Cell division
DNA (deoxyribonucleic acid) are long and complex
They carry the genetic codes that determines the characteristics of an organism.
Identical twins have the same DNA but other people have different.
Gene is a short part of a DNA, it codes for a specific characteristic.
Chromosomes are made form long DNA molecules .
46 are found in normal animal cells' nuclei
Mitosis
Genetic material is copied,
Form X shaped chromosomes
Line up at centre
Spindle fibres pull them apart
New membrane form
Cytoplasm splits
Mitosis happens during growth and repair of normal cells.
Gametes
Sex cells
Sperm and egg.
They contain 1 set of generic information when normal cells have 2
Fertilisation occurs when a sperm fuses with an egg,
They divide by mitosis after.
Meiosis- gametes are formed from this kind of cell diviion.
Chromosomes duplicate,
pair up,
Sections of DNa swapped
Divide
Divide again
Stem cells can be differentiated to become specialised cells.
They come from embryos or adult bone marrow. This can be used to treat conditions such as parkinson's disease and paralysis. However there are social and ethical issues regarding this research
Genetic variance
Alleles are different forms of a gene.
They can be dominant or recessive.
Human body cells have 23 pair of chromosomes.
One of these pair control the inheritance of gender.
XY = male XX = female
Alleles control characteristics eg. one can be brown eyes and one can be blue eyes
Dominant alleles develop on the organism if one of both of the chromosomes are present in the pair
Recessive alleles only develop if both alleles are recessive on both chromosomes in the pair.
Heterozygous = 2 different alleles
Homozygous = 2 same alleles
Homozygous recessive = 2 same but recessive alleles.
Variation only occur at sexual reproduction but no a sexual reproduction
There are 2 possible gametes which each gamete contain one allele from a parent
This makes 4 possible outcomes from 2 parents.
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