Topic 3 + 4 Flashcards
What happens in metaphase?
Chromosomes line up along the equator of the cell and become attached to the spindle fibers at the centromeres.
How does meiosis produce cells that are genetically different ?
Through crossing over of chromatids and independent assortment of chromosomes
What is genetic diversity?
The variation of alleles in the gene pool of a species
How does the structure of sclerenchyma make them good for rope?
Sclerenchyma has thick lignin walls for strength and makes them waterproof.
It is flexible so do not break easily and light because are hollow.
What are histones?
Proteins that DNA wraps around to form chromatin which makes up chromosomes
Why do plants need magnesium ions?
For synthesis of chlorophyll
What are the adaptations of an egg cell ?
- Zona pellucida - a protective layer that sperm cell has to penetrate
- Follicle cells - form a protective coating outside cell
- Cytoplasm contains lipid droplets that are a food store for developing embryo.
What is a niche?
The role of a species within its habitat including both biotic and abiotic interactions.
What does the cell cycle consist of ?
Interphase which is a period of cell growth and DNA replication (G1, S and G2) then Mitosis
How does the new three domain system classify organisms?
All organisms are placed into one of three domains which are above the kingdoms in the taxonomic hierarchy. The three domains are bacteria, archaea and eukaryote
What is pluripotency ?
Ability of a stem cell to produce all the specialised cells in an organism but not extra embryonic cells
What is an operon ?
A section of DNA that contains a cluster of structural genes that are transcribed together as well as control elements and sometimes a regulatory gene
Give examples of X linked disorders colour
Haemophillia and colour blindness
What is the function of the Golgi apparatus?
It processes and packages new lipids and proteins. it also makes lysosomes
What does p stand for in p + q = 1?
The frequency of the dominant allele
What is a loci?
Position of a gene on a chromosome
Describe phase 3 of clinical trials
Testing the drug on thousands of patients and comparing it to existing treatment.
Split the patients randomly into two groups, one group gets new treatment and the other gets existing treatment
Description and function of the amyloplast
A small organelle enclosed by a membrane.
Stores starch granules
Converts starch back to glucose for release when the plant requires it
Define anatomical adaptations
Structural features of an organism’s body that increase its chance of survival
Why is it important that gametes only have one set of chromosomes ?
So that the diploid number of chromosomes can be restored after fertilisation
Why are seeds stored in dry and cold conditions?
Reduces enzyme activity, prevents germination of seeds, prevents microbial growth
What is polygenic inheritance ?
There are multiple genes for a single characteristic on more than one locus. These genes interact. Usually show continuous variation.
what is evolution?
The process by which the frequency of alleles in a gene pool changes over time as a result of natural selection.
what is natural selection
It is the process by which individuals with a favourable phenotype are more likely to survive and pass on their alleles to their offspring.
what does mutation in a species cause
it causes variation in a gene pool in a population
what are the four mechanisms of evolution
- gene flow - genes moving through migration e.g. migration
- mutation e.g. changes in bases in DNA (genetic material)
- genetic drift - change in gene pool due to random event
4.natural selection have a better suited phenotype lead to change in frequency of alleles causing speciation
