Topic 3- Cells, Reproduction, and Differentiation Flashcards
What is the RER and its function?
- fluid filled membranes covered with ribosomes
- folds and processes proteins made at ribosomes
What is the SER and its function?
- fluid filled sacs with no ribosomes
- processes and synthesises lipids
What is the Golgi Apparatus and its function?
- group of fluid filled membrane bound, flattened sacs/ vesicles seen around them
- processes and packages proteins and lipids (sugar chains trimmed or added)
- makes lysosomes
What is the function of pili?
- help prokaryotes stick to other cells
- can be used to transfer genetic material between cells
What are plasmids?
- small loops of DNA that aren’t part of main circular DNA
- contains genes coding for antibiotic resistance
- can be passed onto other prokaryotes
What are the differences between prokaryotic and eukaryotic DNA? (3)
- prokaryotic has curcular DNA while eukaryotic has linear
- eukaryotic DNA is enclosed in a nucleus whereas prokaryotic DNA free floats in cytoplasm
- prokaryotic DNA is not attached to histone proteins
What are prokaryotic cell walls made of and their function?
- made up of the glycoprotein, murein
- suuports cell and prevents it changing shape
Compare light and electron microscopes (5)
- light uses light to form an image whereas electron microscopes use electrons
- electron microscopes have higher resolution so give a more detailed image (1000x)
- can’t use light microscopes to view organelles like ribosomes, ER but both can see nuclei
- maximum magnification for a light microscope is x1500 whereas electron microscope is x1,500,000
- specimens must be dead when using an electron microscope
How to measure the size of a specimen by calibration?
- fit an eyepiece graticule onto eyepiece and place stage micrometer onto stage
- divide the eyepiece divisions by the distance of 1 division on stage micrometer
What is a tissue?
a group of similar cells adapted to work together to carry out a particular function
What is an organ?
a group of different tissues that work together to perform a particular function
Decribe the crossing over of chromatids (4)
- homologous pairs of chromosomes pair up
- non sister chromatids cross over and get entangles at the chiasmata
- entanglement places stress on the DNA and a section of a chromatid from one chromosome breaks and rejoins with the other chromatid
- forms a new combo of alleles on the 2 chromosomes
Describe independent assortment (3)
- each homologous pair can be arranged with either chromosome on top (random)
- the combo of alleles that end up in each daughter cell after the chromosomes separate depends on how they line up
- production of diff combos of allels in daughter cells due to random alignment of homologous pairs along equator of cell during meiosis 1
What is polygenetic inheritance?
- when we inherit more than 1 gene and alleles which affect a single characteristic
- shows continuous variation
What is a linked trait and autosomal linkage?
- when genes are very close together on a chromosome, they are crossed over together
- it is very unlikely that the chiasma will split these genes apart
- autosomal linkage= occurs in non sex chromosomes
Define an operon
a section of DNA that contains a cluster of structural genes that are transcribed together
What is the regulatory gene for?
codes for an activator or repressor
What are epigenetic changes?
- they occur when chemical hgroups are added are removed from DNA
- doesn’t alter base sequence but does determine what genes are expressed
- histone modification (acetylation) and DNA methylation
How may epigenetic changes be passed onto offspring? Why may this be advantageous?
- when cell replicates and divided, epigentic changes may be passed onto resulting daughter cells eg methyl group not being removed when producing gametes
- if epigentic change occured in response to change in environment, offspring will be equipped to deal with changed environment
Outline the process of gene expression/ specialisation
- stimulus (chemical/hormone) activates gene
- sequence of DNA bases are unzipped and transcribed using RNA polymerase
- this is where epigenetics affect gene expression - mRNA produced and translated at ribosome
- polypeptide is folded in RER and modified in GA
- fibrous/globular protein produced
- final phenotype/ specialisation of a cell is achieved
How do stem cells become specialised?
- by differential gene expression where only certain genes in DNA are activated and expressed
What is a stem cell?
- a cell that has the potential to differentiate into a specialised cell or remain as a stem cell
- can divide an unlimited amount of times
What are the risks of using stem cells in medicine?
- low no. stem cell donors
- cultured stem cells could accumulate mutations + lead to cancer
- is it right to create an embryo for the sole purpose of therapy/ destroy after
- people aren’t educated on what they can’t do
Give the structure of the lac operon
- regulatory gene= codes for the repressor protein that controls transcription
- promotor region= section of dNA that initiates transcription
- operator region= section of DNA that repressor binds to to regulate transcription
- structural genes= work together to enable digestion of lactose for energy
Give the similarities and fifferences between mitosis and meiosis
- both increase the number of cells
- mitosis creates 2 genetically identical, diploid daughter cells
- meiosis creates 4 genetically different, haploid daughter cells
