New cells from old Flashcards
(29 cards)
When does DNA replication occur in mitosis?
During interphase, specifically S (growth) phase in the cell cycle which is prior to cell division.
What are homologous pairs?
It is a pair of chromosomes, one maternal (from mum) and one paternal (from dad). They pair up with each other during the initial phases of meiosis.
What is a diploid cell?
A cell consisting of homologous pairs (2n).
In humans, one chromosomes of each homologous pair…
…is inherited from each parent.
What are germ-line cells?
Sex cells - they only have one chromosomes from each homologous pair and is thus deemed haploid (n).
How is a diploid cell formed?
When two haploid cells fuse through fertilisation.
What is similar between the products of binary fission and mitotic division?
Both have the same number and type of chromosomes as the parent, preserving the genetic information from one generation to the next (binary fission).
Describe the step-by-step process of binary fission.
- The DNA untwists, allowing enzymes to aid in its replication.
- After the strands of the double helix have separated, both of the single strands act as templates for new strands to form.
- The result is two DNA double helices (two chromosomes) in circular loops, which are attached separately by proteins to the cell membrane near the middle of the cell. As the cell grows, the cell membrane between the attached loops expands and moves in opposite directions.
- The division into two cells is completed by the synthesis of a new wall material that is created across the equator.
What is aseuxal reproduction?
The process of forming offspring from a single parent without fertilisation taking place; not all reproduction involving one parent is asexual.
How does genetic variation occur in asexual reproduction?
Mutation.
What is the cell cycle?
An alternating cycle of cell division and enlargement consisting of interphase, mitosis and cytokinesis.
What does interphase involve?
It involves the enlargement of the cell due to the synthesis of new cell components, including new organelles and replication of DNA, alongside the intake of water.
How is DNA stored when a cell is not dividing?
As chromatin, which consists of long, thin threads of DNA and protein
What happens to DNA when it is replicated?
The chromatin condenses to form chromosomes. These consist of two identical sister chromatids joined at the centromere.
What occurs during prophase in mitosis?
The nuclear envelope disintegrates, and the nucleoli disappear.
- Centrioles divide to form two pairs which move to opposite poles (centrioles are made up of microtubules); plant cells lack a centriole.
- Spindle apparatus forms (centrioles and spindle fibres)
- Midway between the poles is a region of the spindle called the equator.
What occurs during metaphase in mitosis?
Chromosomes line up at the equator (metaphase plate) and attach to the spindle by their centromeres
- Sister chromatids face opposite poles
What occurs during anaphase in mitosis?
Characterised by the v-shaped appearance of the sister chromatids as they separate and move to opposite poles
- Spindle contraction separates the centromeres and pulls the chromatids towards the poles
What occurs during telophase in mitosis?
New nuclear envelopes form around both sets of chromosomes, nucleoli reappear and chromosomes uncoil, reverting back to chromatin.
What occurs during cytokinesis following mitosis?
It ensures that the cytoplasmic contents are divided between the two new daughter cells. Each daughter cell is genetically identical to each other and to the original parent cell.
Provide the basic definitions for mitosis and cytokinesis.
Nuclear division (mitosis), and division of the cytoplasm (cytokinesis).
What is mitosis crucial for?
It enables the new zygote (sperm and egg) to grow and develop into a fully formed adult, and for repair/replacement of damaged cells and tissues.
Compare the characteristics of binary fission and mitosis (replication prior to division).
Binary fission:yes
Mitotic division: yes
Compare the characteristics of binary fission and mitosis (nuclear division).
Binary fission: no
Mitotic division: yes
Compare the characteristics of binary fission and mitosis (type of chromosomes).
Binary fission: single, circular
Mitotic division: many, linear
