Genes and Health Flashcards
How can you calculate rate of a reaction from a curved line graph
tangent then rise over run
Why are enzymes highly specific?
Enzymes are highly specific due to their tertiary structure. which forms the active site
The permeability of cell membranes is affected by:
e.g. temperature and alcohol concentration.
What does being heterozygous (Ff) mean for cystic fibrosis?
The person is a carrier but does not have CF.
What is Cystic fibrosis and what is it caused by
Cystic fibrosis (CF) is an inherited disorder that mainly affects the respiratory, digestive and reproductive systems . It’s caused by a recessive allele (f), so a person will only have the disorder if they’re homozygous for the allele (ff) — they must inherit one recessive allele from each parent. If a person is heterozygous (Ff), they won’t have CF but they’ll be a carrier.
What is the main function of RNA?
Transfer genetic information from DNA to ribosomes.
Heterozygote
An organism that carries two different alleles for a certain characteristic, e.g. Bb
What is the shape of DNA?
DNA forms a double-helix structure with two antiparallel polynucleotide strands.
What does non-overlapping mean in the genetic code?
Each base triplet is read separately, without sharing bases with others.
What are the four structural levels of proteins?
Primary, secondary, tertiary, and quaternary structures.
What are the monomers of proteins
amino acids
What is Duplication
One or more bases are repeated, e.g. ATGCCT becomes ATGCCCCT (two Cs are duplicated).
Where does the mRNA attach after leaving the nucleus?
To a ribosome in the cytoplasm.
How are proteins really different
different number and order of amino acids. defined by the primary structure which affects the tertiary one
What is the key difference between conservative and semi-conservative replication?
Conservative keeps original strands together; semi-conservative combines old and new strands.
What is the role of CFTR protein and what happens in a mutation?
CFTR is a channel protein. It transports chloride ions out of cells and into mucus — this causes water to move into the mucus by osmosis, which makes mucus watery. Mutant CFTR protein is much less efficient at transporting chloride ions out of the cell, so less water moves out by osmosis. This makes the mucus of people with CF abnormally thick and sticky. This thick and sticky mucus causes problems in the respiratory, digestive and reproductive systems.
What are proteins made from?
Proteins are made from long chains of amino acids. or one or more polypeptides chains
What is the difference between facilitated diffusion and active transport?
Active transport uses energy to move molecules against a concentration gradient, while facilitated diffusion does not.
What is diffusion?
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
difference between channel and carrier proteins
Channel proteins only transport charged particles
carrier proteins transport both
What happens during translation
amino acids are joined together to
make a polypeptide chain (protein), following the sequence of codons carried by the mRNA.
flicks equation what does it mean
rate of diffusion ∝ area of diffusion surface × difference in concentration/ thickness of diffusion surface
The ‘proportional to’ bit means that the rate of diffusion will double if:
* the surface area or the difference in concentration doubles, OR
* the thickness of the surface halves.
The bonds formed between amino acids are called
peptide bonds
How is the Reproductive System affected by CF
In some men with CF, the tubes connecting the testicles (where sperm are produced) to the penis are absent
and can become blocked by the thick mucus in others. So, any sperm produced can’t reach the penis.
In women, thickened cervical mucus can prevent the sperm from reaching the egg. The sperm has to travel
through this mucus to reach the egg — thick mucus reduces the motility of the sperm, reducing its chances
of making it to the egg.
Carrier
If a recessive allele can cause disease, a carrier is someone who has one dominant and one recessive allele
(heterozygous). They won’t have the disease but they carry a copy of the allele for the disease.
How long does it take to get results from CVS
Initial results (which tell you whether any obvious major issues have been found) are availablein a few days, but the results of more in-depth and detailed tests can take two weeks or more.
draw and describe the structure of DNA mononucleotdie
The pentose sugar in a DNA mononucleotide
is called deoxyribose.
Each DNA mononucleotide has the same sugar and a phosphate group. The base on
each mononucleotide can vary though.
There are four possible bases — adenine (A),
thymine (T), cytosine (C) and guanine (G).
What can alter the tertiary structure of an enzyme?
Changes in pH or temperature can alter the tertiary structure of an enzyme.
What does cystic fibrosis affect
respiratory, digestive and reproductive systems.
Genotype
The alleles a person has, e.g. BB, Bb or bb for eye colour.
How You Can Measure How Fast the Product of the Reaction is Made
Catalase catalyses the breakdown of hydrogen peroxide into water and oxygen. It’s easy to measure thevolume of oxygen produced and to work out how fast it’s given off. Using this reaction, you can investigate
the effect of changing the enzyme concentration on the initial rate of reaction — the diagram below showsthe apparatus you’ll need. (You’ll also need a stand and clamp to hold the cylinder upside down, as well as a stopwatch.) During the experiment, the oxygen released displaces the water from the measuring cylinder. You’ll need to decide on a range of catalase concentrations to investigate before you start. Add a set volume and concentration of hydrogen peroxide to a boiling tube. To keep the pH constant, add a set amount of a suitable buffer solution to the tube. (A buffer solution is able to resist changes in pH when small amounts of acid or alkali are added.)
Set up the rest of the apparatus as shown in the diagram. Use a pipette to add a set volume of one of the concentrations of catalase to the boiling tube.
Then quickly attach the bung and delivery tube. Record the volume of oxygen produced in the measuring cylinder every ten seconds for the first minute (60 s) of the reaction. Use a stopwatch to measure the time. Repeat the experiment twice more, and find the average
volume of oxygen produced at each ten second interval. Plot your data on a graph of volume of oxygen produced (cm3) against time (seconds) and draw a tangent (see next page) to determine the initial rate of the reaction. Repeat the whole experiment at each of the other catalase concentrations under investigation. You can then compare the initial rate of the reaction for each
concentration to determine the effect of changing the enzyme concentration on the initial rate of reaction.
How does DNa replicate
Semi-Conservative Replication
melson and sthal experiment
two samples of bacteria were grown — one in a
nutrient broth containing light nitrogen, and one in a
broth with heavy nitrogen. As the bacteria reproduced,
they took up nitrogen from the broth to help make
nucleotides for new DNA. So the nitrogen gradually
became part of the bacteria’s DNA.
A sample of DNA was taken from each batch of
bacteria, and spun in a centrifuge. The DNA from
the heavy nitrogen bacteria settled lower down the
centrifuge tube than the DNA from the light nitrogen
bacteria — because it’s heavier.
Then the bacteria grown in the heavy nitrogen broth
were taken out and put in a broth containing only light
nitrogen. The bacteria were left for one round of DNA
replication, and then another DNA sample was taken
out and spun in the centrifuge.
If replication was conservative, the original heavy
DNA, which would still be together, would settle at the
bottom and the new light DNA would settle at the top.
If replication was semi-conservative, the new bacterial
DNA molecules would contain one strand of the old
DNA containing heavy nitrogen and one strand of new
DNA containing light nitrogen. So the DNA would
settle out between where the light nitrogen DNA settled
out and where the heavy nitrogen DNA settled out.
As it turned out, the DNA settled out in the middle,
showing that the DNA molecules contained a mixture
of heavy and light nitrogen. The bacterial DNA had
replicated semi-conservatively in the light nitrogen.
Explain mRNA
- Made in the nucleus during transcription.
- Three adjacent bases are called a codon.
- It carries the genetic code from the DNA
in the nucleus to the cytoplasm, where it’s
used to make a protein during translation.
What happens when there are more enzyme molecules than available substrate?
The more enzyme molecules there are in a solution, the more active sites
are present and therefore the more likely a substrate molecule is to collide
with an active site and form an enzyme-substrate complex. So increasing
the concentration of the enzyme increases the rate of reaction.
But, if the amount of substrate is limited, there comes a point when there’s
more than enough enzyme molecules to deal with all the available substrate,
so adding more enzyme has no further effect. Substrate concentration has
become a limiting factor.
What enzyme unwinds DNA during replication?
DNA helicase
Carrier proteins function and process
Move large molecules into or
out of the cell, down their concentration gradient. Different carrier proteins facilitate the diffusion of different molecules.
1) First, a large molecule attaches to a
carrier protein in the membrane.
2) Then, the protein changes shape.
3) This releases the molecule on the
opposite side of the membrane.
Why is the genetic code described as degenerate?
there are more possible combinations of triplets than there are amino acids (20 amino acids but 64 possible triplets). This means that some amino acids are coded for by more than one base triplet,
What isotopes were used in Meselson and Stahl’s experiment?
Heavy nitrogen (15N) and light nitrogen (14N).
What are peptide bonds?
The bonds formed between amino acids are called peptide bonds.
What determines the shape of an enzyme’s active site?
The shape of the active site is determined by the enzyme’s tertiary structure, which is influenced by its primary structure.
Two types of enzymes and what do they do
Enzymes can be intracellular (catalyse reactions inside cells) or extracellular
(produced and secreted by cells to catalyse reactions outside cells).
How does gas exchange work in the lungs
Oxygen diffuses out of the alveoli, across the alveolar epithelium (a layer of thin, flat cells) and the capillary endothelium (a type of epithelium that forms the capillary wall), and into the blood. Carbon dioxide diffuses into the alveoli from the blood and is breathed out.
What causes cystic fibrosis in the first place
Cystic fibrosis is caused by a mutation in the gene that codes for the CFTR protein (Cystic Fibrosis Transmembrane Conductance Regulator).
What does flicks law relate
Fick’s Law relates the rate of diffusion to the concentration gradient, the surface area and the thickness of the
exchange surface. It states that:
What is a partially permeable membrane?
A membrane that allows some substances to pass while blocking others.
What is the chance of a child having cystic fibrosis if both parents are carriers?
25% chance of the child having cystic fibrosis.
What are the social and ethical issues of prenatal testing
- Prenatal tests slightly increase the risk of miscarriage.
- False results could provide incorrect information.
- Some people consider it unethical to abort a fetus because it has a genetic disorder.
What is a Gene
A sequence of bases on a DNA molecule that codes for a protein, which results in a characteristic, e.g. the gene for eye colour
How are polypeptides formed?
Polypeptides are formed by condensation reactions between amino acids.
Who determined the double-helix structure of DNA?
James Watson and Francis Crick determined the structure in 1953.
What is chorionic villus sampling (CVS)?
performed around11-14 weeks of pregnancy.
A sample of cells is taken from the chorionic villi (part of the fetus that connects it to its mother). The cells contain fetal DNA, which can be analysed. This procedure is done via either the abdomen (using a fine needle) or the vagina (using a catheter — a thin flexible tube).
Incomplete Dominance
When the trait from a dominant allele isn’t completely shown over the trait produced by the recessive allele,
so both alleles influence the phenotype. Some flowers show incomplete dominance,
e.g. snapdragons can have alleles for red flowers (RR), white flowers (rr) or pink flowers (Rr).
What is genetic continuity in context of DNA replication
during semi- conservative replication half of the strands in each new DNA molecule are from the original DNA molecule. This means that there’s genetic continuity between generations of cells
What is net movement
The overall movement of particles
Describe the whole process of transcription
During transcription an mRNA copy of a gene is made in the nucleus:
Transcription starts when RNA polymerase
(an enzyme) attaches to the DNA double-helix
at the beginning of a gene (start codon).
The hydrogen bonds between the two DNA strands
in the gene break, separating the strands, and the
DNA molecule unwinds at that point.
One of the strands is then used as a template
to make an mRNA copy.
The RNA polymerase lines up free RNA mononucleotides
alongside the template strand. Complementary base pairing means
that the mRNA strand ends up being a complementary copy of the
DNA template strand (except the base T is replaced by U in RNA).
Once the RNA mononucleotides have paired up
with their specific bases on the DNA strand
they’re joined together by RNA polymerase,
forming an mRNA molecule.
The RNA polymerase moves along
the DNA, separating the strands and
assembling the mRNA strand.
The hydrogen bonds between the unwound
strands of DNA re‑form once the RNA
polymerase has passed by and the strands
wind back up into a double-helix.
When RNA polymerase reaches a stop codon
(see previous page) it stops making mRNA
and detaches from the DNA.
The mRNA moves out of the nucleus through
a nuclear pore and attaches to a ribosome in
the cytoplasm, where the next stage of protein
synthesis takes place
What are mutations and what do they do
Mutations are changes to the base sequence of DNA during replication. They can be caused by errors during DNA replication
What is a polynucleotide
its a polymer of mononucleotides.
Both DNA and RNA mononucleotides form
polynucleotides.
What is an active site?
The specific part of an enzyme where substrate molecules bind.
What is a gene?
A sequence of mononucleotide bases on a DNA molecule that codes for amino acids in a polypeptide.
What did Meselson and Stahl’s experiment provide evidence for?
Semi-conservative replication of DNA.
what is The phospholipid bilayer described as
‘fluid mosaic’
The scattered pattern produced by the components within the phospholipid bilayer looks some what like a mosaic when viewed from above The mosaic of phospholipids and proteins can move around within the bilayer by diffusion, hence the mosaic is said to be ‘fluid’ The phospholipids mainly move sideways, within their own layer
The many different types of proteins interspersed through out the bilayer move about within it, although some may be fixed in position
cholesterol function in the membrane
Cholesterol can be found between the phospholipids, where it regulates membrane fluidity
Cholesterol increases the fluidity of the membrane at low temperatures, stopping it from becoming too rigid This occurs because cholesterol stops the phospholipid tails packing too closely together
Interaction between cholesterol and phospholipid tails also stabilises the cell membrane at higher temperatures by stopping the membrane from becoming too fluid
Cholesterol increases the mechanical strength and stability of membranes; without it membranes would break down and cells would burst
What cell membranes do
The cell surface membrane creates an enclosed space separating the internal cell environment from the external environment,
Membranes do not only separate different areas but also control the exchange of substances from one side of a membrane to the other, as well as acting as an interface for communication
What are the two types of prenatal tests?
Amniocentesis and chorionic villus sampling.
what do Genetic diagrams do
can be used to predict the genotypes and phenotypes of the offspring produced if two parents are crossed (bred).You need to be able to interpret genetic diagrams for characteristics
What are some social and ethical issues of carrier testing?
Emotional stress(knowing your a carrier), false results, discovery of other genetic abnormalities, and potential genetic discrimination.
What is released during the formation of polypeptides?
A molecule of water
similarity between endocytosis and exocytosis
They both require ATP
What are start and stop codons?
triplets are used to Signal the beginning and end of protein production. and found at the beginning and at the end of the gene
What is Inversion
a sequence of bases is reversed, e.g. ATGCCT becomes ATGTCC (CCT is reversed).
What happens if a mutation occurs in a gene?
it can cause a genetic disorder, which is then passed on.
E.g. cystic fibrosis (CF) is a genetic disorder caused by a mutation in a gene. The protein the gene codes for is important for mucus production
What do ribosomes do?
Ribosomes are the body’s
‘protein factories’ — they read the RNA to make polypeptides (proteins) in a process called translation. Ribosomes themselves are made from RNA and proteins.
What is the risk of miscarriage with CVS?
1-2%, which is greater than with amniocentesis.
Homozygote
An organism that carries two copies of the same allele for a certain characteristic, e.g. BB or bb.
Exocytosis function and process
Some substances produced by the cell (e.g. digestive enzymes, hormones, lipids) need to
be released from the cell — this is done by exocytosis.
Vesicles containing these substances pinch off from the sacs of the Golgi apparatus and move towards the cell membrane.
The vesicles fuse with the cell membrane and release their contents outside the cell.
Some substances (like membrane proteins) aren’t released outside the cell — instead they are inserted straight into the cell membrane.
Exocytosis uses ATP as an energy source.
