chapter 15: mendelian inheritance
when does first-division nondisjuction occur?
metaphase 1
when does second-division nondisjuction occur?
metaphase 2
what is codominance?
multiple alleles can be fully expressed at the same time in a heterozygous individual
what is a recessive allele?
not expressed allele
this type of trait is influenced by more than one gene
polygenic
what are mendels laws?
principle of segregation and independent assortment
what is a gene?
segment of DNA that codes for a protein
what are variable number of tandem repeats?
short nucleotide sequences organized as tandem repeats
for a simple mendelian trait, a heterozygous (Pp) ____.
shows dominant phenotype
for a simple mendelian trait, a homozygous dominant (PP) ____.
shows dominant phenotype
for a simple mendelian trait, a homozygous recessive (pp) ____.
shows recessive phenotype
what happens in division nondisjuction?
some gametes have extra chromosomes and some gametes are missing chromosomes
what does the independent assortment of genes in different chromosomes reflect?
the fact that nonhomologous chromosomes can orient in either of two ways that are equally likely
what does the segregation of alleles reflect?
the separation of homologous chromosomes during anaphase 1 of meiosis
what happens in copy-number variation?
the size of the duplicated or deleted region can include one or more complete genes
what are polygenic traits?
traits controlled by two or more genes
what is the principle of independent assortment?
two copies of each gene segregate into gametes independently of the two copies of another gene
what is incomplete dominance?
unique heterozygous phenotype
how are single nucleotide polymorphism presented?
in large fractions of the population
what is the principle of segregation?
individuals inherit two copies of each gene
what is a locus?
location of a gene
where do genes come from in the principle of segregation?
1 from mother and 1 from father
suppose that, in humans, the ability to roll the tongue (R) is dominant to being unable to roll (r), and having freckles (F) is dominant to having no freckles (f). If a woman heterozygous for both traits married a man with no freckles who couldn't roll his tongue, what is the probability that they would have a freckled, tongue-rolling child?
1/4
how many individuals per 10,000 human live births have extra or missing chromosomes?
33
what are the early theories of transmission genetics?
hippocrates and darwin, aristotle, lamarck
what does homozygous mean?
homologous chromosomes carry the same alleles
what does heterozygous mean?
homologous chromosomes carry two different alleles for the same gene
conditions in which homologous chromosomes carry the same alleles:
homozygous
what is the different between a gene and an allele?
a gene is a segment of DNA that codes for a protein or RNA; alleles are alternate forms of a gene
what is a single nucleotide polymorphism?
a substitution of a single nucleotide at a specific position on the genome
what is a short tandem repeat polymorphism?
a type of microsatellite polymorphism that leads to different alleles by differing the number of repeated sequence
what is an allele?
alternative variations of a gene/trait
what is a phenotype?
an individuals observable traits
in mendel's peas, an individual that is heterozygous for seed color: a) has only one kind of allele for seed color b) has two different alleles for seed color c) will express the dominant allele d) will express the recessive allele e) has two different alleles for seed color and will express the dominant allele
b) has two different alleles for seed color c) will express the dominant allele
what is a dihybrid cross?
cross between 2 diploid parents but tracking two genes
what does a test cross determine?
determines the genotype of an individual that shows the dominant phenotype
what is polymorphism?
discontinuous genetic variation resulting in the occurrence of several different forms or types of individuals among the members of a singe species
what is a dominant allele?
expressed allele
according to the principle of segregation, a heterozygous plant with alleles Aa will produce:
gametes in the ratio of 1 A allele: 1 a allele
what is genetic variation?
genetic differences that exist among individuals in a population at a particular point in time
what is a genotype?
genetic makeup of an organism
if you crossed a true-breeding yellow-seed plant (AA) with a heterozygous yellow-seed plant (Aa), offspring
genotypes would be 1 AA: 1 Aa
a mutation in a pleiotropic gene ____.
has multiple phenotypic outcomes
an individual is heterozygous for a gene if: a) his or her mother is heterozygous for a gene b) his or her father is heterozygous for a gene c) he or she developed from a sperm and egg that carried different alleles d) he or she developed from a sperm and egg that carried the same allele e) only one allele is present in the population
he or she developed from a sperm and egg that carried different alleles
