Review for Final

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101 terms · Test 1-3

In a diploid organism with 52 chromosomes, how many bivalents/tetrads would be expected to form during meiosis?

26

During interphase of the cell cycle,

DNA content doubles through replication

Name the single individual whose work in the mid- 1800s contributed to our understanding of the particulate nature of inheritance as well as the basic genetic transmission patterns. With what organism did this person work?

Gregor Mendel; Pisum sativum

A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percent of their remaining offspring would be expected to have normal pigmentation?

75%

Polydactyly is expressed when an individual has extra fingers and/or toes. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. Having extra digits is caused by a dominant allele. The couple has a son with normal hands and feet, but the couple's second child has extra digits. What is the probability that their next child will have polydactyly (assume full penetrance)?

1/2

If one is testing a goodness of fit to a 9:3:3:1 ratio, how many degrees of freedom would be associated with the Chi-square analysis?

3

What is the probability of flipping a penny and a nickel and obtaining on head and one tail?

1/2

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a). Two parents with normal pigmentation have an albino child. What is the probability that their next child will be an albino girl?

Aa *Aa
(1/4)*(1/4)
1/8?

Assuming independent assortment, what proportion of the offspring of the cross AaBbCcDd*AabbCCdd will have the aabbccdd genotype?

None of the offspring can have this genotype! Zero.

In a Chi-square test, as the value of the x^2 increases, the likelihood of rejecting the null hypothesis

Increases

With incomplete dominance, a likely ratio resulting from a monohybrid cross would be

1:2:1

A condition in which one gene pair masks the expression of a nonallelic gene pair is called

Epistasis

Typical ratios resulting for epistatic interactions in dihybrid crosses would be

9:3:4 or 9:7

With which of the following would hemizygosity most likely be associated?

X-linked inheritance

In a mating between individuals with the genotype I^Ai *ii, what percentage of the offspring would be expected to have the O blood type?

1/2

The basic structure of a nucleotide includes

Nitrogeneous base, sugar, and phosphate

Considering the structure of double-stranded DNA, which kind(s) of bonds hold one complementary strand to the other?

Hydrogen

If 15% of the nitrogeneous bases in a sample of DNA from a particular organism is thymine, what percentage should be cytosine?

35%

Which of the following clusters of terms accurately describes DNA as it is generally viewed to exist in prokaryotes and eukaryotes?

double-stranded, antiparallel, (A+T)/(C+G) = variable, (A+G)/(C+T) = 1.0

In an analysis of the nucleotide composition of the double-stranded DNA to see which bases are equivalent in concentration, which of the following would be true?

A+C=G+T

DNA polymerase III adds nucleotides

to the 3' end of the RNA primer

DNA replication occurs through a ______ process.

Semiconservative

The complementary sequence of 5' AATTCGCTTA 3' is:

5' TAAGCGAATT 3'

A couple in Indiana are both heterozygous for the autosomal recessive allele for albinism. They have two children. What is the probability that both children will be phenotypically identical with regard to skin color?

(1/4)(1/4) + (3/4)(3/4)
(1/16) + (9/16)
5/8

In mice the allele for color expression is C (c=albinism). Another gene determines color (B=black and b=brown). Yet another gene modifies the amount of color so the D=normal amount of color and d=dilute (milky) color. Two mice that are C/c: B/b: D/d are mated. What proportion of the progeny will be dilute brown (assume complete dominance at each locus)?

3/64

Drosophilla eyes are normally red. Several purple-eyed strains have been isolated as spontaneous variants (mutants) and the purple phenotype has been shown too be inherited as a Mendelian autosomal recessive in each case. To investigate allelism (by complementation) between these different purple mutations, two purple-eyed pure strains were crossed. If the purple mutations are in the same gene (that is they ARE allelic - assume no cross-overs within the gene), the F1 is expected to be

All purple

The percentage of individuals with a given genotype who exhibit the phenotype associated with that genotype

Penetrance

In haploids, the production of wild-type phenotype when two recessive mutant alleles are present in the same cell

complementary gene interaction

In E. coli, the genetic material is composed of

circular, double-stranded DNA

Eukaryotic chromosomes contain two general domains that relate to the degree of condensation. These two regions are

called heterochromatin and euchromatin

Chromatin of eukaryotes is organized into repeating interactions with protein octomers called nuclesomes. Nucleosomes are composed of which type of molecules?

Histones

What makes up the protein component of a nucleosome?

Two tetramers of histone proteins

TRUE/FALSE: In contrast with euchromatin, heterochromatin contains more genes and is earlier repeating.

False

What are VNTRs and how do they relate to DNA fingerprinting?

Variable number of tandem repeats (VNTRs) are adjacent sequences repeated a number of times that varies between individuals comparing the number of repeats (determined by densities in gel electrophoresis) of many VNTRs can provide a unique identification system to distinguish between persons based on their DNA differences.

Which of the following two terms relate most closely to split genes?

Introns, exons

Which of the following contains the three posttranscriptional modifications often seen in the maturation of the mRNA in eukaryotes?

5' capping, 3'-poly(A) tail addition, splicing

When the scientists were attempting to determine the structure of the genetic code, Crick and coworkers found that when three base additions of three base deletions occurred in a single gene, the wild-type phenotype was sometimes restored. These data supported the hypothesis that

The code is triplet

Is has been recently determined that the gene for Duchenne muscular dystrophy (DMD) is more than 2000 kb (kilobase) in length; however, the mRNA produced by this gene is only about 14 kb long. What is the likely cause of this discrepancy?

The introns have been spliced out during mRNA processing.

Introns are known to contain termination codons (UAA, UGA, and UAG), yet these codons do not interrupt the coding of a particular protein. Why?

Introns are removed from the mRNA before translation.

In studies using repeating copolymers, AC . . . incorporates threonine and histidine, and CAACAA . . . incorporates glutamine, asparagine, and threonine. What triplet code can definitely be assigned to threonine?

ACA

Predict the amino acid sequence produced during translation by the following short hypothetical mRNA sequences (note that the second sequence was formed from the first by a deletion of only one nucletide): Sequence 1: 5'-AUGCCGGAUUAUAGUUGA-3'

met-pro-asp-tyr-ser-(term)

Describe the function of the N-formylmethionine (f-Met) in prokaryotes.

F-Met is the amino acid that is attached to the tRNA than binds to the start codon, AUG, in prokaryotes. The formyl group is usually removed following translation. F-Met is sequentially the first amino acid in a polypeptide (prokayotes).

Describe how the sigma subunit (factor) of E. coli RNA polymerase participates in transcription.

Recognizes promoters, starts unwinding DNA and making transcription start site

Suppose that in the use of polynucleotide phosphorlyase, nucleotides A and C are added in a ratio of 1A:5C. What is the probability that an AAA sequence will occur?

(1/6)(1/6)(1/6)
1/216

List two base triplets that are clearly responsible for punctuation (initiation, termination).

AUG = MET
UGA = Stop

The primary structure of a protein is determined by

The sequence of amino acids

The secondary structure of a protein includes

alpha-helix and beta-pleated sheet

A protein is 300 amino acids long. Which of the following could be the number of nucleotides in the section of DNA that codes for this protein? (Remember: DNA is double stranded).

1800

A short segment of an mRNA molecule is shown below. The polypeptide it codes for is also shown: 5'-AUGGUGCUGAAG-3' : methionine-valine-leucine-lysine
Assume that a mutation in the DNA occurs so that the fourth base (counting form the 5' end) of the messenger RNA now reads A rather than G. What sequence of amino acids will the mRNA now code for? (You do not need a copy of the genetic code to answer the question.)

methionine-methionine-leucine-lysine

A sequence of DNA that reads : 5'-ATGCCTGAATCAGCTTTA-3' should code for ______ amino acids after all steps of conversion into protein are complete.

5

The role of the tRNA is

To act as transporters bringing amino acids to the site of protein synthesis

Ribosomes are composed of:

rRNA and protein

The association of seperate amino acid chains to constitute one active protein is called the

Quaternary structure

A protein fragment has the following sequence NH2-His-Met-Leu-Ile-Lys-COOH The DNA template strand sequence (3' -> 5') would be

GTATACAATTATTTT

A single DNA unit that enables the simultaneous regulation of more than one gene in response to environmental changes is called:

operon

In the genotype presented below, what will the expression phenotype for beta-galactosidase be (I^+ p^+ o^c Z^+ Y^- A^+ / I^+ p^+ o^+ Z^- Y^+ A^-)?

Constitutive

A partial diploid of genotype IS P+ O+ Z+ / I+ P+ O+ Z- will show

No production of beta-galactosidase

The primary function of basal transcription factors is to:

assist is associating RNA polymerase with the promoter element.

The gene products encoded by trans-acting elements perform their function by:

Associating with regulatory sequences distant from the gene from which they were transcribed

______ motifs function to promote the DNA-binding activity of many transcriptional activator proteins.

Zinc finger

Which of the following is not involved with the initiation of transcription of human genes?

DNA polymerase

Under the system of genetic control of the tryptophan operon

When there is no tryptophan in the medium, transcription of the trp operon occurs at high levels

Mutations in the lac I and lac O genes in the lactose system often lead to full production of the three structural genes related to the lac operon even with no lactose available to the organism. Such mutations would be called

Constuitive mutations

Two modular elements that appear as consensus sequences upstream from the RNA polymerase II transcription start sites are

TATA and CAAT

TRUE/FALSE: One of the earliest steps in the RNAi pathway involves the association of siRNA or miRNA with an enzyme complex composed mainly of reverse transcriptase

False

The term normally applied when two genes fail to assort independently is

Linkage

What is the relationship between the degree of crossing over and the distance between two genes?

They are directly proportional

One percentage of recombination, or recombination frequency, is a unit of measure called either centimorgan (Mb) or a

Map unit

The pairwise map distances for four linked genes are as follows: A-B = 22 m.u., B-C = 7 mu, C-D = 9 mu, B-D = 2 mu, A-D = 20 mu, A-C = 29 m.u. What is the order of these four genes?

ADBC

The map of a chromosome interval is A 10 B40 C. From the cross Abc/aBC * abc/abc, how many double crossovers would be expected out of 1000 progeny?

40

We spread 10^9 bacteria on a plate with 25 ug streptomycin/ml media. We get four colonies to grow. These colonies are likely to include bacteria that are

resistant to streptomycin

A strain of E. coli is trp- his- lac-. Which medium would this bacterium grow on?

glucose+histidine+tryptophan

TRUE/FALSE: Positive interference occurs when a crossover in one region of a chromosome interferes with crossovers in nearby regions

True

TRUE/FALSE: The cross GE/ge *ge/ge produces the following progeny: GE/ge 404, ge/ge 396, gE/ge 97, Ge/ge 103. From these data, one can conclude that the recombinant progeny are gE/ ge and Ge/ge.

True

Assume that a cross is made between AaBb and aabb plants and that the offspring occur in the following numbers: 106 AaBb, 48 Aabb, 52 aaBb, 94 aabb. These results are consistent with

linkage with approximately 33 map units between the two gene loci

Name two forms of recombination in bacteria

conjugation and transduction

Transduction is a form of recombination in bacteria that involves

Bacteriophages

Bacteriophages engage in two interactive cycles with bacteria. What are these cycles?

lytic and lysogenic

Distinguish between F^+ and F^- bacteria.

F+ = the bacteria that "donates/loses" the DNA.
F- = the bacteria that accepts the DNA.

How does an auxotroph differ from a prototroph?

Auxotrophs requires at least one nutrient from its environment to grow (due to a mutation), while prototrophs can synthesize all compounds required for growth.

The condition that exists when an organism gains of loses one or more chromosomes but not a complete haploid set is known as

aneuploidy

A genomic condition that may be responsible for some forms of fragile-X syndrome, as well as Huntington disease, involves

various lengths of trinucleotide repeats

Describe the maternal age effect associated with Down Syndrome.

"older" eggs are more prone to nondisjunction

In general, which of the following chromosomal abnormalities has a greater chance of lethality than the others?

deletion

Which of the following is not an example of aneuploidy?

tetraploid

A wild-type chromosome can be represented as ABC ~ DEFGH, and from this is a chromsomal aberration arises that can be represented ABE ~ DCFGH. (Note ~ = centromere.) This is known as:

Pericentric inversion

What is the chromosome aberration of the type ABCD ~ EFFGH called?

Duplication

Sometimes a piece of one chromosom attaches to another chromosome. This is known as a

translocation

Words such as DID, MOM, and POP have something in common compared to the fundamental tool of recombinant DNA technology. In the context of recombinant DNA technology, which term would be used to describe such words?

Palindromic

Restriction endonucleases are especially useful if they generate "sticky" ends. What makes an end sticky?

single-stranded complementary tails

Some vectors such as pUC18 and others of the pUC series contain a large number of restriction enzyme sites clustered in one region. Which term is given to the advantageous arrangement of restriction sites?

Multiple cloning site

In the context of molecular genetics, reverse transcription PCR (RT-PCR) refers to

assembling a DNA sequence from an mRNA

Assume that a plasmid (circular) is 3200 base pairs in length and has restriction sites at the following locations: 400, 700, 1400, 2600. Give the expected sizes of the restriction fragments following complete digestion.

300, 700, 1000, 1200

What is a cDNA molecule?

A cDNA is a complementary DNA molecule. It is complementary to the RNA. This is helpful because the RNA tells used us which genes are turned on.

What might be a reasonable function of restriction endonucleases in a bacterium, distinct from their use by molecular biologists?

They protect the bacteria's DNA by being able to recognize viral DNA and digesting it.

Assume that one conducted a typical cloning experiment using a typical plasmid, transformed an appropriate host bacterial strain, and plated the bacteria on an appropriate X-gal medium. Blue and white colonies appeared. Which of the two types of colonies, blue or white, would most likely contain the recombinant plasmid?

white colonies

Which of the following would not have its gene represented in a cDNA library from red blood cell precursors?

an rRNA

A circular DNA molecule has n target sites for restriction enzyme EcoRI. How many fragments will be produced after complete digestion?

n

The recognition sites for the restriction enzymes Bam HI, Xba I and BgIII are G^GATCC, T^CTAGA and A^GATCT, respectively. Which enzymes leave compatible ends that can be ligated together?

Only Bam HI and BgIII fragments are compatible.

A 16 kb linear DNA is cut with EcoRI and BamHI. The EcoRI digest yields fragments of 2, 6 and 8 kb. The BamHI digest yields fragments of 5 and 11 kb. An EcoRI-BamHI double digest yields 2,3,5 and 6 kb fragments. The map of this DNA has:

2 EcoRI sites and 1 BamHI site.

In Sanger (ezymatic extension) sequencing, what causes DNA synthesis to terminate at a specific base?

Nucleotide triphosphates that lack a hydroxyl

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