3.4 Genetic information, variation and relationships between organisms

Eukaryotic DNA

Linear chromosomes that are made up of one long molecule of DNA associated to a histone protein found in the nucleus. Also found in mitochondria and chloroplasts.

Prokaryotic DNA

Short, circular chromosome super coiled and found in cytoplasm.

Codon

A specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid

Genes

sequence of DNA bases that code for either a polypeptide or functional RNA. Order of genes determines order of amino acids.

Functional RNA

an RNA type that plays a role without being translated such as tRNA and rRNA.

Genome

the complete set of genes or genetic material present in a cell or organism

Proteome

an organism's complete set of proteins

Introns

Noncoding segments of nucleic acid that lie between coding sequences.

Exons

Coding segments of eukaryotic DNA.

Allele

Different forms of a gene

locus

Location of a gene on a chromosome

protein synthesis

the formation of proteins by using information contained in DNA and carried by mRNA

mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome, 3 bases makeup codon

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome and has an anticodon site.

Transcription

1. DNA helicase breaks H bonds between strands

2. Each strand acts as template

3. free RNA nucleotides complementary to the DNA align

4. RNA polymerase joins RNA backbone until a stop codon is reached

5. pre-mRNA is formed

6. splicing occurs to remove introns and join exons

Translation

1. occurs at ribosome where mRNA attaches

2. tRNA carries amino acid and binds as tRNA anticodon is complementary to mRNA codon

3. ATP helps bind amino acid and tRNA

4. secondary tRNA binds

5. amino acids join by peptide bond

6. process continues until stop signal and polypeptide chain is produced

genetic code

sequence of base triplets in mRNA which code for specific amino acids.

1. Non-overlapping: codons read separately and don't share bases

2. degenerate: more combinations of codons than amino acids

3. universal: same specific codons for the same amino acids in all living things

Process of Meiosis

1. Before meiosis starts, DNA unravels and replicates so there are two copies of each chromosome - chromatids

2. DNA condenses to form double-armed chromosomes each made from 2 sister chromatids joined by a centromere

3. Meiosis I - the chromosomes arrange themselves into homologous pairs. Chiasmata and independent assortment occur here.

4. The homologous pairs are separated, halving chromosome number and creating two cells

5. Meiosis II - the pairs of sister chromatids that make up each chromosome are separated

6. Four haploid cells that are genetically different are produced

chromosomes in meiosis

four genetically different daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

1. chromosomes condense

2. chromosomes form homologous pairs

3. chiasmata form

4. join to spindle fibres

5. metaphase

6. joined via centromere

7. anaphase

8. chromatids separate in second division

genetic variation in gametes

1. independent assortment

2. crossing over

3. random fertilisation

gene mutation

a change in the base sequence of a gene.

1. addition

2. deletion

3. substitution

4. inversion

5. duplication

6. translocation

Mutagenic agents

mutations are random but factors can increase the rate of mutation

chromosome mutations

errors in meiosis can lead to non-disjunction where they don't separate.

genetic diversity

the number of different alleles of genes in a population

selective breeding

The process of selecting a few organisms with desired traits to serve as parents of the next generation

founder effect

change in allele frequencies as a result of the migration of a small subgroup of a population

genetic bottleneck

an event causes the sudden reduction in the number of alleles in a population

natural selection

1. random mutation

2. variation in alleles

3. advantageous characteristic increases survival

4. more likely to reproduce and pass on beneficial genes

Behavioural adaptation

way an organism acts to survive

physiological adaptation

Processes inside an organisms body that increase its chance of survival

structural adaptation

a physical feature of an organism's body that increases survival

directional selection

occurs when natural selection favours one of the extreme variations of a trait

Stabilising selection

Selection for the middle range against the extremes.

Disrupting Selection

natural selection in which individuals at the upper and lower ends of the curve are favoured

aseptic techniques

1. disinfect work surface

2. disinfect equipment

3. discard equipment safely

4. Bunsen flame to draw away microbes as hot air rises

5. minimise time spent with lid off the agar plate

6. flame neck of bottle of the glass container of broth

Index of diversity

D\= N (N-1) / ∑n (n-1)

Phylogeny

Evolutionary history of a species

Taxonomy

The scientific study of how living things are classified. Domain, kingdom, phylum, class, order, family, genus, species

binomial system

Identifying organisms by their genus and species names

Species

A group of similar organisms that can breed and produce fertile offspring.

Courtship behaviour

Behaviour carried out by organisms to attract a mate of the right species

species richness

the number of different species in a community

technologies used to compare evolutionary relationships

1. the frequency of measurable or observable characteristics

2. the base sequence of DNA

3. the base sequence of mRNA

4. the amino acid sequence of the proteins encoded by DNA and mRNA.

Variation

Any difference between individuals - genetics, environment or both

habitat

Place where an organism lives

Community

All the different populations that live together in an area

impact of agriculture on biodiversity

1. clears woodland

2. clears hedges

3. monoculture

4. Pesticides

5. herbicides

This decreases biodiversity as low variety of habitats , few plant species, few species of herbivores and carnivores so little variety of food.

Conservation schemes

1. legal protection of endangered species

2. protected areas

3. farming schemes