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USF PCB3063 Genetics > Exam 3 Cards > Flashcards

Exam 3 Cards Flashcards

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1
Q

What was Morgan’s Trihybrid Cross?

A

Trihybrid cross of body color, eye color, and wing length

He found that there were higher proportion of the parental traits than the recombinant traits

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2
Q

What are the three criteria for a successful mapping cross?

A
  1. genotype must have recombinant gametes that are heterozygous at all loci
  2. crosses must be made so that genotypes can be understood from phenotypes
  3. a large number of offspring must be produced
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3
Q

What is the number of gametes and phenotypic classes if the three loci are unlinked?

A

8 types of gametes and 9 phenotypic classes

F2 off spring
any a/a or a+/a with any b/b or b+/b with any c/c or c+/c

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4
Q

What is the number of gametes and phenotypic classes if the three loci are completely linked?

A

2 types of gametes and 2 phenotypic classes

F2 Offspring
only abc/abc or abc/a+b+c+

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5
Q

What is the number of gametes and phenotypic classes if the three loci are incompletely linked?

A

8 types of gametes and 8 phenotypic classes depending on the distance of the loci

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6
Q

How do you identify the inside gene double crossed over gene?

A

When there is a double crossover two of the genes compared to the parents would be the same and one will be different this one is the one that that is in the inside between both of the other genes.

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7
Q

How to calculate Recombination Frequency?

A

(number of recombinant offspring)/ total x 100

In the context of a three factor

the total recombinations for the genes Y W and EC

To find the RF between Y and W

All Y recombinants and All W recombinants which could include double crossovers.

look for only the one gene that is different compared to the parentals.

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8
Q

What is important to remember when you are trying to find the total distance between two genes separated by a gene in the middle?

A

Make sure to add the double crossover numbers twice in the calculations.

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9
Q

How to calculate the probability of a double cross over?

A

Calculate the RF value of single crossover of Y and W and W and EC and multiply them together and then multiply by the total number of offspring you have.

.0156x.0406 = .000634 x 10000 = 634 off spring will have double crossover or interference

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10
Q

What is C, the coefficient of Coincidence?

A

C = observed number of DCO / Expected # of DCO

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11
Q

How to calculate Interference?

A

1- C (coefficient of Coincidence)

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12
Q

What do the different values of Interference mean?

A

I = 1 - complete interference
I = 0 - no interference
I > 0 - positive interference
I < 0 - negative interference

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13
Q

If neither the parents of the DCO can be identified what does that mean?

A

Genes are not incompletely linked.

The genes do not assort independently because the classes are not equal in number.

The genes are also not completely linked because the cross is not two classes only

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14
Q

What happens if two genes are linked and the third gene is unlinked?

A

the four largest classes are the parentals and the four lowest are the recombinants

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15
Q

What is cytogenetics?

A

Field that involves the microscopic observations of chromosomes to find abnormal number or shape

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16
Q

What are the four types of chromosomes?

A

metacentric, submetacentric, acrocentric, and telocentric

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17
Q

How to identify between the banding pattern during metaphase and prophase?

A

Metaphase has fewer and thicker bands and prophase has thinner and more numerous bands

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18
Q

What are the three features seen in a karyograph?

A
  1. size
  2. location of centromere
  3. banding patterns
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19
Q

What does FISH mean?

A

Fluorescence in situ hybridization.

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20
Q

What is mosaicism?

A

the presence of two or more cell lines in an individual in which one or more are abnormal and one is normal

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21
Q

What does it mean to be Euploidy?

A
  • changes in the entire set of chromosomes
  • occurs sometimes in animals and more commonly in plants
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22
Q

What does it mean to be Aneupoloidy?

A
  • changes in individual chromosomes rather than the whole set
  • abnormal conditions
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23
Q

What does it mean to be polyploid?

A

To have three of more SETS of chromosomes.

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24
Q

What does it mean to be trisomic?

A

To have one chromosome have three copies rather than 2

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25
Q

What does it mean to be monosomic?

A

One chromosome has only 1 copy instead of 2

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26
Q

Changes in chromosome number has a [more or less] severe effect on survival that changes in chromosomal structure.

A

More

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27
Q

What is monosomy?

A

One homologue is missing

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28
Q

What is trisomy?

A

One extra homologue is present

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29
Q

What is tetrasomy?

A

Two extra homologues

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30
Q

What is Double Monosomy?

A

Two different homologues are missing

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31
Q

What is double trisomy?

A

two different extra homologues are present

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32
Q

What is nulllisomy?

A

A pair of chromosomes is missing

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33
Q

How does aneuploidy commonly cause an abnormal phenotype?

A

by creating an imbalance in the gene products

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34
Q

What is the turner syndrome?

A

Example of Monosomy

Karyotype: 45, X or 45, XO

Frequency is 1 in 10000 females

Characteristics: short, web neck, underdeveloped ovaries, no secondary sexual characteries, 40-50 percent are mosaics

35
Q

What is example 1 of trisomy?

A

Jimson weed is 2n = 24

But every trisomy is viable but it changes the chape of the fruit with every trisomy.

36
Q

What is example 2 (human) of trisomy?

A

Trisomy 13, 18, 21, and X are are survivable but cause developmental abnormalities

37
Q

What is Trisomy 21?

A

Down Syndrome:

Karyotype:

47, XX or XY, + 21

1:700 live births

More likely to happen as the mother is older.

Non-disjunction is more likely to happen in women.

38
Q

What is Trisomy 18?

A

Edwards Syndrome

Karyotype= 47, XX or XY, +18

Frequency = 1:8000 live births

39
Q

What is trisomy 13?

A

Patau Syndrome

Karyotype: 47, XX or XY, + 13

Frequency = 1 : 20000 live births

40
Q

What is trisomy X?

A

Klinefelter Syndrome

Karyotype: 47, XXY

Frequency = 1:1000 live male births

Extreme examples can include 3 Xs or 4 Xs or 2 Ys

41
Q

What is Trisomy X in females?

A

XXX syndrome

1:1000 live female births

Can also include Tetra-X or Penta-X Karyotypes
XXXX, or XXXXX

42
Q

What is an animal that is naturally Euploidy?

A

Bees

43
Q

For euploidy cells how do you calculate x and n?

A

X = number of chromosomes in a set
n = number of chromosomes in a gamete

Hexaploidy = 60 chromosome

x = 10 chromosome in a set
n = 30 chromosomes in a gamete

44
Q

What does it mean to be endopolyploidy?

A

some somatic cells have more sets of chromosomes than other somatic cells

In humans these are:
* liver cells
* megakaryocytes (bone marrow cell that produces platelets)

45
Q

What euploidy are maintained?

A
  • even numbered sets of chromosomes are usually maintained reliably due to balanced gametes
  • odd numbered are not due to unbalanced gametes
46
Q

What is a common trait of euploidy?

A

sterility

gives us seedless fruit

47
Q

What is meiotic disjunction?

A

Nondisjunction - the failure of chromosomes to segregate properly during cell division.

  • if in mitosis then the tissue will have abnormal chromosomes but the rest of the body will be fine
  • if in meiosis the whole new resulting individual will have abnormal sets in all cells
48
Q

What are the offspring if nondisjunction happens during meiosis 1?

A

all 4 gametes are abnormal

50 percent with trisomic for the nondisjunction chromosome

and

50 percent monosomic for the nondisjunction chromosome

49
Q

What happens if nondisjunction happens in meiosis 2?

A

50 percent normal and 50 percent abnormal

50
Q

What is complete nondisjunction?

A

This is when meiosis happens and there is nondisjunction and just go to one daughter cell.

This causes one diploid cell and one cell without chromosomes.

51
Q

What are some Mitotic abnormalities that might happen?

A
  1. mitotic disjunction
  2. chromosome loss
52
Q

What happens in mitotic disjunction?

A

sister chromatids separate improperly and one becomes normal and one becomes monosomic

53
Q

What occurs during chromosome loss?

A

one of the sister chromatids does not migrate to a pole which leads to a normal and a monosomic daughter.

The chromatid for the monosomic daughter cell does not move or go anywhere it just stays on the metaphase plate and remains there.

54
Q

What is a bilateral gyandromorph?

A

Example of chromosome loss causing mosaicism. Drosophila during the first mitotic division loses one of the Xs and divides into two cells of XX and XO. The XX side develops as female and the XO side develops as male within the same body

55
Q

What are the two types of interspecies crosses?

A

Autopolyploid and allopolyploid

56
Q

What are the characteristics of Autopolyploids?

A

They contain multiple copies of the same genome.

Example is a diploid turning into ta tetraploid.

57
Q

What is a allotetraploid?

A

two complete sets of chromosomes from each of the two different species.

For example: Cultivated bread wheat is allohexaploid.

58
Q

What is endoreduplication?

A

chromosomes doubling due to an aborted cell division

A diploid plant undergoes completely nondisjunction and becomes a tetraploid plant

it can happen naturally or by the treatment of colchicine (which binds to tubulin)

59
Q

What could be the benefit of endoreduplication?

A

If there are two species whose comes together to make a allodiploid which is infertile becomes the chromosomes dont match up with each other.

Endoreduplication can cause the doubling of the chromosome so each pair can just pair with itself thus making the once sterile plant, fertile.

60
Q

What does it mean to be homeologous chromosomes?

A

they have different species origins but the same number of chromosomes in their chromosome sets

61
Q

What did Georgi Karpechenko do?

A

He tried to combine radish and cabbage because they both had 18 genes.

F1 was sterile

F2 was fertile containing 36 chromosome instead of 18.

62
Q

What are chromosome deletions?

A
  • loss of a portion of a chromosome
  • could be terminal deletion or interstitial deletion.
63
Q

What kind of mutant phenotypes can deletions cause?

A
  1. break point effects
    - depends where the break occurs within the gene
  2. Position Effects
    - the gene is now shifted to a new location

These deletions may lead to pseudodominance.

When deletions are homozygous they are more likely to be lethal.

64
Q

What is cri-du-chat syndrome?

A

deletion caused about half of the 5p arm to be missing

65
Q

What are chromosome duplications?

A

this is where there is an extra segment of the chromosome

  1. Tandem duplication - where the duplication occurs right next to the original segment
  2. non-tandem duplication - duplication occurs not next to the duplication
  3. Reverse duplication - a flipped version of the segment is placed next to the original segment.
66
Q

What is a gene family?

A

a set of very similar genes usually caused by duplication

67
Q

What is an example of a gene family?

A

the globin gene family

over 14 homologous genes on three different chromosomes

from just one ancestral gene

expressed in human development

68
Q

What kind of globins do you see early in embryonic life and what do you see later on in the second and third trimester and after birth?

A

Embryonic life - myoglobin’s (better for storing oxygen in muscles)

Second/Third Trimesters - alpha chains which turn into hemoglobin (better at binding and transporting oxygen)

After Birth - Beta Chains

69
Q

What kind of globin do plants have and why is it important?

A

They have something called leghemoglobin.

That is important because that means the common ancestor of the gene for globin lies in the shared ancestor of plants and animals.

Also invertebrates have myoglobin but no hemoglobin so duplication occurred after the divergence of vertebrates and invertebrates.

70
Q

What are inversions?

A

rearrangement that reverses the orders of genes in a chromosomes.

Two Types:

Pericentric inversions and Paracentric Inversions

71
Q

What are the two types of inversions?

A

Paracentric Inversions - the arm ratio is unchanged (centromere outside the inverted region which changes the ratios)
Pericentric inversions - the arm ratio is often unchanged (the centromere is inside the inverted region and therefore the ratio is unchanged)

72
Q

What are the phenotypes of inversions?

A

Most of them have no change in phenotype.

But two can occur rarely.

  1. Breakpoint effect
  2. Position Effect
73
Q

Can inversions have an effect on the offspring and cause genetic abnormalities?

A

For the most part no. But some can.

It can cause genetic abnormality due crossing over the inverted segment

Pericentric inversion - 2 normal gametes, 1 Duplicated, 1 deleted

Paracentric Inversions - 2 normal, 1 dicentric chromosome, 1 acentric chromosome

74
Q

What is a translocation?

A

when a segment of one chromosome becomes attached to another

75
Q

What are the two main types of translocations?

A

Intrachromosomal - moves from one part of the chromosome to another
Interchromosomal -

A - chromosomal segment moves from one chromosome to another

B - Two nonhomologous chromosome exchange chromosome segments

76
Q

What usually causes reciprocal translocations?

A
  1. chromosomal breakage and DNA repair
  2. abnormal crossovers
77
Q

What is the Robertsonian translocation?

A

two non-homologous acrocentric chromosome which fuse at the centromere and lose their short arms

78
Q

What causes abnormal phenotype in translocations?

A

Position Effect - one gene arm is not where it is supposed to be

79
Q

What is Chronic Myelogenous Leukemia?

A

tumor of certain WBC.

Cause by t(9q, 22q)

This causes the expression of a BCR/ABL fusion protein that causes this leukemia.

80
Q

What is Familial Down Syndrome?

A

5% of Down Syndrome is caused by Robertsonian translocation of (14/21)

This can be passed down and have a high risk of spontaneous abortion

81
Q

What is the fundamental Number?

A

the number of arms in a cell which is more important the number of chromosomes themselves.

82
Q

What is the genome?

A

all the genetic components of a cell

Called the set of nuclear chromosome in eukaryotes

83
Q
A

USF PCB3063 Genetics (2 decks)

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