B8 Inheritance
Types of variation
Variation is the small differences that exist between members of the same species.
Continuous variation is influenced by both genes and environment, resulting in a range of phenotypes between extremes that are usually bell curved. E.g. height, weight.
Discontinuous variation is caused by genes alone and results in a limited number of distinct phenotypes with no intermediates. E.g. blood type, eye color
Generating genetics
DNA is a carrier of genetic information that is capable of self replicating.
Genes is a length of DNA that is the unit of heredity, codes for a specific protein. Can be copied and passed on to the next generation.
Chromosome is a thread of DNA that is made up of a string of genes.
Inheritance is the transmission of genetic information through generations.
Chromosome > genes > DNA.
Haploid means having a single set of unpaired chromosomes.
Diploid means containing 2 complete sets of chromosomes, one from each parent.
Gamete is a mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction to form a zygote.
Zygote is a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.
Cell division
Mitosis makes body cells with 46 chromosomes.
The nuclear division giving rise to genetically identical cells in which chromosome # is maintained by exact duplication. Look at notebook for details.
Meiosis makes sex cells with 23 chromosomes. It is reduction division where chromosome # is halved from diploid to haploid, and it happens during gamete production. Consult notebook for pretty pictures.
They are important becauses mitosis is for growth and repair while meiosis is for reproduction.
Inheritance
Phenotype is the ‘phenomenon’ – outcome of a certain genetic trait.
Genotype is the specific genes the organism has. (e.g. female XX male XY)
Alleles are 2+ alternative forms of a gene that codes for the same proteins.
Homozygous refers to an individual that has 2 identical alleles of a gene.
Heterozygous refers to having 2 different alleles of a gene.
Dominant refers to a gene is expressed in offspring even when inherited from only one parent.
Recessive refers to a gene that is expressed only when inherited from both parents.
I can draw punnett squares and so can you.
Sex is determined by X and Y sex chromosomes. A female has 2 x chromosomes and eggs only carry an X chromosome. Male has 1 X and 1 Y, and sperm carries either X or Y chromosome. The whole Chromosome is used in the cross rather than the alleles of a gene.
Mutation
Mutation is a change in gene/chromosome caused by chemical/random/radiation.
E.g. sickle cell anemia that causes the red blood cell to take another shape, caused by mutation in gene that codes for hemoglobin.
Artificial selection
People choose the characteristics they want to appear in the next generation. You can do this to everything that breeds except people, because that is very unethical.
E.g. Cattles may be bread for quantity/quality of milk/meat
Sheeps for quant/qual of wool
Plants for taste/pest tolerance/drought tolerance.
Selective breeding
Is when you select two parents with ideal traits and breed them together to pass on those traits. E.g. I take the sweetest strawberries and the biggest strawberries and breed them together so I get both genetic characteristics, I am a perfect strawberry yay.
Natural selection
The process whereby organisms better adapted to their environment tend to survive and produce more offspring, and this is how evolution happens over successive generations. Variation in different members of the same species cause some to be better adapted, and overpopulation ensures that some survive. Better genes get passed on.
Evolution is change in the heritable characteristics of biological populations over successive generations.
Antibiotic resistance
Similarly, the overuse of antibiotics may cause bacteria that are resistant to everything because they have survived over the usage and evolved. They are called superbugs.
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