b5.2 Flashcards
(17 cards)
- What does cell division by mitosis produce?
(two “i”s are identical cells)
-two new cells that are genetically identical to each other and to the parent cell
- What is an organelle?
-any of a number of organized or specialized structures within a living cell
- What is the cell cycle?
-when cells grow (to replace damaged cells) and divide (to produce more cells) repeatedly
- What are the two main processes in the cell cycle?
- cell growth (first)
- cell division through mitosis (second)
- What is the process of cell growth in the cell cycle?
-Molecule DNA splits
-bases on free-floating nucleotides pair up with matching bases on the DNA
-cross links forb between the bases and old DNA strands= nucleotides are joined together
=two molecules identical to original molecule are formed
- What happens in the process of cell growth in the cell cycle?
- numbers of organelles increase
- the chromosomes are copied when the two strands of each DNA molecule separate and new strands form alongside them
- What happens in the process of cell division through mitosis in the cell cycle?
- copies of the chromosomes separate
- the nucleus divides
- What is the process of division through mitosis in the cell cycle?
-cell has two copies of its DNA spread out in long strings
-before cell divides, DNA forms X shaped chromosomes, each arm is duplicate of other
-chromosomes line up at centre
-cell fibres pull them apart, two arms of each chromosome are pulled to opposite ends
-membranes form around each set of chromosomes= nuclei of new cells
-cytoplasm divides
=two new cells genetically identical to each other and the parent cell
- What does cell division by meiosis produce?
(egg + sperm= gametes)
-gametes
- How many chromosomes do gametes have?
- 23, half the number than a normal body cell
- (only one copy of each chromosome)
- What is the process of producing gametes through meiosis?
-before cell divides, DNA forms X shaped chromosomes, each arm is duplicate of other
FIRST DIVISION
-chromosome pairs line up in centre of cell
-pairs pulled apart= new cell has one copy of each chromosome= some of mothers/fathers chromosomes go in each new cell
SECOND DIVISION
-chromosomes line up in centre of cell
-arms of chromosomes pulled apart
=four gametes with single set of chromosomes in each
- Why do gametes produced in meiosis only contain half the chromosome number of the parent cell?
-because two gametes join at fertilisation= zygote with 46 chromosomes like a normal body cell
- What happens to the zygote after fertilisation?
-it grows by repeatedly dividing by mitosis
- How many divisions are involved in meiosis?
-2
- Where does meiosis occur?
-ONLY in the testes and ovaries (reproductive organs)
- What is a zygote?
-a fertilised egg, formed by two gametes (egg and sperm) combining
- How many chromosomes does a zygote have?
- 46 individual chromosomes
- 23 pairs of chromosomes, one from each parent
