DNA bio Flashcards
what is the role of DNA?
to hold the genetic info of a cell
what are chromosomes
thread like structures in the cell containing DNA
what is DNA
deoxyribonucleic acid - a sequence that determines how our bodies are made
what are the four chemicals found in DNA that make up the base sequence (and what are they called)
DNA bases - A, T, C and G
What is the shape of DNA
a double helix - two strands of nucleotides that wind up around each other (like a twisted ladder)
what is the entire genetic material of an organism called?
genome
What is the definition of genetic code
sequence of bases within the DNA that (ultimately) codes for proteins
what is a gene?
section of DNA that contains instructions for a particular characteristic
DNA is a polymer - which means..?
it is made of repeating sub-unite (monomers)
what does 1 DNA nucleotide (monomer contain)
- phosphate group
- 5 carbon sugar (ribose/deoxyribose)
- organic nitrogenous base
DNA has ? strands. these strands run ? to each other. each strand has a ? - phosphate backbone which are held together by ? bonds. the 2 strands are held together by ? bonds between bases
2, anti parallel, sugar, phospodiester, hydrogen
how many hydrogen bonds bond A and T togther
2H bonds
why do A and T bond together
as they always pair - since they are complementary
how many bonds between C and G bases?
3H bonds
why does DNA spiral into a double helix?
in order to protect the bases in the centre - as if exposed to pathogens or carcinogens they could mutate and code for the wrong proteins
what are the two steps in protein synthesis? and what does DNA change to?
transcription - DNA —»> mRNA
translation - mRNA —»> protein
where does transcription happen and what is the first step?
happens in the nucleus, DNA unwinds out of double helix - into a coding strand and a template strand
most ? codes for proteins, which are called ? . some DNA ? not code - it is a binding site for ? . this section is called an ? . both of these sections are ?
DNA, exons, does, enzymes, intron, transcribed
why can’t DNA leave the nucleus?
it is too big - and is double stranded
what part of DNA unwinds out of double helix?
only the section being coded for
- ? polymerase binds to the intron and ? the DNA template strand
- complementary ? nucleotides line up along the DNA ? strand - these are joined up by ? bonds
- this has built a ? strand - called mRNA
- introns are cut off the ?
- mRNA leaves nucleus to go to ?
RNA, ‘reads’, RNA, template, phosphodiester, single, mRNA, ribosomes
base ‘T’ doenst exist in RNA so what is it replaced by?
‘U’ - uracil
the 3 bases on mRNA are called?
a codon
the 3 bases on mRNA are called?
a codon
the 3 bases on tRNA are called?
an anticodon
first 3 steps of translation:
1. mRNA moves to the ?
2. ribosome reads the ? in groups of 3 bases - a ?
3. tRNA molecule ( carrier ? ) binds to the ? with the complementary anticodon for the first mRNA ?. attached to the tRNA is the corresponding ? acid for the mRNA codon
ribosomes
mRNA, codon
molecule, mRNA, codon, amino
first 3 steps of translation:
1. mRNA moves to the ?
2. ribosome reads the ? in groups of 3 bases - a ?
3. tRNA molecule ( carrier ? ) binds to the ? with the complementary anticodon for the first mRNA ?. attached to the tRNA is the corresponding ? acid for the mRNA codon
ribosomes
mRNA, codon
molecule, mRNA, codon, amino
last 5 steps of translation
- ribosome ‘reads’ the next ?. the tRNA binds to the ? codon with its ?. a second amino ? lines up.
- a peptide (strong ? bond) forms between amino ?. the 1st ? can now leave
- a ? amino acid is brought in and attached to the ? with a complementary anticodon to mRNA ?. A peptide ? forms
- once all the ? had been ‘read’ the ? detaches. there is a chain of ? acids left held togther by ? bonds
- many amino acids are called a ?. this folds into a ? shape to become a functioning ?
- codon, mRNA, anticodon, acid,
- covalent, acids, tRNA
- third, tRNA, codon, bond,
- mRNA, ribosome, amino, peptide
- polypeptide, 3D, Protein
what does the t in tRNA stand for
transfer
what does the m in mRNA stand for
messenger
how many bases code for 1 amino acid?
3 bases (one codon)
a change in the DNA base sequence what is this the definition of?
a mutation
what can cause mutations?
pathogens/carcinogens
why can mutations be harmful?
if a mutation occurs in a ? cell it may lead to ?. if a mutation occurs in a sperm or ? it can lead to the offspring having a genetic ?
body, cancer, egg, disorder
how could mutations cause a change in the protein (exons)
- could cause a change in the DNA base sequence
- therefore a different mRNA codon
- so a different amino acid to be coded for
- so our polypeptide chain may be different
- protein would fold up into a different 3D shape and may not function as normal
If the protein was an enzyme, why might a different 3D shape be a problem?
Different ? shape means different shaped active ?, so active ? is no longer ? to the substrate. Therefore no binding so no ? or reaction
3D, site , site, complementary, breakdown
what is a truncated protein?
when a mutation makes a stop ?, to stop building the ? - preventing it from working at ? - meaning it doesn’t code for an ? acid
signal, protein, all, amino
what is a silent mutation?
when a mutation in ? does ? code for a different ? acid - so the ? is made exactly the same as if there was no mutation. and if it was coding for an ? it may not lose its function
DNA, not, amino, protein, enzyme
if there is a mutation in the intron which means that the enzyme cannot bind where it should what does this mean?
the gene is switched off wheee it should not be - and if the enzyme can’t bind - no protein is made eg antibodies and no substances are broken down
if a mutation in an intron means that the RNA polymerase can bind where it should not be able to what does this mean?
the gene is switched on when it should be off - meaning there is a waste of energy (prioritizing making useless protein), lack of protein that we do need and excess protein may also be toxic
what is an allele?
a different version/ form of a gene
if an allele is dominant how many copies does the cell need for the trust to be expressed?
only one copy
if an allele is recessive how many copies does the cell need for the trust to be expressed?
two copies
what is homozygous dominant?
2 dominant alleles
what is homozygous recessive?
2 recessive alleles
what is heterozygous?
1 dominant and 1 recessive allele
how to do a model diagram for alleles?
1. name the parents ? - what they look like eg green and ?
2. name the ? genotype - the ? eg: EE and ee
3. do the ? in circles eg: ‘E’ and ‘E’ in circles
4. do a ? square - like a multiplying column
5. do f? generation
6. do genotypes and then ? of the generation
7. do the ? of colours, or genes
phenotype, yellow
parents, letters
gametes
punnet
1
phenotypes
ratio
in genetics what do the two alleles come from?
one from the maternal, one from the paternal - they are homologous
what is a phenotype?
what the gene looks like, how it is expressed
what is a genotype?
the letters, showing if it is homozygous recessive/dominant or heterozygous
who was Mendel?
father of genetics
why did we only understand how important mendels discoveries were in 20th century?
- as we did not have the understanding of genetics to appreciate his findings
- other members of the scientific community did not have time to review his work
what is sickle cell anaemia caused by?
a recessive allele
what does it mean if a person is a carrier of a disorder?
they aren’t very much affected by the disorder they just carry it, but it also means the allele must be recessive
what is polydactyl caused by and what is it?
caused by a dominant allele so only need one to have it, and it is a condition where a person has extra fingers or toes
what is cystic fibrosis?
a disease that affects the cell membrane - meaning mucus is sticker and stickier than usual, making it difficult to breathe (and moving substances in and out of a cell can be difficult)
what is cystic fibrosis caused by?
a recessive allele
what chromosomes do females have?
XX
what chromosomes do males have?
XY
how to prove that the population is made up of roughly 50% females and 50% males
do a punnet square for female and male and work out there is 50% XX and 50% XY
what is embryo screening?
the process whereby a ? cells are taken from the embryo produced by ? and are checked for ? genes
few, IVF, defective
what does embryonic screening NOT do but do instead?
DOES NOT alter the genetic sequence, but does and can detect if the developing embryo is likely to develop a genetic disorder
4 steps of embryo screening:
- DNA is isolated from ?
- ? probe is mixed with the ? DNA
- probe then binds to ?
- ? light can be used to show if the alleles are ? for a genetic ?
embryo
fluorescent, embryo
DNA
UV, present, disorder
4 pros of screening?
- defective genes may lead to a decreased life expectancy ( meaning a decreased quality of life) so can irradiate this genetic disorder
- could take away suffering from sufferer and caters from a particular disease
- very carefully monitored, can only be done for a select number of genes
- less need for healthcare if you take out the defective gene
cons of screening? (4 examples)
- potential selection of embryos for social reason, eg a child with blue eyes
- embryos that aren’t chosen can be frozen or destroyed
- expensive - high insurance, socio economic divide
- defective gene may not have immediate life threatening consequences
what was the human genome project?
when scientists mapped the typical human genome, could determine which genes were linked to which diseases. also what mutations leads to the development of the disease phenotype
pros (4)of the human genome project?
- better understanding of what mutation causes what disease
- personalized medicine more likely to work
- improved scientific comms/collaboration
- better understanding of evolution
cons(4) if human genome project?
- very expensive - personalised medicine (socio economic divide) and project itself, and insurance
- increased knowledge doesn’t mean it can solve the problem
- takes a very long time!
- risk of editing for non essential reasons, eg: eye colour
