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bio exam 4
Terms in this set (37)
When Thomas M. Hunt crossed his red-eyed F1 (filial 1) generation fruit flies (Drosophila melanogaster) with each other , the F2 generation included both red- and white-eyed flies. All of the white-eyed flies were male. What was the explanation for this result?
The gene involved is on the X chromosome
Red-green color blindness is a sex-linked recessive trait in humans. The normal, dominant allele is notated as XN, and the recessive allele is notated as Xn. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
XNXn and XNY
Two autosomal genes have a recombinant frequency of 16%. Which of the following conclusions can be made regarding these genes?
The two genes are closely linked on the same chromosome
If cell A enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, what will be the result at the completion of meiosis?
¼ of the gametes descended from cell A will be n+1, ¼ will be n-1 and ½ will be n
Which of the following statements regarding down syndrome is correct?
The frequency increases with the age of the mother
At what point in meiosis is a chromosome lost from one daughter cell so that, after fertilization with a normal gamete, the result is an embryo with the chromosomal makeup of 45, X0?
After an error occurring in anaphase I or anaphase II
If a female having cinnabar eyes is crossed with a wildtype male, what percentage of the F1 males will have cinnabar eyes?
One map unit is equivalent to which of the following values?
1% frequency of recombination between two linked genes
One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this alteration called?
How does the recombination of linked genes contribute to natural selection?
it maintains genetic variability in a species
Males are affected by sex-linked traits more often than females because?
males are hemizygous for the X chromosome
What does a frequency of recombination of 50% indicate?
the two genes are likely to be located on different chromosomes
In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?
tortoiseshell females, black males
which of the following statements correctly describes one of Chargaff's rules regarding DNA?
The percentages of adenine and cytosine are roughly equal, as are the percentages of guanine and thymine in the DNA of a given species
in his transformation experiments, which of the following results did Griffith observe?
mixing a heat-killed pathogenic strain of bacteria with a living non-pathogenic strain can convert some of the living cells into the pathogenic form
What is meant by the description "antiparallel" regarding the strands that make up DNA?
the 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive
During DNA replication, which of the following enzymes covalently connects segments of DNA?
If a cell were unable to produce histone proteins, which of the following would be a likely effect?
the cell's DNA would could not be packed into its nucleus
A particular triplet of bases in the template strand of DNA is 5'-AGT-3'. The corresponding codon for the mRNA transcribed is
Which of the following processes only occurs in eukaryotic gene expression?
A poly-A tail is added to the 3' end of an mRNA, and a cap is added to the 5' end
Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
several transcription factors
which of the following statements best describes the function of the TATA box in eukaryotic promoters?
it is the recognition site for a specific transcription factor
in which direction does RNA polymerase move along the DNA?
3' to 5' direction along the template strand
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the
bonding of the anticodon to the codon and the attachment of amino acids to tRNA
Which of the following events in translation is the first to occur in eukaryotes?
the small subunit of the ribosome recognizing and attaching to 5' cap of mRNA
the process of translation in both prokaryotes and eukaryotes requires tRNAs, amino acids, and ribosomal subunits. Which of the following components must also be present for translation to proceed?
polymerase and GTP
Which of the following types of mutation, resulting in an error in the mRNA just after the 5' AUG start codon, is likely to have the most serious effect on the polypeptide product?
a deletion of two nucleotides
Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?
a base deletion near the start of a gene
which of the following statements is correct regarding protein synthesis in prokaryotes and eukaryotes?
translation can begin while transcription is still in progress in prokaryotes, but not in eukaryotes.
which of the following statements correctly describes the role of a molecule that controls a repressible operon?
the molecule binds to the repressor protein and activates it
which of the following environments would most likely lead to the transcription of the lactose operon?
the cyclic AMP and lactose levels are both high within the cell
What effect does methylation have on DNA?
it makes it transcriptionally inactive
Which of the following statements correctly describes the role of histone acetylation and DNA methylation in gene regulation?
DNA methylation reduces transcription, and histone acetylation promotes transcription.
Gene expression might be altered based on post-transcriptional processing in eukaryotes rather than prokaryotes. Which of the following describes this difference?
eukaryotic exons may be spliced in alternative patterns
If cell A enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis I, what will be the result at the completion of meiosis?
half of the gametes descended from cell X will be n+1, and half will be n-1
which of the following events causes recombination between linked genes to occur?
crossovers between the genes results in chromosomal exchange
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