Genetics, Evolution & Ecology P2 Flashcards
State two differences between structure of DNA and RNA
Deoxyribose vs. ribose; thymine vs. uracil; 2 strands vs. 1 strand;
State the names of the structures above.
State the name of a structure on the diagram that has an anticodon.
I: Small sub-unit of ribosome;
II: Large subunit of ribosome;
III: tRNA;
IV: mRNA;
tRNA
Explain why the process used during protein synthesis is called translation.
Each codon in an mRNA molecule (nucleic acid) codes for one amino acid (protein structural unit); hence, genetic code has to be translated;
Explain briefly how termination of translation occurs.
Stop codon reached; polypeptide released; mRNA detaches from ribosome; ribosome subunit separates;
A gene in humans called APC is located on chromosome 5. This gene controls cell division and is known as a tumour suppressor gene. Mutations of APC cause a genetic disease called FAP (Familial Adenomatous Polyposis).
State, with a reason, whether FAP is a sex-linked genetic disease or not.
50% of the gametes produced by a person with FAP have an APC gene with the mutation. Identify, with a reason, whether FAP follows a dominant or recessive pattern of inheritance.
In a person with FAP, each cell contains a copy of the APC gene with the mutation. If a mutation occurs on the cell’s other copy of the APC gene, the cell becomes a tumour cell. Almost everyone with FAP develops cancer before the age of 50. Explain why almost everyone with FAP eventually develops cancer.
Not sex-linked because gene is on an autosome.
Dominant; because person with FAP is heterozygous;
Mutation only has to occur once; tumour develops from one cell; all cells in body could become tumour cells; tumour formation not suppressed if both copies of APC gene in cell are mutant.
In 2004, doctors in Britain were given permission to test embryos to see whether an APC gene with the mutation is present. This test can be used where one of the parents is known to have FAP. The procedure involves the parents using in-vitro fertilisation (IVF) to produce embryos, testing the embryos for the gene and implanting only embryos that do not have the mutation.
State the name of this test.
State one advantage and one disadvantage of testing embryos in this way.
Genetic Screening
Advantage: Prevent birth of children with FAP / Eliminate mutation from population / Reduce stress for parents
Disadvantage: Allows selection of embryos for implantation (unethical) / leads to euthanising of embryos with mutation (unethical) / expensive procedure.
Outline the role of variation in evolution.
Members of population show variation;
Variation occurs as a result of meiosis or mutation; Some variations allow an individual to be better adapted; and survive to reproductive age; which leads to evolution, the cumulative increase in frequency of advantageous alleles over time;
Explain how polygenic inheritance leads to continuous variation.
Polygenic inheritance is when a characteristic/ phenotype is determined by >1 gene;
As the number of genes involved increases, the number of intermediate phenotypes increases;
causing phenotypes to become continuous;
Define the term community as it relates to ecosystems.
Community: Group of populations living (and interacting with each other) in an area.
Define allele.
Alternative forms of a gene on the same locus.
Outline the consequences of a base substitution mutation.
Base substitution mutations change codon; and thus may cause coding for different amino acid; and therefore a different primary structure, which may cause sequence to code for a different protein;
An example of this is sickle cell anaemia, which causes faulty red blood cells to be produced;
Mendel crossed tall, round-seeded plants with short, wrinkled-seeded plants. All F1 produced were tall, round-seeded plants. When F1 plants were crossed with other F1 plants, the F2 generation produced many more than 1/16 short, wrinkled-seeded plants.
Deduce, with reasons, the inheritance of these genes.
The same cross was later repeated but gave fewer F2 short, wrinkled-seeded plants although still more than 1/16. Outline a named statistical test that could indicate if your deduction about the inheritance of these two genes is likely to be correct.
Dihybrid cross would give 9:3:3:1 ratio in this F2 if genes not linked; therefore the genes are linked; more homozygous recessive offspring / 3:1 ratio expected if linked; (only 2 marks)
chi-squared (test); compares observed and expected values/results; producing a (chi-squared) value; a statistical table is used to determine probability of genes being linked or not;
Suggest one role of bacteria in a soil ecosystem.
Decomposers / recycle nutrients / cause decay / nitrification / nitrogen fixation / denitrification.
List two examples of how human life depends on mitosis.
Growth and production of body cells rely on mitosis;
1st stage of gametogenesis requires oogonia/ spermatogonia to undergo mitosis;
Embryo development;
Wound Healing/Tissue repair;
Clonal selection;
Outline the bonding between DNA nucleotides.
H-bonds between complementary bases; covalent/phosphodiester bonds between deoxyribose and phosphate of neighbouring nucleotides;
