Bio Study Guide

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4.3 Theoretical genetics
4.3.1 Define genotype, phenotype, dominant allele, recessive allele, co-dominant alleles, locus, homozygous, heterozygous, carrier and test cross * Genotype- the alleles of an organism
* Phenotype- the characteristics of an organism
* Dominant allele- an allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state * Recessive allele- an allele that only has an effect on the phenotype when present in the homozygous state. * Co-dominant alleles- pairs of alleles that both affect the phenotype when present in a heterozygote. * Locus- the particular position on homologous chromosomes of a gene * Homozygous- having two identical alleles of a gene

* Heterozygous-having two different alleles of a gene
* Carrier- an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele * Test cross- testing a suspected heterozygote by crossing it with a known homozygous recessive 4.3.2 Determine the genotypes and phenotypes of the offspring of a monohybrid cross using a Punnett square

R=white petals
r= red petals
Table 1: Observing genotypes and phenotypes
Genotype:| RR| Rr| Rr| rr|
Phenotype:| White petals| White petals| White petals| Red petals|

( 4.3.3 State that some genes have more than two alleles

Some genes have more than two alleles (multiple alleles). It doesn’t mean that the gene possesses more than two alleles. An individual can only have a maximum of two alleles, one maternal and one paternal, no matter how many alleles.

4.3.12 educe the genotypes and phenotypes of individuals in pedigree charts * Squares represent males/Circles represent females 
* Shaded symbols represent affected individuals/ Un-shaded symbols represent unaffected individuals.

* If most of the...
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