• What is quantitative genetics? How is it different from the other genetics we’ve been doing? When is it used mostly?  Why does it rely on incomplete dominance?

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  • Qyantitative genetics is the study of continuous traits, it is an extension of mendelian inheritance. 

• What is broad and narrow sense heritability?

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  • Broad sense heritability H squared is the proportion of total phenotypic variation due to all genetic effects.

• What are the advantages of doing genetic experiments with haploid organisms instead of diploids?

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  • Haploid organisms are used because there is said to be more mutations in diploid organisms because 1.Changes in gene dose. 2. Dominant mutations 3. recessive x-linked mutations and heterozygosity before selection.

• What are the advantages of doing genetic experiments with ascomycete fungi, which put all their meiotic products into a sac?

The advantages of using ascomycete fungi are that you know exactly what the genotypes of the progeny will be without having to cross them with anything.  Also you will know exactly when something crosses over.  It lets you know where on the chromosome the gene is without having to cross it with another organism.

• What is complementation? Review the complementation table we did in class, for finding out how many different genes are represented among a collection of mutants with the same phenotype. (more below)

Complementation is when 2 different strains of an organism have different mutations but have the same phenotype.  They both have homozygous recessive mutations that will always produce that same mutation when crossed with itself.  When they are crossed with each other they revert to the wildtype. 

Autopolyploidy vs allopolyuploidy

An autotetraploid, for example, has 4 of each chromosome. At meiosis, any one of those 4 can pair with any other of those 4. OR, they can pair in other weird ways (3 vs. 1, or all 4 in a quadrivalent).  Weird pairing and weird segregation often result in gamete inviability.

An allotetraploid for example, is a cross between 2 diploid species (that are closely related, but not identical).

The chromosomes from each species are sort of similar, but not quite homologous. Instead, they are homeologous.

These cannot do meiosis, since pairing can’t happen.

But endoploidy can happen, wherein chromosome duplication happens without mitosis, leading to doubling the number of chromosomes. 

Now, if there are 2 homologues, these can pair and the plant is not longer sterile. It is like a double diploid. Or this can happen if 2 (erroneously) diploid gametes from closely related species fuse.

A syndrome of X-linked mental retardation. The fragile X syndrome is a genetic disorder caused by mutation of the FMR1 gene on the X chromosome. Normally, the FMR1 gene contains between 6 and 55 repeats of the CGG codon (trinucleotide repeats). In people with the fragile X syndrome.

Form when multiple rounds of replication produce many homologous chromatids that remain synapsed together. In addition to increasing the volume of the cell's nuclei and causing cell expansion, polytene cells may also have a metabolic advantage as multiple copies of genes permits a high level of gene expression.

A mutant strain of an organism that cannot synthesize essential molecules required for things such as growth. If this is the case it must have the molecule supplied in the growth medium for it to grow.

What are the 3 ways that foreign DNA gets into bacteria? Which requires a virus? Which requires cell-cell contact? (Hint, all start with T):

I believe only two start with T. They are transformation (Unidirectional transfer of extracellular DNA into cells whereby a phenotypic change is produced in the recipient.), Conjugation (Plasmid mediated process, unidirectional transfer of genetic information direct cellular contact between a donor and a recipient.) and Transduction (Process in which bacteriophages mediate the transfer of bacterial DNA from the donor bacterium to the recipient.)

Transduction requires a bacteriophage.

Conjugation requires cell to cell contact.

The F factor is an example of a plasmid in the fact that it is a “self-replicating”, circular DNA distinct from the main bacterial chromosome.

-          High Frequency Recombination Cell

-               Designation for an E. coli cell that has an F factor integrated into the bacterial chromosome.  When an Hfr cell conjugates with a recipient (F-) cell, bacterial genes are transferred to the recipient with high frequency.

-               Figure 18.5

Also called merozygote: A bacterial cell having a second copy of a particular chromosomal region in the form of an exogenote. A partially diploid Escherichia coli cell formed from a complete chromosome (the endogenote) plus a fragment (the exogenote).

            Exogenote: DNA that a bacterial cell has taken up through one of its sexual processes.

            Endogenote: Bacterial host chromosome

            A partially diploid example is the F’ factor cell that is formed when an F factor is excised from a cell but accidentally takes a piece of adjacent chromosome as well (considered the exogenote).  This is type of conjugation is called F-duction and provides a way to study particular genes in a diploid state in E. coli. 

Specialized transduction can only transduce at certain point in the bacterial chromosome, in contrast generalized can occur at any point in the bacterial chromosome.

Operon is site that is used to induce transcription

The lac operon turns on in the presence of lactose. This is because a small amount of the lac gene is always transcribed. lactose is metabolized into allolactose which induces the lac gene transcription by binding to the lac gene suppressor.

When lactose is no longer present then the allolactose is no longer produces and the protein repressor protein returns to suppression of lac gene transcription.

High levels of lactose turns on the lac operon and transcribes the lac gene.

·         How about high levels of glucose? (turn the lac operon on or off?)

Glucose does not turn the lac operon on.

•       What gene encodes the repressor?

 Jacob and Monod proposed that the lacI+ gene produces the repressor molecule. (pg.520)

•       How do high levels of lactose affect the repressor?

The repressor can only be induced when lactose is present.

•       What does the CAP molecule do, and how is affected by cAMP?

The two main proteins are cI and cro (according to lecture), or rather the lambda repressor and the cro protein. Depending on the amount of transcription of either/both will determine the pathway chosen by the cell. The transcription of one will inhibit the other. The two proteins have opposite affinities for three binding sites that control two major operators for the control of the lambda life cycle.

Following the steps in the figure we see that when the phage grows it begins when RNA polymerase binds to the promoters P_L and P_R which triggers the transcription of N and cro genes, but stops shortly there after. Now there are two genes that have been transcribed. The N protein will act on three different sites and extend RNA synthesis. Proteins O and P allow DNA synthesis to occur and cII  is transcribed begins to effect the rest of the sequence.

[transcription of the “late” genes (cro ->)] The lytic pathway can be triggered by DNA damage. Ths will cause a change in the bacterial protein RecA. When DNA is damaged it will stimulate the lambda (l) repressor to cleave itself and become inactive. The lack of the repressor allows for the normal binding to the operators (O_R) that in turn allow RNA polymerase to join a the promoter (P_R) and transcribe the cro gene and beyond down the sequence. Cro protein acts to decrease the synthesis from the two promoters (P_R and PL) which in turn will block the synthesis of cII proteins and repress the synthesis of the lambda  (l)  repressor. Inhibiting its own initial promoter (P_R) does not stop the lytic pathway. By this time there is enough Q proteins (one of the genes transcribed beyond the cro sequence) that will set the transcription of “late” genes and secure the lytic pathway.