Cell Division Flashcards
Ch 14
Definition of cell continuity?
means that all cells develop from pre-existing cells.
What are chromosomes?
are coiled threads of DNA and protein.
Humans have how many chromosomes in each body cell?
46.
Discuss chromosomes when a cell is not dividing?
they exist as long, thin threads called chromatin.
At cell division, chromatin…?
contracts to form a number of clearly distinguishable chromosomes.
What’s a gene?
a section of DNA that contains the instructions for the formation of a protein.
Definition of a haploid cell?
has one set of chromosomes.
Definition of diploid cell?
has two sets of chromosomes.
Haploid is symbolised by what letter?
n.
Diploid is symbolised as what?
2n.
What’s a homologous pair?
is two chromosomes of similar size with the same sequence of genes.
The cell cycle describes what?
the life cycle of a cell.
Definition of interphase?
state of non division.
What’s the longest phase in the cell cycle?
interphase.
Interphase accounts for over what % of the cycle?
90%.
Name 4 things that happen in interphase?
- photosynthesis,
- respiration,
- DNA replication,
- protein synthesis.
Definition of mitosis?
cell/nuclear division, forming two identical (daughter) cells.
What’s the function of mitosis in unicellular organisms?
reproduction.
What’s function of mitosis in multicellular organisms?
growth/repair of tissue.
Name 4 human cells not produced by mitosis?
- sperm,
- egg,
- sex cell,
- gamete.
What is cancer?
uncontrolled mitosis.
What does benign mean?
kind.
What happens in a benign tumour?
the cells stop dividing after some time.
Are benign tumours life threatening? Why/why not?
no as they don’t invade other tissues.
Give 2 examples of benign tumours and how they are caused?
- warts, caused by a virus.
- skin ‘tags’, small blobs of raised skin.
What cells form a malignant tumour?
abnormal cells.
Are malignant tumours life threatening? Why/why not?
they can be as they can invade other cells and can move from one place to another in the body.
The movement of malignant cells is called?
metastasis.
What are oncogenes?
cancer-causing genes formed from altered normal genes.
What are carcinogens?
cancer-causing agents.
Name 3 common carcinogens?
- cigarette smoke,
- asbestos fibres,
- ultraviolet radiation.
Name 3 treatments for cancer and describe them.
- surgery.
- radiation: burn out cancer.
- chemotherapy: use of chemicals that slow down mitosis.
What’s meiosis?
a form of nuclear division in which the four daughter nuclei contain half the chromosome number of the parent nucleus.
3 functions of meiosis?
- produce gametes (for sexual reproduction).
- allow for diploid number.
- restore chromosome number.
Give 2 reasons meiosis allows for variation?
- rearrange genetic material.
- produces non-identical cells.
Four stages of mitosis in order?
prophase, metaphase, anaphase, telophase.
What starts to chromatin in prophase?
starts to contract early.
What starts to contract in prophase?
chromatin.
What become visible as double-stranded structures in prophase?
chromosomes.
Chromosomes become visible as what in prophase?
double-stranded structures.
The point at which the strands are attached in a double-stranded chromosome is called?
a centromere.
The fibres that appear in the cytoplasm in prophase are called?
spindle fibres.
In prophase the spindle fibres collectively form a structure called the what?
spindle.
What happens the nuclear membrane in prophase?
starts to break down.
What happens the nuclear membrane in metaphase?
completes it’s breakdown.
What happens the chromosomes in metaphase?
line up across the middle, or equator, of the cell.
What happens the spindle fibres in anaphase? What does it cause?
spindle fibres contract causing the centromeres to split.
What happens the chromosomes in anaphase?
pulled apart to opposite poles of the cell.
What happens spindle fibres in telophase?
break down.
What begin to re-form in telophase?
one or more nucleoli (singular: nucleolus).
What forms around the chromatin at each end of the cell in telophase?
nuclear membrane.
What happens at the end of mitosis in telophase?
divided into two identical nuclei.
Cell division follows immediately after what?
mitosis.
Cell division occurs in animals by a process called?
cleavage.
What forms during cell division in animals?
cleavage furrow forms.
What forms during cell division in plants?
plate forms.
Differences between mitosis and meiosis?
Mitosis: 2 cells are formed.
Meiosis: 4 cells are formed.
Mitosis: daughter cells have identical genes on their chromosomes.
Meiosis: daughter cells have different genes on their chromosomes.
Mitosis: chromosome number stays the same.
Meiosis: chromosome number is halved 2n-n.
Describe prophase.
- at end of interphase/early prophase, chromatin starts to contract.
- chromosomes become visible as double-stranded structures. The point at which the strands are held together is called a centromere.The two strands in a chromosome have identical genes, each strand is a chromosome.
- fibres that are in cytoplasm are called spindle fibres. Collectively they form a structure called the spindle.
- nuclear membrane starts to break down.
- double stranded.
Describe metaphase.
- nuclear membrane completes it’s break down.
- a spindle fibre from each end/pole of the cell attaches to each centromere.
- chromosomes lineup across the middle or equator of the cell.
Describe anaphase.
- spindle fibres contract. Causes the centromeres to split.
- one strand/chromosome from each double-stranded chromosome is pulled to opposite poles of the cell. Meaning the cell has 8 chromosomes here. The 4 chromosomes pulled to each pole have identical genes.
Describe telophase.
- the 4 chromosomes at each pole begin to lengthen and become hard to distinguish.
- spindle fibres break down.
- one or more nucleoli (sing: nucleolus) begin to re-form.
- nuclear membrane forms around the chromatin at each end of the cell.
- at end of mitosis the original nucleus has divided into 2 identical nuclei.
Many of the proteins produced by genes are?
Enzymes
All the genes in an organism make up its?
Genome
Name some features controlled by genes in humans, then plants.
Eye colour, production of skin pigment.
Petal colour, leaf shape
Genes are said to be?
Units of inheritance
Units of inheritance refer to?
Genes
Name two haploid cells in humans.
Sperm and eggs
What happens chromosomes in interphase?
Elongated
Cells aren’t dividing in interphase but they are active, how so?
- Producing new organelles. Forms chemicals needed for growth
- Chromosomes at the end produce identical copies of themselves. The duplication produces a chromosome with 2 strands which have identical genes.
Mitosis takes place in what kind of cells?
Non-reproductive cells called somatic cells
Meoisis occurs where in humans? Why there?
ovaries and testes to produce gametes (eggs and sperm).
What’s the centromere?
Point at which the chromosomes are attached in a double-stranded chromosome.
