Topic 4 Biology Flashcards
What are 3 features of prokaryotic DNA?
- Short
- Circular
- Not associated with proteins
What are 3 features of eukaryotic DNA?
- Longer
- Linear
- Associated with the proteins, histones
Why does the double helix wind around histones?
- The DNA double helix winds around histones to take up as little space as possible to fit the nucleus.
What is special about the DNA in mitochondria and chloroplasts?
- The DNA is similar to that of a prokaryotic cell
What is the definition of a gene?
- A base sequence of DNA which codes for the amino acid sequence of a polypeptide and/or functional RNA.
What is a locus?
- The specific location where a gene is located on a chromosome.
What is the genome?
- The genome is the full set of genes in a cell.
What is the proteome?
- The full range of proteins a cell is able to produce.
What is the universal genetic code?
- Universal means the same code is present in all living organisms.
What is the non-overlapping genetic code?
- Non-overlapping means all codons are read consecutively so each base is read only once.
What is the degenerate genetic code?
- Degenerate means that more than one codon codes for an amino acid.
What are 2 features of non-coding DNA?
- Areas of non-coding DNA includes introns and non-coding repeats of base sequences.
What is the role of mRNA?
- To transfer genetic information from DNA to ribosomes, where it acts as a template for protein synthesis.
What is the role of tRNA?
- To transfer amino acids, that are used to make proteins, to ribosomes.
What are 3 structural points about mRNA?
- Very long, single polynucleotide strand.
- Polymers of RNA nucleotides.
- Possesses information in the form of codons.
What are 3 structural points about tRNA?
- Shorter, single polynucleotide strand.
- Possesses information in the form of anticodons.
- Complementary hydrogen bonds form the clover leaf shape.
What is transcription?
- The production of mRNA from DNA
What is translation?
- The production of a polypeptide from an amino acid.
Outline the process of transcription..
1) RNA polymerase binds to the start of the gene and begins to unwind the DNA, exposing some of the bases.
2) Free RNA nucleotides associate with their exposed complementary bases on the template strand of the unwound DNA by complementary base pairing.
3) RNA polymerase adds each nucleotide to the mRNA polynucloetide chain by forming a phosphodiester bond.
4) RNA polymerase reaches the stop triplet code.
Outline the process of translation…
1) RIbosome becomes attached to the start codon at one end of the mRNA.
2) tRNA molecules with an anticodon complementary to the first codon on the mRNA attaches itself to the mRNA by complementary base pairing.
3) Second tRNA attaches itself in the same way.
4) Two amino acids on the tRNA join by a peptide bond.
5) Ribosome moves along mRNA and another codon is now available for the next tRNA molecule to bind, carrying a third amino acid.
6) The first tRNA dissociates, leaving its amino acid behind.
What is the definition of a species?
- A group of organisms that can interbreed to produce fertile offspring.
What is courtship behaviour?
- A necessary precursor to successful mating.
Why is courtship behaviour important?
- Due to the ability to recognise and reproduce with individuals of their own species, making reproduction more successful.
What are 3 signals of courtship behaviour?
1) Visual
2) Auditory
3) Chemical signals
What is the classification system?
- The arrangement of species into groups based on evolutionary origins and relationships.
What is hierarchy?
- Smaller groups being placed within larger groups, with no overlap between groups.
What do common ancestors represent?
- How closely related the species are with one another.
What is taxonomy?
- The study of classification.
How does the taxon classification go?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What is biodiversity?
- The range and variety of genes, species, and habitats within a particular region.
What is the index of diversity?
- The index of diversity puts a figure to biodiversity so we can numerically compare.
What is species richness?
- The measure of the number of different species in a community.
What is species evenness?
- There may be a relative abundance of each species.
Recall the equation of the index of diversity.
How does deforestation have an imbalance on farming and biodiversity?
- Deforestation clears the space for farming
- Destroys tree species in the process
How does removal of hedgerows have an imbalance on farming and biodiversity?
- Makes farming more efficient.
- Destroys habitats by reducing the number of tree species.
How do monocultures have an imbalance on farming and biodiversity?
- More efficient to grow just one crop but may be affected by disease.
What is genetic diversity?
- The number of different alleles of genes in a population.
What happens if there is greater genetic diversity?
- The more likely that individuals in a population will survive an environmental change.
- Due to a wider range of alleles so a wider range of characteristics.
What are 4 factors that increase genetic diversity?
1) Genetic mutations leading to new alleles
2) New alleles are introduced into a population when individuals from other populations migrate into them and reproduce.
3) Meiosis
4) The random fertilisation of gametes during sexual reproduction.
Outline the process of natural selection.
1) New alleles are formed by random mutations in genetic material.
2) Sometimes an allele gives an individual an advantage, leading to increased chances of survival and reproductive success.
3) These individuals pass on advantageous alleles to the next generation
4) Over many generations, the new allele frequency increases in a population.
What is directional selection?
- When individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.
What is an example of directional selection?
- Antibiotic resistance as resistant bacteria survive and reproduce, passing their alleles to the next generation.
What is stabilising selection?
- Where individuals with alleles for characteristics towards the middle range are more likely to survive and reproduce.
What is an example of stabilising selection?
- Human birth weight, as small babies are unlikely to survive due to a weak immune system and large babies may die as they can’t survive during childbirth.
What is a behavioural adaptation?
- The way an organism acts that increases its survival rate.
What is a physiological adaptation?
- The processes inside an organisms which increase its chances of survival.
What is anatomical adaptation?
- The features of an organism’s body that increases its chances of survival.
What is a gene mutation?
- Changes in the DNA base sequence of chromosomes.
How do gene mutations occur?
- They can occur randomly during DNA replication
- Due to mutagenic agents
- Due to meiosis
What is base deletion?
- 1 base is lost and this results in a frame shift, where all bases move along in one direction, so every codon is different.
Why is base deletion dangerous?
- Completely different codons so dysfunctional polypeptides.
What is base substitution?
- Where a base is substituted for another.
How does the danger of substitution compare to deletion?
- Not as dangerous due to the degenerate genetic code, however, if the codon codes for another amino acid, this can lead to a dysfunctional protein.
What are mutagenic agents?
- Substances that increase the rate of mutations.
Examples of mutagenic agents
- Ionising radiation
- UV radiation
- Biological agents
What are 2 points about meiosis?
1) 1 cell divides to form 4 daughter cells that are haploid.
2) Each daughter cell has half the number of chromosomes of the parent cell.
How does meiosis happen?
- DNA unravels and replicates to form copies of each chromosome, called chromatids.
- DNA condenses to form double-armed chromosomes, each made from two sister chromatids, joined by a centromere.
What are 2 sources of variation from meiosis?
- Independent assortment - Where we don’t know which side of the cell the chromosome from each pair ends up in which daughter cell.
- Crossing over - When the homologous pairs of chromosomes come together and pair up, twisting around each other and bits of chromatid cross over.
What is a non-disjunction mutation?
- A change to the number of chromosomes in each daughter cell, either being more or less chromosomes in a gamete.
What are 4 methods of investigating diversity between species?
1) Measuring the frequency of measurable/observable characteristics.
2) Comparing the DNA base sequence between the two species.
3) Comparing the mRNA base sequences between the two species.
4) Comparing the amino acid sequence of proteins enhanced by DNA/mRNA between the two species.
What does distantly related species mean?
- 2 species haven’t had a common ancestor for long enough, allowing mutations to occur and mutations lead to evolution.
What are the limitations of studying the amino acid sequence of proteins between two organisms?
- Protein comparisons are less reliable because organisms may have the same amino acid sequences but different base sequences due to the degenerate nature of the genetic code.
- Protein measurements only take into code one gene and not the entire genetic code.
- You have to find a protein common to both organisms.
How do you investigate diversity step by step?
1) Take random sample of a population
2) Collect data
3) Calculate a mean
4) Calculate the standard deviation of the mean.
5) standard deviation is the measure of the spread of values about the mean.
