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Exam 1 Flashcards

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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
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?
5 carbon ring 5' Phosphase 1' Sugar OH (in RNA) / H (in DNA) on 2' carbon
25
What is the structure of a purine?
6-carbon sugar + 5-carbon sugar
26
What is the structure of a pyrimidine?
6-carbon sugar
27
What two nucleotides are PURINES?
A + G
28
What are the PYRIMIDINES?
C + T (or U, in RNA)
29
What separates in ANAPHASE 1 of MEIOSIS?
``` Homologous chromosomes (NOT sister chromatids) X X ```
30
What separates in ANAPHASE 2 of MEIOSIS?
The sister chromatids | } {
31
When does chromosome number double in meiosis? (Describe what happens here)
Anaphase 2 of meiosis; sister chromatids separate | } {
32
When does the amount of DNA split in half during mitosis?
Telophase
33
When does the amount of DNA split in half during meiosis?
Telophase 1 + Telophase 2
34
What happens to the number of chromosomes in ANAPHASE 2 of MEIOSIS?
It doubles as sister chromatids separate from each other but are not fully separated into individual cells yet.
35
What happens to the number of chromosomes and amount of DNA in ANAPHASE of MITOSIS?
``` # of Chromosomes: Doubles DNA molecules: NO CHANGE ```
36
When does a cell become haploid?
When it splits into 2 (for a total of 4 now) after meiosis 1
37
What does it mean if n=2? What does this look like in G1? In prophase?
- 2 PAIRS of chromosomes (2 from each parent); 4 total chromosomes - in G1: } { ] [ - in G2: }{ }{ ][ ][
38
What does it mean if n=3? What does this look like in G1? In prophase?
- 3 PAIRS of chromosomes (3 from each parent) - in G1: } { ] [ > < - in G2: }{ }{ ][ ][ >< ><
39
If the following represents G1, what do n and 2n equal? | ] [ } { > <
2n=6 | n=3
40
Under what conditions to A-DNA, Z-DNA, and B-DNA occur?
A-DNA: when there is LESS WATER Z-DNA: in HIGH SALT concentrations B-DNA: normal conditions
41
What type of DNA is NOT ATTACHED to histone proteins?
Bacterial
42
What is the POSITION EFFECT?
If a coding sequence is too close to a region of heterochromatin, it may also be silenced.
43
What two distinct structures contain heterochromatin?
Telomeres + centromeres
44
Explain how the telomeric end stabilizes itself.
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
What would you add to DNA to make it supercoil again?
methyl groups
46
What prevents the separation of sister chromatids in anaphase 1 of meiosis? What is it degraded by?
Cohesin is protected (at centromeres only) from degradation by SHUGOSHIN in Anaphase 1 of meiosis; Cehesin is degraded in anaphase 2 my separase.
47
What is the function of shugoshin?
Protects cohesin during anaphase 1 of meiosis and holds the sister chromatids together (at centromeres only)
48
What defines LEPTOTENE?
Chromatin condenses ("first LEAP toward being condensed")
49
What defines ZYGOTENE?
beginning of (Z)synapsis, to produce tetrads
50
What defines PACHYTENE?
Synaptonemal complex begins to PATCH TOGETHER homologous chromosomes, this is where crossing over occurs
51
At what stage of prometaphase does crossing over occur?
Patchytene
52
At what stage of prometaphase 1 do the chromosomes begin lining up?
Zygotene
53
Whats the formula to solve for probability of an outcome?
p= [(n!)/(s!t!)] (p^s)(q^t)
54
Describe what happens in GENE CONVERSION. What is the effect?
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
What defines DIPLOTENE?
The TWO bivalents begin to separate (Di=2)
56
What defines DIAKINESIS?
Chromosomes now only held together at chiasmata; fully condensed
57
Define MONOECIOUS.
"one house" = one organism possesses BOTH sex organs = Hermaphroditic
58
Define DIOECIOUS.
"Two houses" = each organism produces ONE SEX'S organs
59
Define HETEROGAMATIC.
produces 2 different types of gametes
60
Define HOMOGAMETIC.
All gametes have some chromosome content
61
Describe the sex-determination system in grasshoppers.
XX-XO Females: XX Males: XO (produce x-bearing sperm or sperm with no x at all; heterogametic)
62
In grasshoppers, which sex is heterogametic?
The males; XO
63
In humans, which sex is heterogametic?
Males; XY
64
What method of sex determination is used in BIRDS? What defines each gender? Which sex is heterogametic?
ZZ-ZW Males: ZZ (homogametic) Females: ZW (heterogametic)
65
What method of sex determination is used in SNAKES? What defines each gender?
ZZ-ZW Males: ZZ Females: ZW
66
What method of sex determination is used in BUTTERFLIES? What defines each gender?
ZZ-ZW Males: ZZ (homogametic) Females: ZW (heterogametic)
67
Explain the importance of the SRY gene.
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
What is the phenotype of TURNER SYNDROME? What gender is this individual? Give some physical characteristics.
XO; Female; chubby body type, WEBBED NECKS
69
What is the genotype for KLEINFELTER SYNDROME? What gender are these individuals? Give some physical characteristics.
47-XXY; Male (because they have an SRY on their Y-chromosome); secondary female characteristics, male breasts (gynecomastia), very low sex drive, sterile
70
What is the sex-determination system used in FRUIT FLIES?
``` 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
How does the Y-chromosome function as a sex chromosome in fruit flies?
It segregates with the X in meiosis. It does not contribute to sex determination directly.
72
How many haploid sets of autosomes do MOST FRUIT FLIES possess?
2 haploid sets | X Y }{ ][
73
In FRUIT FLIES, what ratio of X:A produces intersex characteristics?
0.5-1 --> Intersex
74
Describe the system of sex determination in WASPS and BEES.
Haplodiploidy: Males develop from unfertilized eggs (no DNA from dad), females develop from fertilized eggs (DNA from both parents).
75
What is the method of sex determination in SLIPPER LIMPITS?
Sequential Hermaphroditism: The male is always "on top"
76
What temperatures produce male and female TURTLES?
Warm --> Females | Cold --> Males
77
What temperatures produce male and female ALLIGATORS and CROCODILES?
Warm --> Males | Cold --> Females
78
Name a species in which the X's do not get inactivated.
Fruit flies
79
What X:A ratio will cause a fruit fly to die?
ZERO: must have at least one haploid set of autosomes to survive
80
Name the order of the stages in prometaphase in meiosis 1.
``` Leptotene Zygotene Pachytene Diplotene Diakinesis ```
81
In the telomere, the LONG STRAND ends in 3' or 5'?
3'
82
What animals use the ZZ-ZW system of sex determination?
Birds, snakes, butterflies
83
Explain equalizing x-linked gene activity in ROUNDWORMS.
activity on both x-chromosomes in halved
84
Explain equalizing x-linked gene activity in FRUIT FLIES.
Activity on males X-chromosomes is increased to bring it up to the level of the females' additional X's
85
Explain equalizing x-linked gene activity in MAMMALS.
Only one X is left active.
86
Do those with Kleinfelter syndrome undergo X-inactivation?
Yes. One of their two X's is inactivated
87
Do those with Turner Syndrome undergo X-inactivation?
No. Always XO...no inactivation, because they only have one X to begin with.
88
What happens with X-inactivation in female humans? (The percentages)
25% escape inactivation TOTAL. 15% in some women. Another 10% is others.
89
What promotes X-inactivation?
XIST: an RNA that fosters methylation
90
What protects an X from inactivation?
TSIX
91
What is the equation for coefficient of coincidence?
OBSERVED double crosses/ EXPECTED double crosses
92
How to calculate expected double crosses using two m.u. values:
(mu1)(mu2)(Total N)

Genetics (6 decks)

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