-
What
are the five modes of genetic recombination and in which type of organisms does
each occur?
•Genetic recombination occurs during
- –Crossing over between
- homologous chromosomes in meiosis (eukaryotes)
- –Co-infection
- of bacterial cells with related bacteriophages (bacteriophage)
- –Transformation
- (bacteria)
-
-
What are synapsis, bivalents (also known as
tetrads), chiasmata, and crossing over?
- synapsis -when homologous chromosomes pair up.
- bivalents- a pair of homologous chromosomes
- Crossing over
- (exchange of DNA segments) occurs in Prophase I
- At the end of
- prophase I, chromosomes separate from their homologues and are connected only
- at the positions of crossovers called chiasmata.
-
in which phase of meiosis does crossing over take
place?
prophase
-
Does crossing over typically occur between
sister chromatids or non-sister chromatids of homologous chromosomes?
sister chromatids
-
What are the ploidy and DNA content of the
parent cell at the beginning of prophase I?
Diploid
-
What
are the ploidy and DNA content of the daughter cells at the end of meiosis I
and at the end of meiosis II?
- two haploid cells at the end of meiosis 1
- four haploid cells at the ends of meiosis 2
-
What
are the similarities and differences between meiosis and mitosis?
Prophase- each condensing chromosomes had two chromatids. In meiosis I, homologous chromosomes synapse, forming a bivalent. Crossing over occurs between nonsister chromatids, producing chiasmata. In mitosis each chromosome acts independently.
- Metaphase
- In meiosis I, the bivalents align at the metaphase plate. In mitosis, individual chromosomes align at the metaphase plate.
- Anaphase
- In meiosis I, chromosomes (not chromatids separate. In mitosis, chromatids separate.
-
Understand
the meiotic bases of Mendel’s law of segregation and law of independent
assortment.
-
What
is the effect of crossing over on the genotypes of the gametes?
Produces recombinant genotypes.
-
What
is the relationship between the frequency of recombination and the physical
distance between the genes on the chromosomes?
- The frequency of
- recombination is a measure of the distance between pairs of genes.
- The percent of nonparental offspring
- corresponds to map distance in map units or centimorgans.
- 1% crossover = 1 mu
-
How
does genetic recombination occur between two related but different
bacteriophages?
- Genetic
- recombination of bacteriophages can occur when a
- bacterial cell is co-infected by two related phage populations of different
- genotypes.
-
What
is transformation? How does it lead to recombinant genotypes?
- Transformation is the
- uptake of exogenous DNA by a bacterial cell and allows recombination between
- the DNA fragment and the bacterial genome.
-
What
is transduction? How is it capable of introducing chromosomal
information from one bacterial cell to another?
- Phage that
- incorporated DNA from a previous host cell can carry that DNA into another
- bacterial host at a subsequent infection.
-
What
is conjugation? What are F+, F-, and Hfr cells?
Bacterial conjugationallows transfer of DNA from a donor cell to a recipient cell. Donor cells (F+)have F factor and develop sex pili to selectively bindto recipient cells (F-).
-
How does conjugation allow the transfer of plasmids between bacterial cells?
-
How does conjugation allow the transfer of chromosomal genes between bacterial cells?
- Conjugation between
- an Hfr cell and an F-
- cell allows transfer of genomic DNA from Hfr
- cell into F-
- cell. Crossing over between similar sequences then creates recombinant F-
- cells.
-
What
is homologous recombination? The current model for this event includes the
formation of a crossed structure called H_______ J_______.
Holliday Junction
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