2.4 How is the CFTR protein made?

Question 1

mutation

Answer 1

Mutation, Mutant, Mutate
A change in the genetic material in a cell. Some mutations are
concerned with very small changes to an organism’s DNA. These are known as gene mutations. Mutations happen by chance, but certain environmental factors called mutagens can increase the rate of mutation. Mutations play an important part in breeding plants with desirable characteristics. Mutations to the genes that control cell division are a cause of cancer.

Question 2

Genetic code

Answer 2

The information in the DNA which controls the manafacture of proteins and determines all the inherited characteristics of an organism. Each triplet of bases on the DNA is transcribed into a codon on messenger RNA; the codon either starts protein synthesis, codes for an amino acid in the protein being synthesised, translation, or is an instruction to stop synthesis of the protein.

Question 3

Gene, Genetic

Answer 3

A piece of DNA which has a specific sequence of nucleotide bases. Each gene codes for a specific protein. An example of this in humans is the CF (cystic fibrosis) gene, which codes for the CFTR protein; this helps to transport chloride ions across cell membranes. An individual gene may have more than one form. These forms or alleles differ from each other in the sequences of their nucleotide bases and, as a result, produce slightly different proteins.

Question 4

Genome

Answer 4

All the DNA inside a cell. The genome contains a full set of all the genes controlling the growth and development of the organism of which the cell is a part.

Question 5

DNA, Deoxyribonucleic acid

Answer 5

The molecule that forms the genetic material of all living organisms. Chemically, DNA consists of two polynucleotide chains forming a double helix. Each chain consists of a sugar-phosphate backbone. One of four nucleotide bases is attached to each sugar in this backbone. These bases are joined, adenine to thymine and cytosine to guanine, by hydrogen bonds. In an animal or plant cell, DNA is found in the chromosomes in the nucleus. There are also small amounts of DNA in the mitochondria and chloroplasts. Genes are sections of DNA that code for particular proteins.

The two nucleotide stands are described as being antiparallel because they run in opposite directions.

Question 6

Nucleotide, Mononucleotide

Answer 6

Nucleic acids are polymers made up from a number of nucleotides joined to each other by condensation. Each nucleotide has three components: a five-carbon or pentose sugar ribose in RNA and deoxyribose in DNA; a phosphate group; a nucleotide base.

Question 7

Deoxyribose

Answer 7

A five-carbon sugar. Deoxyribose is an important component of DNA. DNA is built up of nucleotides. Each nucleotide is formed from deoxyribose, a phosphate group, and a nucleotide base linked together by condensation.

Question 8

Phosphate group

Answer 8

PO4 -3 charge

Question 9

Organic base

Answer 9

In DNA, each nucleotide contains one of the following four organic bases: adenine, cytosine, guanine and thymine.
contains nitrogen

Question 10

Adenine

Answer 10

One of the nucleotide bases found in nucleic acids. When the two strands of nucleotides which make up a molecule of DNA come together, adenine always pairs with thymine. The atoms of the two bases are arranged in such a way that two hydrogen bonds form between them.

two ring structure

Question 11

Cytosine

Answer 11

One of the nucleotide bases found in nucleic acids. When the two strands of nucleotides which make up a molecule of DNA come together, cytosine always pairs with guanine. The atoms of these two bases are arranged in such a way that three hydrogen bonds form between them.

one ring structure

Question 12

Guanine

Answer 12

One of the nucleotide bases found in nucleic acids. When the two strands of nucleotides which make up a molecule of DNA come together, guanine always pairs with cytosine. The atoms of these two bases are arranged in such a way that three hydrogen bonds form between them.

two ring structure

Question 13

Thymine

Answer 13

One of the four nucleotide bases found in DNA. When the two strands of nucleotides which make up a molecule of DNA come together, thymine always pairs with adenine. The atoms of the two bases are arranged in such a way that two hydrogen bonds form between them. Thymine is not found in RNA. It is replaced in RNA by another base, uracil.

one ring structure

Question 14

Phosphodiester bond

Answer 14

The bond that forms between two nucleotides. Its between the sugar of one nucleotide and the phosphate of the next one producing a polynucleotide.

Question 15

Complementary base pairing, Complementary

Answer 15

The nucleotide bases in nucleic acids always pair in a particular way. Adenine always pairs with thymine in DNA and with uracil in RNA. (with 2 hydrogen bonds)

Cytosine always pairs with guanine. (with 3 hydrogen bonds) Complementary base pairing allows exact copies of DNA to be made in DNA replication. Transcription and translation also rely on complementary base pairing.

Question 16

How does DNA code for proteins?

Answer 16

Gene instructs the cel to make a protein. The sequence of bases in the DNA is the genetic code that tells the cell which amino acids to link together to make the protein. Every gene is a sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain. The chain then twists and folds into a functional protein.

Question 17

Protein, Protein synthesis

Answer 17

A polypeptide is a molecule made from a large number of amino acids joined by condensation. This polypeptide, sometimes on its own, sometimes with others, is folded to form a protein. The shape of a particular protein is very important in determining its function. There are twenty different amino acids, and they can be combined in different ways to produce many different proteins. The genetic code is transcribed and translated to convert the triplet base code into a specific sequence of amino acids in the protein.

Question 18

Transcription

Answer 18

The process in which the genetic information contained in a DNA molecule is copied to produce messenger RNA. This is the first stage in protein synthesis. A molecule of DNA unwinds. The sequence of nucleotides on one of the strands, called the template strand, is used to produce a mRNA molecule by complementary base-pairing.

Question 19

RNA

Answer 19

Ribonucleic acid. A single-stranded molecule containing the sugar ribose, a phosphate group and one of the four organic acids: adenine, cytosine, guanine and uracil.
A
substance that plays an important part in the
synthesis of proteins. There are three important
types of RNA. Messenger RNA (mRNA) takes
a copy of the genetic code for a protein from the
DNA in the nucleus to the ribosomes in the
cytoplasm. Transfer RNA (tRNA) collects
amino acids and assembles them in the right
order on the mRNA molecule. Ribosomal RNA
(rRNA) is a component of ribosomes.

Question 20

Ribose

Answer 20

A five-carbon sugar. Ribose is an important component of RNA. RNA is built up of nucleotides. Each nucleotide is formed from ribose, a phosphate group and a nucleotide base linked together by condensation.

Question 21

Uracil

Answer 21

One of the nucleotide bases found in RNA. When a strand of mRNA is formed on the template strand of a DNA molecule during transcription, a nucleotide containing uracil always pairs with an adenine-containing nucleotide on the DNA. Uracil is not found in DNA. It is replaced in DNA by another base, thymine.

Question 22

mRNA, Messenger RNA

Answer 22

A type of RNA which acts as a messenger molecule. Genes are sections of DNA which code for particular proteins. DNA is too large to pass through the nuclear pore, so mRNA takes a copy of the genetic code. RNA passes out into the cytoplasm, where it enables amino acids to be assembled in the correct sequence to make a protein.

Question 23

Translation

Answer 23

A process which takes place on a ribosome, where amino acids are joined to form a polypeptide. In protein synthesis, the process of transcription results in the formation of a molecule of mRNA. This mRNA molecule leaves the nucleus and becomes attached to the ribosome where translation takes place. During translation, tRNA molecules collect the appropriate amino acid from the cytoplasm and bring it to the ribosome where the protein is being synthesised.

Question 24

tRNA, Transfer RNA

Answer 24

A type of RNA involved in assembling amino acids into the correct sequence during translation. There are many different types of tRNA. Each one is specific to a particular amino acid. The function of these tRNA molecules is to collect the appropriate amino acid from the cytoplasm and bring it to the ribosome where the protein is being synthesised.

on one end there is a three base sequence called an anticodon. At the opposite end there is a binding site for an amino acid

hydrogen bonds between paired bases when the molecule folds in on itself.

Question 25

rRNA, Ribosomal RNA

Answer 25

Ribosomal RNA or rRNA is a type of RNA which is found in ribosomes.

Question 26

RNA polymerase

Answer 26

An enzyme involved in the process of transcription. During this process, RNA nucleotides present in the nucleus pair with complementary nucleotides on the template strand of the DNA. RNA polymerase is the enzyme which helps join the RNA nucleotides together to form a strand of mRNA.

Question 27

Template strand

Answer 27

The DNA strand that is copied during transcription. Transcription is the first part of protein synthesis. In transcription, a molecule of DNA unwinds. The sequence of nucleotides on the template strand is used to produce a messenger RNA molecule by complementary base pairing. The other DNA strand is not copied.

Question 28

Nuclear envelope

Answer 28

A layer which surrounds nucleus of a cell. It is called an envelope because it is really composed of two membranes perforated by tiny pores. mRNA leaves the nucleus through these nuclear pores during the process of protein synthesis.

Question 29

Triplet code

Answer 29

The information on DNA and messenger RNA is carried by sequences of three neighbouring bases, so there is said to be a triplet code.

Question 30

non-overlapping

Answer 30

Each triplet code is adjacent

Question 31

degenerate

Answer 31

Several triplets can code for the same amino acids

Question 32

Codon

Answer 32

A sequence of three nucleotide bases on a messenger RNA molecule that codes for a particular amino acid. For example, the messenger RNA codon CCA codes for the amino acid proline.

Question 33

Anticodon

Answer 33

A sequence of three nucleotide bases on a transfer RNA molecule, which is complementary to the corresponding messenger RNA codon. For example, CCA is one of the messenger RNA codons for the amino acid proline. The sequence of nucleotide bases from the corresponding anticodon is GGU.

Question 34

Mutation in the sequence of DNA

Answer 34

• could change a triplet that makes up a gene
• this could then change the amino acid sequence of the primary structure which may alter a protein’s 3d structure and its properties.
• Mutations in DNA include substitutions, insertions, deletions and inversions of base sequences.

Question 35

Insertions and deletions

Answer 35

• cause a frame shift when the Insertion/deletion occurs by a number that cannot be divided by 3
• all subsequent triplets from that point on are affected

Question 36

antiparallel

Answer 36

Two nucleotide strands described as antiparallel because they run in opposite directions

Question 37

Anticodon

Answer 37

A sequence of three nucleotide bases
on a transfer RNA molecule, which is
complementary to the corresponding messenger
RNA codon. For example, CCA is one of the
messenger RNA codons for the amino acid
proline. The sequence of nucleotide bases from
the corresponding anticodon is GGU.

Question 38

Peptide bond

Answer 38

The bond joining two amino acids
in a protein. Amino acids join together by
condensation. When a protein is digested, the
peptide bonds are broken down by hydrolysis.

Question 39

Dipeptide

Answer 39

A molecule that is made up of two

amino acids joined by a peptide bond.