Topic 4 Flashcards
(24 cards)
Define locus
Location of a gene on a chromosome
Define homologous pair
Have the same genes but different alleles
How is DNA in mitochondria and chloroplasts similar to prokaryotic DNA? [3]
1) Short
2) Circular
3) Not associated with histones
What is the function of RNA?
Copy and transfer the genetic code from DNA in the nucleus to the ribosome.
What is the function of rRNA?
Combines with protein to form ribosomes
What are the key features of meiosis? [3]
- Produces genetically different daughter cells
- 2 nuclear divisions
- Four haploid cells
Independent segregation [2]
- Random which side of the equator the maternal and paternal chromosomes from each homologous pair can lie
- Creates a large number of possible combinations of chromosomes in the daughter cells produced
How to calculate the number of combinations made by independent segregation?
2^n
n = number of homologous pairs
Crossing over [3]
1) Homologous chromosomes line up and parts of the chromatids entangle and twist
2) Exchange of alleles
3) Results in new combinations of alleles
How does random fertilisation increases genetic variation?
Random which egg and sperm will fuse
What is non-disjunction?
When chromosomes or chromatids don’t split early during anaphase
What is polyploidy?
Changes in whole sets of chromosomes occur when organisms have more than two sets of chromosomes. For example: non-disjunction in meiosis I where all chromosome fail to separate equally
- Mainly in plants
What is aneuploidy?
Changes in the number of individuals chromosomes. For example individual homologous pairs failing to separate.
- More common in humans
What is genetic diversity?
Number of different alleles in a population
What is the difference between directional and stabilising selection?
- Directional: one of the extreme have selective advantage. Stabilising: Modal trait has selective advantage
- Directional: when there’s a change in environment. Stabilising: No change in environment
What is courtship behaviour?
Attracts a mate of the same species and opposite sex to ensure reproductive success.
How does courtship increases the probability of successful mating?
1) Attracts the same species
2) Attracts the opposite sex
3) Shows sexual maturity
4) Forms pair bond
5) Stimulates the release of gametes
Why is the binomial naming used?
1) Shows how closely related they are
2) Universal
What is a hierarchy?
- Smaller groups within larger groups
- No overlap
Name the classification system
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What are the modern classification systems? [5]
1) Frequency of measurable and observable characteristics
2) Base sequence of DNA
3) Base sequence of mRNA
4) Amino acid sequence
5) Immunological
Define species richness
The number of different species in a community
Define biodiversity
The number of species and the number of individuals of each species within a community
What are the 5 ways farming can reduce biodiversity?
1) Destruction of hedgerows - reduction in habitats
2) Selective breeding - Narrows down the gene pool
3) Monocultures
4) Overgrazing
5) Filling in ponds and draining wetlands
