DNA bio Flashcards by Moji Shorrock

what is the role of DNA?

to hold the genetic info of a cell

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what are chromosomes

thread like structures in the cell containing DNA

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what is DNA

deoxyribonucleic acid - a sequence that determines how our bodies are made

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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

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What is the shape of DNA

a double helix - two strands of nucleotides that wind up around each other (like a twisted ladder)

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what is the entire genetic material of an organism called?

genome

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What is the definition of genetic code

sequence of bases within the DNA that (ultimately) codes for proteins

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what is a gene?

section of DNA that contains instructions for a particular characteristic

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DNA is a polymer - which means..?

it is made of repeating sub-unite (monomers)

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what does 1 DNA nucleotide (monomer contain)

phosphate group
5 carbon sugar (ribose/deoxyribose)
organic nitrogenous base

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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

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how many hydrogen bonds bond A and T togther

2H bonds

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why do A and T bond together

as they always pair - since they are complementary

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how many bonds between C and G bases?

3H bonds

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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

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what are the two steps in protein synthesis? and what does DNA change to?

transcription - DNA —»> mRNA
translation - mRNA —»> protein

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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

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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

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why can’t DNA leave the nucleus?

it is too big - and is double stranded

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what part of DNA unwinds out of double helix?

only the section being coded for

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? 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

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base ‘T’ doenst exist in RNA so what is it replaced by?

‘U’ - uracil

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the 3 bases on mRNA are called?

a codon

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the 3 bases on mRNA are called?

a codon

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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

last 5 steps of translation 4. ribosome ‘reads’ the next ?. the tRNA binds to the ? codon with its ?. a second amino ? lines up. 5. a peptide (strong ? bond) forms between amino ?. the 1st ? can now leave 6. a ? amino acid is brought in and attached to the ? with a complementary anticodon to mRNA ?. A peptide ? forms 7. once all the ? had been ‘read’ the ? detaches. there is a chain of ? acids left held togther by ? bonds 8. 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?

what chromosomes do males have?

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