Question

1. Amounts of which of the components of cell cycle regulation vary with cell cycle phase?

1. Cyclin-dependent kinases
2. Cyclins
3. Checkpoints
4. Kinetochores

  

2. The synaptonemal complex forms to facilitate pairing of homologous chromosomes during

1. prophase of mitosis and meiosis.
2. prophase of meiosis I and II.

c.   prophase of meiosis I only.

d. all stages of meiosis.

3. Mendel’s Second Law of Independent Assortment refers to the separation of

1. two identical alleles of the same gene.
2. two different alleles of the same gene.
3. alleles from two different genes on the same chromosome.
4. alleles from two different genes on different chromosomes.

4. Assuming independent assortment, how many different types of gametes can be produced from an individual that is heterozygous for 5 genes?

1. 5
2. 10
3. 25
4. 32

5. If you determine that the disease Marfan syndrome is dominant but in one family a child with Marfan syndrome is born to two parents with no sign of the disease, how could you explain the absence of the phenotype in the parents?

1. Marfan syndrome exhibits incomplete dominance.
2. Marfan syndrome displays variable expressivity.
3. Marfan syndrome displays variable penetrance.
4. Marfan syndrome is sex-linked.

6. Due to dosage compensation by X-inactivation, females can exhibit a mosaic pattern of sweat glands on only some portions of their body if they carry a particular loss of function allele. Could any of the following genotypes result in males with such a mosaic pattern of sweat glands?

a. X^AY

b. X^AX^AY

c. X^AX^aY

d. Not possible

7. If two genes on the same chromosome, A and B, are completely linked and no crossovers can occur between them, how many phenotypic combinations would be visible in the offspring from a testcross between a heterozygous female (AaBb) and a homozygous recessive male (aabb)?

1. 1
2. 2
3. 4
4. 8

8. Considering the cause and risk factors for aneuploidy, which of the following would you expect to find if you did genetic analysis on an infant with a trisomy to identify the origin of the extra chromosome copy?

1. Two identical copies of a paternal chromosome, plus one maternal copy
2. Two identical copies of a maternal chromosome, plus one paternal copy
3. Two maternal copies of a chromosome, either identical or homologous, plus one paternal copy
4. Two paternal copies and one maternal copy of all chromosomes

provide a detailed explanation of why the correct answer is correct.

Answer 1

1. a)cyclin dependant kinase b) cyclins c) checkpoints can cause cell transitions thus regulating the cell cycle. cyclins are group of related proteins that drive the events of particular phase or group of phases, thus it act as core cell cycle regulators. cyclin dependant kinases are group of other regulatory proteins that help to drive the cell cycle by activating or deactivating cyclins. Checkpoints regulates by internal control of cell cycle. Kinetochores are also structural proteins that helps the spindle attach to centeromere.
2. c) prophase phase of meiosis 1. In the second stage of prophase I of meiosis 1, Zygotene chromosomes start pairing to form synapsis to form, homologous chromosomes, thus chromosome synapsis is accompained by the formation of synaptonemal complex.
3. c) alleles from two different genes on the same chromosome.  According to law of independant assortment, different genes are inherited independently of one another.
4. d) 32 No.of gametes = 2n , where n- no. of heterozygote allele Here, 25 = 32   

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