Exam Qs Flashcards
Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome
+ DNA that does not code for a sequence of amino acids/ primary structure
+ positioned between genes
Suggest one way the structure of the chromosomes could differ along its length
+ differences in base sequence
What is a homologous pair of chromosomes
+ two chromosomes that carry the same geneS
Describe and explain a difference in the structure of pre-mRNA and mRNA molecules
+ mRNA has no introns, only exons
+ because of spilicing
+ pre-mRNA more nucelotides
Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation
+ tRNA brings specific amino acid
+ anticodon binds to codon on mRNA
+ amino acids join by condensation reaction
Describe how mRNA is produced from an exposed template strand of DNA
+ free RNA nucleotides from complementary base pairs
+ phosphodiester bonds form
+ by DNA polymerase
Describe how mRNA is formed by transcription in eukaryotes
+ hydrogen bonds break
+ one DNA strand acts as a template
+ free RNA nucleotides align by complementary base pairing
+ Uracil base pairs with adenine
+ RNA polymerase joins adjacent nucleotides
+ By phosphodiester bonds
+ pre-mRNA is spliced
What is the proteome?
+ number of different proteins that a cell is able to produce at a given time
Explain how pressure is generated inside the phloem tube
+ sucrose activity transported into phloem
+ lowering water potential
+ water moves into phloem by osmosis
Explain why coloured water moved up the stalks
+ water evaporates from leaves
+ water potential gradient causes tension
+ hydrogen bonds/ cohesion maintains column
Describe how digested lipids are absorbed and then transport to the ileum and lymphatic system
+ micelles are made of bile salts, fatty acids, monoglycerides
+ micelles carry the fatty acids to the epithelial cells of the ileum
+ fatty acids are absorbed into the cells of the ileum by simple diffusion
+ Triglycerides or chylomicrons are formed
+ vesicles are removed by exocytosis
Describe the importance of micelles in absorbing lipids into the epithelial cells of the ileum
+ micelles are made of bile salts,fatty acids, glycerol
+ micelles make fatty acids more soluble in water
+ micelles carry fatty acids to the epithelial cells of the ileum
+ the fatty acids are released from the micelle and are absorbed into the cell by simple diffusion
How are Golgi apparatus involved in the absorption of lipids?
+ they modify triglycerides
+ they combine proteins with triglycerides to form chylomicrons
+ these are packaged into vesicles
What is a gene
A sequence of DNA nucleotides that codes for a polypeptide
Describe how the production of mRNA in a eukaryote cell is different from the production of mRNA in a prokaryote cell
+ so mRNA spliced in eukaryotic because contains introns
Describe the role of ATP in the process of translation in protein synthesis
Releases energy so peptide bonds can form between amino acids
Describe how to process of meiosis results in haploid cells
+ DNA replication
+ two divisions
+ separation of homologous chromosomes
+ separation of sister chromatids
+ produces 4 cells
Describe how organisms are grouped in a phylogenetic classification system
+ hierarchy with no overlaps
+ grouped according to evolutionary relationships
Describe how the structure of the insect gas exchange system:
- provides cells with sufficient oxygen
- Limits water loss
- Spiracles, trachea, tracheoles
- Spiracles allow diffusion
- Tracheoles are highly branched so large surface area
- Tracheole walls thin so short diffusion pathway
- Tracheole permeable to oxygen
- Spiracles close so less water loss
Describe how the structure of a protein depends on the amino acids it contains
- Structure is determined by position of R group
- Primary structure is sequence of aa
- Secondary structure formed by hydrogen bonding
- Tertiary structure formed by interactions between R groups
- Quaternary structure contains more than one polypeptide chain
Differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic (evolutionary) relationships between species. Explain how.
- Mutations change base sequence
- Causing change in aa sequence
- Mutations build up over time
- More mutations/ differences between distantly related species
- Distantly related species have earlier common ancestor
Describe the behaviour of chromosomes during mitosis and explain how this results in the production of two genetically identical cells
- chromosomes shorten & thicken;
- chromosomes made from two identical chromatids, due to replication in interphase;
- chromosomes move to equator of the cell;
- Chromosomes attach to individual spindle fibres;
- Spindle fibres contract & the centromeres divide;
- Sister chromatids move to opposite poles;
- Each pole receives all the genetic information;
- Nuclear envelope re-forms around each group of chromosomes
Describe what happens to chromosomes in meiosis
- Chromosomes shorten & thicken;
- Chromosomes associate into their homologous pairs;
- Crossing-over occurs between chromosomes, through the formation of a chiasma;
- Chromosomes join to spindle fibres, via there centromeres
- Whilst at the equator
- Homologous chromosomes move to opposite poles
- Pairs of chromatids separated in 2nd division
Describe and explain how selection will have affected the genetic diversity of a species
- Diversity reduced as fewer different alleles present creating a smaller gene pool;
- As alleles have been chosen or rejected;
Describe the processes involved in the transport of sugars in plant stems
- At source sucrose is actively transported into the phloem/sieve tube;
- By companion cells;
- Lowers water potential in phloem/sieve element/tube and water enters by osmosis;
- This produces a high hydrostatic pressure;
- Mass flow/transport towards sink/roots/storage tissue occurs;
- At sink/roots sugars are removed/unloaded;