Biology Exam #2

what is the first step in the two-step process of producing proteins based on instructions contained in DNA.

transcription

The expression of a gene to form a polypeptide occurs in two major steps. What are these two steps in their correct chronological order?

transcription and then translation

From DNA to protein involves which series of events?

transcription, translation

During transcription, at the point where the DNA strand being copied has an adenine, a(n)_______________ is added to the mRNA.

uracil

Transcription

(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA

Translation

(genetics) the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm

The loss of genetic diversity in crop plants can become disastrous. The Irish Potato Famine is an example of this problem. Which of the following is a correct statement about the Irish Potato Famine?

-Most of the potatoes in Ireland were propagated from cuttings of the same plant. -In the mid-1800s, much of the population of Ireland depended on potatoes. -When the crops were infected by a rot-causing mold, all of the potato plants were susceptible and most were wiped out. -Most of the potatoes in Ireland were genetically the same.

What is True about DNA?

-every DNA nucleotide contains a sugar, a phosphate group, and a base. -DNA consists of two strands of nucleotides joined by hydrogen bonds. -the long strands of nucleotides are twisted into a double helix -All living organisms carry DNA in practically ever cell in their bodies. -DNA can serve as an "individual identifier." -DNA carries instructions for the functions of every cell and enzyme in living organisms. -DNA carries a record of evolutionary history.

The Russian-American biochemist Phoebus Levene was the first to determine that nucleotides may contain one of four different nitrogen-containing bases. Levene believed that the nitrogen-containing bases occurred in equal amounts in DNA. What is the actual proportion of these bases?

DNA contains equal amounts of adenine and thymine, and equal amounts of guanine and cytosine.

What does DNA do?

DNA contains the instructions needed for an organism to develop, survive and reproduce. To carry out these functions, DNA sequences must be converted into messages that can be used to produce proteins, which are the complex molecules that do most of the work in our bodies. Each DNA sequence that contains instructions to make a protein is known as a gene. The size of a gene may vary greatly, ranging from about 1,000 bases to 1 million bases in humans. Genes only make up about 1 percent of the DNA sequence. DNA sequences outside this 1 percent are involved in regulating when, how and how much of a protein is made.

Why has DNA analysis been effective recently at overturning faulty criminal convictions?

DNA evidence is a more reliable individual identifier compared to eyewitness testimony.

Are mutations helpful, harmful, or both? Explain.

Some mutations are helpful and some are harmful. Because more mutations are harmful than are helpful, mutations can be considered to be generally harmful at the level of the individual; however, mutations provide the raw material for evolutionary change and are very important in populations.

Is the size of an organism's genome a clear indicator of its complexity? Why or why not?

There actually does not seem to be any relationship between the size of an organism's genome and its complexity! In humans, genes only make up about 2% of the DNA. A huge proportion of the base sequences in DNA do not code for proteins and have no known purpose; these are known as "non-coding" DNA. Some of this DNA is important in DNA regulation or may have a protective function.

A given section of DNA with the sequence AATGGCTAT is transcribed. What is the corresponding sequence on the mRNA transcription?

UUACCGAUA

Alternate versions of a gene are called _______________. They can code for different ________________ of the same character.

alleles; traits

In any DNA molecule, the number of guanine bases will always be?

always be equal to the number of cytosine bases

Which of the following is a symptom of vitamin A deficiency?

blindness

Mutation rates:

can be affected by environmental factors.

Tomato plants that have pest-resistance genes inserted into the genome can be called:

genetically engineered organisms. transgenic organisms.

You are cloning a sheep. You have just implanted the nucleus from a mammary cell from one sheep into an egg cell from another. What is the next step?

inducing cell division

. Diabetes is a chronic disease in which the body cannot produce ________________, a chemical that allows cells to take up and break down sugar from the blood.

insulin

Gene therapy involves:

introducing non-defective genes into the cells of an individual with a genetic disorder

The full set of DNA an organism carries is called

its genome

Transgenic bacteria are bacteria:

that have a sequence of DNA from another organism inserted into them.

DNA is a macromolecule that stores information. Which component of the DNA is the source of this information?

the base

Transcription is like copying a recipe onto a notecard, EXCEPT:

the copy is made in code.

To get from a gene to a protein, two processes must occur: transcription, in which a copy of ______________, and translation, in which that copy is used to direct the production of a(n) _______________.

the gene's sequence of bases is made; protein

Which of the following is the primary site of protein assembly within eukaryotic cells?

the ribosomes

agriculture

the science or practice of farming, including cultivation of the soil for the growing of crops and the rearing of animals to provide food, wool, and other products.

Short tandem repeats are short sequences of DNA that consist of several two- or three- nucleotide motifs repeated in tandem (e.g., AATAATAAT or GAGAGAGAGAGA). Each allele consists of a different number of repeats. STRs are typically not under selection, and they are inherited through Mendelian inheritance. Given this information, which of the following questions might you answer with the use of STRs?

whether two puppies were sired by the same father

In order for a person's DNA to be used for his/her identification, which of the following tools/techniques must also be used in the process?

-PCR -gel electrophoresis -restriction enzymes

Which of the following is an example of a possible agricultural application for animal cloning?

-cloning cows that produce more milk -cloning chickens that lay more eggs -cloning sheep that produce more wool at a younger age -cloning turkeys that have larger breast muscles

All human DNA is nearly identical. Only about ____ of the DNA sequences of two people will differ. Even so, this difference still translates to roughly ______ base-pair differences.

0.1%; 3 million

About ___ of the non-coding regions occur within genes—in which case they are called introns. About 75% of the non-coding regions occur between genes.

25%

The human genome is composed of approximately how many base pairs?

3 billion

Only a small fraction of the DNA in eukaryotic species is in genes that code for proteins. how much?

5%

Biotechnology

A form of technology that uses living organisms, usually genes, to modify products, to make or modify plants and animals, or to develop other microorganisms for specific purposes.

Define these terms and describe the relationship among them: gene, chromosome, genome.

A gene is a specific sequence of DNA that contains the information necessary to produce all or part of a protein molecule. A chromosome is one or more unique pieces of DNA that make up an organism's genome. A genome is an organism's complete set of DNA. The relationship among these three terms is that the genome consists of chromosomes and individual genes are found on those chromosomes.

What is a mutation? What are the three ways mutations arise?

A mutation is an alteration in the sequences of bases in an organism's DNA. The three types of mutations are: spontaneous mutations, radiation-induced mutations, and chemical-induced mutations.

What are plasmids and where are they used?

At their most basic level, plasmids are small circular pieces of DNA that replicate independently from the host's chromosomal DNA. They are mainly found in bacteria. Generally, scientists use plasmids to manipulate gene expression in target cells. For example the gene for human insulin is incorporated into a plasmid to get it into bacteria.

What is Bt corn? How has it led to reduced pesticide use by farmers?

Bt corn is corn engineered to contain spores of the bacterium Bacillus thuringiensis, a bacterium that kills insect pests, such as caterpillars, but does not harm humans. Bt crystals are produced by the engineered corn plant and are present in all of the plant's cells. Because Bt crystals are toxic to pests, farmers are able to reduce the amount of chemical pesticides they use.

Which of the following is TRUE about cloning?

Cloning refers to a variety of techniques, ranging from whole organism cloning to tissue and organ cloning.

What is DNA?

DNA or deoxyribonucleic acid is a long molecule that contains our unique genetic code. Like a recipe book it holds the instructions for making all the proteins in our bodies. Your genome is made of a chemical called deoxyribonucleic acid, or DNA for short.

Double-stranded DNA that contains a high G-C content requires a higher temperature in order to separate the two DNA strands. This is because:

G-C base pairing involves three hydrogen bonds, whereas A−T pairing involves only two.

Which of the following can be said about a frameshift mutation?

It must involve the insertion or deletion of nucleotides. It changes the reading frame of the protein coding sequence.

Has gene therapy been successful? Why or why not?

More than 500 clinical trials for gene therapies have been conducted. These trials were designed to treat or cure a variety of diseases by inserting a functional gene into an individual's cells to replace a defective version of the gene; however, no clear successes have been achieved. This lack of success is due to a few known difficulties: difficulty getting the working gene into the specific cells where it is needed; difficulty getting the working gene into enough cells and at the correct rate to produce a physiological effect; difficulty arising from the transfer organism; and difficulty regulating gene expression.

What exactly is a double helix?

Picture a long ladder twisted around like a spiral staircase and you'll have a good idea of what a DNA molecule looks like. The molecule has two distinct strands, like the vertical sides of a ladder. These are the "backbones" of the DNA molecule, and each is made from two alternating molecules: a sugar, then a phosphate, then another sugar, then a phosphate, and so on. The sugar is always deoxyribose, and the phosphate molecule is always the same, too. It is the shapes of the molecules in the backbone that cause the DNA "ladder" to twist.

What is a "DNA fingerprint"?

Short tandem repeats, or STRs, are sequences of DNA (four or five nucleotides) that repeat over and over again, occurring in some of the most highly variable regions of an individual's DNA. These STRs allow for a DNA fingerprint to be obtained by looking at the 13 different STR locations in an individual. For a single STR region, two numbers reflecting the number of STR repeats in the copies inherited from the mother and the father express an individual's genotype. The DNA fingerprint essentially is a string of 26 numbers that includes the 2 numbers for each of 13 STRs.

Bt corn is a genetically engineered plant. What feature gives it value as a crop plant?

The plant produces a toxin designed to kill corn borers.

Explain the process of gene expression involving transcription and translation

The process by which DNA is copied to RNA is called transcription, and that by which RNA is used to produce proteins is called translation.

Why is DNA considered the universal code for all life on earth?

You can think of an organism's DNA like a cookbook. Just as a cookbook contains detailed instructions on how to make many different foods, an organism's DNA carries the detailed instructions on how to build an organism and keep it running. Just as a book can be viewed as a sequence of letters, with the book's meaning determined by which letters are strung together, a molecule of DNA can be viewed as a sequence of bases. In a book, letters don't have much meaning on their own. When they are put together into words and sentences, however, their order holds a great deal of information. Similarly, the sequence in which bases appear in a molecule of an organism's DNA makes up a "secret code" that holds the detailed instructions for the building of the organism, whether it is a one-celled amoeba, a giant oak tree, or a human.

One of the four nucleotide bases in DNA is replaced by a different base in RNA. Which base is it, and what is it replaced by?

a) thymine, replaced by uracil

In prokaryotes, the DNA occurs in

circular pieces

When the mRNA copy of a gene is completed and processed, it moves to the cytoplasm, where it can be translated into a ?

polypeptide