Chapter 8: Inheritance and Heredity
Vocab:
Binary Fission – Reproduction of a prokaryote by division of a cell into two comparable
progeny cells
Character – An observable feature (hair color, eye color, height)
Trait – Specific form of a character (eye color is character, brown eyes and blue eyes are
traits)
P1 generation – Parental generation
F1 generation – First filial generation; immediate progeny of a parental (P) mating
Recessive Trait – The allele that doesn’t determine the phenotype in the presence of a
dominant allele (hidden)
Dominant Trait – The allelic form of a gene which determines the phenotype in a
heterozygous individual; overpowers the recessive gene
Incomplete Dominance – Heterozygous phenotype is intermediate between the two
homozygous phenotypes (red + white = pink
Codominance – Condition in which two alleles at a locus produce different phenotypic
effects and both effects appear in heterozygotes (red + white = roan)
Allele – Alternate form of a genetic character found at a given locus on a chromosome
Heterozygous – Having different alleles of a given gene on the pair of homologues
carrying that gene
Homozygous – Having identical alleles of a given gene on both homologous
chromosomes
Law of Segregation – Segregation of alleles, or of homologous chromosomes from
each other during meiosis so that each of the haploid daughter nuclei produced
contains one or the other member of the pair found in the diploid parent cell, but never
both (Mendel)
Punnett Square – Method of predicting the results of a genetic cross by arranging the
gametes of each parent at edges of a square
Test Cross – Mating of a dominant phenotype individual (hetero or homo?) with a
homozygous recessive individual
Dihybrid – A mating in which the parents differ with respect to the alleles of two loci of
interest 9:3:3:1
Monohybrid – Mating in which the parents differ with respect to the alleles of only one
locus of interest
Pedigree – Pattern of transmission of a genetic trait within a family (tree)
Wild Type – The standard or reference type of a gene found in the wild; deviants are
called mutants (not for humans)
Polymorphic – Coexistence of two or more distinct traits within a population
Hybrid Vigor – The superior fitness of heterozygous offspring as compared to that of
their homozygous parents (better to be hetero-)
Quantitative Traits – A set of genes that determines a complex character that exhibits
quantitative variation
Epistasis – Interaction between genes in which the presence of a particular allele of one
gene determines whether another gene will be expressed (epigenetics)
Penetrance – The proportion of individuals with a particular genotype that show the
expected genotype
Gene linkage – Association between two genes on the same chromosome; no random
assortment (closer the genes, less of a chance of recombination)
Sex linkage – Inheritance of a gene carried on a sex chromosome (X or Y)
Cytoplasmic Inheritance – Inheritance of organelle genes only from the mother because
the mother supplies all the organelles and cytoplasm in the egg
Genetic mapping – Positions of genes along a chromosome as revealed by recombination
frequencies
Plasmid – DNA molecule distinct from the chromosomes; extrachromosomal DNA found
in bacteria; replicate independently of the chromosome
Conjunction – Non-reproductive sexual process where bacteria pass DNA from one cell
to another through a conjugation tube
Recombinant Frequencies - The proportion of offspring of a genetic cross that have
phenotypes different from the parental phenotypes due to crossing over between linked
genes during gamete formation
Silent mutations – A change of a genes sequence that has no effect on the amino acid
sequence of a protein; sometimes occurs in noncoding DNA
Somatic Mutations – Permanent genetic change in a somatic cell; affect the individual,
but not offspring
Spontaneous Mutations – Genetic change caused by internal cellular mechanisms, such as
an error in DNA replication
Telomeres – Repeated DNA sequences at the ends of eukaryotic chromosomes
Transformation – Mechanism for transfer of genetic info in bacteria; placing foreign
DNA into the bacteria’s genome/plasmid (insulin)
Transgenic – Containing recombinant DNA incorporated into the genome
Translocation – Rare mutation that moves a portion of a chromosome to a new location
(to a non-homologous chromosome)
Questions:
1) Mendel’s first law is the law of segregation. This states that when a organism
makes gametes, the two copies of a gene separate, so that each gamete receives
only one copy. The 2nd law is the law of independent assortment, which says
during gamete formation alleles of genes assort independently of one another.
2) Mendel was able to create true breeding for plants by figuring out the genotype of
a plant using monohybrid crosses with other plants. Once Mendel determined the
genotype of a plant he could separate plants that where homozygous for these
traits, and breed them to create true breeds.
3) Blended inheritance was a theory in the mid 19th century that states that gametes
contain genes that blend with the parental genes during fertilization. Mendal
disproved this by showing that half of the genes are inherited from each parent.
4) Segregation says that when a organism makes gametes, the two copies of a gene
separate, so that each gamete receives only one copy, and independent assortment
says that during gamete formation alleles of genes assort independently of one
another.
5) Genetic variation occurs because of independent assortment and segregation.
6) The frequency of crossing over can help determine a gene’s location in relation to
another gene by comparing the genotype of the offspring.
7) A monohybrid cross is mating in which the parents differ with respect to the
alleles of only one locus of interest, and dihybrid is mating in which the parents
differ with respect to the alleles of two loci of interest 9:3:3:1
(see packet for 8-27)
28) Nondisjunction is when a cell fails to separate the sister chromatids in meiosis II
or mitosis, or failure of homologous chromosomes to separate in meiosis I. Results in
aneuploidy. Klinefelters syndrome happens when a boy is born with an extra X
chromosome because of nondisjunction (XXY)
29) Turner syndrome is a genetic condition when one of the X chromosomes is lost
because of nondisjunction. (X). Some symptoms include shortness, retrognathia, and
broad chest.
30) Dosage compensation is the inactivation of one of the females X chromosomes
31) Calico cats are cats with a spotted or parti-colored fur that is white, with patches
of other colors. Since the genetics that determine coat colors in cats are linked to the
X chromosome, calico cats are almost always female.
32) X chromosome inactivation is dosage compensation by inactivating one of the X
chromosomes. I occurs because the X chromosome store more information than Y
does so we need to compensate for the extra info stored. It occurs randomly in female
embryos.
33) a.
b.
c.
d.
34)
35) Interaction between genes in which the presence of a particular allele of one gene
determines whether another gene will be expressed (epigenetics is the environmental
influences). Pleiotropy is when one gene influences various unrelated phenotypic traits.
36) Polymorphism is the coexistence of two or more distinct traits within a population.
Genetic interaction between these two traits causes variation, which is advantageous for a
species and helps it evolve.
37) Heterogeneous advantage is when it is detrimental to have two chromosomes with the
same gene for a disease, but only having one chromosome with the disease is an
advantage. Also people with one copy of the disease are more likely to survive than those
without it. For example, in Africa having one copy of the sickle cell disease is
advantageous because it protects against malaria.
38) The Himalayan rabbit is born white at birth. Later darker brown patches of fur appear
on the rabbit as a result of a heat reacting enzyme. The rabbit raised on 35 degrees C will
have less dark spots than the one raised in 25 degrees C.