Unit 2.3 - DNA and Inheritance Flashcards
Describe the structure of DNA.
Two long chains of alternating sugar and phosphate molecules, held together by pairs of bases called adenine, thymine, cytosine and guanine, twisted into a double-helix shape.
Describe the role of the Triplet Code in protein synthesis.
Each triplet of three base pairs codes for a particular amino acid; in the cytoplasm, these triplet codes are used to identify and link amino acids together - the order of the amino acids determines the shape of the protein.
Explain the term Complimentary Base Pairing.
A (Adenine) always pairs with T (Thymine) and C (Cytosine) always pairs with G (Guanine).
Describe the four stages in the process of genetic profiling.
Isolation - DNA is separated from other tissues.
Fragmentation - an enzyme is used to break the DNA into short lengths
Separation - pass an electric current across a layer of gel which has the DNA fragments at one end. The fragments will move different distances across the gel (gel electrophoresis).
Comparison - match the patterns on the gel with other samples of DNA.
Name three uses of genetic profiling (comparing different samples of DNA via genetic profiling)
Paternity cases, criminal cases, and comparisons between species for classification purposes.
Discuss the benefits of genetic profiling.
It is highly unlikely that two individuals would have the same DNA - it can be used to identify genetic disorders early and reduce suffering; can be used to solve crimes by placing suspects at the scene of the crime.
Discuss the disadvantages of genetic profiling.
Insurance companies or employers may refuse service/jobs to those with genetic disorders if they obtained that information; DNA can be planted at the scene of a crime, giving fake evidence; DNA databases are seen as an invasion of privacy and DNA could be stolen.
Define the term ‘gene’.
Genes are short sections of DNA which code for particular proteins and therefore determine inherited characteristics.
Define the terms ‘dominant,’ ‘recessive,’ ‘homozygous,’ and ‘heterozygous.’
Dominant - an allele which is expressed in the heterozygote
Recessive - an allele which is only expressed if the individual has two copies and does not have a dominant allele.
Homozygous - alleles are both identical for the same characteristic (e.g. AA or aa)
Heterozygous - alleles are both different for the same characteristic (e.g. Aa)
Define the terms ‘genotype,’ ‘phenotype,’ ‘F1,’ ‘F2,’ and ‘selfing.’
Genotype - the alleles that an organism has for a particular characteristic (expressed as two letters)
Phenotype - the visible features or characteristics that an organism has, coded for by its genes.
F1 - The first generation of a genetic cross.
F2 - The second generation of a genetic cross.
Selfing - when pollen from one plant lands on the stigma of the same plant (so the plant breeds with itself).
Why is the use of Punnett Squares over-simplistic?
Most phenotypic features are the result of multiple genes rather than single gene inheritance.
Explain the role of chromosomes in sex determination.
One of the pairs of chromosomes, XX or XY, contains the genes that determine sex, and these separate and combine randomly at fertilisation.
Define the term ‘genetic modification.’
The artificial transfer of genes from one organism to another, including to an organism of a different species.
Describe the benefits/uses of genetic modification.
In crops: herbicide/disease resistance, increased yield and modification to produce particular substances, e.g. Vitamin A.
Describe the arguments against genetic modification.
Accidental modification of other organisms, e.g. creating a ‘super-weed’ by pollination of weeds by a herbicide-resistant plant; concerns over effects on health; some GM crops are owned by large companies, so they control the price; less reliance on crops from third-world countries, harming their economies.
