Chapter 8

gene

- a sequence of DNA that contains the information to make at least one protein - genes are found along the length of chromosomes, with each chromosome carrying a unique set of genes - has two parts: regulatory sequence and coding sequence; together they ensure that every gene is expressed only at the right time and in the right cell

gene therapy

- a treatment that aims to cure human diseases by replacing defective genes with functional ones

tRNA (transfer RNA)

- a type of RNA that transports amino acids to the ribosome during translation - structure like an adaptor; one end binds to an amino acid, the other end binds to mRNA

alleles

- alternative version of the same gene that have different nucleotide sequences - most human cells have two copies of every gene, these copies can either be identical, or slightly different in nucleotide sequence - all genes, including Antithrombin, have multiple alleles - a change in one nucleotide is sometimes enough to alter the function of the protein or make it nonfunctional

genetically modified organisms (GMOs)

- an organism that has been altered by humas

Why is recombinant protein production in the milk of transgenic animals an efficient strategy?

- because milk is secreted, so the protein can be obtained noninvasively - because milk is produced in relatively large quantities - because mammary glands naturally secrete large quantities of proteins into milk - because milk is easier to obtain than other secretions (e.g., urine, sweat, and saliva)

What is a genetically modified organism?

any modified organism that produces a product it does not normally make

_______amino acids tend to be found folded inside a protein, whereas _______ amino acids interact with water on the outside of the protein.

hydrophobic; hydrophilic

_______is the product of transcription, and _______ is the product of translation.

mRNA; a protein

mRNA (messenger RNA)

the RNA copy of an original DNA sequence made during transcription - once it's made it leaves the nucleus and attaches to a ribosome in the cytoplasm which is the start of translation

In an antithrombin-producing transgenic goat,

the antithrombin gene construct is present in every cell and expressed only in mammary cells.

Which of the following parts of translation will be disrupted by a mutation in the coding region of a gene?

the codon on the mRNA

transcription

the first step of gene expression, during which cells produce molecules of messenger RNA (mRNA) from the instructions encoded within genes in DNA

What controls the timing of gene expression?

the regulatory sequence for a gene

translation

the second stage of gene expression, during which mRNA sequences are used to assemble the corresponding amino acids to make a protein

A protein is made up of a chain of __________.

amino acids

codon

a sequence of three mRNA nucleotides that specifies a particular amino acid

Why are biotechnology companies eager to design genetically modified organisms to express therapeutic proteins, particularly ones that would otherwise have to be isolated from blood products (e.g., human antithrombin) or animal organs (e.g., insulin, originally isolated from pig pancreas)?

- Biotechnology companies want to produce therapeutic proteins in the most cost-effective way. - There are safety concerns when using proteins from different species or isolating proteins from humans. - It is difficult to collect enough of some low-abundance proteins.

Which of the following accurately describe(s) amino acid side chains?

- They provide unique functions to a folded protein - They allow for the correct folding of proteins

protein

- a macromolecule made up of repeating subunits known as amino acids, which determine the shape and function of a protein - the instructions to make proteins are encoded in our DNA (in our genes)

State two ways in which a person can be deficient in antithrombin activity

- a mutation in the regulatory region of a gene - a mutation in the coding region of a gene

Antithrombin

- is a protein made up of one folded chain of 432 amino acids - the Antithrombin gene is found in chromosome 1 - it helps prevent blood from clotting improperly, produced by cells in the liver and released into the blood it inactivates enzymes that promote blood clotting by doing so it helps prevent heart attacks - inherited Antithrombin deficiency means that one or both copies of the Antithrombin gene are defective (not uncommon in the US; 1 in every 5000) - inherited Antithrombin deficiency can lead to a condition called thrombosis (high risk of developing blood clots inside blood vessels)

transgenic

- refers to an organism that carries one or more genes from different species

amino acids

- the building blocks of a protein - there are 20 different amino acids - all have the same basic core structure, but each also has a unique chemical side chain that distinguishes one amino acid from another, these chains may vary in size, from just a few amino acids to many thousands - the order of amino acids determines a proteins' shape, and the proteins' shape determines its specific function (if the shape changes then the protein may not be able to do its job)

ribosome

- the cellular machinery that assembles proteins during translation - during translation on, it reads the mRNA transcript and translates it into a chain of amino acids - the mRNA transcript specifies what amino acids should be joined together to form a chain; amino acids are specified by groups of three nucleotides

RNA polymerase

- the enzyme that carries out transcription - RNA polymerase copies a strand of DNA into a complementary strand of mRNA - the same rules of base pairing as the ones for DNA structure apply here with one difference: RNA nucleotides are made with the base uracil (U) instead of thymine (T); so the complementary base pairs are C with G and A with U

What determines how a protein folds?

- the interaction of the shared core structure of all the amino acids in the protein - the interaction of the side chains of each individual amino acid - the interaction of the amino acids with water in the proteins environment

coding sequence

- the part of a gene that specifies the amino acid sequence of a protein - coding sequences determine the identity, shape and function of a protein

anticodon

- the part of tRNA that binds to a complementary mRNA codon

regulatory sequence

- the part of the gene that determines the timing, amount, and location of protein production

genetic engineering

- the process of assembling new genes with novel combinations of regulatory and coding sequences - genetic engineered genes are often referred to as a recombinant gene

gene expression

- the process of using DNA instructions to make proteins - the synthesis of proteins from the information encoded in a gene - when a cell is making the protein encoded by that gene, the gene si said to be "expressed"

What determines a protein's function?

- the sequence of amino acids - the three-dimensional shape of the folded protein

genetic code

- the set of rules relating particular mRNA codons to particular amino acids - the code is redundant: multiple codons specify the same amino acid - the code is universal: it is virtually the same in all living organisms

_______ on mRNA interact with _______ on tRNA to allow the _______ to connect amino acids in the correct order during translation.

Codons; anticodons; ribosome

Which of the following statements, if any, accurately describe how genes, chromosomes, and proteins are related?

FALSE - A gene contains many chromosomes. FALSE - Each chromosome encodes a protein. FALSE - A protein encodes a gene. TRUE - None of these statements are accurate

Which of the following statements correctly indicates a functional location?

FALSE - RNA polymerase works in the cytoplasm. FALSE - Ribosomes work in the nucleus. TRUE - tRNAs work in the cytoplasm. FALSE - mRNA is used in the nucleus. FALSE - Genes work in the cytoplasm.

Which of the following statements about genetically modified organisms is TRUE?

FALSE - The proteins made in genetically modified organisms are produced in small quantities so that they do not interfere with normal cell function. FALSE - The DNA in goats uses the same genetic code as humans use, but hamster cells grown in cell culture use a different code. FALSE - Although it is more expensive than cell culture, producing genetically modified organisms is considered more ethical than cell culture. TRUE - Scientists can produce more complex proteins with genetically modified organisms than they can with cell cultures. FALSE - Humans are genetically more similar to goats than hamsters, so goat "pharming" produces fewer complications.

Type 1 diabetes results from a loss of insulin production from the pancreas. People with diabetes take recombinant human insulin expressed in bacteria. How would you cure the disease instead of treating it?

Replacing the defective insulin gene in a patient through gene therapy would allow for a cure.

How do the redundant properties of the genetic code protect humans from some mutations?

Some mutations will not change the amino acid coded by the mRNA codon.

Melanin is a pigment expressed in skin cells; melanin gives skin its color. If you wanted to express a different gene in skin cells, which part of the melanin gene would you use and why?

The melanin regulatory region would allow for the specific expression of a different gene in the skin.

Heating a protein can cause it to denature, or unfold. What do you think would happen to the function of a protein in a denatured state?

The protein would not be functional because the three-dimensional shape dictates protein's function.

How did scientists alter the gene for antithrombin so that it could be isolated from milk?

They attached the regulatory sequence of the goat antithrombin gene to the human coding sequence of antithrombin.

A gene has the sequence ATCGATTG. What is the sequence of the complementary RNA?

UAGCUAAC

What is the final product of gene expression?

a protein