Genetics of living systems Flashcards
DNA codes for proteins within the cell. Some regions of DNA are described as non-coding.
Explain why some regions of DNA can be described as ‘non-coding’.
Non coding means it is not present in the mRNA and cannot be translated.
Non-coding regions of DNA show more variation than coding regions. This makes non-coding regions useful in DNA profiling.
Suggest why non-coding regions of DNA show more variation.
It is not selected against
Genes are not expressed during cell division because chromosomes are more tightly wound around histone proteins than during interphase.
Which of the following shows the level at which gene expression is being controlled when DNA is more tightly wound during cell division?
Transcriptional
The reason fruit flies are used is that there are fewer public concerns about the ethics of using flies.
Suggest two other reasons why fruit flies are chosen for research into genes controlling the development of body plan.
Low cost
Can be reproduced rapidly
There are some public concerns about the ethics of using mice in these investigations.
Suggest two reasons why mice are chosen as a suitable species for investigation.
Low cost
Genetics are well understand, and mice are more similar to humans
Explain how the structure of galactose allows it to be used as a respiratory substrate.
The bonds contain energy which can then be broken down by enzymes and allows it to be a respiratory substrate.
E.coli usually grows in conditions where the extracellular concentration of lactose is low. In such conditions lactose does not easily cross the bacterial cell surface membrane.
Suggest and explain why lactose is unable to cross membranes.
Lactose is too big and cannot pass through the phospholipid bilayer
In order for lactose to enter the cytoplasm of E. coli a protein is required.
The E. coli living in the digestive system of young mammals are more likely to contain this protein than E. coli living in the digestive system of old mammals.
Suggest an explanation for this observation.
lactose permease gene is more switched on in young mammals
Name all the kingdoms of living organisms that use homeobox genes to control the development of body plans.
animal and plant and fungi
A gene mutation is a change in the sequence of nucleotides within a gene.
Explain how it is possible for a mutation to have no effect on the protein produced from that gene.
Some of the triplets are degenerate so the amino acid sequence is not altered and will not change the shape of the protein.
Explain how a mutation could alter the protein so that it no longer performs its correct function in the cell.
Insertion/Deletion which can cause a frame shift, this causes the triplets further on in the amino acid to be different and no longer code for the correct protein
describe how transcription can be controlled in eukaryotes.
hormone enters cell and binds to a transcription factor causing the activation of the transcription factor which then travels and binds to a promoter region initiating transcription.
A gene mutation is a change in the sequence of nucleotides within a gene.
Hox genes code for transcription factors and control the development of the body plan.
Explain how failure of the control mechanism during development could lead to such a deformity.
Failure of control mechanism means that hox gene does not activate transcription factor and so apoptosis does not occur.
Describe how gene expression can be regulated after transcription.
primary mRNA is modified, the introns are removed to produce mature mRNA and cAMP binds and causes shape of protein to change
What feature of a pathogen such as Mycobacterium tuberculosis could be altered by a mutation, making a vaccine ineffective?
Shape of antigen on the cell surface membrane
