Where genetic information from two organisms is combined to produce offspring that are genetically different to either parent
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Are gametes haploid or diploid and why?
Haploid because they contain half the number of chromosomes of a normal human body cell
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At fertilisation, the male gamete fuses with a female gamete to produce a...?
Zygote
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The zygote then undergoes...... and develops into an......
mitosis...... embryo
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How does sexual reproduction introduce variation?
Because the embryo inherits its characteristics from both parents and it has received half of its chromosomes from its mother and half from its father
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What happens before cells undergo meiosis?
It duplicates its DNA
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What does meiosis produce?
4 haploid daughter cells called gametes. They each have only a single set of chromosomes and they are all genetically different.
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Describe the structure of DNA?
Two strands coiled to form a double helix. The strands are made from sugar and phosphate. Each unit contains one of four different bases. Each base links to a base on the opposite strand of the helix.
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Give the complementary base pairings
Adenine and Thymine-- Cytosine and Guanine
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How are the complementary base pairs joined together
By weak hydrogen bonds
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What is a chromosome?
A long coiled up molecule of DNA, found in the nucleus of eukaryotic cells
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What is a gene?
A section of DNA on a chromosome that codes for a particular protein. The sequence of bases in the gene determines what protein is produced.
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What is a genome?
All of an organism's DNA
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What is the first stage of extracting DNA?
Putting the fruit into a detergent to break down the cell and nuclear membranes to release DNA
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What is the second stage of extracting DNA?
Placing the beaker in a water bath at 60 degrees for 15 minutes to speed up the breakdown of membranes and destroy enzymes that might break down DNA.
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What is the third stage of extracting DNA?
Standing the beaker in iced water to cool the mixture to prevent the breakdown of DNA.
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What is the fourth stage of extracting DNA?
Blending the mixture to break open the onion cells
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What is the fifth stage of extracting DNA?
Filtering the mixture to help remove solid cell debris
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What is the sixth stage of extracting DNA?
Adding enzyme to break down the proteins so that DNA precipitates out into the ethanol
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What is the seventh stage of extracting DNA?
Pouring ice cold ethanol down the side of the tube to precipitate DNA, which is soluble in water but not ethanol
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What is the eighth stage of extracting DNA?
Lifting out some precipitated DNA using a glass rod
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What is an allele?
A different version of the same gene
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Define homozygous
Two alleles for a particular gene that are the same
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Define heterozygous
Two alleles for a particular gene that are different
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Alleles shown with a capital letter are...........
Dominant
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Which allele determines what characteristic is present?
Dominant allele
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Define genotype
The combination of alleles you have
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Define phenotype
The characteristics you display
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How is genetic variation caused?
Organisms having different alleles, therefore this may slightly affect the phenotype.
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What are environmental variations in phenotype known as?
Acquired characteristics
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Define mutation
Changes to the base sequences of DNA
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What is continuous variation?
Where the characteristics can take any value in the data set
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What is discontinuous variation?
Where the characteristic can take one option of a limited set of values in a data set
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Other cards in this set
Card 2
Front
Are gametes haploid or diploid and why?
Back
Haploid because they contain half the number of chromosomes of a normal human body cell
Card 3
Front
At fertilisation, the male gamete fuses with a female gamete to produce a...?
Back
Card 4
Front
The zygote then undergoes...... and develops into an......
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