Unit 2 AS Biology

Flash cards on unit 2 AS Biology.

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Definition of Interspecific variation?
The variation that exists between DIFFERENT species.
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Definition of Intraspecific variation?
The difference that occur WITHIN a species.
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Causes of INTRAspecific variation?
*Genetic factors-different alleles means different make up of genotype results in variation of phenotype(characteristics displayed by organism). *Environment-e.g the amount of nutrients available for plant growth.*Both
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How do you use twin studies for variation?
Can use identical/non-identical twins to determine if it is genetic or environmental.
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How do you investigate variation?
*Use a sample of the population, * Random sampling *It involves:Describing data,Drawing conclusions,Suggesting reasons for any differences.*You can use Mean and Standard deviation.
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Function of DNA?
Contains genetic information-to grow and develop from egg to fully grown adult.
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Structure of DNA?
Double helix. Made up of many nucleotides-Phosphate and deoxyribose sugar with a nitrogenous base. These create a "sugar-phosphate backbone".
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Describe specific base pairing?
Two DNA polynucleotide strands join together by HYDROGEN bonds between the bases. Each base can only join with one particular partner= A-T and C-G.
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How is structure linked to function?
Double helix makes it very stable so doesn't break down or get easily damaged. *Tightly coiled so a lot of genetic information can fit into a small space. *Semi-conservative replication is important for cell division.
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How is DNA stored in EUKARYOTIC cells?
* Contains linear DNA that exists as chromosomes. *The DNA is wound up to fit in the nucleus and wound up around proteins- called histones(they also help support the DNA)
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How is DNA stored in PROKARYOTIC cells?
*Carry DNA as chromosomes-but it is shorter and circular. *DNA isn't wound around proteins-it condenses to fit in the cell by SUPERCOILING.
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What are Genes?
Genes are sections of DNA- they are found on chromosomes. *They code for proteins.
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How is a protein made using genes?
The order of the nucleotide bases in a gene determines the order of amino acids in a particular protein.Each amino acid is coded for by a sequence of three bases in a gene.Different sequences of bases code for different amino acids.
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*Genes in eukaryotic DNA contain sections that DONT code for amino acids. These sections are called INTRONS. Introns are removed durning protein synthesis. * Eukaryotic DNA also contains regions of multiple repeats outside of genes-also non-coding.
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Define Homologous chromosomes
Pairs of matching chromosomes.-Both chromosomes are the same size and have the same genes, although they could have different alleles.Alleles coding for the same characteristic will be found on the same position on each chromosome in homologous pair.
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What effect can a Gene mutation have on a structure and function of a protein?
*Mutations change the base sequence of DNA. *Mutations can produce new alleles of genes. These changes can produce a non-functional protein or a different protein.(This can also be applied to enzymes)
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What are diploid and haploid cells?
Normal body cels have a diploid number(2n) of chromosomes-meaning each cell contains two of each chromosome. Gametes have haploid(n) of chromosomes- only one copy of each chromosome.
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Outline meiosis?
It is a type of cell division.Cells that divide by meiosis are diploid at the start and cells formed by meiosis are haploid- chromosome number halves.
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Outline Steps 1-4 of meiosis
Step one-man unravels and replicates to create chromatids. Step 2-DNA condenses to form chromosomes from two sister chromatids. Step 3-Chromosomes arranged into homologous pairs. Step 4-First division homologous pairs are separated.
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Outline steps 5-6 of meiosis
Step 5-Second division- the pair of sister chromatids that make up each chromosomes are separated. Step 6-Four haploid cells that are genetically different from each other are produced.
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What is crossing over?
During meiosis one, homologous pairs of chromosomes pair up. The chromatids twist around each other and bits of chromatids swap over-this creates a different combination of alleles.
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What is independent segregation?
When gametes are produced, different combinations of those maternal and paternal chromosomes go into each cell.
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What is Genetic diversity?
The variety in DNA-it can help a population or species to survive i.e if the environment changes, they are likely to be some organisms with the alleles that enable them to survive the new conditions.
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Name the factors that increase genetic diversity
*Mutations in the DNA that form new alleles. *GENE FLOW- different alleles move between populations when individuals from one population migrate to another and reproduce.
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Name factors that DECREASE genetic diversity
*Genetic bottleneck *The Founder effect *Selective breeding
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What is a Genetic Bottleneck?
An event that causes a big reduction in a population. ~It reduces the number of different alleles in the gene pool and so genetic diversity is reduced. The survivors reproduce and a larger population is created from a few individuals.
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What is "The Founder effect"?
This is what happens when just a few organisms from a population start a new colony. Only a small number of organisms contribute their alleles to the gene pool so genetic diversity is reduced.
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Why would the founder effect occur?
It could be as a result of migration leading to geographical separation.
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What is Selective Breeding?
Involves humans selecting which domesticated animals or strains of plants reproduce together in order to produce useful characteristics, e.g high-yield - it reduces genetic diversity.
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Give arguments FOR selective breeding
* Can produce high-yields *Can produce animals/plants with increased resistance to disease.
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Give arguments AGAINST selective breeding
*Can cause health problems e.g deformity. *Decreased genetic diversity which in turn increase likelihood of genetic disease.
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What is the role of haemoglobin?
Carries oxygen around the body.
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What is oxyhaemoglobin?
In the lungs, oxygen joins to haemoglobin in red blood cells to form oxyhaemoglobin. When oxygen joins haemoglobin it's referred to as "loading", and when oxygen leaves oxyhaemoglobin it's referred to as unloading.
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Whats does the Affinity for oxygen mean?
The tendency a molecule has to bind with oxygen.
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pO2 is a measure of oxygen concentration. The greater the concentration of dissolved oxygen in cells, the higher the partial pressure. As pO2 increases, haemoglobin's affinity for oxygen also increases.Oxygen loads haemoglobin=High pO2.
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What does a "Dissociation Curve" show?
It shows how saturated the haemoglobin is with oxygen at any given partial pressure. The affinity of haemoglobin for oxygen affects how saturated the haemoglobin is.
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Name the 5 main components a animal cell has.
*Plasma membrane *Mitochondria *Ribosomes *Nucleus *Cytoplasm.
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Name the 3 main components a plant cell has.
*Rigid cell wall *Permanent vacuole *Chloroplasts
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Explain the structure of a Chloroplast.
They are surrounded by a double membrane, and also have thylakoids stacked up.These thylakoid stacks are called grana. Grana are linked together by lamellae.
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What is a polysaccharide?
Many monosaccharides joined by a glycosidic bond.
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What is cellulose?
A major component of cell walls in plants, made of long unbranched chains of BETA-GLUCOSE. B-glucose is joined but a condensation reaction - when joining two, one has to be flipped upside down to form the glycosidic bond.
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Explain the structure of cellulose.
The cellulose chains are straight and the chains are linked by hydrogen bonds to form strong microfibrils.-These provides rigidity for the cell wall.
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What is Starch?
It is the main energy store material in plants.It is insoluble in water so it doesn't affect osmosis.Starch is a mixture of two poly saccharides of alpha-glucose-amylose and amylopectin.
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What is glycogen?
The main energy store in animals.It is extremely branched which means that stored glucose can be released quickly.Very compact also=good storage.
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How is DNA replicated (STAGE 1)?
The enzyme DNA HELICASE breaks the hydrogen bonds between the two polynucleotide DNA strands. The helix unzips to form two single strands.
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Card 2


Definition of Intraspecific variation?


The difference that occur WITHIN a species.

Card 3


Causes of INTRAspecific variation?


Preview of the front of card 3

Card 4


How do you use twin studies for variation?


Preview of the front of card 4

Card 5


How do you investigate variation?


Preview of the front of card 5
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