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Genetics Chapter 11 BIO Cheat Sheet by

Gregor Mendel's Peas

- gregor mendel (austrian monk)
- fertil­iza­tion: process where male and female reprod­uctive cells join
- self pollin­ation: sperm cells in one flower fertilize egg cells in same flower
- true breeding: if self-p­oll­inate -> produce identical offspring
- mendel wanted to cross pollinate

Genes & Dominance

- trait: specific chract­eristic
- original (paren­tal), first generation (F1), second generation (F2)
- hybrids: offspring of crosses
- genes: chemical factors that determine traits
- alleles: different forms of genes
- principle of dom: some alleles are dom & some are recessive


- recessive alleles seemed to disappear in F1 and reapear in F2
- this happened b/c of segreg­ation (separ­ation of alleles)
- alleles segreate during the formation of gametes (sex cells)
- two gametes; each gamete carries a single copy of each gene

Genetics & Probab­ility

- principles of probab­ility can be used to predict the outcomes of genetic crosses

Punnet Squares

- homozygous (TT); hetero­zygous (Tt)
- phenotype: physical charac­ter­istics; genotype: genetic makeup

Probab­ility & Segreg­ation

- mendel's model: 3/4 (domin­ant), 1/4 (reces­sive)

Indepe­ndent Assortment

- mendel performed the two-factor cross
- indepe­ndent assort­ment: alleles for one trait segregated indepe­ndently from the alleles for another trait
- principle of ind assort­ment: genes for different traits can segregate indepe­ndently during formation of gametes

Beyond Dominant & Recessive Alleles

- some alleles are neither dominant bi recessive & many traits r controlled by multiple alleles or multiple genes
- incomplete dominance: cross btwn red flower & white fl = pink fl
- codomi­nance: chicken feathers r black & white
- multiple alleles: many genes have multiple alleles (rabbit coat, blood type)
- polygenic traits: traits controlled by two or more genes (skin, eye colors)

Chromosome Number

- homolo­gous: a pair of chromosoes (one inherited from mother & one from father)
- haploid: two pairs (4)
- diploid: four pairs (8)

Phases of Meiosis

- meiosis is a process of reduction division where the number of chromo­somes per cell is cut in half through the separation of homologous chromo­somes in a diploid cell
- meiosis 1:
inter 1
pro 1 (crossing over)
meta 1
ana 1
telo 1 & cytoki­nesis
- meiosis 2:
pro 2
meta 2
ana 2
two 2 & cytoki­nesis

Meiosis & Mitosis

- mitosis -> produces two geneti­cally identical diploid cells
- meiosis -> four geneti­cally different haploid cells


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