Mock Exam Revision Flashcards
How does the genetic code relate to DNA?
The genetic code is carried on the DNA which is found in the chromosomes.
What is the genetic code?
Fertilisation creates a single cell (zygote) - this cell contains the instructions for the growth and development of the full organism.
The bases of a gene are read in sets of three (triplets). Each triplet codes for an amino acid which forms a protein.
Explain the relationship between DNA, alleles, genes, and chromosomes.
DNA is the molecule that carries the genetic code, it is coiled into chromosomes which are long strands of DNA containing a specific set of genetic information. Genes are specific segments of DNA on a chromosome which code for proteins using it’s unique base sequence. Alleles are alternative versions of genes and are created by variation in the base structure.
What is a mutation and how does it create genetic variation?
A mutation is a permanent change in the DNA. It changes the base sequence which codes for a protein (trait). These changes in the base sequence form alleles which creates genetic variation.
True or False
Mutations aren’t passed on when they occur in somatic (body) cells, but they are passed on when they occur in gametic cells.
True
How does sexual reproduction cause genetic variation.
Sexual reproduction utilises meiosis (crossing over and independent segregation) which means offspring are a combination of both parents’ genes/alleles.
What could result from small population sizes?
Inbreeding and inbreeding depression.
Why do larger population sizes have better genetic variation than smaller populations?
Larger populations have a higher number of different alleles. More individuals are reproducing, increasing the likelihood of mutations.
What could cause small population sizes?
Population bottlenecks (when a population experiences a decrease in population due to a catastrophic event) or the founder effect (when a small group breaks off from a larger population and starts a new one).
What is natural selection?
The fittest organisms are more likely to survive and pass their genes onto their offspring, producing a population better suited to the environment.
How can genetic variation cause phenotypic variation?
Differences in the genetic code code for different amino acids which create different traits (phenotypes)
Is environmental change to phenotype inherited?
No
Why is genetic variation important?
Genetic variation allows populations to better survive because they have a wider variety of alleles that can be used to adapt to environmental changes such as disease or news predators.
