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Define Inheritance

Inheritance is the transmission of genetic information from generation to generation


Where are the chromosomes located

nucleus of cells


What are chromosomes?

thread-like structures of DNA, carrying genetic information in the form of genes


Define gene.

A gene is a short length of DNA found on a chromosome that codes for a specific protein


Define allele

different versions of a particular gene


What are female and male sex chromosomes.

female- XX
male -XY


Describe the process of protein synthesis.

i. Proteins are made by ribosomes with the sequence of amino acids controlled by the sequence of bases contained within DNA
ii. as DNA is too big to travel out of the nucleus pore, so the base code is transcribed onto RNA molecule called messenger RNA.
iii. mRNA then moves out of the nucleus and attaches to a ribosome
iv. the ribosome reads the code on mRNA in groups of three.
v. in this way ribosome translates the sequence bases into a sequence of amino acids that make up a protein
vi. Once the proteins are assembled, they are released from ribosome so it can fold an form a structure of a PROTEIN.


How does DNA controls cell function?

By controlling the production of proteins- protein synthesis
The proteins could be enzymes, antibodies or neurotransmitters.


Why are some genes in the body not expressed?

Although all body cells in an organism contain the same genes, many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs


Define Mitosis.

Mitosis is defined as nuclear division giving rise to genetically identical cells


What is mitosis used for?

is used for growth, repair of damaged tissues, replacement of cells and asexual reproduction and is known as mitosis


Describe the process of mitosis?

Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x – shaped chromosomes)
Chromosomes line up along the centre of the cell where cell fibers pull them apart
The cell divides into two; each new cell has a copy of each of the chromosomes


What is the importance of mitosis?

All cells in the body (excluding gametes) are produced by mitosis of the zygote
Mitosis is important for replacing cells e.g, skin cells, red blood cells and for allowing growth (production of new cells e.g. when a zygote divides to form an embryo)


Mitosis occurs in-

Growth: mitosis produces new cells
Repair: to replace damaged or dead cells
Asexual reproduction: mitosis produces offspring that are genetically identical to the parent


Stem cells-

Many tissues in the human body contain a small number of unspecialised cells
These are called stem cells and their function is to divide by mitosis and produce new daughter cells that can become specialised within the tissue and be used for different functions


Define Meiosis

Meiosis is a type of nuclear division that gives rise to cells that are genetically different


What is Meiosis used for-

It is used to produce the gametes (sex cells)


Describe the process of Meiosis.

Each chromosome makes identical copies of itself (forming X-shaped chromosomes)
First division: chromosomes pair up along the centre of the cell, recombination occurs and then cell fibres will pull the pairs apart, each new cell will have one of each recombinant chromosome pair
Second division: chromosomes will line up along the centre of the cell, cell fibres will pull them apart (as with mitosis)
A total of four haploid daughter cells will be produced


What is the importance of Meiosis.

Production of gametes e.g. sperm cells and egg cells, pollen grains and ovum
Increases genetic variation of offspring


What is genotype?

The combination of alleles that control each characteristic is called the genotype


What is phenotype?

The observable characteristics of an organism (seen just by looking – like eye colour, or found – like blood type) is called the phenotype


Define dominant allele.

A dominant allele only needs to be inherited from one parent in order for the characteristic to show up in the phenotype


Define recessive allele.

A recessive allele needs to be inherited from both parents in order for the characteristic to show up in the phenotype.


Define Monohybrid inheritance.

Monohybrid inheritance is the inheritance of characteristics controlled by a single gene


what is codominance?

a situation in which both alleles in heterozygote have an effect on the phenotype.


Define sex-linked characteristics?

a characteristic in which the gene is responsible is located on a sex chromosome, which makes it more common in one sex than in another.