long biology Flashcards
what is mitosis?
cell division that produces 2 daughter cells that have the same number of chromosomes so are genetically identical.
what is the role of mitosis?
growth and repair, plus replacement.
what is meiosis?
cell division that produces 4 daughter cells, known as gametes, which have a single set of chromosomes (are haploid), each with different combinations of parent cells’ dna.
what is the role of meiosis?
reducing the chromosome number so that the full chromosome complement is restored at fertilisation.
what does asexual reproduction produce?
clones
how many parents does asexual reproduction involve?
1
are offspring of asexual reproduction genetically identical?
yes
in most mammals, what are the female sex chromosomes?
XX
in most mammals, what are the male sex chromosomes?
XY
what is a gene?
a section of dna that codes for a specific protein.
what is an allele?
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
what is a dominant trait?
a trait that is phenotypically expressed in heterozygotes.
what is a recessive trait?
the variant of a gene for a particular characteristic that is masked or suppressed in the presence of a dominant variant.
what is homozygous?
If the two alleles at a locus (fixed position on a chromosome) are identical to each other, they are homozygous eg bb
what is heterozygous?
If the two alleles at a locus (fixed position on a chromosome) are different to each other, they are heterozygous eg Bb
what is a phenotype?
the set of observable characteristics of an individual.
what is a genotype?
the genetic constitution of an individual organism.
how is cystic fibrosis screened in the UK?
all newborn babies are screened for cystic fibrosis as part of the newborn blood spot test (heel prick test) carried out shortly after they’re born.
if the cystic fibrosis test is positive, what additional tests confirm the baby has it?
1) a sweat test – to measure the amount of salt in sweat, which will be abnormally high in someone with cystic fibrosis.
2) a genetic test – where a sample of blood or saliva is checked for the faulty gene that causes cystic fibrosis.
what is cystic fibrosis?
an inherited condition that causes sticky mucus to build up in the lungs and digestive system. This causes lung infections and problems with digesting food.
is cystic fibrosis dominant or recessive?
recessive
what is polydactyly?
an inherited condition in which a person has extra fingers or toes.
is polydactyly dominant or recessive?
dominant
how and when is huntington’s screened?
PGD, only available at certain clinics licensed by the Human Fertilisation and Embryology Authority. or PND, prenatal diagnosis, only used if the couple intend to terminate if the test is positive (testing once the embryo is implanted)
what does pgd involve?
removing a cell from an IVF embryo to test it for a specific genetic condition before transferring the embryo to the uterus.
what are chromosomes made of?
dna lol
what is the bond between the sugar residue and the phosphate group in dna?
covalent bond formed by condensation reaction- phosphodiester bond.
how many h-bonds between adenine and thymine?
2
how many h-bonds between guanine and cytosine?
3
what does a triplet of bases code for?
an amino acid.
what does protein synthesis involve?
the production of proteins from amino acids.
what is a genetic mutation?
“a change in the gene/DNA” apparently
how is the genetic code “read”?
as triplets.
what does genetic modification involve?
1) taking a cope of a gene from dna/ chromosomes of one organism.
2) insertion of that gene into the dna of another organism.
as an animal matures, what happens to its stem cells?
they lose the ability to turn into any cell type.
what are the types of stem cells they want us to know?
embryonic
adult
what is the sequence of natural selection?
1) variation within a population
2) leads to differential survival
3) because those best adapted survive.
4) these organisms can reproduce
5) and pass on advantageous genes to next generation.
what is 1 example of evolution through natural selection?
antibiotic resistance of mrsa
what are the sources of variation?
- genetic/inherited
- environmental
when can extinction occur?
if organisms cannot adapt quickly enough.
what are enzymes?
biological catalsysts
why are enzymes called biological catalysts?
they’re organic biomolecules that accelerate the rate of the chemical reactions in a biological system and are neither consumed nor changed in the reaction.
how does pH affect bonds within biological molecules?
excess hydrogen ions interfere with h-bonds and ionic forces, so active site changes shape. it also alters charges on active site because more protons cluster around negatively charged groups, interfering with bonding of substrate.
how does pH affect rate of enzyme controlled reactions?
- small changes of pH, either side of the optimum, slow the rate of reaction but if normal pH is restored the h-bonds can reform and the active site’s shape is restored.
- at extremes of pH, the enzyme’s active site may be permanently denatured.
where is amylase produced and where does it act?
produced in: salivary glands and pancreas
acts in: mouth and small intestine
what does amylase do?
digests the polysaccharide starch to the dissaccharide maltose.
what does protease do?
breaks down proteins into amino acids. different proteases act in the stomach and small intestine.
what does lipase do?
breaks down dietary fats into fatty acids and glycerol.
what is the word equation for anaerobic respiration in animals?
glucose → lactic acid (+ ATP made)
what are the differences between anaerobic and aerobic respiration?
anaerobic: not enough oxygen, incomplete oxidation of glucose, produces lactic acid, produces smaller amount of atp but more quickly.
what are the dendrites and axons like in motor neurons?
short dendrites
long axons
what are the dendrites and axons like in sensory neurons?
long dendrites
short axons
what are the dendrites and axons like in relayneurons?
short dendrites
long/short axons
what are the 4 main blood groups?
A-has A antigens on RBCs and anti-B antibodies in plasma.
B-has B antigens on RBCs with anti-A antibodies in plasma.
O-has no antigens on RBCs but both anti-A and -B in plasma.
AB-both A and B antigens, no antibodies.
what is RhD and why is it important?
RBCs sometimes have another antigen, known as the RhD antigen-you can be RhD negative or positive.
what is the nephron?
the functional unit of the kidney.
what is homeostasis?
the maintenance of a constant internal environment.
how and where do hormones travel?
in the blood to their target organs.
what are the functions of white blood cells?
producing antibodies
engulfing pathogens
(at least somethings easy)
what limits the length of a food chain?
energy flow
what is the flow of energy in a food chain and the effect of this?
energy is lost as you go up a food chain.
consequence-each trophic level can support fewer organisms.
what is the pyramid of biomass?
just shows there are less organisms as you go up trophic levels due to energy flow
what is nitrogen fixation?
when nitrogen in earth’s atmosphere in converted to ammonia or other molecules available for living organisms.
when does nitrogen fixation happen?
nitrogen-fixing bacteria in soil or root nodules, or lightning.
what is nitrification and what does it?
turning ammonia to a nitrate-nitrogen fixing bacteria in soil.
what is decomposition+its role in nitrogen cycyle?
nitrogen compounds in organic matter reenter soil where they’re broken down by decomposers, producing ammonia.
what is denitrification and where does it happen?
turning a nitrate to nitrogen. denitrifying bacteria do this usually in waterlogged soil.
HAPLOID=?
SINGLE set of chromosomes
What kind of process is glucose absorption from the small intestine lumen to the villi?
Active transport
