Gene Expression - Paper 1

What is Transcription?

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The first step of gene expression where an enzyme called RNA polymerase copies a specific segment of DNA into an RNA molecule.

Where does does transcription occur?

In the nucleus of the cells of eukaryotes.

State the processes that occur in transcription.

Transcription is the process where the information in DNA is copied into mRNA. The DNA unwinds and one strand is used as a template. RNA polymerase adds complementary RNA nucleotides to form an mRNA strand. The mRNA then leaves the nucleus and travels to a ribosome, where it can be used for translation.

Transcription Definiton

Where one DNA strand is used as a template so that an RNA molecule that is an exact copy of the coding strand can be created.

What makes up chromosomes?

DNA (Deoxyribonucleic acid) which contains hereditary information

Where is the genetic code found?

Sections of chromosomes, which are called genes.

What is protein synthesis?

Translates genetic code into proteins via instructions encoded in the DNA which make up the structure and functions of living organisms.

What are protein coding sequences?

Exons are protein coding sequences that are expressed that is interrupted by non-coding sequences which interrupt between the genes. The introns need to be removed before a protein is assembled. This happens in the mRNA ( lead to mutations if it occurs in the DNA)

What is DNA?

DNA (deoxyribonucleic acid) is a double-stranded polymer made up of repeating units called nucleotides. Each nucleotide contains a phosphate group, a deoxyribose sugar, and a nitrogenous base. The complementary base-pairing rules are adenine–thymine (A–T) and guanine–cytosine (G–C).

What is RNA.

RNA (Ribonucleic acid) is a single-stranded polymer made up of repeating units called nucleotides, each containing a phosphate group, ribose sugar and nitrogenous base. The complementary base-pairing rules are adenine-uracil (A–U) guanine - cytosine (G–C)

What is mRNA?

messenger RNA, is a single-stranded RNA molecule that carries genetic information from DNA to the ribosome for protein synthesis.

What is tRNA?

transfer RNA, it’s job is to bring the correct amino acid to the ribosome during protein synthesis. tRNA has an anticodon that pairs with the complementary codon on mRNA, making sure the correct amino acid is added to the growing protein.

What is rRNA?

ribosomal RNA is a type of RNA that combines with proteins to form ribosomes, which are the site of protein synthesis.

What is redundancy and degeneracy?

The genetic code contains multiple codons that code for the same amino acid. This means some mutations can occur without changing the amino acid (silent mutations).

What is a metabolic pathway?

A series of chemical reactions controlled by enzymes where the product if one reactions becomes the substrate of the next reaction.

What is a mutation?

A permanent change in the DNA sequence of genetic material of an organism.

What is a mutagen?

Mutagens are substances that can cause permanent mutations.

What is a silent mutation?

A change in the DNA nucleotide sequence that does not change the resulting amino acid sequence of a protein.

What is a harmful protein?

Changes in a DNA sequence that lower and organisms fitness or cause disease by producing non-functioning proteins.

What is a beneficial mutation?

A permanent change in an organism’s DNA sequence that increases it’s fitness, helping it survive, reproduce, or adapt to it’s environment.

What is a neutral mutation?

A change in a DNA sequence that does not help or hurt an organism’s ability to survive or reproduce.

What is a genotype?

An individuals’s unique set of genetic instructions, stores as a specific sequence of DNA in cells.

What is a phenotype?

The set of observable traits or characteristics of a living organism, shaped by both it’s genetic makeup and it’s environment.

What is an environmental factor?

Something in the environment that can affect an organism's characteristics, growth, survival, or development.

What is gene translation?

Process where the genetic code carried by the mRNA is decoded to produce the specific sequence of amino acids in a polypeptide protein chain.

Where does translation occur?

In eukaryotes, where it is in the cytoplasm of the cell at a cellular structure called the ribosome.

State the process in gene translation.

Translation is the process where mRNA is used to make a protein. The mRNA attaches to a ribosome, which reads its codons. tRNA brings specific amino acids to the ribosome, with its anticodon matching the mRNA codon. The amino acids join together with peptide bonds to form a polypeptide chain. This continues until a stop codon is reached, and the chain is released and folds into a functional protein.

What is a base substitution?

Replacement of one base by another. May or may not change the amino acid that is coded for.

What are the results of base substitution?

Silent Mutations, Mis-sense Mutations and Non-sense mutations

What is a mis-sense mutation?

occurs when one DNA nucleotide is changed so that a different amino acid is inserted into a protein, resulting in a codon that codes for a different amino acid eg. when one letter changes the whole word.

What is a nonsense mutation?

A mutation that changes a codon into a STOP codon, causing translation to end too early.

What is a frame-shift mutation?

A mutation caused by an insertion or deletion of bases that changes the way the DNA sequence is read in groups of 3 (codons).