Genes, Chromosomes and DNA
Nucleus is found in a cell it contains GENETIC MATERIAL.
The gentic material is arranged forming a CHROMOSOME ( there 23 pairs in the body).
From each chromosome there is one very long coiled up chain called DNA.
Opposite to that is short chains called GENES.
Genes control your looks e.g hair colour, and how an organism functions.
Genes can come in DIFFERENT VERSIONS such as a box of chocolates. Some genes contain blue eyes and some brown eyes.
DIFFERENT VERSIONS are called ALLELES.
More on Genes.
GENES make PROTEIN.
PROTEINS are the building blocks for cells.
DIFFERENT VERSIONS of proteins means that we end up with different CHARACTERISTICS.
STUCTUAL = SKIN HAIR BLOOD
FUNCTIONAL = BREAKAGE IN THE DIGESTIVE SYSTEM.
GENOTYPE all the genes it has.
PHENOTYPE are the organism displayed in characteristics.
HUMAN CHARACTERISTICS are eye colour
ENVIRONMENTAL CHARACTERISTICS are scars and skin colour as it changes on where you are.
Genes and Variation
SPERM & EGG have half the normal amount of DNA.
The SEX CELLS only contain 23 pairs on chromosome for each pair.
SPERM fertiilisers the EGG during SEXUAL REPRODUCTION and 23 from the sperm and 23 egg combine.
Two CHROMOSOMES in a pair always carry the same genes.
But because the two chromosomes came from each parent it will have different versions in the chromosome. This is called ALLELES.
ALLELES are the different versions of the same gene.
CHILDREN will look a bit like their parents becaus they have half of each of their genes.
They don't look exactly the same because they don't have all alleles.
Children are unique.
Recap on Genes and Variations.
When producing sperm and egg cells there CHROMOSOMES seperate and go into different cells
Chromosomes in a pair ARE NEVER IDENTICAL because of DIFFERENT ALLELES.
We have 23 CHROMOSOMES that seperate indepently.
SEX CELLS produce by one indivial will probably all be GENETICALLY DIFFERENT.
When releasing an EGG it can be fertilised by any one of millions of SPERM.
BROTHERS AND SISTERS tend to look a bit alike, but they are ALWAYS DIFFERENT.
The COMBINATION OF ALLELES determine the PHENOTYPE.
When you have TWO COPIES of a gene, usally ONLY ONE of them can be expressed in the PHENOTYPE.
HOMOZYGOUS two alleles the SAME
HETROZYGOUS two alleles that are DIFFERENT
DOMINANT strong allele gets want it wants.
RECESSIVE weak allele
DOMINANT CAPITAL VS RECESSIVE small letter
Dominant will win with a recessive. Only recessive will win if there are two the same.
This is a punnet square showing how the child could look like or get.
100% as all have Aa
Male or Female
There are 23 PAIRS of CHROMOSOMES in every human body. The 23 PAIR are labeled XY.
These are the SEX CHROMOSOMES they decide if you are male or female.
ALL MEN HAVE A X and Y chromosome. ( the y makes them male, but no one knowns Y?)
ALL WOMEN have a X and X chromosome
One GENE determines which SEX ORGANS you develop
Some DISORDERS are INHERTITED one or both parents carry a faulty gene.
EXAMPLE are CYSTIC FIBROSIS and HUNGTON'S DISEASE are only caused by one fautly single gene
Most of the DEFECTIVE ALLELES that are responsible for genetic disorders are recessive.
CYSTIC FIBROSIS is a gentic disorder of the cell membranes caused by a faulty recessive allele.
Results on having this are...
- Thick sticky mucus in the air passage, gut and pancreas
- Breathing differculty
- Chest infections
- Differeculty digesting food.
The allele which causes cystic fibrosis is a recessive allele 'f' carried by 1 in 25 people.
For a child to suffer both parent s must be CARRIERS or SUFFERES.
HUNGTINGTON'S DISEASE is caused by a dominant allele.
The results are...
- Memory loss
- Mood changes
- Poor concentration THERE IS NO CURE......
The dominant allele means there is a 50% chance on inheriting the disorder if there is a carrier
Carriers will not know as the disorder starts at the age of 40
GENETIC TESTING can be used on EMBRYOS, CHILDREN AND ADULTS....
When embryos are produced using IVF ( in vitro ferilisation), doctors test the embryo to check if they have got genetic disorders. This is Called PRE- IMPLANTATATION GENETIC DIAGNOSIS. Only the healthy ones are implantedinto the womb.
ISSUES ON GENETIC TESTING...
- The results of gentic tests are not 100%. There are often errors due to things like samples getting contaminated or misinterpretation. This means healthy could be told that they have gentic disorders leaving a FALSE POSITIVE.
- Tests carried out in a pregnancy can cause miscarriage because they are testing the fluids.
Is right to to pass a disorder to that child? Is it right to let a child suffers? Etc..
Insurance compaines may want to know as they may not give life insurance. Work places may not want not want to employ you as you are likely to get ill. Employers may try to give you jobs that don't cause harm.
CLONES are GENETICALLY IDENTICAL organisms.
SEXUAL REPRODUCTION produces offspring that are gentically different. BUT BACTERIA, in SOME PLANTS and ANIMALS can reproduce asexually (with out sexual reproduction) to form clones.
Clones are GENETICALLY IDENTICAL ORGANISMS they have the same GENES and the same alleles of those genes.
CLONES ARE IDENTICAL but can change in the envrionemental factors.
Nature makes Clones
ASEXUAL REPRODUCTION means that there is only one parent, and the offspring are gentically IDENTICAL to each other and the parent.
Most BACTERIA reproduce and divide 1, 1+1, 1+1+1, etc
Some plants reproduce by horizontal stems called RUNNERS that run out of the plant to form a NEW CLONE at there tips.
UNDERGROUND FLESHY STUCTURES clone to form a new identical plant
Identical twins are clones. They are formed just like a baby but then splits into two to form two embryos that are genically identical. So two gentically identical babies are born.
SCIENTISTS can know make ANIMAL CLONES in the LAB
The nucleus of an egg is removed, now the egg is empty, nucleus from a donor is put in the egg, then the cell is simulated so it can divide like a normal embryo. The embryo is now GENTICALLY IDENTICAL to the donor
STEM CELLS can become OTHER types of cells. Most cells in your body are SPECIALISED for a particular job. White blood cells are brilliant at fighting invaders, but they do NOT carry oxygen like red blood cells
Most cells in multicelluar organisms become specialised in early development of the organism
Some cells are unspecialised. They can develop into DIFFERENT TYPES of cells depending on what INSTRUCTIONS they are given. These cells are called STEM CELLS
EMBRYONIC stem cells
- These are unspecialised cells found in early embryos.
- The stem cells are removed from the embryo, embryo is DESTROYED!!
- Scientists find it great as they have protenical to change into ANY kind of cell
ADULT stem cells
- They are unspecialised cells found in adult animals
- They're involved in MAINTAINING AND REPAIRING old and damaged tissue.
- These stem cells can be SAFETLY REMOVED eg. by bone marrow no embroyes are destroyed
STEM CELLS may be used to treat many illnesses.
Medicine already uses ADULT STEM CELLS to cure disease. For example people with BLOOD DISEASES eg. sickle cell anaemia can be treated by bone marrow transplants.
EMBROYONIC stem cells could also be used to REPLACE faulty cells in sick people you could make a beating HEART MUSCLE CELLS for people with heart disease for example.