TBR 9 - Genetic Information Flashcards
Pangenesis.
The theory that states that each part of the body produced tiny particles. Pangenes were thought to be miniature replicas of each organ or tissue by the body. These pangenes were carried to the reproductive organs by the circulatory system where they are packed to sperm or egg.
What made pea plants easy for Gregor Mendel to study?
There were many true breeding varieties. The pea plants could be distinguished by 7 different pair traits. Pea plants were rather easy to grow, have a short generation time, and they are small and wouldn’t take up space.
Describe Mendel’s experiment.
Crossed for a pair of traits (like true breed purple versus white). This F1 generation expressed one of the two parental characteristics. He then allowed F1 to self-pollinate for one generation, and then noticed in the F2 generation, each of the characteristics re-appeared.
When mendel crossed two pairs of true breeds and then allowed them to self-pollinate, what is the ratio of the parental trait to the other parental traits.
3 to 1 ratio.
Based on Mendel’s pure cross and subsequent hybrid cross experiment, he concluded that:
1) Traits are either dominant or recessive.
2) The alternative form of a hereditary factor, which leads to an alternative form of a given trait is called an allele.
3) An individual who possesses two identical alleles is said to be homozygous, while an individual who possesses two diff alleles is said to be heterozygous.
4) two alleles from each parent to an offpsring do not influence each other in any way. They don’t form intermediate alleles.
5) the presence of hereditary characters in an individual doesn’t ensure that it will be expressed/
Test cross.
Ex. Crossing purple flowers of unknown genotype (WW or Ww) from the F1 generation in order to determine its genotype. Involves crossing the purple flowers with a homozygous recessive white plant.
Law of segregation.
Alternate alleles segregate from each other in heterozygous individuals and retain their identity. Two members of a pair of a gene pair segregate from each other into gametes, so that 1/2 of the gametes carry one member and the other 1/2 of gametes carry the other member of the gene pair.
What phenotypic ratio does a dihybrid cross result in?
9:3:3:1
What did Mendel’s dihybrid cross show?
Hereditary factors for different traits like color and shape assort independently from one another.
Mendel’s law of independent assortment.
Segregation of one gene pair is independent of other gene pairs during the formation of the gametes.
What is the law of segregation essentially, in terms of cell division?
Meiosis.
Genes.
Basic units of hereditary (DNA), are located at specific locations along the chromosomes.
Independent assortment of genes will only occur in two instances:
1) genes are located on different chromosomes (because the chromosomes themselves assort independently)
2) they are very far apart on the same chromosome
3) through recombination, two genes close to one another can end up on different genes.
Sex-linked.
If a given trait is determined by a gene on the X chromosome, it is said to be sex-linked.
Experiment with the sex-linked gene.
XY male with recessive white eye gene crossed with dominant red eye XX female. F1 generation is all red-eye, but all females are XwWr. The F1 generation was allowed to mate, and the resulting F2 generation had white-eyed males again (unlike F1)
True or false. A given genetic locus has ONE designated allele.
A given locus can have many alleles. Ex. ABO blood group.
Many genes can control a phenotype. One example is tryptophan, an essential amino acid (an AA an organism cannot synthesize itself). Explain how this works for this for an organism.
The biosynthesis of may compounds within the cell there can be many sequential steps. Each step is controlled by a separate EZ which in turn is controlled by a particular gene. One example would be tryptophan.
Tryptophan experiment - auxotroph.
A mutant that will grow only when its medium is supplemented with a particular compound which is not required by the normal wild-type organism.
Tryptophan experiment - prototroph.
A wild type organism.
Name the important components of the trrytophan experiment. Show the general pathway.
Chorismate - trpE -> ANTHRANILATE> Gene2, 3, 4 > trp A-> INDOLE -> trpB > TRYPTOPHAN
Tryptophan experiment - with a trp E- mutant, under what conditions in the medium would the organism grow.
The auxotroph will grow if either anthranaliate, indole, or trytophan is added.
Tryptophan experiment - with a trp A- mutant, under what conditions in the medium would the organism grow.
The mutant will NOT grow if nothing or anthranilate is added. It will grow if eithe rindole or tryptophan is added.
Tryptophan experiment - with a trp B mutant, under what conditions in the medium would the organism grow.
The bacterium will not grow if nothing, anthranilate, or indole is added to the minimal medium. This auxotroph will only grow if tryptophan is added.
Epistasis.
Two different genes which are not alleles of one another may affect the same outcome. Ex. inability to synthesize tryptophan. For the tryptophan synthesis, the dominant allele of all the genes involved in the particular biosynthetic pathway must be present.
There are some genes which may act in an additive fashion. Give one example.
1) There are 7 genes in yeast that control the synthesis of invertase which converts sucrose > glucose + fructose. If the yeast posses the dominant allele in any of these it ferments sucrose, but if it contains more than one, it ferments sucrose at a quicker rate.
2) height are also probably controlled in an additive fashion.
Pleiotrophy.
Where an individual allele has more than one effect on the phenotype. Ex. Mouse with a yellow coat with one allele present or death if both are.
The chromosomes that are not sex chromosomes are called ___.
Autosomes.
The long arm is designated as this letter. The short arm of a chromosome is designated as this letter.
The long arm is designated as “q”. The short arm is designated as “p”.
How many base pairs of DNA in a human cell? Genes?
6*10^9; 100,000 genes per haploid set.
What do the circles and squares represent on a pedigree? What about a slash through a box? Colored in? Left to the right arrangement?
1) circles = female; square = males
2) slash = heterozygous
3) colored in = has genetic defect
4) Birth order of the offspring is arranged from oldest to youngest from left to right.
Monosomy and trisomy.
Genetic abnormalities that occur during meiosis. One copy of the chromosomes called monosomy.
Genetic diseases due to nondisjunction.
Nondisjunction of XX can lead to XX in one gamete and none in the other, resulting in XXY, Klinefelters. Or XO female can result, called Turners syndrome.
