Biology Unit 2, Part 2: DNA, heredity, Mendel, probability

Diploid

contains 2 chromosomes from homologous pair, one from each parent

Haploid

contains only 1 chromosome from homologous pair

Alleles

alternative versions of genes, reside at the same genetic locus

When alleles are segregated in Meiosis

Meiosis I, anaphase I

Mendel’s Law of Segregation

If an individual has identical alleles at locus, that allele is present in all gametes. If an individual has two different alleles, half its gametes receive one allele and the other half the other allele.

Punnett square

Used to determine equal frequency of two parent genotype cross, can also use a testcross to determine genotype of parent from its offspring

Dihybrid cross

dependent assortment: 1 allele depends on presence of another

Mendel’s Law of Independent Assortment

Alleles at each locus segregate independently of alleles at other loci

Probability of both events happening (p&q)

= product of each event happening independently (p x q)

Probability of either of two events happening (p or q)

= sum of probability of each event happening individually (p+q)

Tetrad

structure formed by pair of homologous chromosomes during early meiosis (prophase I), formed during synapsis, allows non-sister chromatids to overlap and swap DNA pieces (recombination)

Wild-type

most common phenotype in a population

If n alleles, there are _______ homozygotes

n

If n alleles, there are ______ heterozygotes