Cell Division, Genetic Variation and Genetic Disorders

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In cells, what are the chromosomes usually found in?
Pairs.
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How do body cells divide?
Mitosis.
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What do chromosomes contain?
The genetic information.
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What happens when a body cell divides by mitosis?
Copies of the genetic material are made and then the cell divides once to form 2 genetically identical body cells.
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When does mitosis usually occur?
For growth or to produce replacement cells.
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How many sets of chromosomes do body cells have? And how many sets of chromosomes do sex cells (gametes) have?
Body Cells = 2 and sex cells = 1.
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Cells in reproductive organs (testes and ovaries) divide to form what?
Gametes.
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What is the type of cell division in which a cell divides to form gametes called?
Meiosis.
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What happens when a cell divides to form gamete?
Copies of the genetic information are made and then the cell divides twice to form four gametes, each with a single set of chromosomes.
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What happens when gametes join at fertilisation?
A single body cell with new pairs of chromosomes is formed. A new individual the develops by this cell repeatedly dividing by mitosis.
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What is difference in the differentiation of animal and plant cells?
Animal cells usually differentiate at an early stage in their life whereas many plant cells retain the ability to differentiate throughout their life. In mature animals, cell division is restricted to repair and replacement.
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What are stem cells? What can they do?
Cells from human embryos and adult bone marrow. They can be differentiated into many different types of cells (eg. nerve cells).
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What kind of treatment can human stem cells be used for?
Paralysis.
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How are offspring produced through asexual reproduction?
Mitosis from the parent cells (they contain the same alleles as the parent cells).
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How does sexual reproduction help genetic variation?
When gametes fuse, one of each pair of alleles comes from each parent.
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What are the sex chromosomes in females?
**
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What are the sex chromosomes in males?
XY
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What is a recessive allele?
An allele that controls the development of characteristics only if the dominant allele is not present.
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What is a dominant allele?
An allele that controls the development of a characteristic when it is present on only one of the chromosomes.
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What are chromosomes made up of?
Large molecules of DNA - which has a double helix structure.
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What is a gene?
A small section of DNA.
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What does each gene code for?
A particular combination of amino acids which make a specific protein.
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What does each person (apart from identical twins) have? And why is this useful?
Unique DNA. This can be used to identify people through DNA fingerprinting.
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What is Polydactyly? How is it passed on?
Having extra fingers or toes. It is caused by a dominant allele of a gene and can be therefore passed on by only one parent who has the disorder.
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What is cystic fibrosis? How is it caused?
A disorder of cell membranes. It has to be inherited from both parents as it is a recessive allele of a gene.
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How can disorders be either prevented or prepared for?
Through embryo screening.
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Other cards in this set

Card 2

Front

How do body cells divide?

Back

Mitosis.

Card 3

Front

What do chromosomes contain?

Back

Preview of the front of card 3

Card 4

Front

What happens when a body cell divides by mitosis?

Back

Preview of the front of card 4

Card 5

Front

When does mitosis usually occur?

Back

Preview of the front of card 5
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