Two sources of variation in sexual reproduction?
Reveal answer
Meiosis (new allele combinations) + random fertilisation.
Key words: random
4(b) INHERITANCE · RECALL
4.31 Random fertilisation and variation
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What is meant by the term recombination?
Reveal answer
Production of new allele combinations, including through crossing over.
Key words: recombination
What is meant by the term population?
Reveal answer
Members of one species living in the same area at the same time.
Key words: population
Sources of inherited variation, Crossing over. When it occurs? Effect?
Reveal answer
When it occurs: Meiosis I. Effect: Recombines alleles within homologues.
Key words: Crossing over
Sources of inherited variation, Independent assortment. When it occurs? Effect?
Reveal answer
When it occurs: Meiosis I. Effect: Distributes whole homologues randomly.
Key words: Independent assortment
Sources of inherited variation, Random fertilisation. When it occurs? Effect?
Reveal answer
When it occurs: Gamete fusion. Effect: Combines any sperm with any egg.
Key words: Random fertilisation
Sources of inherited variation, Mutation. When it occurs? Effect?
Reveal answer
When it occurs: Before/during DNA copying. Effect: Creates new allele sequences.
Key words: Mutation
True or false, and why? “Random fertilisation creates new alleles.”
Reveal answer
False. It creates new combinations; mutation creates new allele sequences.
True or false, and why? “Siblings have exactly half the same DNA in every region.”
Reveal answer
False. They share ancestry but receive different recombined allele combinations.
True or false, and why? “Variation is always useful.”
Reveal answer
False. Its effect depends on the environment and trait.
Why does random fertilisation increase variation?
Reveal answer
Any one of millions of genetically different sperm can fuse with any egg → a huge number of combinations.
Key words: sperm
Do brothers and sisters from the same parents inherit the same alleles?
Reveal answer
No (unless identical twins): each child gets a different mix.
Key words: No
Why are identical twins genetically identical?
Reveal answer
Both develop from one zygote that split.
Key words: one zygote
Suggest why variation helps a species survive a new disease.
Reveal answer
Some individuals may have alleles that give resistance → they survive and reproduce.
Key words: resistance
Which type of reproduction produces genetic variation in the offspring?
Reveal answer
Sexual reproduction.
Key words: sexual