Bio Sci 97 quizzes midterm 1

Suppose you provide an actively dividing culture of E. coli with radioactive dTTPs, which can be incorporated into newly synthesized DNA. What would you expect to see if the cell replicates its DNA and divides once in the presence of the radioactive base?

DNA in both daughter cells will be radioactive

The polymerase chain reaction (PCR) is used to amplify fragments of DNA. During a PCR reaction, what breaks hydrogen bonds between nucleotides?

95 degree C incubation

You are setting up a dideoxysequencing reaction. What is the correct ratio of dNTPs (deoxyribonucleotides) to ddNTPs (dideoxyribonucletides)?

Adding more dNTPs than ddNTPs

The sequence of the coding strand of DNA is:

5'-TTAGATGCCTGTCAAGTAACTG-3'

Assuming that is sequence for the entire mRNA transcript for this gene, how many nucleotides are the in 5' UTR?

4

Which of the following is true about promoter sequences?

They are found upstream of the transcription start site.

There is a mutation in a bacterial gene's promoter that changes a nucleotide from a T to an A in a postition between the -10 and -35 elements. What does this mutation do?

Nothing

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The anticodon loop of the first tRNA that will complement this mRNA is:

3' GGC 5'

Life as we know it depends on the genetic code: a set of codons, each made up of three bases in a DNA sequence and corresponding mRNA sequence, that specifies which of the 20 amino acids will be added to the protein during translation.

Imagine that a prokaryote-like organism has been discovered in the polar ice on Mars. Interestingly, these Martian organisms use the same DNA → RNA → protein system as life on Earth, except that

there are only 2 bases (A and T) in the Martian DNA, and

there are only 17 amino acids found in Martian proteins.

Based on this information, what is the minimum size of a codon for these hypothetical Martian life-forms?

5 bases (because 2^5=32. need more bases than amino acids)

Bicoid is an important transcription factor for early Drosophila development. The 11th codon in its protein sequence is usually 5'-UUA-3'. A mutation has been introduced that changes the codon to 5'-UUG-3'. What is the consequence of this mutation?(NOTE: you may always use your book or the internet to find a codon table -- there is no need to memorize it!)

Nothing, since this is a silent mutation

DNA within the cell is wrapped around nucleosomes to form chromatin. When chromatin is in the form of a 30 nm fiber, how many copies of H1 and H2A histone proteins would be found in a stretch of chromatin containing 20 nucleosomes?

20 H1, 40 H2A

The pattern of transcription for a pair of identical twins (Tweedledee and Tweedledum) is very similar at the age of 10. However by the time they are 50, transcription of the leptin gene is much lower in Tweedledum than in Tweedledee. This could be due to what change in Tweedledum?

DNA methylation at the site of Tweedledum's leptin gene

Housekeeping genes are genes which are expressed in virtually every cell in your body because they encode proteins required for all cells to function. For example, actin and RNA polymerase are housekeeping genes. In which type of chromatin would housekeeping genes lie?

Euchromatin

Humans have a gene, T, that is involved in muscle formation of the tongue. Individuals homozygous for one allele can roll their tongues, while individuals homozygous for the other allele cannot. If both parents can roll their tongues, but their child cannot, what can be said about the mode of inheritance?

Tongue rolling is dominant, and both parents were heterozygous (Tt).

Which of the following DOES NOT describe why pea plants were a good model system for Mendel?

Pea plants have fewer chromosomes than humans.

By convention, when the p-value for the difference between the observed experimental outcomes and the expected outcome is less than 5 percent (< 0.05), the experimental results are considered to be

statistically significantly and different from the expected outcome.

A scientist observes a congenital birth defect in a breed of cats and predicts that in a cross between heterozygotes, 25% of the kittens will be born with the birth defect. She surveys several litters, and finds that 44 out of 128 kittens have the defect. To see if her hypothesis is correct, she decides to use Chi-square analysis and determines that the expected number of UNAFFECTED kittens should be:

96

With what form of inheritance is this pedigree consistent? (given a pedigree in the quiz)

autosomal recessive

Using the pedigree above, assume that person 1's father is a carrier. What is the probability that person 1 is a carrier? (given a pedigree in the quiz, mother is a carrier and father is not)

1