PM1A hard to memorise part 2 Flashcards
Other than non-disjunction what are other errors during meiosis?
Region of homology exist on different chromosomes (e.g. repetitive sequences).
if area is long and similar enough then recombination can begin.
Causes chromosome abnormalities or deletions.
Mitosis and meiosis topic?
What is the hayflick limit
Adult cells will continue to divide until telomeres are critically short, cancer cells and embryonic stem cells often reactivate telomerase and do not age, they catalyse DNA replication at ends of linear chromosomes.
What are the 5 types of meiosis and chromosome mutations?
Deletion- removal of a large chromosomal region, leading to loss of genes.
Duplications: lead to multiple copies of a chromosomal region, increasing the no of genes.
Insertion: addition of material from one chromosome to a non-homologous chromosome.
Inversions: reversing the orientation of a chromosomal segment.
Translocation: interchange of genetic material.
What are the 3 types of gene mutations (frame shift mutations)?
Point mutation: only one base is changed in DNA sequence (substitution).
Addition: nucleotide base is added into DNA sequence, all bases after the insertion are affected, new gene no longer makes sense.
Deletion: nucleotide base removed from DNA sequence.
Bacterial diseases topic:
Describe the normal microflora in GI tract
The GI tract contains the largest reservoir of human flora- around 500 species of bacteria. The GI microorganisms perform several functions such as:
Preventing the growth of harmful pathogenic bacteria, training the immune system and producing vitamins for the host.
The stomach is a hostile environment for bacteria.
Acidity (due to gastric acid) lowers the bacterial count.
Some helicobacter species can colonise in stomach leading to gastritis and peptic ulcer.
The UPPER PART of the SMALL INTESTINE (duodenum and jejunum) have low bacterial count- mainly Lactobacilli and streptococci.
The ILEUM has decreased peristalsis and low acidity- maintains a more diverse microflora and a higher bacterial pop.
Strict anaerobic conditions and bacterial waste inhibits the growth of other sp. in LARGE BOWEL.
BACTERIAL DISEASES TOPIC:
Describe the normal microflora in urogenital tract.
The type of bacteria present in the female urogenital tract depends on pH, age and hormone levels.
Lactobacilli in female urogenital tract produces lactic acid, that lowers pH preventing colonisation of bacteria.
The upper urinary tract (kidney ,ureter), posterior urethra and bladder are normally sterile and do not contain any normal microflora.
Only the lower part of the urethra is colonised by bacteria.
The shorter female urethra makes infections more common than in men, can reach kidneys and blood.
When asked for urine sample
(due to suspc infec), midstream sample is asked for to avoid contamination.
VIRUSES TOPIC:
Describe the life cycle of viruses with animal hosts (the infection stages)
- Attachment- the virus recognises and bind to the host cell via a receptor on the cell surface.
- Penetration- virus enters the cell.
- Genome replication and gene expression- the viral genome is the copied and its genes are expressed to make viral protein.
- Assembly- the new viral particles (virions) are assembled from the genome copies and viral proteins.
Mechanisms of penetration, nucleic acid synthesis and release differ between bacterial and animal viruses/
After binding to host receptors, animal viruses enter through the endocytosis (engulfment by the host cell) or through membrane fusion.
CELL SIGNALLING TOPIC:
What are the three phases of signal transduction and give a brief description of each.
Could be asked a q like this: ‘Transduction is one of the three different phases that characterize cell signalling. Give the names (2 marks) and a brief description of the other two phases (2 marks) (4 marks in total)’
- Reception: is the target cell’s detection of a signal coming from outside the cell. A biochemical signal (ligand) is detected when it binds to a cellular protein (receptor) at the surface.
- Transduction: converts one type of signal (e.g. the initial stimulus or ligand) into another signal and may amplify the signal in the process.
- Response: the transduced signal finally triggers a specific cellular response:
Target ( response) proteins- these are signalling components at the end of a signalling pathway that bring about a change in cell activity contributing to overall response.
Target transcription factors roles:
may regulate expression of proteins that inhibit signalling.
response might be activation of a transcription factor leading to a change in gene expression.
Homeostasis is defined as ‘the control or stabilization of the internal environment’.
a) What is the name of the fluid that represents the overall internal environment (1 mark)
b) Which THREE components combine to make up this fluid? (3 marks)
a) Extracellular Fluid
b) Plasma
Interstitial fluid
Transcellular fluid
why eukaryotic genes transcripts must be spliced.
DNA in eukaryotes contain introns (non coding) and exons (coding).
introns are cut out and exons are spliced together.
Splicing makes gene more modular, allowing new combinations of exons to be created during evolution. Also new exons can be inserted into old introns, creating new proteins without disrupting the function of genes.
briefly explain the role of telomeres in cellular ageing and cancer cells.
Telomeres shorten with each cell division, this has thought to correlate to ageing due to DNA polymerase and discontinuous replication at the lagging strand of DNA- formation of okazaki fragments.
When no telomeres are left, cell division stops leading to senescence .
However in cancer cells, telomeres do not age as they do in normal cells, allowing them to divide and grow uncontrollably.
Cancer cells reactivate an enzyme called telomerase which elongates the telomeres, catalysing DNA replication.
Describe the features of chromosomes
(centromeres and chromatids)
chromosomes consist of two identical sister chromatids joined at the centromere.
the centromere divides the chromosome into two arms, short arm ( p arm) and long arm (q arm)
Centromeres are also called primary constrictions on a chromosome based on their microscopic appearance.
Describe mycobacteria cell wall
Mycobacteria are also known as….
mycobacteria have an extra layer of mycolic acids in their cell walls.
Also known as acid-fast bacteria, as acid-fast staining is used to penetrate mycolic acids during staining
Acid staining detects cell walls rich in mycolic acids.
BACTERIA TOPIC:
THREE types of filamentous appendages are fimbriae, pili and flagella.
Describe the difference between fimbriae and pili structures and function
FIMBRIAE-:
Are short bristle-like proteins that extend from the cell surface.
Are SHORTER AND NUMEROUS.
Enable a cell to attach to surfaces and other cells.
For pathogenic bacteria, adherence to host cells is important for: infectivity, colonisation and virulence
Adherence to surfaces is important in biofilm formation.
PILI:
longer and less numerous, they are protein appendages that aid in attachment to surfaces.
F pilus or sex pilus is important in transfer of DNA between bacterial cells which are members of the same generation, the two cells physically exchange parts of their respective genomes.
Flagella are examples of filamentous appendages
Describe the function and structure of flagella.
function- allow bacterial cells to move in aq environments.
Structure:
propellers- stiff spiral filaments composed of flagellin protein subunits that extends outwards from the cell and SPIN IN SOLUTION.
Basal body- the motor and is embedded in plasma membrane.
Hook region- connects the basal body to the filament.
Flagella are either polar or peritrichous:
Polar flagella: a single flagellum, typically located at one end of the bacterial cell.
Peritrichous- flagella distributed over entire cell surface.
