Inheritance - DNA Flashcards
Where is DNA found
in the chromosomes
what is DNA
a polymer made up of two strands forming a double helix
why is DNA our genetic material
because our DNA determines our inherited features
what is a gene
a small section of DNA on a chromosome
how are proteins made
by joining together amino acids
what do genes do
each gene codes for a specific sequence of amino acids to make a specific protein
what is the genome
the entire genetic material of an organism
what are the benefits of the human genome
- understanding the human genome will help us search for genes that are linked to a specific disease, e.g - genes that are linked to cancer or Alzheimer’s
- Understanding the human genome may help us understand and treat inherited disorders such as Cystic fibrosis
- We can use the human genome to trace human migration patterns from the past, and this can help people discover their ancestry
what are DNA strands made from
nucleotides
what are nucleotides made up of
- a sugar
- a phosphate
- a base
what does the circle represent in a nucleotide
the phosphate group
what does the pentagon represent in a nucleotide
the sugar
what does the rectangle represent in a nucleotide
the base
what does complementary mean in terms of DNA bases
the same bases always pair on opposite strands
which bases pair to which in DNA
A and T pair
C and G pair
how many different amino acids are there in humans
20
what is the order of amino acids in a protein determined by
the sequence of bases in the gene for that protein
Stages of protein synthesis
- Proteins are made in the cell cytoplasm on tiny structures called ribosomes
- To make proteins, ribosomes use the code in the DNA, and dna is found in the nucleus, and cant move our as its too big, so the cell needs to get the code from the DNA to the ribosomes
- This is done using a molecule called mRNA which is made by copying the code from the DNA. The mRNA acts as a messenger between the DNA and ribosomes- carrying the code between the two
- the correct amino acids are brought to the ribosomes in the correct order by carrier molecules
what are proteins
polymers of amino acids
what does the order of amino acids in a protein determine
its shape and function
what is mRNA
a single stranded molecule
what is a mutation
a change to a base of DNA
why might mutations not change an amino acid sequence
because different base triplets can sometimes encode for the same amino acid
why might a mutation which changes the shape of a protein, have a massive effect on it
- because the active site of the enzyme may change shape, so it’ll no longer attach to the substrate
- if the mutation changes the shape of a structural protein such as collagen, it may lose it’s strength
what do non coding parts of DNA do
they switch genes on and off, they tell genes when to produce proteins
what would happen if a non - coding part of DBA was mutated
a gene may be turned off when it’s meant to be turned on, or vice versa
- meaning a cell would produce a protein that its not meant to have at the time
- this could have a very significant effect on the cell, eg uncontrolled mitosis leading to cancer
what are alleles
versions of genes
what is a genotype
something that tells us what alleles are present in a person
meaning of homozygous alleles
having two copies of the same allele
what is a phenotype
something that tells us the characteristics caused by the persons alleles
what is heterozygous
when someone has two different alleles
what is a dominant allele
an allele that will show in the phenotype even if there is only one copy present
what is a recessive allele
an allele that will only show in the phenotype if two copies are present( so if no dominant alleles are present)
what is cystic fibrosis
a disorder of the cell membranes
what needs to happen in order for a person to have cystic fibrosis
they need to have two copies of the defective allele
what is meant by a carrier of cystic fibrosis
when a person has one defective allele and one normal allele
What is polydactyly
a disorder where someone is born with extra fingers or toes
what type of allele is polydactyly caused by
dominant
what is embryo screening
a process in which embryos are tested to see if they have the alleles for inherited disorders
how does embryo screening work
- cell is taken out of and embryo is tested to see if it has the alleles for an inherited disorder
- Embryo which do not have the defective alleles are implanted into the woman
- These can help them develop healthy offspring
what are issues around embryo screening
- its expensive, and people think that the money should be spent elsewhere un the health service
- implies that people with genetic problems are undesirable and this may cause prejudice
- in the future we may be able to screen embryos to produce offspring with desirable features, this is also unethical
- often, a large number of embryos are created, but only a small number are implanted, meaning that some healthy embryo are destroyed and people think its unethical
what is gene therapy
- correcting faulty alleles and using these to treat inherited disorders
what chromosomes do males have
XY
what chromosomes do females have
XX
where does the first stage of protein synthesis happen
nucleus
where does the second stage of protein synthesis take place
cytoplasm
Summarise the stages of protein synthesis
- Transcription - the base sequence of the gene is copied into a complementary template molecule
- scientists call this template mRNA and it is a single stranded molecule
- the mRNA then passes out of the nucleus into the cytoplasm
- Translation - In this stage, the mRNA molecule attaches to a ribosome. amino acids are then brought to the ribosome on carrier molecules
- these carrier molecules are called tRNA
- the ribosome then reads the triplets of bases on the mRNA and uses this to join the correct amino acids in the correct order
- once the protein chain is complete, it now folds into its unique shape
what happens when a protein formed
it folds into a unique shape
What has to happen in order for someone to inherit cystic fibrosis
The person has to have two copies of the defective allele
Why aren’t punnet squares that accurate?
Because they are just probabilities
how do DNA bases in a gene code for specific chains of amino acids
- each sequence of the three bases codes for one specific amino acids, so the order of the bases in the gene decides the order of amino acids in the chain
advantages of embryo screening
- will help people stop suffering from genetic disorders
- treating these disorders. it’s the government and taxpayers a lot of money, screening to reduce the number of people suffering from these disorders could save money
- parents can’t use it to select desirable characteristics as there are laws to stop screening going to far
