Week 2 Flashcards
Why would new DNA have to be made?
If new DNA was not formed, your skin would wear away, cuts would not heal and you would run out of blood.
You also would not be able to reproduce.
What is the process of making new DNA called?
Replication
Describe the first step of replication?
The parent DNA molecule starts to unzip at one end.
Describe the second step of replication?
Copying of the DNA has begun with complementary bases attaching to both strands of the DNA.
Describe the third step of replication?
The sugar and phosphate molecules bond with neighbouring nucleotides and new strands of DNA are formed.
What is a chromatid?
Each of the two threadlike strands into which a cell divides during cell division.
Name the two types of cell division?
Mitosis and meiosis
While type of cell division would occur to repair damaged muscle tissues?
Mitosis
Which type of cell division begins around the time of puberty (in some parts of the body)?
Meiosis.
Is mitosis a stop start process?
No
Does mitosis occur in stages?
Yes
Stage 1 of mitosis?
Chromosomes replicate to become double stranded
Has the cell divided before or after stage of mitosis?
Before
Are individual chromosomes visible during stage one of mitosis?
No
Stage 2 of mitosis?
Double stranded chromosomes become visible.
What happens to the DNA in stage two of mitosis?
It coils up.
Are individual chromosomes visible during stage two of mitosis?
Yes
What is each chromosome composed of?
Two chromatids
What happens to the nuclear membrane between stage two and three of mitosis?
It breaks down
Stage 3 of mitosis?
Double stranded chromosomes line up along the equator of the cell
Where is the cell equator?
The middle of the cell
Where are the cell poles?
At opposite ends of the cell
What is the purpose of the network fibres?
To contract and pull the chromosomes to opposite poles.
Stage 4 of mitosis?
The chromosomes move to opposite ends of the cell
Sage 5 of mitosis?
Two nuclei form, each with the diploid number of chromosomes.
Stage 6 of mitosis?
Membranes form, separating the two nuclei into the two daughter cells
What does the cell division process of meiosis produce?
Gametes (eggs and sperm)
Are the the processes of mitosis and meiosis exactly the same? Explain?
No. Meiosis produces four daughter cells whereas mitosis only forms two.
Stage 1 of meiosis?
Pairs of double stranded chromosomes line up.
Stage 2 of meiosis?
One double stranded chromosome of each pair move to each pole.
Stage 3 of meiosis?
Two cells are formed
Stage 4 of meiosis?
Double stranded chromosomes line up
Stage 5 of meiosis?
Chromosomes separate and move to poles
Stage 6 of meiosis?
Four daughter cells result with a haploid number of chromosomes
Contrast mitosis and meiosis?
Meiosis produces gametes while mitosis repairs and makes the body grow.
Meiosis occurs in sex cells while mitosis occurs in all other cells.
Mitosis produces two daughter cells while meiosis produces 4 daughter cells.
Mitosis produces a diploid number of chromosomes while meiosis produces a haploid number of chromosomes.
What is a zygote?
The cell produced by the union of two gametes.
Are all the cells in your body the same cells as when you were born?
No. Cells die and are replaced over and over again. They divide over and over again too.
What does XX represent?
Females
What does XY represent?
Males
What does the haploid number (n) represent?
The number of chromosomes found in sex cells
What does the diploid number (2n) represent?
The number of chromosomes found in body cells
How many chromosomes come from your mum?
23
How many chromosomes come from your dad?
23
If you have 46 chromosomes, how many of them are sex chromosomes?
2
If you have 46 chromosomes, how many of them are autosomes?
44
Define homologous?
Chromosomes of the same length
44 autosomes = 22 homologous pairs
What does n represent?
The haploid number of chromosomes (23).
What does 2n represent
The diploid number of chromosomes (2 × 23 = 46)
