Sex cell (sperm or egg)have 1/2 number of chromosomes as they need to make correct number when they fuse together
Chromatids
One of the two strands that make up a single chromosome when it is preparing to divide
Phenotype
The physical characteristics of an organism. Described by words (brown eyed)
Genotype
The genetic content of an organism, describing the alleles an organism has. Represented by letters (Bb)
Homologous
A pair of chromosomes that contain the same genes in the same locations, their alleles may differ
Haploid
The number of chromosomes contained in a gamete is referred to as this
Diploid
The number of chromosomes contained in all somatic (body) cells are referred to ad this
Heterozygous
When 2 different alleles are present for a gene in the genotype (Bb)
Homozygous
When the 2 alleles for a gene are the same in the genotype (BB)if both chromosomes in a pair contain the same allele of a gene, the individual is homozygous for that gene
Dominant allele (capital letter)
Always expressed even if only 1 copy is present (brown eyes allele = B, Bb or BB)
Recessive allele (lowercase letter)
2 copies needed for it to be expressed in the phenotype (blur eyes = bb, phenotype)
Clone
An organism that is genetically identical to its parent
At fertilisation ..
Gametes join to form a single body cell with new pairs of chromosomes. This cell repeatedly divides by meiosis to form many cells.
Genetic variation examples
Eye colourHair colourBlood group
Environmental variation examples
Height Weight Teeth condition
Polydactyl
Genetic disorder - Having extra fingers or toes DOMINANT ALLELEcan be passed on by only one parent who has the disorder
Cystic fibrosis
Genetic disorder - disorder of cell membranes, causes production of sticky mucus - can affect several organs; lungs, pancreasRECESSIVE ALLELEcan be passed on by parents who may be carriers, and not actually have the disorder themselves
Sickle cell anemia
Genetic disorder - affects red blood cells, affects shape of RBC, which cannot carry O2 efficiently + may block small blood vessels->painRECESSIVE ALLELE
Downs syndrome
Extra chromosome
Embryo screening
-DNA isolated from embryo cells -gene probe that will bind onto the gene for a specific disorder is produced -probe usually has fluorescent chemical attached to it -probe added to mixture containing DNA sample from embryo-UV light used to detect probe attached to gene for the disorder
How DNA controls you?
-genes made from DNA-code for proteins-proteins such as enzymes control reactions in body/characteristics
plantsDNA comes from adult plantcut piece of plant offsometimes use hormones and nutrient mixes
tissue culture:
plantsDNA comes from adult plantuse a cell scraped from a planthormone solutions, nutrients required
embryo cloning:
animalsDNA comes from embryopull apart embryo into separate cells before they become specialised - these grow into clonesneed surrogate mothers
adult cell cloning:
animalsDNA comes from adult animalfuse nucleus from one animal with empty egg - clones nucleus donorneed surrogate mothers
genetic engineering?
changing DNA of an organism
Cloning?
making a genetically identical organism
For questions on genetic engineering remember...
plasmids are only used to transfer DNA to microorganisms (bacteria)if youre trying to engineer an animal/plant, you insert DNA directly into them when theyre still an embryo
For ethics questions on gene technology, cover the following:
-benefits-economics/costs-effects on environment-religious opposition-morality/ethics-health and safety
difference in the characteristics of individuals of the same kind may arise due to differences in:
- genes they've inherited (genetic causes)- condition in which they have developed (environmental causes)- a combination of the above
Size order or gene, nucleus and chromosome?
nucleus containschromosomes carry genes
genetic diagrams:
biological models used to predict outcome of crossesGreger Mendel was the first to suggest separately inherited factors which we now call genes
chromosome made up of ...
large molecules of DNA (deoxyribonucleic acid)
DNA contains?
coded information that determines inherited characteristics