Biology
Genetics
Outline
Text: sec 10.1, 12.1-3, 13.1
I. Genotypes (_____________________) and phenotypes (______________________)
A. Traits (________________________) are a product of nature and nurture.
________________________ traits are a product of nurture, while
_____________________________ traits are a product of nurture. An example of
a heritable trait is ______________________________ and an example of an
acquired trait is _____________________________.
B. Chromosomes are convoluted structures made of ______________________
_______________. In eukaryotic organisms, __________________ copies of
paired chromosomes are found in the nucleus of soma (______________) cells.
Each chromosome pair is referred to as _______________________
chromosomes because they contain DNA for the same traits. In asexually
reproducing individuals chromosomes are ____________ copies of the parent,
while in sexually reproducing individuals, ________________ of each
chromosome pair comes from each parent when the diploid _____________ is
formed during fertilization, thus increasing ____________ for natural selection.
C. Genes are particular portions of a chromosome which code for a particular
_______________________. Each organism has two genes for each protein, one
on each homologous chromosome at the same loci (__________________).
Single proteins or groups of proteins determine an organism’s characteristics
(_______________________ and _________________________). If one
characteristic (one ______________________) is controlled by a single gene pair
the characteristic is called ______________________. An example of a single
gene pair that code for a single protein and single characteristic is
________________________________. Sometimes a characteristic is controlled
by several gene pairs, this is referred to as ____________________. An example
of a polygenic trait is _________________________ . The cumulative genes that
an organism has are referred to as its ______________________, while the traits
that result from these genes are referred to as ___________________________.
D. Alleles are variations (____________________ ____________) of a particular
gene. Given that organisms have a gene pair for each protein, they may have the
same or different _______________________ for that gene. Examples of alleles
of a particular gene are ______________________________. Sometimes there
exist only one form of a gene for a trait, which is referred to as a _____________
allele trait. More often there exist several alleles for a given trait, these are known
as _____________________ alleles. An example of a monogenic trait (trait
controlled by one gene) that has multiple alleles is ________________________.
E. Homozygous is the term that refers to an individual with the ___________ allele
for any one trait. Individuals that have ________________ alleles for any one
gene are considered to be heterozygous for that trait.
F. Dominant alleles are expressed to the exclusion of another within a gene pair. The
allele not expressed is termed ________________. An example of a dominant
recessive gene pair is _______________________________. In some gene pairs
both alleles can be expressed, which is called ______________________. An
example of codominance is _________________________________. If neither
allele is fully expressed, but both partially expressed it is called ______________
dominance. An example of incomplete dominance is
_______________________________________.
II. Mendelian genetics
1. Gregor Mendel was a monk who lived in __________________in the
middle1800’s. His diligent application of the scientific method and careful
data collection with the artificial selection of pea plants resulted in much of
what we know about the nature of genetics today. Mendel first identified
what we now call genes as a unit factor.
B. Theory
1. The rule of dominance states that some alleles are _______________and thus
expressed over other alleles for a given gene. An example of this is
____________________________________
2. The law of segregation states that during meiosis (formation of haploid
gametes), alleles for the ___________ gene are separated into different
gametes. An example of this is _____________________
3. The law of independent assortment states that alleles for ___________ genes
are separated independently of one another. An example of this is
____________________________________________
III. Genetic crosses
A. Monohybrid crosses predict the possible genotypes and thus phenotypes of
offspring that would result from a sexual mating of two _____________________
individuals. Traditional monohybrid crosses result in a __________ phenotypic
ratio and a ______________ genotypic ratio. This type of cross may also be
applied to matings of homozygous individuals, but results in ________ variation
within offspring.
1. Indicating parental (P1) diploid genotypes
2. Possible haploid gametes
3. The Punnett square
4. Predicting diploid offspring (F1)
a. Ratios are a comparison of one portion to the other portion(s), and are
expresses in decreasing order separated by colons. An example of this is
__________________________________________________________
b. Percentages are a comparison of one portion to the whole, considering the
whole is equal to 100. An example of this is ______________________.
c. Probability are comparisons of one portion to the whole and are expresses
as a statement An example of this is ______________________________
___________________________________________________________
B. Sex linked traits are genes found on the ‘sex’ chromosomes. Females have two
‘_____’ chromosomes, while males have one _____ and one ____. Thus the only
way a child can inherit a Y chromosome is from his _______. The genes found on
the X chromosomes (both for males and females) contain the same genes (but not
always the same _________), the Y chromosome contains some of the same
genes and some different and some not at all. Some genes that are found on the X
chromosome will then be the only __________ for a male and any gene found
only on the Y chromosome will not be found in _________ at all.
C. Dihybrid crosses predict offspring results from _________________ matings
considering __________traits. Traditional dihybrid crosses result in a 9:3:3:1
phenotypic ratio.
D. Pedigrees show familial relationships over several ___________________. These
usually show sex of individuals and at least one trait. General indicators include
males as __________ (blockheads) and females as _______________ (curvy);
black for homozygous ____________________, gray for heterozygous and white
for homozygous ____________________. Generation I is at the top, with each
successive generation below. Mated individuals are connected with a
____________________line and offspring are indicated by __________________
lines attached to the horizontal. Patterns that can be assessed include dominant,
recessive (parents do not have the phenotype and offspring does) and X linked
recessive (mother does not have phenotype but son does) alleles.
E. Consanguity is the interbreeding of closely related individuals. The danger of this
practice (common in artificial selection for domestic animals for desired traits) is
that undesirable __________________alleles may become homozygous. An
example of this has resulted in_________________________________________.