genes and health Flashcards
describe the role of tRNA
tRNA molecules transport amino acids to the ribosome. tRNA molecule has a complimenteray anticodon that binds to a codon on the mRNA. each tRNA carries a particular amino acid. tRNA binds to ribosome
compare and contrast the process of endocytosis and exotycosis
- both processes involve vesicles and both involve energy/ATP
- exocytosis involves substances leaving the cell whereas endocytosis involves substances entering the cell. exocytosis involve vesicles fusing with cell surface membrane whereas endocytosis involves the formation of vesicles
function of glycoprotein
cell recognition/receptors/antigens
explain how the structure of a phospholipid molecule contributes to the partial permeability of the membrane
contains hydrophilic phosphate head and hydrophobic fatty acid chains. it allows non-polar molecules to pass through the membrane. polar molecules cannot pass through the phospholipid bilayer
how do phopsholipids form bilayer
hydrophilic parts associate with water. hydrophobic parts repel with water. a bilayer forms with hydrophobic parts pointing towards the centre of the bilayer
why are phospholipids arranged into two layers in a membrane
hydrophilic region orientated towards water and hydrophobic regions away from the water. solution either side of the cell membrane
function of carrier proteins
involved in facilitated diffusion. movement of large molecules from a high to low concentration. involved in active transport.
describe the structure of the cell surface membrane
it is phospholipids and protein. phospholipids form a bilayer. proteins float in the phospholipids
how does primary sturcture of leptin allow it to be soluble
primary structure determines the folding of the polypeptide forming a globular structure. hydrophobic r groups are located in the centre of the protein. water forms hydrogen bonds with protein
how does substitution base affect fucntion of molecule
different triplet is produced which changes the codons in mRNA resulting in a different amino acid. but this may code for the same amino acid. due to the degenerate nature of the genetic code
why can enzymes that arent correctly folded not carry out its function
teriary structure would be different so active site of enzyme wouldn’t bind with the enzyme/wouldn’t be able to form enzyme susbtratwe complex. therefore, it wouldnot be able to catalyse the reaction
compare and contrast globular and fibrous proteins
both are chains of amino acids joined by peptide bonds. both contain hydrogen and ionic bonds, disulfide bridges.
globular proteins have hydophilic groups on the outside whereas fibrous proteins have little or no tertiary structure.
globular are folded into compact shapes whereas fibrous have long chains
how is a peptide bpnd formed
condensation reaction between amine group and carboxyl group of adjacent amino acids
products when several amino acids are joined toegther
water and polypeptide
compare transcription and DNA replication
both involve formation of polynucleotide. both involve DNA helicase. transcription uses RNA nucleotides and RNA polymerase whereas replication uses DNA nucleotides and DNA polymerase. transcription produces single strand of mRNA whereas replication produces double stranded DNA
what deos a frameshift do
changes triplet code so introduces a new coodn which codes for a shorter sequence of amino acids. more likely to affect the position of a start/stop coodn
describe how mRNA is synthesised at a template strand
RNA nucleotides align with complementary bases. RNA nuclepotides joined together by RNA polymerase/phosphodiester bonds
compare RNA and DNA
DNA is double stranded whereas RNA is single stranded. DNA contains deoxyribose while RNA contains ribose. DNA contains thymine whereas RNA contains uracil
which type of bond holds strands of dna together
hydorgen
describe how nucleotides join together to form dna
condensation reaction. phosphodiester bonds. DNA polymerase
why did they accept one of the dna replication models and not the otger
semi-conservatvie model was accepted because generation 1 has a single band which is halfway between 15N and one 14N. the dna has one strand containing 15N and one strand containing 14N. further generations would have a band halfway between 15N and 14N
why does antibiotics that binds to ribosome affect production of protein
mRNA is prevented from binding to the ribosome. so translation cant occur so protein can’t be synthesised
describe the role of CFTR in ensuring that mucus produced in the lungs is the right consistency
chloride ions leave the cell. sodium ions leave the cell. this increases the solute concentration in the mucus. water moves out of the cells by osmosis
describe the roles of translation and transciption
the gene for the protein is transcribed. complementary base pairing between RNA nucleotides and DNA. mRNA leaves the nucleus and attaches to the ribosome. pairing between codons on mRNA and anticodons kn tRNA. tRNA provides specific asmino acids. the sequence of bases determione the primary structure
explain why different mutations in the CFTRNgene can lead to differences in the severity of the symptoms of cystic fibrosis
different mutations will have different effects on the protein produced
chloride ion transport affected by the extent of changes
varying the stickiness of mucus
why does cystic fibrosis affect the rate of oxygen uptake in lungs
thick sticky mucus
which cannot be moved by cilia
restricting air flow trhough bronchioles
reduced surface area for gas exchange in the alveoli
how many hydrogen bonds between a-t
2
how many hydrogen bonds between c-g
3
why do children with cystic fibrosis need dietary supplements and digestive enzymes
cystic fibrosis causes the production of stuckier thicker mucus
this blocks the pancreatic duct which prevents pancreas enzymes from reaching the intestine
prevents enzymes elnde digesting in intestines
resulting in reduced absorption of products of digestion into the blood
digestive enzymes and dietary supplements would increase growth rate
what does CFTR gene code for
a channel protein
why may parents choose not to do CVS
Test result may be innacurate
increased risk of miscarriage
false positive may lead to termination of healthy fetus
against values or beliefs of the parents
definition of inherited recessive disorder
caused by a faulty allele
only expressed in the homozygous condition
what is it called when many different siblings are different genotype
incomplete dominance
Both alleles expressed
allele definitin
alternative form of a gene found
at the same locus
how to know if parents are heterozygous
if some of the children have the recessive disease
what is cvs
chorionic villus sampling
cells taken from placenta between 10-14 weeks of pregnancy
benefit of earlier diagnosis
amniocentesis definition
amniotic fluid containing cells collected betwen 14-20 weeks of pregnancy
lower risk of miscarriage
horse can be either red or white but it is orange what happened?
heterozygous
therefore incomplete codominance occurs
because both alleles are expressed
advantage of genetic screening
prevents child dying late in pregnancy and parents can prepare for child. less stress for parents
difference between substitution and addition
loss causes frame shift
replacement only changes one codon so number of amino acids remain the same
template
RNA nucleotides attach to this strand
what is pre implantation genetic diagnosis
an embryo created by IVF can be screened before it is placed in the mothers uterus
fluid mosaic meaning
fluid refers to the movement of the phospholipids in the plane of the membrane
mosaic refers to the random association of proteins within the membrane
properites of cells that allow them to enter cells by diffusion
small, non-polar, lipid soluble
compare facilitated diffusion and active trasnsport
both transport molecles. hoewver active transport is against a concentration gradient while facilitated diffusion is down it. facilitated diffusion doesnt require ATP
how is channel protein involved in passive transport
allows movement of large molecles by diffusion down a concentration gradient
why do people with cf hage breathing difficulties
stickier thicker mucus
blocking brocnhioles
mucus cant move it out of lungs
reduced flow of air to alveoli
reduced gaseous exchange
loss of surace area redyuced concentration gradient
trapped bacteria may result in more lung infectioons
recessive allele
different forms of a gene and both need ti be present in order for the recessive phenotype to be express
between bases
hydrogen bonds
Non overlapping
Base triplets don’t share their bases. These are seperate
Degenerate
More possible combinations of triplets than there are amino acids. One amino acid can be coded for by more than one base triplet
Mono hybrid inheritance
Inheritance of single characteristic determined by one gene with two alleles
Screening embryos for genetic disorders before they’re implanted in a woman
Preimplantation genetic diagnosis
explain why a fertilised egg cell will contain only maternal mitochondria
only nucleus of sperm enters ovum
therefore all mitochondria comes from the egg cell
inheritance of parental characteristics in offspring
DNA in nucleus comes from sperm and egg of parents
characteristics determined by DNA in nucleus is inherited by parents
Exaplin why stem cells from heart can’t be used to grow cells from cornea
Cells aren’t totipotent
Some genes already activated/ deactivated
Will not be able to specialise into cornea cells
