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Biology Exam 1 2


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You are part of an archeological expedition to unearth the remains of an ancient
monastery in Egypt. Historical documents give the age of the monastery as
approximately 700 years old. You need physical evidence to support this claim.
As pa
No. The evidence suggests the bowl is about 2850 years old (about 2000 years older than
the historical documents suggest the monastery is). The age of 2850 is found by
multiplying 5700 by .5 (75% is .5 half-lives).
Darwin’s examination of fossils relied on __________ dating to determine the
evolution of species.
A paleontologist estimates that when a particular rock formed, it contained 36 mg
of the radioactive isotope potassium-40. The rock now contains 4.5 mg of
potassium-40. The half-life of potassium-40 is 1.3 billion years. About how old
is t
The rock is approximately 3.9 billion years old (3 half-lives old).
In some breeds of dogs, progressive retinal atrophy (PRA) is inherited as an autosomal
recessive disorder and causes blindness. Two dogs that are carriers of the PRA allele but have
normal vision are mated and have a litter of puppies. What pro
½ x ½ = 1/4 will be afflicted
1-1/4=3/4 will not be afflicted
In humans, albinism is caused by a single gene. A homozygous recessive individual (aa) will
not have skin pigmentation. Ann is albino. Her husband Mike is not albino. They have two
children, Sarah (who has skin pigmentation) and Martha (who is
Answer: Ann = aa, Mike = Aa, Sarah =Aa, Martha = aa
b) What is the probability that their next child will be an albino?
Answer: 50%
c) If Ann remarries and has five more children, all with normal pigmentation, what is
most likely the genotype of her new husband?
Answer: He is most likely AA
d) If Ann remarries a man who is heterozygous for albinism, what is the probability that
her second family will have three children that are pigmented and one child that is albino.
Answer: 4/16 or 1/4
Three step solution:
First, how many different ways can birth order fulfill the conditions? Or how many ways
can you arrange 3 and 1?
Second, The individual probability of each possible arrangement= ½ x ½ x ½ x ½ =1/16
Third, add the probabilities (i.e., Rule of addition)=4/16=1/4
Given two separate, independently assorting genes, A and B, with A dominant to a and B
dominant to b, answer the following questions:
a) What is the probability of getting an AB gamete from an individual who is
heterozygous at both loci?
a) What is the probability of getting an AB gamete from an individual who is
heterozygous at both loci?
Answer: ½ x ½= ¼
b) What is the probability of getting an Ab gamete from an individual who is
heterozygous at both loci?
Answer: ½ x / ½ = ¼
c) What is the probability of getting an AB gamete from an individual who is AABb?
Answer: 1 x ½=1/2
d) What is the probability of getting an AABB child from a cross of two people
heterozygous at both loci?
Answer: (From part a prob(AB) = 1/2 x ½=1/4) so pro(AABB) = ¼ x ¼=1/16
e) From a cross of two people heterozygous at both loci, what is the probability of having
a child that expresses the dominant phenotype for both loci?
Answer: ¾ x ¾ = 9/16
A phenotypic ratio of 1:2:1 in the F2 generation of a monohybrid cross is best explained by:
incomplete dominance
If a plant of genotype AaBbCcDd is selfed and the genes assort independently, how many
different genotypes will be found among the progeny?
If 2 mice of genotype FfGgHhIiJj are repeatedly mated, and the genes assort
independently, how many different phenotypes will be found in the progeny?
In a cross between a female AaBbccDdee and a male AabbCcDdee, what proportion of
the progeny will be phenotypically identical to the female parent? (Assume independent
assortment of all genes and complete dominance).
a single gene has effects on several aspects of an organism’s phenotype
more than one gene affects one aspect of an organism’s phenotype
polygenic effect
List five reasons why simple Mendelian inheritance is often NOT observed for most traits.
Incomplete dominance, codominance, polygenic inheritance, pleiotropy, epistasis, environmental
3. Blood must be ‘typed’ before patients can be transfused or given blood. This is because
individuals with the A allele add the sugar galactosamine to the surface of their red blood cells
while individuals with the B allele add a different
3. Blood must be ‘typed’ before patients can be transfused or given blood. This is because
individuals with the A allele add the sugar galactosamine to the surface of their red blood cells
while individuals with the B allele add a different sugar, galactose. AB individuals add both
sugars while O individuals add neither type. When type A individuals receive type B blood,
their immune system mounts a response to reject the galactose-containing blood and vice-versa.
A) Based on this, which blood type is considered the universal donor and which is the universal
Universal Donor: Type O
Universal Acceptor: Type AB
B) If someone with type B blood mates with someone of type AB blood, is it theoretically
possible for this couple to have a child with type A blood? Why or why not?
Yes, this is possible. If the parent with type B blood is heterozygous (IBi) then a child with type
A blood is possible.
Czar Nicolas II and Czarina Alexandra who ruled Russia during the Bolshevik revolution of
1917 had four girls (one being the famous Anastasia) before finally having their last and most
prized child, a boy named Alexis who was destined to succee
Alexis had a 50% chance of inheriting hemophilia because his mother was a carrier. Because
hemophilia is X-linked, only the mother can pass it to her son.
From a cross of two people heterozygous at two loci, what is the probability of having a child
that expresses the dominant phenotype for both loci?
Parents: AaBb x AaBb
What is probability of child A_B_?
Probability of A_ = 3/4
Probability of B_ = 3/4
Overall probability = 3/4 * 3/4 = 9/16
What is the probability of getting an AaBB child from a cross of two people heterozygous at
both loci?
Parents: AaBb x AaBb
What is probability of child AaBB?
Probability of Aa = 1/2
Probability of BB = 1/4
Overall probability = 1/2 * 1/4 = 1/8
The most common phenotype in a population. In Drosophila, for example,
red eyes is wild-type.
wild type
How do genes get named?
In Drosophila, a gene is names after the first mutant phenotype that
is discovered.
How is the wild-type allele labeled?
The wild-type allele is labeled with a "+".
How is the dominant allele labeled?
The letter identifying the mutant is lowercase if the allele
is recessive (as in white eyes), or it is uppercase for those mutations that are dominant to the wild
type allele
big bang was how many years ago?
13.7 billion years
first eukaryotes?
1 billion years ago
fossil record how old
3 billion years
exchange or recombination of genetic material
what are the advantages of doing sexual over asexual reproduction?
genetic variation
what are the advantages of asexual over sexual reproduction
saves time and energy
when there is haploid and diploid states
alternation of generations
any of a series of genes that occupies the same positon on a chromosome
any chromosome that isnt a sex chromosome
that which is subject to natural selection
process by which a population becomes adapted to an environment over time
natural selection
gives an estimate of how old something is
absolute dating
universe arose when matter was flung outward from the central origins
big bang
method of aging specimens, works for things up to 40,000 years old
carbon 14 dating
period that started 65 million years ago to present, divided tertiary and quaternary age of mammals
cenozoic era
theory that earth started with one continet, pangea, and since has broken into 7
continental drift
technique of absolute dating, uses rings in trees
remains or traces of an organism that lived in the geological past
time scale from when earth started, about 4600 million years ago to present
geological time scale
chemical compound, has same molecular formula but different molecular structures or different arangements of atoms in space
one of two or more atoms of the same element that have the same number of protons but different number of neutrons
248 million years ago to 65 million years ago, age of reptiles
mesozoic era
one who studies extinct organisms or their fossils
590 million years ago to 248 million years ago
first continent
theory that earth surface is covered in plates which move as time goes on
plate techtonics
5 billion years ago to 570 million years ago
precambrian era
chemical conversion of L-form amino acids to D-form amino acids after an organism dies
uses decay of radioactive elements to date specimens
radio carbon dating or carbon dating
used the most for fossil age
radiometric dating
dates specimens in relation to one another
relative dating
formed by layers of minerals that settle in water
sedimentary rock
continents move this far a year
2.5 to 15 cm
pangaea broke into these pieces
northern laurasia and southern gondwana
three clues to pangaea
1. continents fit together like puzzle pieces 2. rock formations on africa and south america are same age and structure
3. geologists have found similar scratches on rocks on SA, africa, india, australia, and antarctica
earths crust is composed of??
silicates, mainly 02 and silicon
what is the crust floating on?
a very hot, nearly liquid layer of the earth called the core
crust is seperated into sections known as
techtonic plates
half life is determined by the number of these given off a minute
beta radiations
number of possible chromosome combinations at metaphase one
independent assortment
this only occurs when there is a genetic variation in a population
evolution through natural selection
points where paired chromosomes stay in contact
group of cells arising from an ancestral cell
union of male and female gametes
parent cell divides to form two or more similar daughter cells
reproductive cell
generation of a plant life cycle in which gametes are produced
made of DNA, part of a chromosome, determins a particular characteristic
seperation of cells into alleles independent of the way other alleles have seperated
independent assortment
number and structure of the chromosomes in the nucleus of a cell
sequence of organism from fusion of gametes in one generation to the same stage in the next
life cycle
position of a gene on a chromosome
rearrangement of genes that occurs when gametes are formed
reproductive cell that can develop into an individual without first fusing with another reproductive cell
generation of plants that produce spores
the result of fertilization
two parts of genetic variation
independent assortment and recombination
a distinctive inherited feature of an organism
traits with simple dominant/recessive expression patterns
mendelian traits
study of the form and structure of organisms especially their external form; physical appearance
male and female gametes are derived from the same individual; autogamy
self fertilization
male and female gametes are derived from the same individual; self fertilization
particular variant for a character
all of the offspring of that individual have the same trait as the parent when the offspring are produced by self-pollination
heritable feature for which variants exist
each trait controlled by two alleles which seperate and pass into seperate reproductive cells
law of segregation
pairs of factors segregate independently of each other when reproductive cells are formed
law of independent assortment
outcome of a probability event is unaffected by what has happened in previous trials
independent event
outcome of event is affected by what has happened in previous trials
non-independent event
a cross made to identify hidden recessive alleles in an individual of unknown genotype
test cross
condition that arises when both alleles in a heterozygous organism are dominant and are fully expressed in the phenotype
when offspring have one parental character and not the other
complete dominance
only classified as either-or ex. red or white
discrete characters
gene interaction in which one gene suppresses the effect of another gene that is at a different locus
neither allele is dominant and aspect displayed results from the partial influence of both alleles
incomplete dominance
3 or more alternative forms of a gene that occupy the same locus
multiple alleles
an allele that has more than one effect
determination of a particular characteristic by many genes, each having a small individual effect
polygenic inheritance
controlled by more than one gene
qualitative character
more than two alleles for a trait
multiple alleles
both alleles are exhibited ex. blood type
skin color is many different shades!
polygenic inheritance
one gene has multiple effects
color blindness also means a greater frequency of crossed eyes
a gene at one locus can affect the expression of a gene at a different locus
hair can be brown or blonde, but another gene codes for whether or not hair will be white or colored
demonstrates a continuum of phenotypes
polygenic inheritance
law of segregation say alleles segregate when?
in meiosis one
find independent probabilities and multiply together
rule of multiplication
if an event can occur more than one way, find individual probablilities and add together
rule of addition
both alleles contribute equally to a phenotype
analysis of mating that has already occurred
caused by a mutant allele that codes for a protein involved in chloride ion transport, leads to extreme mucous build up
cystic fibrosis
afflicted individuals accumulate salt in epithelial cells, cells become hypertonic, mucous around cells thickens
cystic fibrosis
disease is pleiotropic, can lead to lung infections, sterility in males
cystic fibrosis
1/50 whites are carriers, 1/64 asians
phenylketonuria PKU
main symptom is mental retardation
phenylketonuria PKU
leads to high lebels of phenylalanine metabolites, which leads to mental retardation
phenylketonuria PKU
can be prevented by eating a life long low protein diet
phenylketonuria PKU
sufferers have anemia, pain, fever, and fatigue
sickle cell disease
10 percent of blacks are carriers
sickle cell disease
affects the hemoglobin molecule found in red blood cells, is involved in oxygen transport
sickle cell disease
linked to preventing malaria, found where malaria is present
sickle cell disease
possibly the best example of natural selection in humans
sickle cell disease
causes progressive damage to the nervous system
huntington's disease
characterized by uncontrollable movements, dementia, and psychiatric disturbances
huntington's disease
caused by autosomal dominant mutation
huntington's disease
offspring 50 percent..does not skip generations
huntington's disease
not prevalent in early history, occurs in 30s-40s, life expectancy was only around 40
huntington's disease
when a gene codes for whether or not another gene is expressed

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