Gene Expression Flashcards
4.1.6. Define the terms genome and gene
The genome is a complete set of DNA sequences found in all the chromosomes of an organism. A gene is a segment of DNA that carries the instructions for the production of a protein. Therefore genes are a segment of DNA while genomes are the entire genetic material of an organism. A gene is a locus on a DNA molecule whereas genome is a total nuclear DNA.
4.7.1. Understand that genes include ‘coding’ (exons and ‘noncoding’ DNA (which includes a variety of transcribed proteins: funational RNA, centromeres, telomeres, and introns. Recognise that many functions of ‘noncoding’ DNA are yet to be determined).
Differentiate between coding and non-coding DNA.
Coding DNA is DNA that is transcribed and translated. Non-coding DNA is DNA which does not get translated into mRNA, and so does not code for proteins. The role of non-coding DNA is still unknown.
4.7.1. Understand that genes include ‘coding’ (exons and ‘noncoding’ DNA (which includes a variety of transcribed proteins: funational RNA, centromeres, telomeres, and introns. Recognise that many functions of ‘noncoding’ DNA are yet to be determined).
What are three types of non-coding DNA?
Structural DNA helps maintain the structure of chromosomes in eukaryotes. A telomere is a repeating DNA sequence (for example, TTAGGG) at the end of the body’s chromosomes. Telomeres function by preventing chromosomes from losing base pair sequences, protects chromosomal DNA from degradation, at their ends. They also stop chromosomes from fusing to each other. The centromere is the part of the chromosome which attaches to the spindle fibres during cell division. Functional RNA includes any type of RNA that isn’t messenger RNA. tRNA is used to carry amino acids to ribosomes during protein synthesis. rRNA plays an important role in the ribosomes. Introns are sections of DNA that are transcribed but removes from mRNA before translation through splicing.
4.1.8. Explain the process of protein synthesis in terms of:
i) transcription of a gene into messenger RNA in the nucelus.
ii). Translation of mRNA into an amino acid sequence at the ribosome (refer to transfer RNA codons and anticodons)
What is the difference between an amino acid and a codon?
Amino acids are molecules that combine to form proteins. The order of amino acids in each protein follows a sequence which is coded for by its gene. Each set of three bases codes for one particular amino acid in the polypeptide chain ( a string of amino acids connected together by peptide bonds. The word poly means many, and the word peptide refers to proteins). The order of codons and the bases within them determine which amino acids are produced and in what order.
4.1.8. Explain the process of protein synthesis in terms of:
i) transcription of a gene into messenger RNA in the nucelus.
ii). Translation of mRNA into an amino acid sequence at the ribosome (refer to transfer RNA codons and anticodons)
Describe transcription and translation.
Transcription involves the production of RNA from a gene. Translation involves the production of protiens from amino acids uding mRNA. Transcription takes place in the cell of the nucleus. It involves RNA polymerase (an enzyme that is responsible for copying a DNA sequence into an RNA sequence, duyring the process of transcription) copying a gene’s DNA sequence to make an mRNA molecule. The newly formed mRNA is processed to remove the introns during splicing. The final mature mRNA can then leave the nucelus via the nuclear pore. Translation is when the mRNA is ‘read’ by ribosomes to produce a specific amino acid chain, or polypeptide. tRNAs carry specific amino acids that enter the ribosome when the anticodon on the tRNA is complementary to codon on the mRNA. The amino acid attached to this tRNA is then chemically bonded to the growing polypeptide chain. Translation beins at an AUG start codon and ends at a STOP codon.
Summarise transcription into key points.
Transcription
A gene is used as a template to make mRNA
The DNA double helix is unwound in the region of the correct gene
complementary mRNA nucelotides bind to form an mRNA strand, catalysed by RNA polymerase.
The introns are cut out and the exons are joined together, which is known as splicing.
mRNA leaves the nucelus through a pore and enters the cytoplasm.
4.1.7. Explain the process of protein synthesis in terms of:
i) transcription of a gene into messenger RNA in the nucleus
ii) translation of mRNA into an amino acid sequence of the ribosome (refer to transfer RNA, codons, and anticodons).
Explain the genetic code.
The genetic code is a set of rules by which the information in DNA or mRNA is translated in proteins. The information needed for the assembly of amino acids is stored as three-base-seqeunces called codons. Each codon represents one of 20 amino acids used to make protiens and is the same in all lviing organisms. For example, mRNA sequence of CGA codes for Arginine or R.
4.1.7. Explain the process of protein synthesis in terms of:
i) transcription of a gene into messenger RNA in the nucleus
ii) translation of mRNA into an amino acid sequence of the ribosome (refer to transfer RNA, codons, and anticodons).
How is a mature mRNA different from the DNA it was coded from?
Mature mRNA will contain U isntead of T. Mature mRNA will also have introns removed and thus be shorter sequence than the DNA it was coded from.
4.1.7. Explain the process of protein synthesis in terms of:
i) transcription of a gene into messenger RNA in the nucleus
ii) translation of mRNA into an amino acid sequence of the ribosome (refer to transfer RNA, codons, and anticodons).
Decribe the two functions of non-protein coding DNA.
Regulatory sequences (promoters, enhancers)
holding chromatids together (centromeres)
protection of DNA from degradation (telomeres)
4.1.7. Explain the process of protein synthesis in terms of:
i) transcription of a gene into messenger RNA in the nucleus
ii) translation of mRNA into an amino acid sequence of the ribosome (refer to transfer RNA, codons, and anticodons).
What is gene expression?
Genes are sections of DNA that code for proteins. Genes are expressed when they are transcribed into mRNA and then translated into a protien. Gene expression is the process by which the information in a gene is used to synethsise a gene product (protein or functional RNA). It involves transcription of the DNA into mRNA and translation of the mRNA into protein. The genome includes all the genetic material in the haploid set of chromosomes of an organism, including all its genes and DNA sequences.
4.1.9 Recognise that the purpose of gene expression is to synthesis a functional gene product (protein or functional RNA); that the process can be regulated and is used by all known life.
4.1.10
Identify that there are factors that regulate the phenotypic expression of genes.
Explain control of gene expression.
Proteins are not required by cells all the time. Therefore, some genes involved in metabolic pathways may be always be transcribed, while other genes may only be activated under certain circumstances. For example, genes that are important for while blood cells are “switched off” (repressed) in muscle cells. If all genes were switched on (activated), excessive amounts of energy would be wasted producing unecessary proteins.
4.1.9 Recognise that the purpose of gene expression is to synthesis a functional gene product (protein or functional RNA); that the process can be regulated and is used by all known life.
4.1.10
Identify that there are factors that regulate the phenotypic expression of genes.
What factors can be used to control transcription and translation at four different points.
Pre-transcriptional control
Post- transcriptional control
Translational control
Protein activity control
These factors include:
Regulatory genes that produce RNA or proteins that are used to control the expression of other genes.
environmental factors (eg. Fatty acids) that can influence transcription or translation
4.1.9 Recognise that the purpose of gene expression is to synthesis a functional gene product (protein or functional RNA); that the process can be regulated and is used by all known life.
4.1.10
Identify that there are factors that regulate the phenotypic expression of genes.
Idenitify the function of pre-transcriptional control.
Regulatory genes can produce transcription factors that attach to the promoter region (the section just in front of the coding region) of a strcutural gene to:
Block the attachment of RNA polymerase and stop gene being expressed ( repressed) or
Help the RNA polymerase attach to the promoter to increase the rate at which the gene is expressed (activator)
4.1.9 Recognise that the purpose of gene expression is to synthesis a functional gene product (protein or functional RNA); that the process can be regulated and is used by all known life.
4.1.10
Identify that there are factors that regulate the phenotypic expression of genes.
Identify the role of post-transcriptional control.
Once mRNA has been transcribed, cells can still regulate the amount of protein being produced by changing the longevity of the mRNA molecule (i.e. controlling the length of time the mRNA survives before being degraded by enzymes). Non-coding RNAs can alter or block the splicing of the mRNA, or binding to the mRNA ti make it double stranded so it is either broken down or to block translation from occurring.
4.1.9 Recognise that the purpose of gene expression is to synthesis a functional gene product (protein or functional RNA); that the process can be regulated and is used by all known life.
4.1.10
Identify that there are factors that regulate the phenotypic expression of genes.
Describe the function of translational control.
Certain factors can affect the speed that mRNA is translated by the ribosome. This results when the ribsome doesn’t correctly assemble on the mRNA.
