Genetics
2: The Chromosomal Basis of Inheritance
1) Chromosomes and genes share all of the
following characteristics except that
2) The improvement of
microscopy techniques in the late 1800s set the stage for the emergence of
modern genetics because
3) When Thomas Hunt Morgan crossed his red-eyed
F1 generation flies to each other,
the F2 generation included both red- and white-eyed flies.
Remarkably, all the white-eyed flies were male. What was the explanation for
this result?
4) Which of the
following statements is (are) true?
5) How would one explain a testcross involving F1
dihybrid flies in which
more parental-type offspring than recombinant-type offspring are
produced?
6) New combinations of linked genes are due to
which of the following?
7) What does a frequency of recombination of 50%
indicate?
8) The reason that linked genes are inherited
together is that
9) What is the
mechanism for the production of genetic recombinants?
10) There is good evidence for linkage when
11) The frequency of crossing over between any
two linked genes is
12) Sturtevant provided genetic evidence for the
existence of four pairs of chromosomes in Drosophila
by showing that
13) Map units on a linkage map cannot be relied
upon to calculate physical distances on a chromosome because
14) A map of a chromosome that includes the
positions of genes relative to visible chromosomal features, such as stained
bands, is called a
15) Males are more often affected by sex-linked
traits than females because
16) In cats, black fur color is caused by an X-linked allele; the other allele at
this locus causes orange color. The heterozygote is tortoiseshell. What kinds
of offspring would you expect from the cross of a black female and an orange male?
Use
the list of chromosomal systems below to answer the following questions.
A. haploid-diploid
B. X-0
C. X-X
D. X-Y
E. Z-W
17) What is the chromosomal system for
determining sex in mammals?
18) What is the chromosomal system for sex determination
in grasshoppers and certain other insects?
19) What is the chromosomal system for sex
determination in birds?
20) What is the chromosomal system of sex
determination in most species of ants and bees?
21) SRY is
22) Red-green color blindness is a sex-linked
recessive trait in humans. Two people
with normal color vision have a color-blind son. What are the genotypes of the parents?
23) Most calico cats are female because
24.
Natural selection tends to reduce variation in gene pools. Which process serves to balance natural
selection by creating new alleles?
25.
Failure of chromosomes to separate during meiosis.
26. What can cause change in allelic frequencies
due to an influx of new members into a population?
27. Cattle breeders have improved the quality of
meat over the years by which process?
28. Beard is a trait in
humans that ordinarily expresses in males only.
With just this information available, which of the following could
explain how beard is inherited in humans?
29. Movement of individuals from one population
to another is the
30. Kleinefelter's syndrome results from a zygote
having
31. The inheritance of the ABO blood type in
humans is an example of
32. When we say that one organism is better
adapted than another organism we mean that it
33.
Genes moving from one place on a chromosome to another.
34) A
recessive allele on the X chromosome is responsible for red-green color
blindness in humans. A woman with normal vision whose father is color-blind
marries a color-blind male. What is the probability that a son of this couple
will be color-blind?
35) A man who carries
an X-linked allele will pass it on to
36) A Barr body is normally found in the nucleus
of which kind of human cell?
37) Which of these syndromes afflicts mostly
males?
38) If a human interphase nucleus of a person
contains three Barr bodies, it can be assumed that the person
39) If
nondisjunction occurs in meiosis II during gametogenesis, what will be the
result at the completion of meiosis?
40) If a pair of homologous chromosomes fails to
separate during anaphase of meiosis I, what will be the chromosome number of
the four resulting gametes with respect to the normal haploid number (n)?
41) A cell that has 2n + 1 chromosomes is
42) If a chromosome lacks certain genes, what has
most likely occurred?
43) One possible result of chromosomal breakage
is for a fragment to join a nonhomologous chromosome. This is called a (an)
44) A human individual
is phenotypically female, but her interphase somatic nuclei do not show the
presence of Barr bodies. Which of the following statements concerning her is
probably true?
45) In humans, male-pattern baldness is
controlled by a gene that occurs in two allelic forms. Allele Hn determines nonbaldness, and allele Hb determines pattern baldness. In
males, because of the presence of testosterone, allele Hb is dominant over Hn. If a man and woman both with genotype HnHb have
a son, what is the chance that he will eventually be bald?
46) Of the following human trisomies, the
one that generally has the most severe impact on the health of the individual
is
47) What do all human males inherit from their
mother?
48) Mutant
tetraploid plants
are unable to breed with a diploid plant.
49. A man is brought to
court in a paternity case. The alleged
father has blood group B, Rh positive.
The mother has blood group A, Rh negative. Which blood group of the child will exclude
the alleged father from possible paternity? Choose from group
50. In 1989 an earthquake in
Mutations
A. All DNA in cells results from multituces of
replications.
B. Mechanisms evolved to avoid errors during
replication.
C. Replication errors still occur
GENE
MUTATION
A. Mutation is change in the genetic message of
the cell
1.
Point mutations
a. Alterations in coding sequence
b. involve only one to a few nucleotides
c. Result from chemical or physical
damage to DNA
d. Chemical mutagens damage DNA
2.
Transposition
a. Genes move from place to place on
chromosome
b. May alter expression of it or
neighboring genes
3.
Chromosomal rearrangement
a. Occurs in eukaryotes only
b. Large segements change location or
undergo duplication
4.
Chemicals that damage DNA are called mutagens
B.
DNA damage
1.
Ionizing radiation
a. High energy ejects electrons from
outer shells and the resultant molecule becomes a free radical.
2. Ultraviolet radiation
C. Spontaneous
mispairing
1. Not caused by radiation or chemicals.
2.
Nucleotides change to other conformations
a. Form different kinds of hydrogen bonds
b. Polymerase chooses wrong base to pair
3.
Slipped mispairing during chromosome pairing
a. Sequences misalign and a portion of
one strand loops out
b. Generally a self-correcting problem
1.
Repair enzymes may excise unreverted loop
2. Deletion of hundreds of
nucleotides
D. Consequences dependent on identity of mutated
cell
1. In germline cells
destined to be gametes
a. passed on to subsequent generations
b. Raw material for natural selection and
evolution
2.
In somatic cells that become the body
a. Somatic mutations not passed on to
next generation
b. Effects only progeny of damaged cell
causing cancer.
CHANGES
OF ALLELE RATIOS
A.
Hardy-Weinberg predicts consistency
1.
Large,randomly mating population used as
baseline to measure changes
2.
Factors that effect equilibrium
a. Mutation
b. Migration
c. Genetic drift
d. Nonrandom mating
e. Selection
B. Mutation
1.
Change from one allele to another
2.
Alters proportion of alleles in a population
3. Generally low rate with slow
accumulation of mutations
C. Migration
1.
Movement of individuals from one population to another
a. Immigration into populations
b. Emmigration out of populations
2.
Subtile movements of drifting immature stages or gametes
3.
Gene pool: all alleles present in given population
4.
Gene flow: movement of genes between populations
a. via
migration
b. vis hybridization between adjacent
populations
D. Genetic Drift
1.
Changes in allele frequency in small population
a. appears to be random, drifting event
b. small
isolated populations become different
2. May be major factor in human
evolution
3.
Founder principle
a. Few indiviuals begin new, isolated
population
b. Source population rare allele may be
significant in new population
c. Important factor in oceanic evolution.
4. Bottle-neck effect
a. Populations greatly reduced in size
b. Surviving individuals represent random
genetic sample of original populations
c. Example: current cheetah population
E. Nonrandom mating
1.
Mating of certain individuals more common than expected.
2.
Inbreeding: mating with relatives
a. Increases proportion of homozygotic
individuals
b. Promotes occurrence of double
recessive combinations
c. Increases likelihood of genetic
disorders
d. Rare in
3.
Outcrossing: mating with non-relatives
a. plants breed with individuals other
than self
b. Have higher proportion of
heterozygotes
F. Selection
1. Artificial Selection
a. Breeder selects characteristics
(pigeons)
2. Natural selecion
a. Environment selects characteristics
b. Conditions in nature favor
reproduction of most fit
c. Proportions of genes of future
populations affeced
3. Selection acts directly on phenotype
a. Determined by interaction of genotype
and environment
b. Link between aalleles and
characteristics is variable