Module 1 Practice Exam and Review Flashcards
Imagine that a human characteristic is determined by genotype only, with no environmental influence. Based on the amount of shared genetic information in MZ (monozygotic) and DZ (dizygotic) twins, would you expect concordance values to be the same or different in these two sets of twins? Give a brief explanation of your answer.
MZ twins share 100%genetic information; Dz twins share on average 50%. Therefore, if a trait is determinedby genotype only, concordance value will be different in the two tyes of twins. Values will be around 100% in MZ twins and 50% DZ twins.
You are working with a new species of beetle. You have isolated lines that breed true for either blue shells and long antenna, or green shells and short antenna. Crossing these lines yields F1 progeny with blue shells and long antenna. Crossing F1 progeny with beetles that have green shells and short antenna yield the following progeny:
blue shell, long antenna: 82 green shell, short antenna: 78 blue shell, short antenna: 37 green shell, long antenna: 43 total: 240
a. Which shell color and antenna length alleles are dominant?
b. Are the shell color locus and antenna length locus linked?
c. Check your answer to the previous question with the chi-square test.
d. If the genes are linked, calculate the recombination frequency between them.
??
Describe the centromere and kinetochore.
The centromere is the attachment point for spindle microtubules. Kinetochore is a protein complex that assembles in the centromere; later spindle microtubules attach to the kinetochore.
- Kinetochore is a protein complex. Centromere is a constricted region found on a chromosome with highly specialized, repetitive DNA sequences.
- Kinetochores assembles on the centromere.
- Centromeres are clearly visible with a light microscope as a constricted region on the condensed chromosome while kinetochrores can only be seen with the aid of an electric microscope.
- Unlike in the centromeres, three different layers can be found in the kinetochore.
- Kinetochore has corona while no such structures are found in centromeres.
- Centromeres cannot bind the microtubules. Only the kinetochores that are associated with centromeres have the ability to bind microtubules.
Your teaching assistant for class spent all night in the research lab on an experiment, and in trying to review transcription and translation keeps interchanging the words during his lecture. Which one(s) of these statements your teaching assistant has made is true?
DNA is translated into RNA by RNA ploymerase. mRNA is translated to a nucleotide sequence to make a protein. During translation, amino acids are brought to the ribosome by a tRNA molecule.
DNA is transcribed to RNA.
During translation, amino acids are brought to the ribosome by a tRNA molecule.
_______ is the change in allele frequency in a population over time.
Evolution
Which of the following statements about homologous chromosomes are true?
They are always genetically identical. They always contain the same alleles. They occur together in diploid cells. They occur together in haploid cells.
They occur together in diploid cells.
Homologous chromosomes are those that can be matched by virtue of their similar structure and function within a nucleus.
What chromosomes making up the human genome do not follow the same characteristics of homology?
sex chromosome
Chromosomes are randomly partitioned during _____ , contributing to genetic diversity.
Meiosis I anaphase
The “distance” between two linked gene pairs can be expressed as a percentage. Name the unit based on percent recombination that was created in honour of the scientist who pioneered the use of fruit flies for genetic research.
centimorgan
What inheritance is suggested by each description?
Pedigree analysis on a characteristic shows all of the following:
- males and females are affected equally.
- affected fathers may have affected daughters, but never affected sons.
- half the children of affected mothers are affected.
x-linked dominant
Crossing over (genetic recombination) occurs in…
Meiosis I prophase
A form of a gene that has a slightly different sequence than other forms of the same gene but encodes the same type of an RNA or protein, is called a(n)
allele
_____ refers to the splitting of the cytoplasm, separating one cell into two.
cytokinesis
Permanent, heritable changes in genetic information (DNA) are called
mutations
Genetically speaking, brown eyes (B-) are dominant to blue eyes (bb). However, an individual can wear colored contacts in order to change his or her eye phenotype. Suppose a man with blue eyes (bb) marries a woman who appears to have blue eyes and together they have five children. Listed below are three possible outcomes. For each of the outcomes, predict the woman’s genotype.
Three children have blue eyes and two have brown eyes
All five children have brown eyes.
All five children have blue eyes.
- The woman naturally has blue eyes (bb).
- The woman naturally has brown eyes and is heterozygous for the trait (Bb).
- The woman naturally has brown eyes and is homozygous for the trait (B
__2__ Three children have blue eyes and two have brown eyes
__3__ All five children have brown eyes.
__1__ All five children have blue eyes.
- The woman naturally has blue eyes (bb).
- The woman naturally has brown eyes and is heterozygous for the trait (Bb).
- The woman naturally has brown eyes and is homozygous for the trait (BB).
If they live long enough, the penetrance of individuals carrying the Huntington’s Disease allele will be what?
100%
If a typical somatic cell has 32 chromosomes, how many chromosomes are expected in each gamete of that organism?
16
Which term refers to mating between closely related people?
consanguinity
In eukaryotes, chromosomes do not contain:
proteases
During the cell cycle, chromosomal replication occurs in
Interphase
In order to be functional, a chromosome requires all of the following except:
centromeres
origins of replication
nucleomeres
telomeres
nucleomeres
In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be genotypically AaBbCcDd ?
81/256
4/256
8/256
1/16
1/16
Ability to roll the tongue is caused by a dominant allele. A woman is a “roller,” but one of her parents is not.
The woman is expecting a child with a man who is a “nonroller.” What is the probability that their child will be a “roller”?
Ref 6-2
1/2
Homologous chromosomes move toward opposite poles of the dividing cell during
meiosis I
The following are features and characteristics of the DNA molecule
composed of four nitrogenous bases
is capable of being replicated
can be mutated
NOT the genetic material used by all animals, just most
Genes contain the instructions for building proteins. Where are those instructions located?
In the order of the DNA bases.
A trihybrid cross is a cross between two individuals who are heterozygous for three genes. For example: AaBbCc x AaBbCc. Assuming these three genes are unlinked and assorting independently, what segregation ratio would be observed?
27:9:9:9:3:3:3:1
How many different F2 genotypes would you expect in a cross with 4 heterozygous gene pairs?
81
Genes come in different versions called:
alleles
A poison suppresses the ability of the body to manufacture amino acids. Knowing this, the poison interferes most with the production of:
Proteins
The following is a map of four genes on a chromosome:gene map
A _____ W ___ E ________ G
Between which two genes would you expect the highest frequency of recombination?
a) W and E
b) E and G
c) A and E
d) A and G
A and G
Genes A and G are furthest apart. Map units reflect recombination frequency
A Barr body is a(n)
inactivated X chromosome, visible in the nucleus of a cell that is from a female mammal.
A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males.
Reference: Ref 2-1
What is the total number of chromosomes present in the cell during metaphase I of meiosis?
42
A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males.
Reference: Ref 2-1
What is the total number of telomeres in a rat cell in G2
168
In a mating between individuals with the genotypes IAi × ii, what percentage of the offspring would be expected to have the O blood type?
50%
X inactivation is used in humans for dosage compensation. What other mechanisms are (could be) employed
up regulation of X chromosome in males
up regulation of every single X chromosomal gene in males
How does one get haploid bees (that are develop as males)?
unfertilized eggs, not fertilized eggs
If X inactivation “turns off” all but one X chromosome, why aren’t Klinefelters individuals XXY normal?
The second X is only partially inactivated, not completely inactivated.
When can we detect a 1:1:1:1 ratio in the phenotype of the progenies from a dihybrid cross (unlinked genes)?
Testcross, which is a cross against homozygous recessive
If crossover happens 100% of the time between linked genes in meiosis, what will be the OBSERVED percentage of recombinant gametes?
50%
What is a test cross?
unknown genotype X homozygous recessive
Epistasis
Phenotype of one gene A suppresses phenotype of gene B
Codominance
Both phenotypes are expressed
Incomplete dominance
intermediate phenotype
9:3:3:1 ratio
dihybrid cross
Epistasis: Interaction between non allelic genes, such that one gene………..the expression of ………………..
Epistasis: Interaction between non allelic genes, such that one gene masks the expression of another’s phenotype.
Agouti is dominant, but is it…?
not clear from the shown data
An individual with blood type B can receive blood from a donor with blood type:
B and O
0! =
1
probability calculation review
How many boxes in a tetrahybrid cross?
256
Human haploid and diploid numbers
haploid: 23
diploid: 46
haploid
A cell or an organism having one member of each pair of homologous chromosomes. Also referred to as the gametic chromosome number.
diploid (2n)
A condition in which each chromosome exists in pairs; having two of each chromosome.
Dihybrids, Monohybrids, and
Degrees of Freedom
Degrees of Freedom = n-1, where n = the # of expected phenotypes
Dihybrids: 4-1 = 3
Monohybrids: 2-1 = 1
A perfect chi square value is __
0
More variables =
more variability
prababilty, degrees of freedom
What events during sexual reproduction are significant in contributing to genetic diversity?
Crossing over and random distribution of maternal and paternal chromosomes
If the recombination frequency between genes (A) and (B) is 5.3%, what is the distance between the genes in map units on the linkage map?
5.3
The first stage after which a dividing cell that started as a diploid would be haploid
Meiosis I anaphase
What does it mean if a human female oocyte is no longer arrested in metaphase II of meiosis?
she is pregnant
A spontaneously aborted human embryo is characterized with respect to karyotype, and it is found to be normal except that it contains only one chromosome number two. This is an example of what type of aneuploidy?
monosomy
Name one characteristic of X-linkage that is often used to identify X-linked genes in pedigree analysis.
Criss-cross pattern of inheritance-where all sons exhibit mutant mother phenotype, the phenotype largely or exclusively affects males.
Affected fathers with unaffected mothers pass trait only to daughters, never sons
Affected mothers with affected fathers pass trait to sons
Sister chromatids separate during what phase(s)?
Meiosis II anaphase
Mitosis anaphase
Two- and three-factor testcrosses can both be used to _____________ and _____________.
map gene loci and determine genotypes
In G1 of the cell cycle, the genus Ooompa lumpa has a DNA content (C) of 2.5 picograms. Following DNA synthesis (in G2 of the cell cycle) what will be the DNA content (in picograms) of the Oompa lumpa cell?
5
Human females with XY chromosomes and a mutation in their receptor gene have ____________________ syndrome.
androgen insensitivity syndrome
Chromosomes are in unseparated, sister-chromatid form, at the end of which phase(s)?
??Meiosis I prophase
Meiosis I anaphase
Meiosis II prophase
Mitosis prophase
Meiosis I prophase, Mitosis prophase??
Where on the chromatid are the microtubules attached?
Kinetochore
10% recombination is equal to how many map units?
10mu
In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be phenotypically recessive?
1/256
What is the probability of obtaining 3 heads in four flips of a fair coin?
.25
In one strand of DNA, the nucleotide sequence is 5’-ATGC-3’. The complementary sequence in the other strand must be:
3’-TACG-5’
In the following cross, what proportion of individuals will have the Bombay phenotype?
AB Hh x AB Hh
1/4
Purple flower color and yellow seed color are dominant traits. An individual with purple flowers and yellow seeds is crossed to an individual with purple flowers and green seeds. The offspring of these two parents were as follows:
Purple flowers, yellow seeds 57
Purple flowers, green seeds 62
White flowers, yellow seeds 18
White flowers, green seeds 20
Ppyy
The contribution Charles Darwin made to genetics was to
propose that evolution occurs by natural selection.
In the G0 stage of the cell cycle, which of the following is true:
stem cells are produced
the cell exits the cell cycle
RNA replicates
DNA content doubles
the nuclear membrane disappears
the cell exits the cell cycle
What is the mechanism that ensures Mendel’s First Law of segregation?
Segregation of homologous chromosomes
An allele is
an alternate form of a gene.
If a couple with Sickle cell disease genotypes Ss and Ss mate and have one child with the disease, what is the chance the next child has the disease as well?
0.25
Red-green color blindness is X-linked recessive. A woman with normal color vision has a father who is color blind. The woman has a child with a man with normal color vision. Which phenotype is NOT expected?
a color-blind female
What phenomenon describes a genetic trait that is expressed more strongly or earlier in development with each generation?
anticipation
The primary structure of a protein is:
A linear chain of amino acids
Which of the following are examples of monohybrid crosses?
Aa x aa Aa x Aa AaBb x aabb AaBb x AaBb AaBB x AaBB
??
List 2 methods that we have discussed used to map human genes.
Somatic Cell Hybridization
Lod Score Method
Synteny Test
FISH
Human gametogeneis from one oogonium and one spermatagonium results in how many mature gametes of each?
4 sperm, 1 ovum
4 male spermatids, 1 ovum?
In order to determine if mutations from different organisms that exhibit the same phenotype are allelic, which test would you perform?
allelic series test
Linked genes ____________.
co-segregate
Crossing over occurs during
prophase I of meiosis.
Explain the differences between incomplete dominance and continuous variation.
incomplete dominance: one allele is not completely dominant over the other allele, so an intermediate phenotype is observed.
continuous variation: variation within a population where there are many intermediates that fall between the extremes (ex: height in people)
While doing field work in Madagascar, you discover a new dragonfly species that has either red (R) or clear (r) wings. Initial crosses indicate that R is dominant to r. You perform three crosses using three different sets of red-winged parents with unknown genotype and observe the following data:
- 72 red-winged, 24 clear-winged
- 4 red-winged
- 96 red-winged
a. What is the most likely genotype for each pair of parents?
b. Do you think there are a sufficient number of progeny to support each of your answers in the previous question?
Cross 1 results in a 3:1 ratio of red-winged to clear-winged progeny; therefore, the parents are most likely both Rr. Crosses 2 and 3 result in only red-winged progeny, therefore, the parents are most all RR.
Crosses 1 and 3 have a sufficient number of progeny , but the low number of progeny from cross 2 is insufficient to make any conclusions
The cellular organelles with inheritance independent of the nucleus are the ____ and the ____ .
chloroplasts, mitochondria
What is the probability of rolling two six-sided dice and obtaining the following numbers:
a) 2 and 3?
b) 6 and 6?
c) at least one 6?
d) Two of the same number (two 1s, or two 2s, or two 3s, or two 4s etc.)?
e) An even number on both dice?
f) An even number on at least one dice?
Enter all answers as fraction (e.g. 1/3 ). When possible use the simplest form
a. 2 and 3
Use the product and additive rules. There are two possible ways in which to obtain the 2 and the 3 on the dice.
There is a 1/6 chance of rolling a 2 on the first die and a 1/6 chance of rolling a 3 on the second die. The probability of this taking place is therefore 1/6 × 1/6 = 1/36.
There is also a 1/6 chance of rolling a 3 on the first die and a 1/6 chance of rolling a 2 of the second die. The probability of this taking place is 1/6 × 1/6 = 1/36. So the probability of rolling a 2 and a 3 would be 1/36 + 1/36 = 2/36 or 1/18.
b. 6 and 6
There is only one way to roll two 6’s on a pair of dice: the first die must be a 6 and the second die must be a 6. The probability is 1/6 × 1/6 = 1/36.
c. At least one 6
There are 3 ways to get at least one 6 in the roll of two dice. The first is to roll 6 on both dice, which we determined has a probability of 1/36. The second way is to roll a 6 on the first die (1/6) and something other than a 6 on the second (5/6). When the multiplication rule is applied to this second possibility, we achieve an overall probability of 5/36. The third way would be to roll something other than a 6 in the first die (5/6) and a 6 on the second die (1/6) for an overall probability of 5/36. Using the addition rule to add the probabilities of these three different ways to achieve at least one 6, we arrive at the final answer of 11/36 chance.
d. Two of the same number (two 1’s, or two 2’s, or two 3’s, etc.)
There are several ways to roll two of the same number. You could roll two 1’s, two 2’s, two 3’s, two 4’s, two 5’s, or two 6’s. Using the multiplication rule, the probability of rolling two 1s is 1/6 × 1/6 = 1/36. The same is true of two 2’s, two 3’s, two 4’s, two 5’s, and two 6’s. Using the addition rule, the probability of rolling either two 1’s, two 2’s, two 3’s, two 4’s, two 5’s, and two 6’s is 1/36 + 1/36 +1/36 +1/36 +1/36 + 1/36 = 6/36 = 1/6.
e. An even number on both dice
Three out of the six sides of a die are even numbers, so there is a 3/6 probability of rolling an even number on each of the dice. The chance of having an even number on both dice is (3/6)(3/6) = 9/36, or ¼.
f. An even number on at least one die
Three out of the six sides of a die are even numbers, so the probability of rolling an even number on the one die is 3/6. The probability of not rolling an even number is 3/6. An even number on at least one die could be obtained by rolling (a) an even on the first but not on the second die (3/6 × 3/6 = 9/36), (b) an even on the second die but not on the first (3/6 × 3/6 = 9/36), or (c) an even on both dice (3/6 × 3/6 = 9/36). Using the addition rule to obtain the probability of either a or b or c, we obtain 9/36 + 9/36 + 9/36 = 27/36 = ¾.
What is the purpose of synteny testing?
To correlate the presence of particular chromosome with a particular gene product.
Suppose you heard of an animal alleged to be the hybrid of a rabbit and a cat. If the cat (Felis domesticus) has a diploid chromosome number of 30 and a rabbit (Oryctolagus cuniculus) has a diploid chromosome number of 46, what would be the expected chromosome number in the somatic tissues of this alleged hybrid?
38
The attachment point on the chromosome for spindle microtubules is the
Kinetochores
Phenotypically, what two general categories of offspring did Sturtevant and Morgan observe in the F2 generation of their fly crosses?
red eyes/white eyes
(All females had red eyes, 1/2 of males had white eyes, 1/2 of males had red eyes)
wild type and mutant
In prokaryotes, replication usually begins at a specific place on the chromosome called the
origin of replication
A measurable or observable trait or characteristic is called a(n)
phenotype
The complete genetic makeup of any organism is its
genome
Microscopy to look at a cell’s chromosomes is often done when the cell is in mitotic metaphase. For example, karyotypes that extract chromosomes from a single cell and photograph them to look for abnormalities are done on metaphase, rather than interphase, cells. Why?
In metaphase, chromosomes are condensed and are more easily visualized.
Multi-factorial traits are influenced by _______ and ________.
a. pleiotropy
b. multiple genes
c. dominance
d. environment
e. genetic imprinting
multiple genes
environment
Within cells, DNA and genes are organized into structures called ________.
chromosomes
In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be genotypically AABBCCdd ?
1/256
The difference between the homogametic sex and heterogametic sex is that ______________ .
the heterogametic sex determines the gender of the offspring
In anaphase….
a) chromosomes move to opposite poles
b) the nuclear membrane is dissolved
c) homologous chromosomes are paired
d) chromosomes replicate
Chromosomes move to opposite poles
An organism has a haploid number of 6. How many possible assortments of chromosomes are possible based on the independent assortment of the chromosomes?
2^6 = 64
How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?
The daughter cells have the same number of chromosomes and the same amount of DNA
Polygenic traits ______________________ .
may be measured quantitatively and have continuous variation
are influenced by both genes and the environment
Genetic distances within a given linkage group
are dependent upon crossover frequencies between paired, non-sister chromatids.
are measured in centiMorgans.
Codominant alleles are expressed in individuals that are ________.
penetrant
homozygous
polymorphic
heterozygous
mutually exclusive
heterozygous
If thymine makes up 15% of the bases in a certain DNA sample, what percentage of the bases must be cytosine?
35 percent
In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be phenotypically ABCD ?
81/256
If a crossover event happened in one half of all tetrads, how many recombinant gametes would be produced?
25 percent
In snapdragons, heterozygotes for one of the genes have pink flowers, whereas homozygotes have red or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring will have pink flowers?
100%
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)?
n+1, n+1, n-1, n-1
When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
50%
If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a wild-type male, what proportion of female progeny will have the mutant phenotype?
0%
Which of the following is not a component within a single nucleotide of a nucleic acid?
polymerase
A woman who has blood type A has a daughter who is type O and a son who is type B. Which of the following is a possible genotype for the son?
IBi
0.1% frequency of recombination is observed…
In genes located very close to one another on the same chromosome.
Genetic information can be carried in which of the following biomolecules?
Either DNA or RNA
In corn, small pollen (sp) is recessive to normal pollen (sp+) and banded necrotic tissue, called zebra necrotic (zn), is recessive to normal tissue (zn+). The genes that produce these phenotypes are closely linked on chromosome 10. If no crossing over occurs between these two loci, give the types of progeny expected from the following crosses:
??
Other than genes, name 3 other regions of chromosomes? What are their functions?
Which of them represent euchromatin? Heterochromatin?
Centromeres, telomeres, intergenic regions. Correct
??
- Centromere - the attachment point for spindle microtubules (heterochromatic)
- Telomeres - natural ends, the tips of linear chromosomes that serve to stabilize the chromosome (Heterochromatic)
- Origin of replication - where DNA synthesis begins (euchromatic) ??
For a particular plant, red flowers (A) are dominant over yellow flowers (a). An initial cross was made between a plant that was true-breeding for red flowers, and another plant true-breeding for yellow flowers. F1 progeny, all having red flowers, were allowed to form seeds (through self-fertilization), which were then planted to generate F2 progeny. Pollen from all the resulting F2 plants was pooled and used to fertilize true-breeding yellow plants. What proportion of the progeny resulting from this cross would be expected to have yellow flowers?
?? 1/2
What inheritance is suggested by each description?
Reference: Ref 6-5
Extensive pedigree analysis on a characteristic shows all the following:
- if a woman with an affected father has children with an unaffected man, half of the sons and none of the daughters are affected.
- affected females always have an affected father and an affected maternal grandfather.
- the trait is never passed from father to son.
x-linked recessive
Male mammals inherit an X chromosome from which of their parents? Their _____.
mother
A photograph of a chromosome squash is called a….
karyotype
Interactions among the human ABO blood group alleles involve _____ and ______.
complete dominance
co-dominance
Genes can be located in which organelles?
nucleus, chloroplast, mitochondria
What inheritance is suggested by each description?
Reference: Ref 6-5
Extensive pedigree analysis on a characteristic shows all of the following:
- the characteristic affects males and females equally.
- two unaffected parents can have an affected child.
- in families in which the parents are unaffected but the children are affected, 1/4 of the children are affected.
autosomal recessive
Extensive pedigree analysis on a characteristic shows all of the following:
•only males are affected.
•affected fathers always pass the trait to sons.
What does this pedigree indicate:
y-linked
During prophase I of meiosis, crossing over is indicated by what microscopically visible structure? The ______.
chiasma
Sister chromatids separate during what phase(s)?
Mitosis anaphase
Meiosis II anaphase
Phenotypically, what two general categories of offspring did Sturtevant and Morgan observe in the F2 generation of their fly crosses?
??
A form of a gene that has a slightly different sequence than other forms of the same gene but encodes the same type of an RNA or protein, is called a(n)
allele
What inheritance is suggested by each description?
Extensive pedigree analysis on a characteristic shows all of the following:
- males and females are affected equally.
- affected fathers may have affected daughters, but never affected sons.
- half the children of affected mothers are affected.
x-linked dominant
How many Barr bodies would you expect to see in an XXY individual?
1
Mendel’s law of independent assortment has its physical basis in the:
random arrangement of chromosomes on the metaphase plate in meiosis I.
What is the probability of obtaining 3 heads in three flips of a fair coin?
1/8
The contribution of Gilbert and Sanger to modern genetics was to
develop a method for sequencing DNA.
Which of the following human genotypes is associated with Klinefelter syndrome?
XXY
XXYY
XXXY
Assuming Mendel’s Second Law is correct, what is the expected segregation ratio for traits in a dihybrid cross?
9:3:3:1
Mitosis ends with _____, while meiosis ends with _____.
Mitosis ends with 2 diploid cells, while meiosis ends with 4 haploid cells.
Hemizygosity would most likely be associated with which of the following?
sex-linked inheritance
Cytokinesis is
the formation of two cells at the end of mitosis in both plants and animals
Ability to roll the tongue is caused by a dominant allele. A woman is a “roller,” but one of her parents is not.
Reference: Ref 6-2
What is the woman’s genotype?
heterozygous
Mice homozygous for mutations in one gene exhibit polydactyly (i.e. extra toes) while in another gene (limb deformity), homozygous mutants lack all parts of the limb below the wrist. A mutant that is doubly homozygous for extra toes and limb deformity mutations will NOT exhibit polydactyly because it is missing the distal limbs, where the toes are located. This type of genetic relationship is called
epistasis
Embryonic stem cells are the subject of a great deal of research. What characteristic of embryonic stems cells accounts for this scientific interest?
potentially totipotent
Purple flower color and yellow seed color are dominant traits. An individual with purple flowers and yellow seeds is crossed to an individual with purple flowers and green seeds. The offspring of these two parents were as follows:
Purple flowers yellow seeds: 57 Purple flowers green seeds: 62 White flowers yellow seeds: 18 White flowers green seeds:20 What genotypes are possible for the offspring with white flowers and yellow seeds?
??
Males with an X-linked gene are said to be ____ for these X-linked genes.
hemizygous
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?
The gene involved is on the X chromosome
Prokaryotic chromosomes do not have telomeres because:
they are circular.
A chromosome with a centromere at the very end is called
telocentric
Which of the following species is considered a genetic model organism?
The worm, Caenorhabditis elegans
What is the fundamental difference with respect to the chromatids between metaphase of mitosis and metaphase I of meiosis? How does the resulting cell differ in mitosis vs. meiosis I?
??
What is the chi-square test used for, and what does it tell you?
The chi-square test is used to evaluate the role of chance in producing deviations between observed and expected values. It tells you how well observed values fit the expected values.
Trisomy 21 or Down syndrome occurs when there is a normal diploid chromosomal complement of 46 chromosomes plus one (extra) chromosome #21. Such individuals therefore have 47 chromosomes. Assume that a mating occurs between a female with Down syndrome and a normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome? Justify your answer.
The proportion of offspring with Down syndrome would be 50%. Because down syndrome is a genetic defect, the mother would have a genotype that is homozygous recessive (dd). The father would be heterozygous (Dd) because everyone has the possibility of having a child with down syndrome. If a punnett square was done, you would have offspring that were either homozygous recessive for Down syndrome of heterozygous- Dd, Dd, dd, dd. That would make a 50% chance.
What inheritance is suggested by each description?
Reference: Ref 6-5
Extensive pedigree analysis on a characteristic shows all the following:
•
if a woman with an affected father has children with an unaffected man, half of the sons and none of the daughters are affected.
•
affected females always have an affected father and an affected maternal grandfather.
•
the trait is never passed from father to son.
x-linked recessive
Human gametogeneis from one oogonium and one spermatagonium results in how many mature gametes of each?
??
Human blood types are an example of codominance because:
The A and B alleles both express equally in individuals with both alleles.
The DNA of a eukaryotic chromosome is:
one long double helix.
If a typical somatic cell has 44 chromosomes, how many chromosomes are expected in each gamete of that organism?
22
The F1 offspring of Mendel’s classic pea cross always looked like one of the two parental varieties because
one allele was completely dominant over another
A rare dominant trait, when exhibited in men, is transmitted to half their sons and to half their daughters. The gene for this trait is carried:
on an autosome.
A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males.
What is the total number of chromosomes in a polar body cell from a rat?
21
Which of the following parental genotypes will produce only heterozygous F1 offspring?
a) aa x aa
b) Aa x aa
c) AA x Aa
d) Aa x Aa
e) AA x aa
AA x aa
In a germ-line cell from a human male that is dividing, when do the X and Y chromosomes segregate?
during meiosis I, anaphase
Where on the chromatid are the microtubules attached?
Kinetochore
If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a wild-type male, what proportion of female progeny will have the mutant phenotype?
0%
Discuss the difference between “cytoplasmic inheritance” and “genetic maternal effect.”
Cytoplasmic inheritance - some characteristics of a cell are encoded by genes located in the cytoplasm (chloroplast and mitochondria). Present in both males and females and are passed from mother to offspring. No mechanism ensures cytoplasmic genes are evenly distributed.
Genetic maternal effect - the phenotype of the offspring is determined by the genotype of the mother. Genes are inherited from both parents, but offspring phenotype is determined by the genotype of its mother.
You are conducting a cross using Drosophila melanogaster. The results of your cross indicate that the recombination frequency is very high. How do you feel about the accuracy of your map unit calculations based on this cross?
The larger the recombination frequency, the less accurate it is as a measure of map distance.
Albinism is a somatic recessive condition resulting from the inability to produce the dark pigment melanin in skin and hair. A man and woman with normal skin pigmentation have two children. The man has one albino parent; the woman has parents with normal pigmentation, but an albino brother.
a. What is the probability that at least one of the children is albino?
b. What is the probability of both children being albino?
a.) 11/36
First, calculate the probability of the couple having an albino child each time a child is born. If the woman is Aa, then the mating is Aa x Aa, and P(albino) = 1/4. However, there is only a 2/3 chance that she is Aa. So overall for this mating, P(albino) = P(man is Aa) x P(woman is Aa) x 1/4 = 1 x 2/3 x 1/4 = 2/12 = 1/6. Conversely, the probability that a child will be normal P(normal) = 1 – P(albino) = 5/6.
The probability of at one child being normal can be solved two ways: by summing the
probabilities of: first child normal, second child albino + first child albino, second child normal + both children albino; or by 1 – P (no child is albino). These methods give: 11/36)
The cellular organelles with inheritance independent of the nucleus are the _____________ and the ____________ .
chloroplast and mitochondria
