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FCH 532 Homework 1
Ans Key
1. Define the terms as they are related to biochemistry:
a. Complementary base pair - Base pair formed between complementary bases
based on Watson-Crick rules. A forms 2 H-bonds with T (or U) and G forms 3 Hbonds with C.
b. Transcription-Process by which an RNA polymerase produces an mRNA
transcript from a DNA template (replacing T with U in the process). This is the
first stage of expression of genetic information.
c. Translation-the production of a polypeptide chain from an mRNA template. This
process is catalyzed by ribosomes which link together the amino acids from
activated aminoacyl-tRNA carriers to form the polypeptide based on decoding of
the triplet codon nucleotide sequence.
d. germ cell-sperm and ova cells that are directly descended from germ cells from
the previous generation.
e. somatic cell-all other cells but germ cells-derived from germ cells but do not give
rise to them.
f. haploid number-the number of unique chromosomes in a somatic cell.
g. Dominant-If, by crossing parents with two different phenotypic traits, all the
progeny in the first generation (F1-first filial generation) have the same phenotype
as one of the parents and not the other, that phenotype (and thus genotype) is said
to be dominant.
h. Recessive-the recessive phenotype is not observed when a dominant allele is
present. However, homozygous allele for a recessive genotype display the
recessive phenotype.
i. Gametes-sex cells; Meiosis leads to the formation of sex cells (gametes) that are
haploid (N) in the number of chromosomes.
j. Zygote-The result of the fusion of two gametes (sperm and ovum) resulting in a
return to the full complement of chromosomes (2N) from the haploid (N) cells.
k. Cistron- functional genetic unit of a cis-trans test that indicates a gene or
complementation group (tells whether or not the mutations are on the same (cis)
or different (trans) chromosomes.
l. Cis-two mutations on the same chromosome.
m. Trans-two mutations on physically different chromosomes.
n. Phage-short for bacteriophage; a virus that infects bacteria
o. permissive conditions-conditions environment under which an organism or virus
can produce progeny.
p. restrictive conditions-conditions in the environment which hinder the ability of an
organism or virus to produce progeny.
q. Complementation-When one allele can “complement” the mutation in another
allele to show the wild-type phenotype. A complementation group is a group of
mutant genes which do not complement each other as determined by the cis-trans
complementation test.
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r. Nucleotide-Indvidual monomers for DNA or RNA consisting of phosphate esters
of five carbon sugar (deoxyribose or ribose) that are covalently linked to a
nitrogenous base (A, G, T, C, or U) through a glycosidic bond to the C1’ carbon
of the sugar residue.
s. Nucleoside-5-carbon sugar and base (A,T,G,C, or U); essentially a nucleotide
without the phosphate.
t. keto-enol tautomerism-transformation of molecule from the keto to enol form (or
vice-versa) catalyzed by the movement of a proton and double bond within the
molecule
2. What are the main differences between mitosis and meiosis. Use diagrams or
tables to explain your results.
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3. Problems 8, 9, and 10 in your textbook (Chapter 1, p. 38)
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4. What are the differences between allelic and non-allelic genes? Allelic genes are
different forms of the same gene, meaning they occur on different chromosomes.
Nonallelic genes are capable of complementing one another (two recessive
phenotypes crossed will result in a wild-type phenotype). Nonallelic genes are
not able to complement one another, so that two recessive traits results in a nonwild-type trait.
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5. What are Chargaff’s rules? The quantity of A=T and G = C in double stranded
DNA. Structural basis derived from H-bonding between specific bases.
6. Draw the chemical structures of the nucleotides A, T, C, G, and U. Using these
structures draw the base pairs according to Chargaff’s rules. Draw keto-enol
tautomerisms for bases.