MEIOSIS & MITOSIS

Question 1

Which is correct about the process of MEIOSIS?

1. Occurs in all somatic cells
2. Involves 2 rounds of DNA duplications and 2 cell divisions
3. Involves genetic recombination and pairing of specific chromosome homologues
4. Produces daughter cells that are genetically identical to the parent cell

Answer 1

2 and 3 are correct

Question 2

Which is true checkpoints during the cell cycle?

1. Are present only in selected cells in the body.
2. Occur only in G1 of the cell cycle
3. Assess DNA damage before entering the Metaphase
4. Determine whether the cell should enter an Apoptotic pathway

Answer 2

3 and 4

Question 3

The stage of meiosis where cells become haploid is:

1. prophase 1
2. prophase 2
3. anaphase 1
4. anaphase 2

Answer 3

1. anaphase 1 (remember: 2nd meiosis mainly mitosis division)

Question 4

During replication of the DNA molecule, one of the original DNA strands:

1. combines with the other original DNA strand
2. is broken down for nucleotide units
3. combines with one the new strands of DNA
4. is converted in carbohydrates for energy metabolism

Answer 4

3. Combines with one of the new DNA strands

Question 5

The metaphase spindle has

a. 1 type of microtubes
b. 2 types of microtubules
c. 3 types of microtubules

Answer 5

3. 3 types of microtubules

Question 6

which is correct. In meiosis, metaphase 1

1. The bivalent chromosomes align on the spindle
2. Microtubules from the same pole of the spindle attach to sister chromatids
3. The kinetochores of sister chromatids are adjacent to each and orientated in the same direction

Answer 6

all correct

https://cdn-ccnli.nitrocdn.com/hPbgvskpJmIfLTeYLYGdGpfRfGKbrYYq/assets/static/optimized/rev-85c4fa1/wp-content/uploads/2019/02/Meiosis_2-768x1077.png

Question 7

e68..In Meiosis Anaphase 1 Is Initiated By The Disruption Of The Chiasmata.

1. TRUE
2. FALSE

Answer 7

1. TRUE

Question 8

Meiosis of vertebrate oocytes is arrested in:

1. leptotene
2. pachytene
3. zygotene
4. diplotene
5. diakinesis

Answer 8

4. diplotene

Question 9

Which Is The Correct Sequence Of The Different Stages Of The Prophase In Meiosis 1 ?

1. leptotene, pachytene, zygotene,diakinesis,diplotene
2. diplotene, zygotene, diakinese, pachytene, leptotene
3. diplotene, leptotene, diakinese, pachytene, zygotene
4. leptotene, zygotene, pachytene,diplotene ,diakinesis

Answer 9

4. correct

*Sequences of prophase 1 of Meiosis–

Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis

remember : (Lazy person die in dikernis)

Question 10

Which is correct In prophase of meiosis 1?

1. zygotene is the second stage
2. diakinesis is the last stage
3. pachytene is the fourth stage
4. leptotene is the third stage

Answer 10

1, 2

lepto……zygo….patchy……diplo. dikinasis

(la zy person die in dikenis)

Question 11

Which Is True. In Meiosis Methapase 2 Arrest Is .

1. maintained by c-mos
2. maintained by Cyclic AMP
3. maintained by MAP Kinase
4. maintained by MPF (maturation promoting factor: a complex of Cdc2 and cyclin B)

Answer 11

all correct

Question 12

which is correct? In humans’ oocytes remain in the diplotene stage of the first meiotic division

1. only for a few hours
2. up to 40 years
3. up to puberty

Answer 12

3. up to puberty

Question 13

Which Is Correct? During The Diplotene Arrest.

1. Chromosomes decondense and are actively transcribed
2. Important amounts of mRNAs and proteins are stored
3. there is no transcriptional activity

Answer 13

1, 2

Question 14

Which Is Correct ?

1. Chiasmata become visible in the diplotene
2. the “crossing over” starts already in the pachytene
3. close association of homologous chromosomes (synapsis) starts during leptotene

Answer 14

1, 2

close association of homologous chromosomes (synapsis) starts NOT during leptotene (correct is in zygotene)

Question 15

How Much Percent Oocytes Have the Second Polar Body Extruded 1 Hour After Sperm Injection In ICSI?

1. already 1 in 2
2. 78 % (after 3h; after 2h 56%)
3. about 30 %
4. none it is far too early

Answer 15

3. about 30 % of Oocytes Have the Second Polar Body Extruded 1 Hour After Sperm Injection In ICSI

Question 16

Which Is NOT Correct? Maturation Promoting Factor

1. Is composed of cyclin A and p34cdc2
2. Is composed of cyclin B and p34cdc2
3. Is activated by removal of the phosphate from tyrosine 15 of the p34cdc2
4. Is involved in germinal vesicle breakdown

Answer 16

1 not correct

Maturation Promoting Factor MPF composed of cyclin B and p34cdc2,

its involved GV Breakdown , while its inactivated during arrest period by removal of phosphate from tyrosine 15 of p34cdc2

Question 17

Which Factors Have to be Present in High Concentrations to Ensure Germinal Vesicle Breakdown?

1. phosphorylated p34cdc2
2. active p34cdc2
3. MPF
4. c-mos
5. MAP kinase
6. cyclic AMP

Answer 17

1,2 and 3

The resumption of meiosis (GV Breakdown) in response to the LH surge is initiated by the cumulus (granulosa) cells, because the oocyte itself does not possess LH receptors. Responding to LH, the cumulus cells shut down their gap junctions . This reduces the transfer of both cAMP and cGMP from the cumulus cells into the oocyte. The resulting reduction of cGMP in the oocyte allows the activation of PDE3A. The activated PDE3A then breaks down the intra-oocytic cAMP into 5′AMP. The decline in the concentration of cAMP sets off a signaling pathway leading to the activation of MPF and the subsequent resumption of meiosis.

Question 18

During Meiosis Tetrads become Visible in

1. Telophase 2
2. Prophase 2
3. Anaphase 1
4. Prophase 1

Answer 18

4. Tetrad become visible in prophase 1 (zygotene)

Question 19

The Stage of Meiosis I During Which Recombination (synapsis) Takes Place Between Homologous Chromosomes is Called

1. leptotene
2. zygotene
3. pachytene
4. diplotene
5. diakinesis

Answer 19

3. Pachytene- Prophase1: recombination or synapsis between homologous chromosomes

leptotene: chromosomes appear thin and long, in initial stage of the extended prophase of meiosis 1 ,the homologous chromosomes pair before condensation.

zygotene: Tetrad appear ,chromosomes side by side by their length

pachytene: synapsis, crossing over, recombinant chromatids or homologous chromosomes

diplotene: chiasmata, DNA sequences exchange(Homologous Chromosomes Separate Along Their Length But Remain Associated At Chiasmata)

diakinesis: final stage of prophase 1 and start metaphase1 of Meiosis

Question 20

the stage of meiosis 1 during which homologous chromosomes separate along their length but remain associated at chiasmata is called:

1. leptotene
2. zygotene
3. pachytene
4. diplotene
5. diakinesis

Answer 20

diplotene stage (chiasmata)

Question 21

The Final Stage Of Prophase Of Meiosis 1 During Which The Chromosomes Fully Condense And The Cell Progress To Metaphase Is Called

1. leptotene
2. zygotene
3. pachytene
4. diplotene
5. diakinesis

Answer 21

5. diakinesis

Question 22

The Initial Stage Of The Extended Prophase Of Meiosis 1 During Which Homologous Chromosomes Pair Before Condensation Is Called

1. Leptotene
2. zygotene
3. pachytene
4. diplotene
5. diakinesis

Answer 22

1. Leptotene

Question 23

During meiosis:

when does chromosome disjunction occur?

When does chromatid disjunction occur?

Answer 23

Chromosome disjunction occurs during anaphase I.

Chromatid disjunction occurs during anaphase II.

Question 24

Perform a chi-square test to determine if an observed ratio of 30 tall to 20 dwarf pea plants is consistent with an expected ratio of 1:1 from the cross Dd × dd.

Answer 24

X^2​= (O-E)²/E

(O) Observed= 30 (E) Expected= 25 (المتوقع من اجمالي 50)

x² = (30 − 25)² /25 + (20 − 25)² /25 = 2,

which is less than 3.84, the 5% critical value for a chi-square statistic with 1 degree of freedom من الجدول; consequently,

the observed segregation ratio is consistent with the expected ratio of 1:1

Question 25

**Albinism i**n humans is caused by **a recessive allele** * a. From marriages between people known to be carriers (Aa) and people with albinism (aa), what proportion of the children would be expected to have albinism? * Among three children, what is the chance of one without albinism and two with albinism?

Answer 25

Half the children from Aa × aa matings would have albinism. In a family of three children, the chance that one will be **unaffected** and two **affected** is **3** × **(1/2)**¹ × **(1/2)**² = 3/8.

Question 26

If both husband and wife are known to be **carriers** of the allele for **albinism**, what is the chance of the following combinations in a family of **four** children: * (a) all four unaffected. * (b) three unaffected and one affected. * (c) two unaffected and two affected. * (d) one unaffected and three affected.

Answer 26

(a) (3/4)⁴ = 81/256. (b) 4 × (3/4)³ × (1/4)¹ = 108/256. (c) 6 × (3/4)² × (1/4)² = 54/256. (d) 4 × (3/4)¹ × (1/4)³ = 12/256.

Question 27

If a man and a woman are heterozygous for a gene, and if they have three children, what is the chance that all three will also be heterozygous?

Answer 27

Aa \* Aa AA, Aa, AA, Aa Aa = 0.5 chance of all heterozygous = (probability of event)³ =(1/2)³ =**1/8**

Question 28

In fetal Ovary: Germ cells divided ......... But at ....... weeks start.......... division then before birth meiotic arrest at ................................................

Answer 28

In fetal Ovary: Germ cells divided **mitotically** But at **11-12** weeks start **Meiotic division** then before birth meiotic arrest at **prophase (diplotene stage) of 1st meiosis GV stage**

Question 29

Pros and cons Sexing by FISH to exclude X-linked affected males?

Answer 29

affected and unaffected males will be discarded, and can't distinguish between carrier and unaffected females

Question 30

compare **twining** differences

Answer 30

**1. Dizygotic (fraternal) twins** * **a.** Result from the fertilization of two different secondary oocytes by two different sperm; the resulting two zygotes form two blastocysts, which implant separately into the endometrium of the uterus. * **b.** Hence, the twins are no more genetically alike than are siblings born at different times. * **c.** Dizygotic twins and 35% of monozygotic twins have two placentas, two amniotic sacs, and two chorions (i.e., a diamnionic-dichorionic membrane). **2. Monozygotic (identical) twins** * **a.** Result from the fertilization of one secondary oocyte by one sperm. The resulting zygote forms a blastocyst in which the inner cell mass (embryoblast) splits into two. * **b.** Hence, the twins are genetically identical. * **c.** In 65% of the cases, monozygotic twins have one placenta, two amniotic sacs, and one chorion (i.e., a diamnionic-monochorionic membrane). **3. Conjoined (Siamese) twins** * **a.** Form exactly like monozygotic twins, except that the inner cell mass (embryoblast) does not completely split. * **b.** Hence, two embryos form, but they are joined by tissue bridges at various regions of the body (e.g., head, thorax, or pelvis)

Question 31

Syndactyly ?

Answer 31

Syndactyly is the most common congenital malformation of the limbs fusion of fingers or toes