Biology Unit 2

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What two types of variation are there?
Interspecific- between different species, Intraspecific- between same species
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What two factors cause intraspecific variation?
Genetics- different alleles in a species, this makes up a genotype. Genotypes result in a variation in phenotypes. Environmental- appearance (phenotype) of an individual is also affected by the environment (e.g. minerals for growth).
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What factors need to be in place to study variation?
1) Sample of a population 2) Sample has to be random (unbiased and not due to chance)
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What is standard deviation?
Average variation from the mean.
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What is DNA made of?
DNA is a polypeptide (made up of many nucleotides), a nucleotide is made up of deoxyribose, phosphate and a nitrogenous base (A/T/C/G)
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What is a double helix made up of?
Two polynucleotide strands joined by hydrogen bonds. A sugar phosphate backbone is created. Each base is partnered by complementary base pairing.
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Why does DNA's structure make it good for function?
Genetic information (growth and development), long, coilded strand (small area), paired structure (replication), double helix (stable).
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What is DNA like in a eukaryotic cell?
linear, long strands wound around histone proteins and compacted into a chromosome (strong support)
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What is DNA like a prokaryotic cell?
DNA molecules are short and circular, super coiling.
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What are genes?
Genes are sections of DNA, they are found on chromosomes, genes code for proteins (they contain the information to make them).
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What do proteins code for?
Proteins code for amino acids, the order of nucleotide bases determines what amino acid is coded for (read in triplet code).
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Why doesn't all DNA code for proteins?
Introns do not code for amino acids, these are removed during protein synthesis. There are also area of repetition which do not code for amino acids either. Exons are the coding part of DNA.
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How does DNA determine our nature and development?
DNA sequence determines the amino acid sequence, proteins and enzymes are formed, enzymes enable metabolic pathways, metabolic pathways help determine nature and development.
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What is an allele?
Different form of the same gene. (e.g. eye colour)
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How do gene mutations result in non-functioning proteins?
Mutations are changes in the base sequence of DNA, these mutations can produce new alleles of genes, if this changes a different protein or a non-functioning protein (change in the structure leading to a wrong active site) can be produced.
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What are gametes?
Sex cells, they are haploid as there is only one copy of each chromosome, so when an egg and sperm fuse they for a diploid cell. All genetically different.
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How are gametes formed?
Meiosis- DNA unravels and replicates, condenses to form double armed chromosomes, they arranged into homologous pairs, these are then separated halfing the chromosome number, the pairs of chromotids are separated and four haploid cells are produced.
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In what two ways can meiosis produce cells that are gentically different?
Crossing over, independent segregation.
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What is crossing over?
The crossing over of chromatids in meiosis 1 resulting in four gentically different daughter cells.
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What is independent segregation?
all cells have a combination of maternal and paternal chromosomes, when gametes are produced random amounts of maternal and parternal chromosomes go in each cell, forming four genetically different daughter cells.
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How has variation led to genetic diversity?
Mutations within the DNA or gene flow (when a new member is introduced into a population, migrate and reproduce).
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What is a genetic bottleneck?
This is when there is a big reduction in the population, this reduces the number of different alleles in the gene pool, so when they reproduce the amount of alleles is fewer.
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What is the founder effect?
When a few organisms from a population start a new colony, there are fewer alleles in the gene pool, there is more inbreeding and this can lead to a higher incidence of genetic disease.
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What is selective breeding?
An organism is selected for a certain trait (meat/yield), they are then breed to produce offspring with the same characteristic, and the offspring reproduce to produce higher yielding breeds. This leads to a reduction in genetic diversity.
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What are the arguments for genetic breeding?
1) high yielding 2) resistance to disease 3) intolerance to bad conditions.
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What are the arguments against genetic breeding?
1) cause health problems (low life expectancy) 2) reduces genetic diversity (increased genetic disease).
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Card 2

Front

What two factors cause intraspecific variation?

Back

Genetics- different alleles in a species, this makes up a genotype. Genotypes result in a variation in phenotypes. Environmental- appearance (phenotype) of an individual is also affected by the environment (e.g. minerals for growth).

Card 3

Front

What factors need to be in place to study variation?

Back

Preview of the front of card 3

Card 4

Front

What is standard deviation?

Back

Preview of the front of card 4

Card 5

Front

What is DNA made of?

Back

Preview of the front of card 5
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