TOPIC 2: GENES AND HEALTH

Compare and contrast molecular structures of globular and fibrous proteins (4)

both are amino acid chains joined by peptide bonds(1)
both contain hydrogen/ionic or disulfide bonds (1)
globular proteins have hydrophilic on outside whereas fibrous proteins have hydrophobic groups on the outside (1)
globular have tertiary or quaternary structures whereas fibrous have little or no tertiary (1)
globular are folded into compact shapes whereas fibrous have long chains (1)

Describe the function of carrier proteins (4)

involved in facilitated diffusion (1)
movement of large/polar molecules (1)
involved in active transport (1)
needs ATP to move molecules against concentration gradient (1)

Describe how nucleotides join together to form DNA (2)

condensation reaction (1)
phosphodiester bonds (1)

Compare and contrast structure of ATP and DNA nucleotide (3)

both contain phosphate, pentose sugar and base (1)
DNA nucleotide contains deoxyribose whereas ATP contains ribose (1)
DNA nucleotide could contain other bases but ATP contains adenine only (1)
a DNA nucleotide contains one phosphate whereas ATP contains three phosphates (1)

Compare and contrast procedures used in amniocentesis and chorionic villus sampling to obtain fetal cells (3)

fetal cells obtained from amniotic fluid
fetal cells obtained from placental cells in cvs (1)
use needle in both (1)
amniocentesis via abdomen and cvs either via abdomen or vagina (1)

Explain one treatment used to reduce the lung symptoms of people with cystic fibrosis (2)

physiotherapy dislodges mucus (1)
therefore more efficient gas exchange (1)

Describe how transcription is involved in the synthesis of an enzyme (4)

DNA unzips and hydrogen bonds between complementary stands broken (1)
The template/antisense strand used for mRNA synthesis (1)
RNA polymerase used to join RNA nucleotides (1)
complementary base pairing A with U, not T (1)

Compare and contrast diffusion and active transport

both molecules move through the phospholipid bilayer (1)
both molecules move through proteins (1)
diffusion occurs down a concentration gradient whereas active transport is against the concentration gradient (1)
diffusion is passive wheres active transport is not passive(1)

Explain how phospholipids form cell surface membrane (3)

hydrophilic parts associate with water (1)
hydrophobic parts repel water (1)
bilayer forms with hydrophobic parts pointing in towards the centre of bilayer (1)

Genetic code (2)

Each triplet is read once (1)
Non-overlapping (1)

Describe translation (5)

mRNA attached to ribosome (1)
each tRNA molecule is attached to specific aa with anticodon (2)
Anticodon binds to codons on mRNA forms hydrogen bonds (2)
Peptide bonds form between amino acids (1)

Explain DNA replication (5)

semi-conservative (1)
DNA unwinds, hydrogen bonds broken (1)
Nucleotides line up along both strands (1)
Complementary base pairing (1)
Phosphodiesther bonds (1)
Ref. DNA helicase and polymerase (1)

Explain the meaning of activation energy (1)

minimum energy required to start a reaction (1)

Explain the meaning of the term recessive allele (3)

both allele have to be present for that recessive phenotype to be expressed (1)
different form of a gene (1)
same locus(1)

Explain why people with CF have breathing difficulty (4)

produce thicker mucus (1)
blocking airways (1)
reduces flow to alveoli (1)
reduces flow of 02 to alveoli (1)
reduces gaseous exchange (1)

Explain how the expression of a gene mutation in a person with CF fibrosis causes a build-up of mucus in respiratory system (5)

CFTR protein has a different structure and function (1)
role of transporting chloride ions (1)
chloride ions not moving out of cells into mucus (1)
water does not move in to cells (1)
mucus is becomes thicker (1)
cannot be moved by cilia (1)

Describe the difference between somatic gene therapy and germ line gene therapy (2)

somatic involves cells and germ line involves gametes (1)
somatic can't be inherited/ germ line therapy can be inherited (1)
somatic legal/ germ line therapy illegal (1)

Suggest how somatic gene therapy works (4)

inserting gene that codes for the CFTR protein(1)
CFTR protein made via transcription/ translation (1)
allows chloride ions to leave cells (1)
water leaves cell by osmosis (1)
mucus is less sticky (1)

Explain why globular proteins are soluble in water (3)

hydrophilic groups on the outside and hydrophobic on the inside (1)
exposed R groups are polar (1)
form hydrogen bonds with water (1)
water is a polar solvent (1)

Describe what is meant by the secondary structure of a protein (2)

folding of polypeptide chain (1)
into a a-helix or beta pleated sheet (1)
forming hydrogen bonds(1)

Why does glycogen release energy more slowly than glucose (2)

glycogen is a polysaccharide (1)
glycosidic bonds need to be broken to be used (1)

State what is meant by the term gene mutation (1)

change in the base sequence of DNA

Explain how the structure of the membrane controls the transport of polar molecules (4)

hydrophilic phosphate heads on outside and hydrophobic fatty acid tails on the inside (2)
so polar substances cant pass through the hydrophobic centre (1)
so pass through carrier/channel proteins (1)

Define allele (2)

different version of a gene(1)
found at the same locus on a chromosome (1)

Explain ethical issues relating to using prenatal genetic screening (2)

it may result in a abortion (1)
unethical to cause death of a foetus (1)
risk of false positive/negative (1)
parents not prepared for child with genetic disease(1)

Explain the term recessive genetic disorder (1)

results from defect in genes (1)
both alleles need to be present (1)

Describe the structure of a cell membrane (5)

phospholipid bilayer(1)
phosphate heads hydrophilic on inside, fatty acid hydrophobic tails on inside (2)
proteins in membrane (1)
glycoproteins/ glycolipids (1)
cholesterol within membrane (1)

Explain how a polar glucose molecule enters through the cell membrane (2)

carrier proteins (1)
facilitated diffusion (1)

Describe the function of carrier proteins in cell surface membrane (4)

involved in facilitated diffusion (1)
movement of polar molecules (1)
involved in active transport (1)
needs ATP to move molecules against concentration gradient (1)

Describe one similarity and one difference between facilitated diffusion and active transport (2)

S: use carrier/ channel proteins (1)
D: active transport requires energy and diffusion does not require energy (1)

Lipids enzymes hydrolyse...

ester bonds to produce fatty acids

Devise an investigation to determine whether pH affects beetroot membrane permeability (4)

solutions with range of pH values (1)
piece of beetroot with same surface area (1)
control volume of solution/ time (1)
measure of absorbency using colorimeter (1)
Repeat and calculate mean (1)

DNA and mRNA both...

have a sugar-phosphate backbone

Advantage of DNA having 2 complementary strands

semi-conservative replication is possible

Which sugar is found in a nucleotide

pentose

Name of bond that joins amino acids together

peptide

Explain the effects of having smaller quantities of CFTR protein in membrane (5)

fewer chloride ions transported across cell membrane (1)
less regulation of sodium ion channel (1)
less water moves from the cell into the mucus by osmosis (1)
makes mucus more viscous (1)
cilia can't remove mucus (1)

Explain how a mutation in mitrochondrial DNA could defective ATP synthase being produced (3)

random change in the sequence of bases in the DNA (1)
this affects the triplet code/ changes sequence of amino acids(1)
change in the shape of active site (1)

Describe 3 differences between replication and transcription (3)

replication uses DNA polymerase transcription uses RNA polymerase (1)
copies both strands, only copies one gene (1)
makes double helix-replication, makes single strand - translation(1)

Explain why removing one base will affect the primary structure of a protein (1)

deletion could affect every codon on mRNA(1)
more likely to affect the position stop/start codon (1)
results in a different sequence of amino acids(1)

Explain why changing one base for another may not affect the primary structure of a protein (2)

substitution may code for the same amino acid (1)
same amino acid due to genetic nature of the genetic code (1)

Give one function of a glycoproteins

act as receptors/ antigens

Compare endocytosis and exocytosis(3)

both involve the use of vesicles to move contents (1)
both involve bulk transport (1)
endocytosis involved transport into cell, exocytosis transports substances out of the cell (1)

Explain how primary structure of a protein is important in determining its shape (2)

relates to the sequence of amino acids (1)
specific folding of the chain/ tertiary structure (1)

Explain why most enzymes are specific to only one substrate (2)

enzymes have a specific active site (1)
will only fit for substrate with correct shape (1)
lock & key/ enzyme-substrate complex (1)

Base that pairs with thymine

adenine

Explain why melanin cannot be produced in the absence of the enzyme tyrosinase (2)

enzymes are substrate specific therefore no other enzyme will breakdown tyrosine

Suggest why a child who's parents do not have achondroplasia may still suffer (2)

mutation (1)
spontaneous change in DNA (1)

Describe the principles of gene therapy in CF treatment (4)

copy of normal allele inserted into loop of DNA (1)
restriction enzyme (1)
DNA ligase forms liposome-DNA complex (1)
CF patient breathed in aerosol containing complex (1)
Normal allele enters nucleus and CFTR protein is transcribed (1)

Gene (2)

a series of base sequences (1)
that code for an amino acids in a polypeptide chain (1)

Describe the structure of collagen (3)

three polypeptide chain (1)
coiled around each other (1)
cross-linking between chains (1)

Explain how mRNA is produced (4)

DNA unzips and a strand acts as a template (1)
Free nucleotides pair up with complementary bases (1)
RNA polymerase joins together pre-MRNA (1)
Removal of introns (1)