Topic 4 Booklet Flashcards
What does degenerate mean?
More than one triplet for each amino acid
Define non-overlapping
Each base is part of only one triplet
What are some aseptic techniques?
- Keep lid on Petri dish/ open lid as little as possible
- to prevent unwanted bacteria contaminating the dish - Wear gloves/mask / wash hands
- to prevent contamination from bacteria on hands/mouth - Use sterile pipette/ flame the loop
- to maintain a pure culture of bacteria
Give the two types of molecule form which a ribosome is made
Ribosomal RNA and amino acids
Describe the role of a ribosome in the production of a polypeptide.
- mRNA binds to the ribosome
- Two codons/ binding sites
- Allows tRNA with anticodons to bind
- Catalyses formation of peptide bond between amino acids
- Moves along (mRNA to the next codon)
Define species
A group of organisms that are able to produce fertile offspring
Define species richness
The number of different species in a community
Explain how the chromosome number is halved during meiosis
- Homologous chromosomes
- One of each pair goes to each daughter cell
Describe the process of crossing over and explain how it increases genetic diversity
- Homologous pairs of chromosomes form a bivalent
- Chiasmata form
- Alleles are exchanged
- Producing new combinations of alleles
Explain how differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic relationships between species
- Mutations change base/ nucleotide sequence
- Causing change in amino acid sequence
- Mutations build up over time
- More mutations between distantly related species
Describe and explain the appearance of one chromosome during meiosis (before division)
- Chromosome is formed of two chromatids
- Because DNA replication
- Sister chromatids held together by centromere
Describe what happens in meiosis I
- Chromosome in homologous pair
- One of each into daughter cells
Identify one event that occurs in meiosis II but not meiosis I
Separation of chromatids
Name two ways in which meiosis produces genetic variation
- Crossing over
Independent segregation
Explain the importance of meiosis in the life cycles of organisms which reproduce sexually
- Meiosis produces haploid cells
- When gametes fuse, the diploid number is restored
- This keeps the chromosome number constant
- Introduces GENETIC variation
Suggest one source of DNA from deceased organisms
Preserved remains, skin, bones
Suggest reasons why populations might show very low levels of genetic diversity
- Inbreeding
- Population might have been very small
What is genetic diversity
The number of different alleles of a gene in a population
Describe the process of natural selection
- New alleles for a gene are created by random mutations
- If the new alleles increases the chances of the individual to survive in that environment, they are more likely to survive and reproduce
- Reproduction passes on the advantageous allele to the next generation
- Over many generations the allele increases in frequency in the population
What is directional selection
- One of the extremes has the selective advantage
- Occurs when there is a change in the environment
- The model trait changes
What is stabilising selection
- The modal trait has the selective advantage
- Occurs when there is no change in the environment
- Standard deviation decreases, as individuals with the extreme trait decrease
Why do different species look similar?
- Live in a similar environment
- Have similar selection pressures
- Similar alleles will have the selective advantage
- Produces similar/same proteins and therefore have similar characteristics
What is as hierarchy?
- Smaller groups arranged within larger groups
- No overlap between groups
What are the modern and accurate classification methods?
- DNA sequence
- mRNA sequence
- Amino acids sequence
- Immunological - comparing similarity in self-antibody shape
What are the farming techniques that reduce biodiversity?
- Destruction of hedgerows
- Selective breeding
- Monocultures
- Over-grazing
- Filling in ponds and draining wetlands
What is the index of diversity
- A measure of species diversity
- A calculation to measure the relationship between the number of species in community and the number of individuals in each species
What does ‘N’ represent in the index of diversity
Total number of organisms of all species
What does the ‘n’ represent in the index of diversity
Total number of organisms of a particular species
What does the ‘D’ represent in the index of diversity
Simpson’s diversity index
