B5 Flashcards
Cells divide by two processes which are?
Mitosis and Meiosis
What do similar cells form?
Tissue
What do groups of tissues form?
Organ
What do groups of organs do?
Make up systems within the whole organism
List three reasons why Mitosis occurs?
For growth, repair and to replace old tissues
After Mitosis occurs, what does each new cell have?
Identical sets of chromosomes as the parent cell and the same number of chromosomes as the parent cell and the same genes as the parent cell
To enable Mitosis to take place, what do cells have to go through?
A cycle of growth and then division
What happens when the cell enters the growth phase of the cycle during Mitosis?
The number of organelles increase and the chromosomes are copied - the two strands of each DNA molecule separate and new strands form alongside
What two places does Meiosis only take place in?
Testes and ovaries
What does Meiosis produce?
Gametes for sexual reproduction
How many chromosomes do gametes contain?
Half the number of chromosomes as the parent cell
What happens during fertilisation?
A male gamete and a female gamete fuse together to produce a single boy cell, called a zygote
How many chromosomes does the zygote have?
One whole set of chromosomes because gametes only contain half the number of parent cells, so when both form together it creates a full set
In each new chromosome, how many chromosome come from each parent?
One chromosome from the father and one chromosome from the mother
When the zygote divides, what does it produce?
A cluster of cells called an embryo
Genes are present in the chromosomes in each cell nucleus. What do the genes control?
Growth and development in organisms and the development of characteristics
How do genes control characteristics?
By providing instructions for the production of proteins
The instructions used to help create characteristics are in the form of a code which is made up of four bases. These bases always pair up in what way?
Adenine (A) pairs with thymine (TY) and cytosine (C) pairs with guanine (G)
DNA is too large to leave the nucleus meaning it has to stay inside. The production of proteins takes place outside the nucleus in the cytoplasm. How does this work?
Information stored in the genes has to be transferred into the cytoplasm
How is information in the genes transferred to the cytoplasm?
1- The relevant section of DNA is unzipped
2- Instructions are copied onto smaller molecules called mRNA
3- These molecules leave the nucleus and carry instructions to the ribosomes
4- The ribosomes follow the instructions to make the relevant protein
A group of three base pairs codes for one amino acid in a protein chain, called what?
A triplet code
The structure of the protein depends on what?
The amino acids which make it up
Up to the eight cell stage, all cells in a human embryo…?
Are unspecialised
Can have any gene switched on to form any kind of specialised cell
After the eight cell stage, the cells in an embryo…?
Become specialised
Form different types of tissue
Stem cells could potentially be used to…?
Help treat diseases and disorders
Repair damage to various tissues
What are the three sources of stem cells?
1- Embryos
2- Blood from the umbilical chord
3- Adult stem cells from bone marrow
What process do plant cells divide by?
Mitosis
New cells in plants specialise into the cells of…?
Roots
Leaves
Flowers
Which area of the plant does plant growth occur in?
Meristems - sites where unspecialised cells are dividing by mitosis
What are the two types of meristem?
Lateral, which leads to increased girth
Apical, which leads to increased height in longer roots
If the hormonal conditions in their environment are changed, the unspecialised plant cells can develop into other…?
Tissues - e.g xylem and phloem
Organs - e.g leaves, roots and flowers
Xylem tubes are used by the plant to…?
Transport water and soluble mineral salts from the roots to the stem and leaves
Replace water lost during transpiration and photosynthesis
What are phloem tubes used by the plant for?
To transport dissolved food to the whole pant for respiration or storage
What is one way plants can be reproduced?
1 - Cuttings are taken from the plant
2 - The cuttings are put into a rooting hormone
3 - Roots start to form and the new plants develop
When plants respond to light, they change direction in which they grow. What is this called?
Phototropism
