genetics 1 - the cell cycle Flashcards
What does the cell theory state?
- All living things are made up of one or more cells
- Cells are the smallest units of living organisms
- New cells only come from pre-existing cells by cell division
Where do daughter cells come from
Parent cells
Somatic cells contain twice the number of…
Twice the number of chromosomes as gamete cells
What do gamete cells consist of
Ovum and sperm
How many chromosomes do humans have
46
What is the difference between a haploid and diploid cell?
Haploid cells only consist of one set of chromosomes.
Diploid cells consist of two sets of chromosomes
Somatic cells are diploid. Examples include:
Body (somatic) cells (nerve, muscle, bone)
Gamete cells are haploid. Examples include:
sex cells (sperm & egg)
What are the functions of cell division?
- Growth of Organisms
- Repairing of tissue and/or organs
- Replacing dying/dead cells
(and reproduction, but only for unicellular organisms such as bacteria)
What are chromosomes made up of?
DNA containing genetic information and protein
Chromatins are ___, whereas chromosomes are __
chromatins are long, thread-like, and spread out
whereas chromosomes are tightly condensed
What is a chromatid?
A half of a duplicated chromosome
Before mitosis, DNA replicates to form..
Two genetically identical sister chromatids held together at the centromere
How many chromosomes and chromatids are on this?
xx xx xx ( xx xx (
22 chromatids
12 chromosomes
What is the longest phase of interphase
The G1 phase
What happens in the G1 phase?
Cell growth, development, duplication of organelles, and metabolic activity. Proteins and RNAs are synthesized, and the centromere is made.
Why is the G1 checkpoint important?
It ensures that the cell is large enough to divide and has enough nutrients to support daughter cells, and checks that DNA isn’t damaged
Why are there G (Gap) phases?
Before mitosis occurs, the parent cell has to be large enough in size and have created the required organelles so that daughter cells will operate normally
What happens in the synthesis phase?
Chromosomes are replicated and DNA exists as an uncondensed chromatin (looks like a bowl of spaghetti)
What happens in the G2 Phase?
Growth of cells and the duplication of organelles continues. More metabolic activity going on to prepare for mitosis
Why is the G2 checkpoint important?
It ensures that DNA replication (synthesis phase) has been completely successful
What would happen if the G2 checkpoint failed?
The daughter cells would carry damaged or incomplete DNA within chromosomes. This could lead to mutations, genetic instability, and potentially harmful cellular functions which can lead up to cancer.
What happens in the M phase (mitotic phase)?
Mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis (division of cytoplasm into daughter cells)
Why is the M phase checkpoint important?
It ensures that all chromosomes are attached to the spindle fibres, preventing unequal distribution of genetic material in daughter cells which could lead to genetic abnormalities, cell dysfunction, or cancer
What would happen if the M phase checkpoint failed?
The daughter cells wouldn’t have the correct number of chromosomes
What happens during prophase?
The chromatin coils to condense into chromosomes.
Two copies of a chromosome (called sister chromatids) are joined by the centromere.
Spindle fibres begin to form and attach to centromeres on chromosomes; centromeres are made of microtubules.
The nuclear membrane and nucleolus disappear.
What happens during anaphase?
The centromeres split apart. The sister chromatids are pulled apart by spindle fibres as they shorten and pull it to opposite poles of the cell.
Each chromatid becomes a chromosome, and each pole has a full set of chromosomes.
What happens during metaphase?
The spindle fibres guide the chromosomes to the equator (centre) of the cell – remember as metaphase = middle.
The spindle fibres attach to centromeres from either pole.
What happens during telophase?
The spindle fibres disintegrate and the chromosomes de-condense back into the chromatin state (noodle).
A new nuclear envelope forms around each set of chromosomes, and the nucleolus forms within each new nucleus.
What happens during cytokinesis?
An indentation forms in the middle and pinches through. The cytoplasm divides to form two genetically identical daughter cells.
In plants, cytokinesis would result in a cell plate forming in between 2 daughter cells to form new cell walls.
Since prokaryotic cells don’t have a nucleus, they complete cell division with..
A process called binary fission, which is asexual reproduction by a separation of the body into two new bodies
What happens when checkpoints fail?
Since the cell cycle isn’t regulated, uncontrolled cell division occurs and forms cancer cells. This results in two types of tumours: Benign (localised) and metastatis (spreads to other parts of the body)
What are the three techniques of treating cancer?
Radiation, chemotherapy, and surgery
What does anticancer medicine/drugs do?
They’re applied to the whole body through an injection and kills rapidly dividing cancer cells/causes them to stop in the G1 phase before progressing
Side effects of chemotherapy?
Hair loss, nausea, weight loss, and weakness
Why do people lose hair when taking chemotherapy?
The chemicals of chemotherapy kill normal cells that rapidly divide, such as intestinal cells and hair follicles.
What is the DNA structure?
DNA is a polymer of nucleotides –> Adenine, Guanine, Cytosine, and Thymine
What does DNA look like?
It appears as a twisted ladder called a double helix, and is made up of two strands of nucleotides twisted around an axis.
The upright of the ladder is made up of phosphate and pentose sugar, and the rings of the ladder are made up of thymine, cytosine, adenine, and guanine
How do you determine the name of the nucleotide?
You look at the base, since it uses the same word
What is DNA supported by?
The phosphate backbone which provides structural support to the molecule.
What are the complementary base pairs?
Adenine binds to thymine with 2 hydrogen bonds.
Guanine binds to cytosine with 3 hydrogen bonds.
What do purines include?
Purines include adenine and guanine, which participate in DNA and RNA formation. It’s made up of two rings
What do pyrimidines include?
Pyrimidine includes cytosine, thymine, and uracil as bases used for DNA or RNA.
When do mutations occur?
When the nucleotide sequence changes due to a mutagen (chemicals, UV radiation) and causes a non-functional (nonsense) protein to form
What is a semi-conservative replication?
When the double helix is unwound and the parent strand splits into two parts.
The two new parts merge with a newly synthesized/formed strand –> both parts include half a parental strand, and half a newly formed strand.
What are sex chromosomes?
One pair of the 23 pairs of chromosomes.
How do you tell if it’s a biological male or female?
XY –> Male
XX –> Female
What are autosomes?
Every other chromosome except for the sex chromosome (22/23 of the chromosome pairs are autosomes)
What is a homologous chromosome?
Pairs of chromosomes that appear similar by banding pattern, length, or centromere location; but are NOT identical to each other. They carry the same genes and can be different forms such as allele
What is an allele?
An alternative version of a specific gene.
What are spindle fibres made up of?
Hollow tube-like structures called microtubules.
