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Chromosomes and DNA – Checkpoint Sec 1 Biology
1. Stage _9/2023/Paper_1/No.8
fertilization
Each egg always contains an X chromosome, while the sperm can carry either an X or a Y
chromosome. If a sperm carrying an X chromosome fertilizes the egg, the offspring will
have XX chromosomes and will be female. If a sperm carrying a Y chromosome fertilizes
the egg, the offspring will have XY chromosomes and will be male.
Since there is an equal chance of a sperm carrying an X or a Y chromosome fertilizing the egg, there is a 50%
chance of the offspring being male (XY) and a 50% chance of it being female (XX).
Because they also have chromosome from their grandparents or randome genes.
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2. Stage _9/2022/Paper_1/No.9
X
Y
XX
XY
XX
Type of ears
DNA, genes from parents
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XY
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3. Stage _9/2022/Paper_2/No.8
23
The sperm cell contributes half of the total chromosomes (23) to the fertilized egg.
Similarly, the egg cell also contributes 23 chromosomes, resulting in a total of 46
chromosomes in a fertilized egg.
It damaged the sperm, so it ís unable to fertilize the egg which means it can't reproduce
affecting the human species.
population
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