DNA and DNA in cells Flashcards Preview

Biology B2 > DNA and DNA in cells > Flashcards

Flashcards in DNA and DNA in cells Deck (29):

What are chromosomes?

Really long molecules of DNA


What does DNA stand for???

Deoxyribonucleic acid


What does the DNA contain? Basic..

All of the instructions to put an organism together and make it work.


Where is the DNA found?

In the nucleus of the animal and plant cells.


The nucleus holds the ....
These are made up of the double helix structure called ...
A section of this ... is called a ... containing the specific instructions to make a specific protein.

The nucleus holds the chromosomes.
These are made up of the double helix structure called DNA. A section of this DNA is called a gene containing the specific instructions to make a specific protein.


A gene codes for a ...
What does it "say"?

specific protein
which order to put the amino acids in.


How do cells make proteins?

They string amino acids together in a particular order.


How many amino acids are used, how many proteins do they make.

20, they make thousands of different proteins.


What does DNA determine?
What does this then determine?

What protein each cell will produce, therefore what cell it will be, e.g the cell making haemoglobin will have to be a RB cell


What can you use DNA for in industry?

To identify a father or to catch a criminal.


Is DNA unique?

Everyone has unique DNA except for same sex twins who are clones.


What is DNA fingerprinting?
How does this help?

Where you cut up a person's DNA into small sections and then separate them.
As everyone's is different you an compare them to tell people apart.


Where is fingerprinting used?

In forensic science - (hair skin semen etc) can be taken from a crime scene and compared with DNA from a suspect
Paternity testing


Views on genetic databases...
For, why?
Against, why?
Scientific problems?

DNA from a crime scene could be checked against everyone in the country to see who it was.
A big invasion of privacy, how safe would the data be and what else it may it be used for...
False positives can occur if there are errors in the procedure or if the data is misinterpreted.


Why do cells have to divide?

So we can survive and grow.


What is the purpose of mitosis?

To make new cells for growth and repair.


What do body cells normally have (chrom)

Two copies of chromosomes, one from the father, the other, from the mother.


How many chromosome pairs do we have?



When body cells divide it needs to make new cells what?

Identical to itself, with the same number of chromosomes.


Definition of mitosis...

When a cell reproduces itself by splitting to form two identical offspring.


Describe what happens in Mitosis...
1. Strings
4. membranes
5. cyp
6. Two

1. A cell than hasn't divided has all it's DNA spread in long strings
2. If it receives a signal to divide it will duplicate it's DNA so there's one copy for each cell. The copied DNA forms and x shaped chromosome, with each arm being an exact duplicate of the other.
3. The chromosomes line up at the centre of the cell and cell fibres pull them apart, the two arms of each chromosome go to opposite ends of the cell.
4. Membranes form around each of the sets of chromosomes. The sets become two nuclei.
5. The cytoplasm divides.
6. Now there are two new cells, nucleus each, with exactly the same DNA and genes, identical, there is no variation.


What reproduction uses mitosis? e.g

Asexual, e.g strawberry plants form runners to spread using this process.


MiTosis =
MEIosis =

Two full sets of chromosomes
Mei - One set, singular, of chromosmes


Gametes have how many chromosomes?

Half the number of normal cells.


What do the two gametes do in sexual reproduction? How does the offspring only receive 23 pairs of chromosomes?

Produce one offspring.
The gametes only have 23 chromosomes each instead of 46.


How does sexual reproduction produce variation?

With two sets of chromosomes there is variation as the offspring inherits characteristics from both parents.


Why does meiosis happen?

Meiosis happens so that the cells only have half the number of chromosomes.


Describe how meiosis happens...
1. Mitosis
2. Division one
3. One x in each
4. Division 2
5. Four

As with Mitosis the DNA duplicates itself before the cell starts to divide, into x s with identical arms.
The first division is when the the chromosome pairs (xx) line up in the centre of the cell.
The two x s are pulled apart so each new cell only has one copy of each new chromosome. Some of the F in one, some of the M in the other.
In the 2nd division the chromosomes line up again in the centre and are pulled apart by fibres, as they are still in x form.
Now there are 4 cells with only single sets of chromosomes inside.


Why does meiosis happen, to get 4 cells?

It does this so that from one cell it can multiply to get 4, then the single armed chromosomes replicate again to make even more, this is how the cells grow and multiply in number.