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Imprinting and replication

Instructions: In your own words, define the pairs of terms given below. Write in complete sentences, stating the differences and relationships between the two terms, and give specific examples where appropriate.
A complete answer usually requires four to eight sentences. Each question is worth four marks, for a total of 40 marks.

1. chiasmata / non-disjunction
2. Barr body / sex chromosomes
3. topoisomerase / DNA polymerase
4. leading strand / Okazaki fragment
5. miRNA / RNA interference
6. inducible operon / repressor
7. gene therapy / DNA fingerprinting
8. transduction / conjugation
9. cytoplasmatic inheritance / genomic imprinting

Solution Preview

Biology Questions

1. chiasmata / non-disjunction

Chiasmata are "specialized chromosomal structures that hold the homologous chromosomes together until anaphase I." Chiasmata are formed at sites where programmed DNA breaks generated by Spo11 undergo full recombination pathway to generate crossovers.
Nondisjunction is the failure of homologous chromosomes or chromatids to segregate during Mitosis or Meiosis with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none.

2. Barr body / sex chromosomes

Barr body is the inactive X chromosome in a female somatic cell or the inactive Z in a male, rendered inactive in process called lionization in those species in which sex is determined by the Y or W chromosome rather than the diploidy of X or Z.

3. topoisomerase / DNA polymerase

Topoisomerase are enzymes that can relax DNA or remove supercoils by nicking and closing one strand of duplex DNA. Topoisomerase change DNA topology by breaking and rejoining double stranded DNA. The enzymes can introduce or remove supercoils and can separate two DNA duplexes that are intertwined.

DNA polymerase are enzymes that create new DNA molecule from existing DNA template. It is essential for replication to occur. DNA polymerase "reads" the existing DNA strands to create two new strands that match the existing ones. Every times cell divides, DNA polymerase is required to help duplicate the cell's DNA so a copy of original DNA molecule can be passed to each of daughter cells. DNA polymerase adds new nucleotide to 3' end of the newly forming strand, elongating it ina 5' to 3' direction. DNA polymerase cannot begin ...

Solution Summary

Chiasmata are "specialized chromosomal structures that hold the homologous chromosomes together until anaphase I." Chiasmata are formed at sites where programmed DNA breaks generated by Spo11 undergo full recombination pathway to generate crossovers.
Nondisjunction is the failure of homologous chromosomes or chromatids to segregate during Mitosis or Meiosis with the result that one daughter cell has both pairs of parental chromosomes or chromatids and the other has none.

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