B2.5- Inheritance

Why are new cells needed?
To grow, to replace or repair
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What must the cells have so they can do the same job?
The same genetic information
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What is a gene?
A small packet of DNA that controls a characteristic or part of a characteristic
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What are alleles?
Different forms of the same gene
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How many chromosomes are in the nucleus of each of your body cells?
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How are these chromosomes arranged?
In 23 pairs
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What is mitosis?
The cell division in normal body cells that produces two identical daughter cells
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What happens in the parent cell before it splits into two daughter cells?
It makes a copy of each of its chromosomes.
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Where does this process happen continuously?
In your skin
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What is a stem cell?
A cell which is completely unspecialised and can become any type of cell that is needed
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How do cells become specialised?
They switch on the genes they need and switch off the ones they do not. Remember, every cell has all the genetic information for the whole body.
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Can an adult muscle cell divide and become a skin cell? Why?
No, because it is already fully specialised and can only divide into more muscle cells
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What is different with plant cells?
Most plant cells can differentiate throughout their whole life.
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Where are undifferentiated cells produced in plants?
At the active regions of the stems and roots
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Can plant cells re-differentiate?
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Why is it more difficult to clone animals than plants?
Because animal cells differentiate permanently early in the life of the embryo and the cells cannot change back.
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What types of cells does meiosis result in? What is special about these cells?
Sex cells or gametes, they have only half the number of chromosomes
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What are the male and female gametes called?
Male = sperm Female = ova
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Where are the male and female gametes made?
Male = Testes Female = ovaries
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How many cell divisions are involved in meiosis?
Two cell divisions
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How many gametes are produced from each cell undergoing meiosis?
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Are each of the gametes identical?
No, they contain random mixtures of the original chromosomes in pairs
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How many chromosomes are in each gamete?
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After fertilisation how many chromosomes does the resulting cell have?
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By what process does a fertilised ovum divide?
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Is there any variation in mitotic division?
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Does meiosis produce variation? Why?
Yes, as every gamete produced from a parent is slightly different, two of these are combined (one from the mother and one from the father) so there is quite a lot of variation between parent and daughter cell.
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What is a zygote?
A new cell formed by the fusion of an egg and a sperm
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Where are the stem cells found in an embryo?
On the inner layer of the hollow ball of cells (embryo)
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Where is a good source of stem cells in adult humans?
Bone marrow
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When might a stem cell in your muscle need to divide?
If your muscle tissue is injured or affected by disease
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What breakthrough in stem cell technology happened in 1998?
Two American scientists managed to culture human embryonic stem cells that were capable of forming other cell types.
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How could embryonic cells be used to help some people with spinal injuries?
Scientists have been able to grow nerve cells from these stem cells and they may be able to be replanted into the body so that damaged nerves can be fixed.
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What is the major problem with embryonic stem cells?
They come from aborted embryos or spare embryos from fertility treatment and many groups think this is highly unethical.
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What problem with the use of stem cells has been seen in mice, which worries some people?
The stem cells could cause cancer if used to treat sick people.
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Where is a potential new source for embryonic stem cells?
The umbilical cord blood of newborn babies
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What have adult stem cells been used to treat?
Some forms of heart disease and to grow some new organs such as tracheas
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Why would growing organs from a person’s own stem cells be so beneficial?
Their body would not reject the transplant as sometimes happens when people receive donor organs from other people.
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What did Mendel investigate to make his findings?
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How did Mendel explain his results?
He suggested there were separate units of inherited material.
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When was Mendel’s work finally accepted? What finding led to this change of thought?
In about 1900, by this time people had seen chromosomes through a microscope
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Other cards in this set

Card 2


What must the cells have so they can do the same job?


The same genetic information

Card 3


What is a gene?


Preview of the front of card 3

Card 4


What are alleles?


Preview of the front of card 4

Card 5


How many chromosomes are in the nucleus of each of your body cells?


Preview of the front of card 5
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