Midterm SP07

Molecular And Cell Biology 110 with Scheffler at University of California - San Diego

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By: Jennifer Wang
Created: 2011-11-01
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What are the essential elements of a plasmid cloning vector?

Origin of replication (to get started)
Target (gene for selecting host bacteria containing the vector, like Amp resistance)
Multiple cloning site with multiple restriction sites where the vector can be cut

Advantages of a YAC over a BAC? What's needed for YAC?

Can be used to clone much bigger pieces of DNA compared to just plasmid vector.

YAC must be linear, with telomeres at the end, an origin of replication, a centromere functioning within the yeast (CEN), the inserted DNA, and selectable markers flanking

Differences between Northern and Southern blot?

Northern Blot detects mRNA while Southern blot detects DNA. Southern blot with digested with restriction enzymes can reveal several different bands.

What's VNTR polymorphisms; use schematic diagrams to show how PCR could be used to show that such polymorphisms are inherited in a Mendelian fashion

“Variable number of tandem repeats”; sequences repeated in tandem, but the number of repeats is different in different individuals. Unique regions constitute a locus, and define different alleles.

A man has two alleles with 3 and 15 repeats, his wife has two alleles with 3 and 6 repeats, respectively. What can their children have?

15,3 15,6 3,3 3,6

Explain the difference between a cloned animal and a transgenic animal expressing a novel gene (e.g. encoding the green fluorescent protein)

A cloned animal is obtained from an enucleated oocyte into which a diploid nucleus from a somatic cell has been inserted., then implanted. A live-born animal (sheep) would be a genetically identical clone of the nuclear donor cell.

Explain the difference between a cloned animal and a transgenic animal expressing a novel gene (e.g. encoding the green fluorescent protein)

A cloned gene/complete cDNA with a promoter and a poly(A) site is injected into a pro-nucleus of a fertilized zygote. The heterologous DNA is integrated into a chromosome of the host cell. Expressed in all cells or in only a few cells.

How could one restrict the expression of the transgene to a particular chosen tissue, e.g. heart muscle?

The transgene coding sequence would have to be preceded by a promoter that is active only in the desired tissue.

The repeat DNAs have been categorized into two major classes; what are they?

Tandem repeats: a sequence is repeated many times in tandem; the size of the repeat and the repeat number depends on the type of sequence

The repeat DNAs have been categorized into two major classes; what are they?

Interspersed repeats; a sequence short/long is present in many copies in the genome, which are inserted at random locations, in all or most chromosomes. The repeat number is also variable

Southern blot looks like a “smear” ranging from the top to the bottom of the gel. What is the problem?

It is most likely that the probe contains an interspersed repeat sequence, i.e. is not a purely unique DNA. The repeat sequence of the probe will hybridize to many different restriction fragments if the repeat is very abundant.

A child has trisomy 18 (Edwards) from a father who is aa and a mother who is ab. How did this nondisjunction happen to give rise to this 47, XY, +18?

The child has three chr 18. One comes from the father (haplotype a), and the two others come from the mother. Since both haplotypes from the mother are found in the affected child, nondisjunction must have occurred in meiosis I in the mother.

What chromosomal abnormality would suggest that the risk of another Down’s syndrome child is considerable; matter where the karyotype was found?

If either were found to have a Robertsonian fusion involving chr 21 and one other telocentric chromosome, meiosis I in either parent could yield a secondary oocyte/spermatocyte with two copies of the long arm of chr 21 (21q).

What chromosomal abnormality would suggest that the risk of another Down’s syndrome child is considerable; matter where the karyotype was found? (cont)

Meiosis II would yield a gamete (mature egg or sperm) with two copies of the long arm of chromosome 21. Fertilization by a normal gamete yields a trisomy 21. The probability of having another child with Down’s syndrome would be very much higher.

Give an explanation for the observation of a mosaic retina in a heterozygous female with sex-linked ocular albinism.

There is X inactivation (for dosage compensation) in somatic cells, which is random in early embryogenesis. The retina of the female would have patches of cells with the normal X active (pigmented) and some with the chromosome silenced (not pigmented).

What explanations are offered for the observation that in the case of X - autosome translocations in females the normal X is usually inactivated?

Inactivation of the translocation X might lead to a spreading of the inactivation into the autosomal segment. Could be functionally equivalent to a deletion of a significant portion of an autosome (partial monosomy), and such an embryo is not viable.

What explanations are offered for the observation that in the case of X - autosome translocations in females the normal X is usually inactivated? (cont)

Alternatively, the segment of the X chromosome attached to the autosome might escape X inactivation. For a significant portion of the X chromosome there would thus be no dosage compensation, and this is also not compatible with normal development.

About this deck

By: Jennifer Wang
Created: 2011-11-01
Size: 20 flashcards
Views: 0

About StudyBlue

“I have been getting MUCH better grades on all my tests for school. Flash cards, notes, and quizzes are great on here. Thanks!”
Kathy