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How many pairs of Chromosomes are in the human body?
In humans there are 23 pairs of chromosomes in a normal body cell, or 46 altogether. This is called the diploid number of chromosomes.
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 Pairs of chromosomes are called...
homologous chromosomes.
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What are chromosomes made up of?
Chromosomes are made up of long molecules of DNA.
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What is a gene?
A gene is a small section of DNA molecule that codes for a specific protein  this controls a particular characteristic in the body. (The DNA controls the sequence of amino acids that make up the different proteins.)
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What shape does a DNA molecule have?
The DNA molecule has a double helix shape.
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What does the final chromosome pair determine?
The final chromosome pair determines the sex of the person.
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The pair will either be labelled XX or XY. What does this mean?
All men have an X and a Y chromosome  XY The Y chromosome causes male characteristics. - All women have two X chromosomes  XX The XX combination allows female characteristics to develop.
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What 3 important conclusions did Mendel reach in plants?
1) Characteristics in plants are determined by genes. 2) Genes are passed on from both parents; one gene from each parent. 3) Genes can be dominant and recessive – if an individual has both for a particular characteristic then the dominant character
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What are alleles?
Alleles are different variations of the same gene
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What is a genotype?
The alleles that an organism contains is called its genotype.
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What does homozygous mean?
If the alleles are the same the genotype is homozygous.
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What does heterozygous mean?
If the alleles are different the genotype is heterozygous.
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What is a Phenotype?
The effect of the genotype on the person’s characteristic is called the phenotype.
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Facts about Cystic Fibrosis
Caused by a recessive allele.  Both parents need to carry the cystic fibrosis allele.  Affects many organs in the body, particularly the lungs and the pancreas. - Pancreatic duct can become blocked so enzymes from the pancreas can not get into t
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Process of Embryonic screening
Multiple eggs are removed from the mother’s ovary.  They are then fertilised in a laboratory using the father’s sperm cells.  The embryos are grown in a dish until they have grown into approximately thirty cells each.  One cell is removed from e
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Advantages of embryonic screening
Allows parents to know if their child could have a potentially life threatening disease.  There a laws that stops the screening from creating designer babies – at the moment, parents are not allowed to select the sex of their babies (unless ther
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Disadvantages of Embryonic Sceening
The embryos could become discarded for having less serious characteristics (designer babies).  Ethical issues – destroying the unsuitable embryos ends a potential human life.  Could lead to prejudice as those with disabilities may be seen as ‘un
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 Pairs of chromosomes are called...


homologous chromosomes.

Card 3


What are chromosomes made up of?


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Card 4


What is a gene?


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Card 5


What shape does a DNA molecule have?


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