genetics exam 2 Flashcards
Genes exhibit linkage while on the same chromosome or on different chromosomes?
same chromosomes
what type of gametes result from complete linkage?
parental or non-crossover gametes
The percentage of offspring resulting from recombinant gametes will vary depending on what?
the distance between the two genes along the chromosome
The distance between two loci on a single chromosome`
interlocus distance
what is chiasmata?
synapsed chromosomes that wrap around each other
Two genes located close to each other along the chromosome are less likely or more likely to have a chiasma form between them?
less likely
The frequency of exchange is an estimate of what?
the relative distance between two genes along the chromosome
What are map units and what is another name for them?
stands for 1 percent recombination between two genes on a chromosome. / centimorgans
A single crossover alters the linkage between two genes only if what?
if the crossover occurs between those genes
What could be expected when two linked genes are 50 map units apart?
crossovers in 100% of tetrads
What can double crossovers determine?
the order of three genes on the chromosome
What must the genotype of the parent be for three point mapping to be conducted?
heterozygous for all three genes under consideration
In DCO’s, non-crossover F2 phenotypes occur how much?
in the greatest proportion of offspring
In DCO’s, double crossover phenotypes occur in what proportion?
in the smallest proportion
What did the Luria-Delbruck experiment of fluctuating numbers of colonies with mutations prove?
that mutations are spontaneous not produced
Bacterial resistance arise from mutations that exist before or after exposure to bacteriocide?
Before
When do mutations generally occur?
randomly
What is bacterial genetic recombination?
a non-reciprocal transfer of genetic material from one bacterium to another
What are the three types of genetic recombination in bacteria?
Conjugation
Transformation
Transduction
What is an auxotroph?
a mutant organism that requires an additional nutrient that the normal strain does not
What is a prototroph?
a microorganism that has the ability to synthesize its own cell constituents
What is the F factor in F+ bacteria?
a small circular, double standed DNA molecule
How many genes are on the F factor?
40
What is a cell called when the plasmid integrates into the chromosome?
Hfr cell
What is a merozygote?
partially diploid cell
What is a heteroduplex?
when a piece of DNA from outside the cell comes in and becomes part of the chromosome
What are the two types of transduction?
generalized and specialized
what does a bacterial chromosome fold into?
nucleoid body
Mutations that create auxotrophs have lost what?
the ability to synthesize a substance required for growth
What is the nomenclature for a gene?
leu2+ —> wild type gene required for leucine synthesis
What is the nomenclature of a phenotype?
Leu+ —> a bacterium that does not need leucine to grow
Leu —> a bacterium that needs leucine to grow
What does 90% of E. Coli genome encode?
proteins
How many base pairs does E. Coli have?
4.6 million
What do plasmids do for E. coli?
can carry resistance to antibiotics and toxic substances.
What is the size range of plasmids?
1kb-3Mb
What does virulence mean?
relative ability to initiate illness
what are the symptoms of tuberculosis?
persistent cough, shortness of breath, weakness
How long are the antibiotics prescribed for TB?
6 months
What is LHON?
Leber’s hereditary optic neuropathy
-maternally inherited disease resulting from a mutation in the mitochondrial gene that causes reduced oxidative phosphorylation
what is infectious heredity?
cytoplasmic microorganism that affects phenotype
what is organelle heredity?
inheritance from only one parent (usually maternal)
- mitochondria
- chloroplast
what is a nucleoid?
the DNA-containing region within the cytoplasm in prokaryotic cells
how many tRNA genes does the human mtDNA have?
22
Mitochondrial and chloroplast genomes are semiautonomous because why?
they require cooperation between organelle and nuclear genomes
why do mtDNA and cpDNA have higher mutation rates than nuclear DNA?
- more exposure to oxidative damage
- lack of protection from histone proteins that bind eukaryotic DNA
What is the difference between homo and heteroplasmic cells?
homo contain only one type of organelle genome and hetero contain a mixture of genomes
What are the three petite mutants of saccharomyces?
- segregational
- neutral
- suppressive
What did Griffith find out in his experiments?
that something from the heat-killed S bacteria transformed the living R bacteria into S
How many sub-units make up DNA and how many make up Protein?
4 / 20
Who provided convincing evidence that DNA is genetic material?
Alfred Hershey and Martha Chase in 1952
What was found when bacteriophage infected e. coli are grown in 32P medium?
that the progeny are radioactive unlike that of 35S medium grown progeny.
When did Watson and Crick propose their double helix model of DNA structure?
1953
What were the three major findings of chargaff’s base-composition studies?
- A is proportional to T; C is proportional to G
- The sum of purines = sum of pyrimidines
- Percentage of C+G is not necessarily equal to percentage of A+T (refutes the ____tetranucleotide hypothesis____, which stated that A,C,G,&T are in equal amounts)
how wide is a DNA strand?
20A
How does RNA differ from DNA?
- Ribose replaces deoxyribose
- Uracil replaces Thymine
What are the three major types of RNA?
- mRNA
- rRNA
- tRNA
What are the techniques for characterizing DNA and RNA?
- Absorption
- Sedimentation behavior
- Denaturation/renaturation
- electrophorisis
