6.1 Genetics of Living Systems Flashcards
What is a codon ?
Each amino acid in a protein id coded for by a sequence of 3 nucleotide bases on mRNA called a codon.
What is degenerate ?
More codon than amino acids so different codons code for the same amino acid.
What is non-overlapping ?
Codes for 1 codon at a time for 3 bases.
What is the universal code ?
All organisms have DNA.
What is a mutation ?
A mutation is a change in the sequence of bases in dan. This can disrupt the protein synthesis. It is caused by insertion, deletion or substitution.
What is substitution ?
Swapping base changes codon. May change amino acid leading to a change in primary structure, but same amino acid may be brought as DNA is degenerate.
What is insertion or deletion ?
Insert or deletion of one or more bases. Leads to frameshift mutation buy shifting the reading frame of bases. This changes every successive codon from the point of mutation.
What is a mutagen ?
Physical or chemical or biological agent that causes mutations.
What are silent mutations ?
They do not change proteins so has no overall impact to organism.
What is a nonsense mutation ?
Change in codon to a stop codon. Protein is shortened and is usually non-functional.
What is a missense mutation ?
Results in the change of amino acid into primary structure. Result depends on the amino acid so can be severe or minimal.
What is deletion ?
Selection of chromosome breaks off and is lost within a cell.
What is duplication ?
Sections of DNA are duplicated.
What is translocation ?
Section of one chromosome breaks off and joins another non-homologous chromosome.
What is inversion ?
Section of chromosome breaks off, is reversed and joins back on to the chromosome.
What is neutral affect of mutation ?
Caused by silent mutations, where normal proteins are still synthesised.
What is the harmful effect of mutations ?
Proteins are not synthesised or are non-functional.
What is the effect of beneficial mutations ?
Proteins synthesised with new and useful characteristics.
What is transcriptional gene regulation ?
Genes are turned on or off.
What is post- transcriptional gene regulation ?
mRNA can be modified which regulated translation and proteins used.
What is translational gene regulation ?
Genes can be stopped or started.
What is post-translational gene regulation ?
Proteins modified after synthesis which changes the function.
What is chromatin remodelling ?
Heterochromatin is tightly wound DNA causing chromosomes to be visible. Euchromatin is loosely wound DNA present in DNA. Transcription of genes is not possible when DNA is tightly wound because RNA polymerase cannot access genes.
What is histone modification ?
DNA coils around histones because they are positively charged. Addition of acetyl or phosphate groups reduces the positive charge of histones so DNA coils less tightly allowing certain genes to be transcribed. Addition of methyl groups makes histones bind more tightly preventing transcription.
What Is the transcription factor ?
Binds to inhibitor to stop transcription. Hormones also bind to release the inhibitor and to bind to the promoter.
What is an operon ?
An operon is a group of genes that are under control of the same regulatory mechanism and are expressed at the same time.
What is Lac Operon ?
Group of 3 genes involved in the metabolism of lactose. They are structural genes as they are transcribed onto a single long molecule of mRNA. Regulatory gene is located near to operon coding for repressor protein that prevents transcription of structural genes in absence of lactose. binds to operator to prevent RNA polymerase.
What is cyclic AMP ?
Binding of cAMP increases rate of transcription when bound o CRP. Transport of glucose in E Coli decreases levels of cAMP, reducing transcription.
What is RNA processing ?
Product of transcription is a precursor molecule, which is modifies forming mature mRNA before binding to a ribosome. A cap is added to help stabilise mRNA and delay degradation.
What is degradtion of mRNA ?
More resistant the molecule, the longer it lasts in the cytoplasm so the more protein synthesised.
What are protein kinases ?
Enzymes that catalyse addition of phosphate groups to proteins. Addition of phosphate groups changes tertiary structure and function of protein. Many enzymes are activated by phosphorylation. They are important regulators of cell activity. Often activated by secondary messenger cAMP.
What is morphogenesis ?
Regulation of pattern of anatomical development.
What are homeobox genes ?
Group of genes which all contain a homeobox, which is a section of DNA coding for protein 60 amino acids long. They are regulatory genes.
What are Hox genes ?
One group of homeobox genes only present in animals responsible for correct positioning go body parts. Order in which genes appear along the chromosome in order in which their effects are expressed in the organism.
How are body plans represented throughout the body ?
Represented as cross-sections through organism showing fundamental arrangement of tissue layers.
-Diploblastic = 2 primary tissue layers.
-Triploblastic = 3 primary tissue layers.
What are somites ?
Individual vertabrae have all developed from segments in embryo called somites, directed by the Hot genes to develop in a particular way.
What is apoptosis ?
Shaping of body parts by removing unwanted cells and tissues. Cells undergoing apoptosis release chemical signals which stimulate mitosis and cell proliferation leading to the remodelling of tissues.
How does apoptosis work ?
Nucleus condenses causing cell to shrink. Nucleus fragments and cell splits forming apoptic bodies. Apoptic bodies are engulfed by phagocytes. Can be influenced by environment from both internal and external factors.
