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Genetics > Exam 1 > Flashcards

Exam 1 Flashcards

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Biology 101 flashcards
0
Q

When does the nuclear envelope disintegrate? (Be specific)

A

Late prophase

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1
Q

Is what stage of the cell cycle does chromatin begin to condense?

A

Prophase

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2
Q

When do the centrosomes start moving towards the poles? (be specific)

A

EARLY prophase

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3
Q

When do the spindle fibers BEGIN reaching?

A

Prophase

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4
Q

What is the check point in metaphase?

A

check if spindle fibers are attached

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5
Q

What degrades cohesin and when does this happen?

A

Separase; in anaphase

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6
Q

What is the function of DYNEIN? With what does it interact?

A

a motor protein that interacts with the spindle fibers to move the chromatids apart.

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7
Q

Separase degrades _______ so that the _______ can separate during ______.

A

Separase degrades COHESIN so that the SISTER CHROMATIDS can separate during ANAPHASE.

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8
Q

When does the nuclear envelope reform?

A

TELOPHASE

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9
Q

When do the spindle fibers degrade?

A

Telophase

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10
Q

When is the cell membrane synthesized?

A

Telophase

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11
Q

When does the nuclear envelope disintegrate? (Be specific)

A

LATE prophase

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12
Q

What happens in the G2 checkpoint?

A

check for

  • cell size
  • DNA replication
  • accumulation of MPF (mitosis promoting factor)
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13
Q

How is MPF activated and what keeps it from being activated?

A
  • Activated by DEphosphorylation

- DNA damage halts DEphosphorylation

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14
Q

What is the purpose of supercoiling?

A

Brings regulatory sequences close enough together that transcription factors can bind to them and regulate gene activity properly; also helps DNA fit in the nucleus

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15
Q

NEGATIVE vs POSITIVE supercoiling

A

Negatively Supercoil: DNA is undercoiled; wrong direction (easier to replicate)
Positively Supercoiled: DNA is overcoiled; same direction (hard to replicate)

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16
Q

Supercoiling can only take place in _____ DNA

A

Circular

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17
Q

What enzyme is necessary in supercoiling? What does it do?

A

topoisomerase; add or remove rotations by breaking nucleotide strands

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18
Q

Nucleosome vs Chromatosome

A

Nucleosome: 8 histone molecules
Chromatosome: Nucleosome + H1 histone (binds the joining segments together)

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19
Q

What is the function of the H1 histone?

A

joins chromatosomes together

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20
Q

What part of the nucleosome interacts directly with DNA?

A

Each of the 8 histones in a nucleosomes contains a tail of positive amino acids (+ lysines) that interacts with the negative (-) phosphates on DNA.

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21
Q

What binds to histone proteins so that they loosen their grip on DNA? What enzyme facilitates this reaction?

A

Histone acetyltransferase adds (-) acetyl groups to (+) lysines on the histones so that they loosen their grip on the (-) phosphates

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22
Q

What helps the centromeres coil so tightly?

A

A special type of H3 histone protein

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23
Q

Where is tRNA located?

A

cytoplasm

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24
Q

Draw the structure of a DNA/RNA nucleotide.

  • On what carbon is the phosphate group?
  • On what carbon is the sugar?
  • How do RNA and DNA differ in structure?
A

5 carbon ring
5’ Phosphase
1’ Sugar
OH (in RNA) / H (in DNA) on 2’ carbon

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25
Q

What is the structure of a purine?

A

6-carbon sugar + 5-carbon sugar

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26
Q

What is the structure of a pyrimidine?

A

6-carbon sugar

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27
Q

What two nucleotides are PURINES?

A

A + G

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28
Q

What are the PYRIMIDINES?

A

C + T (or U, in RNA)

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29
Q

What separates in ANAPHASE 1 of MEIOSIS?

A 
Homologous chromosomes (NOT sister chromatids)
X  X
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30
Q

What separates in ANAPHASE 2 of MEIOSIS?

A

The sister chromatids

} {

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31
Q

When does chromosome number double in meiosis? (Describe what happens here)

A

Anaphase 2 of meiosis; sister chromatids separate

} {

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32
Q

When does the amount of DNA split in half during mitosis?

A

Telophase

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33
Q

When does the amount of DNA split in half during meiosis?

A

Telophase 1 + Telophase 2

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34
Q

What happens to the number of chromosomes in ANAPHASE 2 of MEIOSIS?

A

It doubles as sister chromatids separate from each other but are not fully separated into individual cells yet.

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35
Q

What happens to the number of chromosomes and amount of DNA in ANAPHASE of MITOSIS?

A 
# of Chromosomes: Doubles
DNA molecules: NO CHANGE
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36
Q

When does a cell become haploid?

A

When it splits into 2 (for a total of 4 now) after meiosis 1

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37
Q

What does it mean if n=2?
What does this look like in G1?
In prophase?

A
  • 2 PAIRS of chromosomes (2 from each parent); 4 total chromosomes
  • in G1: } { ] [
  • in G2: }{ }{ ][ ][
38
Q

What does it mean if n=3? What does this look like in G1? In prophase?

A
  • 3 PAIRS of chromosomes (3 from each parent)
  • in G1: } { ] [ > <
  • in G2: }{ }{ ][ ][ >< ><
39
Q

If the following represents G1, what do n and 2n equal?

] [ } { > <

A

2n=6

n=3

40
Q

Under what conditions to A-DNA, Z-DNA, and B-DNA occur?

A

A-DNA: when there is LESS WATER
Z-DNA: in HIGH SALT concentrations
B-DNA: normal conditions

41
Q

What type of DNA is NOT ATTACHED to histone proteins?

A

Bacterial

42
Q

What is the POSITION EFFECT?

A

If a coding sequence is too close to a region of heterochromatin, it may also be silenced.

43
Q

What two distinct structures contain heterochromatin?

A

Telomeres + centromeres

44
Q

Explain how the telomeric end stabilizes itself.

A

The end of the LONG STRAND (ending with 3’) binds to itself at a complementary sequence, forming the t-loop. The shorter end (ending in 5’) wraps around the outside of the t-loop.
SHELTERIN shelters telomeres from replication.

45
Q

What would you add to DNA to make it supercoil again?

A

methyl groups

46
Q

What prevents the separation of sister chromatids in anaphase 1 of meiosis? What is it degraded by?

A

Cohesin is protected (at centromeres only) from degradation by SHUGOSHIN in Anaphase 1 of meiosis; Cehesin is degraded in anaphase 2 my separase.

47
Q

What is the function of shugoshin?

A

Protects cohesin during anaphase 1 of meiosis and holds the sister chromatids together (at centromeres only)

48
Q

What defines LEPTOTENE?

A

Chromatin condenses (“first LEAP toward being condensed”)

49
Q

What defines ZYGOTENE?

A

beginning of (Z)synapsis, to produce tetrads

50
Q

What defines PACHYTENE?

A

Synaptonemal complex begins to PATCH TOGETHER homologous chromosomes, this is where crossing over occurs

51
Q

At what stage of prometaphase does crossing over occur?

A

Patchytene

52
Q

At what stage of prometaphase 1 do the chromosomes begin lining up?

A

Zygotene

53
Q

Whats the formula to solve for probability of an outcome?

A

p= [(n!)/(s!t!)] (p^s)(q^t)

54
Q

Describe what happens in GENE CONVERSION. What is the effect?

A

Cross-over occurs between two middle strands, but one cross-over will be “repaired” to what it was before the cross-over occurred. The effect is that an expected ratio of 1/2 to 1/2 will often end up being 3/4 to 1/4 instead.

55
Q

What defines DIPLOTENE?

A

The TWO bivalents begin to separate (Di=2)

56
Q

What defines DIAKINESIS?

A

Chromosomes now only held together at chiasmata; fully condensed

57
Q

Define MONOECIOUS.

A

“one house” = one organism possesses BOTH sex organs = Hermaphroditic

58
Q

Define DIOECIOUS.

A

“Two houses” = each organism produces ONE SEX’S organs

59
Q

Define HETEROGAMATIC.

A

produces 2 different types of gametes

60
Q

Define HOMOGAMETIC.

A

All gametes have some chromosome content

61
Q

Describe the sex-determination system in grasshoppers.

A

XX-XO
Females: XX
Males: XO (produce x-bearing sperm or sperm with no x at all; heterogametic)

62
Q

In grasshoppers, which sex is heterogametic?

A

The males; XO

63
Q

In humans, which sex is heterogametic?

A

Males; XY

64
Q

What method of sex determination is used in BIRDS? What defines each gender? Which sex is heterogametic?

A

ZZ-ZW
Males: ZZ (homogametic)
Females: ZW (heterogametic)

65
Q

What method of sex determination is used in SNAKES? What defines each gender?

A

ZZ-ZW
Males: ZZ
Females: ZW

66
Q

What method of sex determination is used in BUTTERFLIES? What defines each gender?

A

ZZ-ZW
Males: ZZ (homogametic)
Females: ZW (heterogametic)

67
Q

Explain the importance of the SRY gene.

A

If you express SRY, you develop as a male. If the SRY gene, by accident, get switched over from the Y to the X chromosome during meiosis (at an area called the “pseudoautosomal region”) then it is possible to develop into an XX-male.

68
Q

What is the phenotype of TURNER SYNDROME? What gender is this individual? Give some physical characteristics.

A

XO; Female; chubby body type, WEBBED NECKS

69
Q

What is the genotype for KLEINFELTER SYNDROME? What gender are these individuals? Give some physical characteristics.

A

47-XXY; Male (because they have an SRY on their Y-chromosome); secondary female characteristics, male breasts (gynecomastia), very low sex drive, sterile

70
Q

What is the sex-determination system used in FRUIT FLIES?

A 
Ratio between X-chromosomes and haploid sets of autosomes;
X:A Ratio --> Sex
0-0.5 --> Metamale (sterile)
0.5 --> Male
0.5-1.0 --> Intersex
1.0 --> Female
>1.0 --> Metafemale (sterile)
71
Q

How does the Y-chromosome function as a sex chromosome in fruit flies?

A

It segregates with the X in meiosis. It does not contribute to sex determination directly.

72
Q

How many haploid sets of autosomes do MOST FRUIT FLIES possess?

A

2 haploid sets

X Y }{ ][

73
Q

In FRUIT FLIES, what ratio of X:A produces intersex characteristics?

A

0.5-1 –> Intersex

74
Q

Describe the system of sex determination in WASPS and BEES.

A

Haplodiploidy: Males develop from unfertilized eggs (no DNA from dad), females develop from fertilized eggs (DNA from both parents).

75
Q

What is the method of sex determination in SLIPPER LIMPITS?

A

Sequential Hermaphroditism: The male is always “on top”

76
Q

What temperatures produce male and female TURTLES?

A

Warm –> Females

Cold –> Males

77
Q

What temperatures produce male and female ALLIGATORS and CROCODILES?

A

Warm –> Males

Cold –> Females

78
Q

Name a species in which the X’s do not get inactivated.

A

Fruit flies

79
Q

What X:A ratio will cause a fruit fly to die?

A

ZERO: must have at least one haploid set of autosomes to survive

80
Q

Name the order of the stages in prometaphase in meiosis 1.

A 
Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis
81
Q

In the telomere, the LONG STRAND ends in 3’ or 5’?

A

3’

82
Q

What animals use the ZZ-ZW system of sex determination?

A

Birds, snakes, butterflies

83
Q

Explain equalizing x-linked gene activity in ROUNDWORMS.

A

activity on both x-chromosomes in halved

84
Q

Explain equalizing x-linked gene activity in FRUIT FLIES.

A

Activity on males X-chromosomes is increased to bring it up to the level of the females’ additional X’s

85
Q

Explain equalizing x-linked gene activity in MAMMALS.

A

Only one X is left active.

86
Q

Do those with Kleinfelter syndrome undergo X-inactivation?

A

Yes. One of their two X’s is inactivated

87
Q

Do those with Turner Syndrome undergo X-inactivation?

A

No. Always XO…no inactivation, because they only have one X to begin with.

88
Q

What happens with X-inactivation in female humans? (The percentages)

A

25% escape inactivation TOTAL.
15% in some women.
Another 10% is others.

89
Q

What promotes X-inactivation?

A

XIST: an RNA that fosters methylation

90
Q

What protects an X from inactivation?

A

TSIX

91
Q

What is the equation for coefficient of coincidence?

A

OBSERVED double crosses/ EXPECTED double crosses

92
Q

How to calculate expected double crosses using two m.u. values:

A

(mu1)(mu2)(Total N)

Genetics (6 decks)

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