

Monosomies

A

1 missing chromosome (autosomic monosomies die, but works only in turner syndrome - missing X)

48
Q

Trisomies

A

1 extra chromosome (autonomic trisomies for large chromosomes are lethal)

49
Q

Why are trisomies and monosomies so deleterious?

A

too much transcription (trisomies) as well as too little (monosomies) are problematic as they disturb the relative amount of protiens needed to correctly perform a given function

50
Q

Effect of chromosome size on chromosome imbalances

A

Larger chromosomes = more genes, likelihood of disrupting several pathways is greater

51
Q

Chromosome imbalances in chromosome 1

A

trisomies or monosomies of chromosome 1 are always embryonic lethal

52
Q

Why cells are able to deal with abnormal # of Xs more effeciently than of autosomes?

A

Imbalance in Y will restrict fertility because it encodes mostly for sex determinationand function
Imbalance in X will have minor effect because it has naturally evolved to be dosage compensated between 2 sexes

53
Q

Embryonic cells in female embryos _______ silence a single X

A

Randomly

54
Q

Male cells _____ silence their X chromosome

A

Never

55
Q

Correct disjunction of homologs produce ….

A

haploid gametes

56
Q

Nondisjunction of homologs in the 1st meiotic division produces….

A

aneuploid gametes

57
Q

Nondisjunction of homologs in the 2nd meiotic division produces…

A

aneuploid and haploid gametes

58
Q

Why are non-disjunction events mostly associated with maternal gametes?

A

Aging eggs are arrested in meiosis 1 as soon as they are made. Progress is triggered by fertilization. Since it can take a while before this happens, association between homologs weakens over time, making them disjoin more frequently when fertilization does happen

59
Q

Unbalanced chromosomal arrangements

A

changes result in loss or gain of genetic material that leads to gene dosage problems or chromosome instability

60
Q

Balanced chromosomal rearrangements

A

Changes do not result in gain or loss of genetic material such that gene dosage is not normally affected, but can cause chromosome instability issues

61
Q

Normal chromosome

A

A single centromere region
Telomeres in each end (stability)

62
Q

Dicentric chromosome

A

More than 1 centromere (chromosome break)

63
Q

Acentric chromosome

A

No centromere (spindle fails to capture)

64
Q

Haploinsufficiency

A

genes that need to be expressed in both homologs to provide enough protein

65
Q

pseudodominance

A

recessive alleles uncovered by the deletion will appear as if they are dominant

66
Q

Chromosomal loops

A

association of opposite ends between the inverted region and normal homolog that produces a loop that disrupts homolog segregation in meiosis 1

67
Q

______ are the most common chromosomal rearrangement in humans

A

translocations

68
Q

Robertsonian translocations

A

produces a large chromosome that is a fusion of both original chromosomes (viable) and a small fragment of remaining part of chromosome (not viable)

BIO 226 (6 decks)

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