MCAT Bio Genetics and Evolution Flashcards
The two nonidentical copies of a chromosome are called____
homologous chromosomes
Different versions of a gene are called ___
alleles
___ in males undergo meiosis
Spermatogonia
___ in females undergo meiosis
Oogonia
The product of meiosis in males occurs in testes with production of ____
haploid spermatozoa
In females meiosis occurs in the ovaries producing ___
ova
In meiosis ___ occurs between homologous chromosomes
Recombination
During prophase 1 of meiosis ____ pair
Homologous chromosomes
The longest phase of meiosis is ___
prophase because of the complexity of crossing over
Meiotic recombination occurs between ____
homolgous chromosomes, NOT sister chromatids
____ states that two alleles of an individual are separated and passed on to the next generation singly
Law of segregation
At what stage during meiosis are different alleles of a gene separated?
During meiosis 1 at the time when homologous chromosomes separate
During this stage the replicated homologous chromosomes are pulled to opposite sides of the cell
Anaphase 1
During ___ stage, the sister chromatids are finally separated at their centromeres and pulled to opposite sides of the cell
Anaphase 2
A situation in which a heterozygote displays the phenotype associated with each of the alleles
Codominance
A form of evolution in which different organisms are placed into the same environment and exposed to the same selection pressures. This causes the organisms to evolve along similar lines. As a result, they may share functional, but not structural similarity (because they possess different starting material)
Convergent evolution
The exchange of DNA between paired homologous chromosomes (tetrads) during prophase 1 of meiosis
Crossing over
A form of evolution in which the same organism is placed into different environments with different selection pressures. This causes the organisms to evolve differently; The resulting (new) species may share structural similarity
Divergent evolution
___produces homologous structures
Divergent evolution
The frequencies of alleles in a given gene pool do not change over time
Hardy-Weinberg Law
What are the five assumptions of Hardy-Weinberg?
- No mutations
- No natural selection
- No migration
- Random Mating between individuals
- Large population
Experiments with phage and bacteria that definitively determined DNA to be the genetic information of the cell
Hershey-Chase experiments
___states that genes found very far apart on the same chromosome sort independently of one another during gamete formation
Law of Independent Assortment
States that the two alleles of a given gene will be separated from one another during gamete formation (meiosis)
Law of segregation
The failure of two separate genes to obey the Law of Independent Assortment, as might occur if the genes were found close together on the same chromosome
Linkage
During ___ the paired homologous chromosomes (tetrads) align at the center of the cell (the metaphase plate)
Metaphase 1
During __ replicated chromosomes align at the center of the cell (metaphase plate)
Metaphase
___ is identical to mitotic metaphase except the number of chromosomes was reduced by half during meiosis
Metaphase 2
The failure of homologous chromosomes or sister chromatids to separate properly during cell divison. This could occur during anaphase 1 of meiosis (homologous chromosomes),or during anaphase 2 of meiosis or anaphase of mitosis
Nondisjunction
The percentage of individuals with a particular genotype that actually display the phenotype associated with that genotype
Penetrance
A subset of a species consisting of members that mate and reproduce with one another
Population
During __ the replicated chromosomes condense, homologous chromosomes pair up, crossing over occurs between homologous chromosomes, the spindle is formed, and the nuclear envelope breaks apart into vesicles.
Prophase 1
__ is identical to mitotic prophase, except that the number of chromosomes was reduced by half during meiosis 1
Prophase 2
The RF value is the percentage of recombinant offspring resulting from a given genetic cross.
Recombination frequency
The ___ is proportion to the physical distance between two genes on the same chromosome
Recombination frequency
If the recombination frequency is low, the genes under consideration may be __
linked
Pairing of homologous chromosomes in a diploid cell, as occurs during prophase 1 of meiosis
Synapsis
A structure that forms in early prophase 1 that mediates synapsis (pairing of homologous chromosomes)
Synaptonemal complex
__ is identical to mitotic telophase, except that the number of chromosomes is now reduced by half. After this phase the cell is considered to be haploid. The chromosomes still replicated, and the sister chromatids must still be separated during meiosis 2
Telophase 1
Identical to mitotic telophase, but that chromosome number was reduced by half during meiosis 1
Telophase 2
A genetic cross between an organism displaying a recessive phenotype (homozygous recessive) and an organism displaying a dominant phenotype, done to determine the unknown genotype
Testcross
A pair of replicated homologous chromosomes. Formed during prophase 1 of meiosis so that homologous chromosomes can exchange DNA in a process known as “crossing over”
Tetrads
Gene is said to have __ if its expression alters many different, seemingly unrelated aspects of the organism’s total phenotype
Pleiotropism
A mutation in a gene may cause altered development of heart, bone, AND inner ears, it altered many unrelated aspects of the organism’s total phenotype
Pleitropism
Expression of alleles for one gene is dependent on a different gene. For example, a gene for curly hair cannot be expressed if a different gene causes baldness
Epistasis
___ are ligands that bind to receptors and elicit responses
Receptor agonist
__ are ligands that bind to the receptor but elicit no response, blocking receptor agonists from binding.
Receptor antagonist
A right shift on the oxyhemoglobin curve indicates ____
Decreased hemoglobin-oxygen binding affinity
What things will cause a decrease in the hemoglobin-oxygen binding (right shift on ODC)
- Low (acidic) pH of plasma
- Increased levels of CO2
- 2,3 bisphosphoglycoric acid (2,3-BPG)
With decreasing temperatures, air is able to hold ___
less H20
During elongation, ribosomes read the mRNA in the ____
5’ to 3’ direction
During synthesis of proteins, the direction of addition of amino acids is in the ___
N terminus to C- terminus direction
__ are sugars that differ at only one stereocenter
Epimers
Arachidonic acids are an important precursor molecule of __,__and __
Prostaglandins, thromboxanes, and leukotrienes
__ are a large family of lipids derived from arachidonic acids, they give rise to prostaglandins
Eicosanoids