Transcript Chapter 11 Section Assessments

Chapter 11 Review
Section Assessments
11-1
1. What are dominant and recessive alleles?
Dominant alleles are the form of an allele whose
trait always shows up if it is present; Recessive
alleles are the form of an allele whose trait only
shows up when the dominant allele is not present.
For plant Tallness:
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11-1
2. What is segregation? What happens to alleles
during segregation?
Segregation is the separation of paired alleles;
The alleles are sepatated during the formation
of gametes with the result that each gamete
only carries a single allele from the original pair.
11-1
3. What did Mendel conclude determines
biological inheritance?
Mendel’s first conclusion was that biological
inheritance is determined by factors that are
passed from one generation to the next.
Today, scientists call the chemical factors that
determine traits genes.
11-1
4. Describe how Mendel cross-pollinated pea
plants.
Mendel cut away the the male parts of one
flower, then dusted it with pollen from another
flower.
11-1
5. Why did only about one fourth of Mendel’s F2
plants exhibit the recessive trait?
Only one fourth of the possible gamete
combinations did not have a dominant allele.
11-1
6. Critical Thinking: Why were true-breeding pea
plants important for Mendel’s experiments?
True-breeding pea plants have two identical
alleles for a gene, so in a genetic cross each
parent contributed only one form of a gene,
making inheritance patterns more detectable.
11-2
1. How are the principles of probability used to
predict the outcomes of genetic crosses?
The way in which the alleles segregate is random,
and probability allows the calculation of the
likelihood that a particular allele combination will
occur in offspring.
11-2
2. How are Punnett squares used?
To predict and compare the genetic variations
that will result from a cross.
3. What is probability?
The likelihood that a particular event will
occur.
11-2
4. Define the terms genotype and phenotype.
Genotype refers to the actual alleles present
for a trait or the genetic makeup.
Phenotype refers to the visible expression of
the alleles, or the physical characteristics.
11-2
5. Critical Thinking: An F1 plant that is
homozygous for shortness is crossed with a
heterozygous F1 plant. What is the probability
that a seed from the cross will produce a tall
plant?
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Tt
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11-3
1. Explain what independent assortment
means.
During gamete formation, pairs of alleles for
different traits segregate, or separate,
independently of one another.
11-3
2. Describe two inheritance patterns besides simple
dominance.
Incomplete dominance- cases in which one allele
is not completely dominant over another.
Codominance- in which both alleles contribute
to the phenotype.
Multiple alleles- cases in which genes have more
than two possible alleles.
Polygenic traits- traits that are produced through
the interaction of several genes.
11-3
3. What is the difference between incomplete
dominance and codominance?
In incomplete dominance, two alleles
combine their effects to produce a single inbetween phenotype.
In codominance, each allele is expressed in
the offspring.
11-3
4. Why are fruit flies an ideal organism for
genetic research?
They are small, easy to keep in the laboratory,
and produce large numbers of offspring in a
short period of time.
11-3
5. Critical Thinking: A geneticist studying coat
color in animals crosses a male rabbit having the
genotype CC with a female rabbit having
genotype Ccch.
The geneticist then crosses a ccch male with a Ccc
female. In which of the two crosses are the
offspring more likely to show greater genetic
variation?
11-3 review of multiple alleles
Full Color: CC, Ccch, Cch, or Cc
Chinchilla: cchch, cchcch, or cchc
Himalayan chc or chch
Albino: cc
Each individual only has two alleles.
More than two alleles exist within the
population.
11-3
Answer to #5
The offspring in the 2nd cross will show greater
variation because 100 percent of the offspring
from the first cross (CC x Ccch) will be full color.
11-4
1. Describe the main results of meiosis.
From the original cell, Four haploid cells are
formed that are genetically different from one
another.
2. What are the principle differences between
mitosis and meiosis?
Mitosis produced two genetically identical
diploid cells; Meiosis produces four genetically
different haploid cells.
11-4
3. What do the terms diploid and haploid mean?
Diplod = two sets of chromosomes
Hapolid = one set of chromosomes
4. What is crossing over?
Homologous chromosomes pair up and form
tetrads, which may exchange portions of their
chromatids, resulting in the exchange of alleles
between the homologous chromosomes.
11-4
5. Critical Thinking: In human cells, 2N= 46. How
many chromosomes would you expect to find in
a sperm cell? In an egg cell? In a white blood
cell? Explain.
Both sperm and egg cells have 23
chromosomes because they are gametes.
A white blood cell has 46 chromosomes because
it is a diploid body cell.
11-5
1. How does the principle of independent
assortment apply to chromosomes?
It is the chromosomes that assort
independently, not individual genes.
11-5
2. What are gene maps, and how are they
produced?
A gene map shows the relative locations of
genes on a chromosome.
The frequency of crossing-over between genes is
used to produce a map of distances between
genes.
11-5
3. How does crossing-over make gene mapping
possible?
The farther apart two genes are, the more likely
they are to be separated during a crossover in
Meiosis. Therefore, the frequency of crossingover is equal to the distance between two
genes.
11-5
4. Critical Thinking: If two genes are on the same
chromosome but usually assort independently,
what does that tell you about how close
together they are?
The two genes are located very far apart from
each other.
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