genetics test 2

monoecious

"one house" - has both female and male reproductive structures

dioecious

"two house" - individual has either female or male reproductive structures

If a male with Klinefelter syndrome undergoes spermatogenesis (without nondisjunction), how many chromosomes would be present in the sperm?

23 and 24

Which of the following statements about cotransformation is true?

A bacterial cell receives two adjacent genes on a single piece of DNA from the medium. Cotransformation makes it possible to map pairs of genes that are located near each other.

Which of the following arrangements would yield the greatest reduction in gamete viability?

An inversion heterozygote for a large inversion. A large heterozygous inversion will result in greater numbers of genes that are duplicated or deleted when crossing over occurs.

XX-XY

Chromosomal Sex Determination system for some plants, insects, reptiles, all mammals

ZZ-ZW

Chromosomal Sex Determination system. male is homogametic, female is heterogametic Female produces two different gametes, half with Z chromosome, the other half with W (found in birds, moths, some amphibians, and some fishes)

Mendel predicted that some genes would be carried in the same chromosome.

False

Which of the following are properties of a Barr body?

It is formed as part of a mechanism for dose compensation. It is an inactivated X chromosome. It is a darkly stained region near the nuclear envelope of interphase cells.

How can the order of three linked genes (A, B, and C) on the same chromosome be determined?

Look for double-crossover phenotypes involving the wild-type and mutant alleles of genes A, B, and C. Offspring with a double-crossover phenotype will occur less frequently and will therefore be easy to identify. The three possible gene orders are then compared to the double-crossover genotypes to determine which gene order fits the observed pattern.

Why didn't Mendel find linkage in his studies?

Most of the genes he studied were not close together on the same chromosomes.

The incidence of Down syndrome, also known as trisomy 21, increases with increasing maternal age. Which of the following errors most likely produces this condition?

Nondisjunction during either meiosis I or II in female gamete Nondisjunction during either meiosis I or II can produce a gamete that will result in a trisomic zygote. Since the incidence of Down syndrome increases with maternal age, it is likely that this error occurs in the female gamete.

All EXCEPT which of the following are mechanisms by which sex can be determined? The presence of two X chromosomes or an X and a Y chromosome. The ratio of X chromosomes to the number of sets of autosomes. The number of Barr bodies present. The temperature at which the eggs are incubated.

The number of Barr bodies present.

Why is it easier to identify spontaneous mutations in bacteria than in most eukaryotes?

They are expressed directly in descendant cells because bacteria are haploid..No mutants are hidden as recessive alleles within heterozygote genotypes.

Which of the following statements about allopolyploid individuals is true?

They may be sterile and unable to produce offspring. Polyploid individuals are sterile if they produce genetically unbalanced gametes; both autopolyploid and allopolyploid individuals may be sterile.

All EXCEPT which of the following statements about bacteriophages are true? View Available Hint(s) All EXCEPT which of the following statements about bacteriophages are true? They use the metabolic machinery of a bacterial cell to produce more copies of themselves. Within their heads, they can pack the entire main bacterial chromosome from one cell and transfer it to another. They can pick up bacterial genes during the process of infecting a bacterial cell. They are viruses.

Within their heads, they can pack the entire main bacterial chromosome from one cell and transfer it to another. The bacteriophage head is only large enough to pack a small portion of the bacterial genome.

All of the following could result from meiosis in a pericentric inversion heterozygote in which a single crossover occurred within the inversion loop except a _______. View Available Hint(s) All of the following could result from meiosis in a pericentric inversion heterozygote in which a single crossover occurred within the inversion loop except a _______. chromosome with some duplicated regions chromosome with two centromeres completely normal chromosome chromosome with some deleted regions

a chromosome w two centromeres

In humans, the genetic basis for determining the sex "male" is accomplished by the presence of ________.

a portion of the Y chromosome

The condition that exists when an organism gains or loses one or more chromosomes but not a complete haploid set is known as ________

aneuploidy

Transduction is a form of recombination in bacteria that involves ________

bacteriophages

A pericentric inversion includes the____

centromere

Assume that a cross is made between AaBb and aabb plants and that all the offspring are either AaBb or aabb. These results are consistent with ________.

complete linkage

sex (noun)

defined by phenotype of individual (not genotype!)

Inversion loops do NOT form during meiosis in paracentric inversion heterozygotes. t or f

f. Loop formation allows pairing within inverted regions of homologous chromosomes regardless of whether the centromere is included in the inversion.

wilson

female butterflies= 2 x chromosomes males = one x

stevens

female mealwroms= 20 large chrom male=19 and one smaller Y ---x and y separate into different sperm cells, while egg cells all get a single x

What are pseudoautosomal regions on the sex chromosomes?

homologous regions of the X and Y chromosomes. The pseudoautosomal regions refer to regions of homology between the X and Y chromosomes in humans that undergo recombination during meiosis.

What is the specific term that describes the loss of a single chromosome (2n − 1)?

monosomy involves the loss of a single chromosome (e.g., an X chromosome in Turner syndrome).

Heteromorphic chromosomes

occurring in two or more different forms

lyon

proposed Barr body was inactive X chromosome

A bacteriophage that is capable of entering either a lytic or lysogenic cycle is called a(an) ________.

temperate bacteriophage

who typically has genetic sex determination

some protozoans and plants

bridges-

student of Morgan-hypothesized nondisjuntction

homogametic sex

the sex that produces identical gametes

Which of the following statements about the products produced when nondisjunction occurs during meiosis I is true?

Two products of the second meiotic division have both the maternal and paternal chromosomes of a set and the other two products have none for that set. Nondisjunction during meiosis I yields two gametes that are missing a particular chromosome after meiosis II.

A human with the karyotype 49, XXXYY forms _______ Barr bodies.

2. All but one X chromosome is inactivated in every human somatic cell.

If two genes on the same chromosome exhibit complete linkage, what is the expected F2 phenotypic ratio from a selfed heterozygote with the genotype a + b + ⁄⁄ ab?

3:1. Each parent produces two types of gametes, a + b + and ab, giving the simple Mendelian ratio of 3 a + b + : 1

What is the theoretical limit of observed recombination due to crossing over?

50%. When two genes are very far apart (> 50 mu), then it is theoretically possible for crossing over to occur in 100% of tetrads. Since the other two nonsister chromatids in the tetrad remain unchanged, the maximum percentage of recombinant gametes that could be produced is 50%.

Females with only one X chromosome do not develop; this condition is lethal. T or F

False. Females with only one X chromosome are viable but have Turner syndrome, which is characterized by underdeveloped ovaries. Males that lack an X chromosome do not develop; this condition is lethal.

True or false? A bacterial strain that is pro+ thi+ leu− met− will grow on minimal media plus leucine and thiamine.

False. The strain is auxotrophic for leucine and methionine, meaning that it cannot synthesize those nutrients. Thus, it requires those two nutrients to be added to minimal media for growth.

sexual reproduction

Formation of offspring that are genetically distinct from parent

Mapping bacterial genes by conjugation is based on which of the following assumptions?

Genes are transferred from donor to recipient in a linear fashion.

Why do mapping experiments become less accurate when the distances between genes become large?

Multiple crossovers are more common.Multiple recombination events that do not separate the genes being studied will not be recovered during mapping, leading to an underestimation of the distance between genes.

How does nondisjunction in human female gametes give rise to Klinefelter and Turner syndrome offspring following fertilization by a normal male gamete?

Nondisjunction results in ova that carry either two X chromosomes or none. The former results in Klinefelter syndrome when fertilized by a Y-containing sperm, and the latter results in Turner syndrome when fertilized by an X-containing sperm.

A cross between a tetraploid and a diploid member of the same species will produce offspring that can undergo sexual reproduction.

Offspring from this cross would be triploid and produce gametes with an uneven number of homologous chromosomes, making sexual reproduction unlikely.

Which of the following statements about gamete formation during meiosis is false? Parental gametes contain the same combinations of linked genes as found in the parent cell. Recombinant gametes contain combinations of alleles not found in the parent cell. Parental gametes can be formed only if there is no crossing over during meiosis. Complete linkage results in the formation of only parental gametes.

Parental gametes can be formed only if there is no crossing over during meiosis. This statement is false. If crossing over occurs, half of the gametes formed are parental and the other half are recombinant.

How is a merozygote formed?

The F factor and several adjacent genes are excised from the chromosome of an Hfr cell and transferred to an F− strain. A merozygote is formed when the F factor and several adjacent bacterial genes are excised from the bacterial chromosome of an Hfr cell (making it an F′ cell) and transferred to an F− cell.

Jill is heterozygous for gene A and is going to have a child with Jack, who is homozygous recessive for gene A. Which of the following offspring genotypes could result from fertilization of a normal haploid sperm with an egg that had undergone nondisjunction in meiosis I?

a or Aa. During meiosis I, homologous chromosomes separate. If nondisjunction occurs, both homologous chromosomes migrate into the same daughter cell instead of different daughter cells. If this happens in the mother, Jill, the chromosome containing gene A and the chromosome containing gene a end up in one cell, leaving the other daughter cell without a chromosome containing the gene. After meiosis II, Jill would produce gametes containing either Aa or gametes lacking that gene. If these gametes are fertilized with a normal haploid sperm containing gene a, offspring with Aaa or a genotypes are possible.

Which term specifically refers to the gain of extra chromosome sets from individuals of the same species?

autopolyploidy

t or f In order to create the possibility of generating a trisomy, nondisjunction must occur during meiosis II.

f. Correct. Nondisjunction during either meiosis I or meiosis II creates gametes that will generate trisomies if fertilized.

Klinefelter syndrome in humans, which leads to underdeveloped testes and sterility, is caused by which chromosomal condition?

47, XXY

def

A deletion is the loss of part of a chromosomal segment. A duplication is the repetition of a segment. The repeated segment may be located next to the original or at a different location, and its orientation may be the same as the original or the reverse. An inversion is the removal of a segment followed by its reinsertion into the same chromosome in the reverse orientation. A translocation is the transfer of a segment to a nonhomologous chromosome. Translocations may be reciprocal (two nonhomologous chromosomes exchange segments) or nonreciprocal (one chromosome transfers a segment without receiving one).

Which of the following offspring genotypes could result from fertilization of a normal haploid sperm with an oocyte that had undergone nondisjunction in meiosis II? (Because a nondisjunction event in meiosis II could involve the chromosome containing gene A or the chromosome containing gene a, be sure to consider both possibilities in your final answer .)

AAa aaa Aa aa a During meiosis I, the chromosome with gene A and its homolog containing gene a would have separated. During meiosis II, sister chromatids separate. If nondisjunction occurs, both sister chromatids migrate into same daughter cell, instead of different daughter cells. If this occurs in Jill, there are two possible outcomes. It is possible to produce gametes containing two copies of gene A or none at all with the nondisjuction event, with normal division occurring in the other daugher cell, producing gametes with one copy each of gene a. Alternatively, gametes containing two copies of gene a or none at all could be produced by the nondisjunction event, with normal division occurring in the other daughter cell, producing gametes with one copy each of gene A. Considering Jack is giving sperm containing one copy of gene a, all of the following offspring genotypes are possible: AAa, aaa, Aa, aa, and a.

Now, suppose that the three tomato genes from Part A did not assort independently, but instead were linked to one another on the same chromosome. Would you expect the phenotypic ratio in the offspring to change? If so, how? Which statement best predicts the results of the cross MmDdPp x mmddpp assuming that all three genes are linked?

All eight possible phenotypes could occur, but a greater proportion of the offspring would have the parental phenotypes. Because all three genes are linked, it is more likely that the parental allele combinations would stay together rather than be recombined through a crossover event. That is why a greater proportion of the offspring would have parental phenotypes. Nevertheless, some crossing over would likely occur, which is why a small proportion of the offspring would have recombinant phenotypes.

XX-XO

Chromosomal Sex Determination system. simple system, females have two XX, males have single X (O = no chromosome) ex: some insects ie butterflies At meiosis, half sperm receive X, other half get no sex chromosome

Which of the following statements about conjugation is true?

DNA is transferred from an F+ cell to an F− cell.

Which of the following statements about conjugation is true? View Available Hint(s) Which of the following statements about conjugation is true? The F factor is an element that is found in the chromosome of an F+ cell. One strand of DNA from an F+ cell integrates into the chromosome of an F− cell, and the other strand is degraded. Only competent cells can undergo conjugation. DNA is transferred from an F+ cell to an F− cell.

DNA is transferred through a pilus from an F+cell to an F‑ cell.

Methods for determining the linkage group and genetic map in humans involve _______

DNA markers

Which of these three human chromosomal abnormalities--Down, Patau, or Edwards syndrome--has the longest average survival time? Why is that the case?

Down syndrome, because trisomy 21 involves the smallest chromosome of the three.

Linkage (viewed from results of typical crosses) always occurs when two loci are on the same chromosome.

False

A linkage group __________.

Genes located on the same chromosome will show evidence of linkage to each other.

A diploid cell with 4 chromosomes (one pair metacentric, the other telocentric) begins meiosis, and nondisjunction occurs during the second meiotic division.

If nondisjunction occurs during meiosis II, sister chromatids fail to separate. In this case, 50% of the gametes that are produced are normal haploid gametes, 25% of gametes have an extra chromosome, and 25% are missing a chromosome.

Which one of the following statements best describes the major difference between sex determination in Drosophila and in humans?

In Drosophila, the ratio of X chromosomes to the number of haploid sets of autosomes determines the sex while in humans the presence of the Y chromosome determines maleness. (XX does not determine femaleness)

How do mammals, including humans, solve the "dosage problem" caused by the presence of an X and Y chromosome in one sex and two X chromosomes in the other sex?

In females, one of the X chromosomes is condensed and largely inactive so that each sex has one active X chromosome.

A couple has a daughter with Turner syndrome, a condition in which only a single copy of the X chromosome is present. This results from nondisjunction, the failure of the X chromosome to segregate properly during meiosis. During which meiotic division, and in which parent, could nondisjunction have occurred to produce a child with this condition? Hint: It may be helpful to sketch a diagram depicting the outcome of nondisjunction in meiosis I and II of both parents to solve this problem.

Meiosis I in the mother Meiosis II in the mother Meiosis I in the father Meiosis II in the father During meiosis I, homologous chromosomes separate. If nondisjunction occurs, both homologous chromosomes migrate into the same daughter cell instead of different daughter cells. If this happens in the mother, both X chromosomes end up in one cell, with no X chromosome in the other cell. If this happens in the father, both the X and Y chromosome end up in one cell, with no sex chromosome in the other cell. In both cases it is possible for one parent to not give a sex chromosome to the child. If the other parent gives an X chromosome, the child will be XO and have Turner syndrome. During meiosis II, sister chromatids separate. If nondisjunction occurs, both sister chromatids migrate into same daughter cell, instead of different daughter cells. If this happens in the mother, two identical copies of an X chromosome end up in one cell, with no X chromosome in the other cell. If this happens in the father, either two identical copies of the X chromosome end up in one cell, with no sex chromosome in the other cell - or - two identical copies of the Y chromosome end up in one cell, with no sex chromosome in the other cell. In all cases, it is possible for one parent to not give a sex chromosome to the child. If the other parent gives an X chromosome, the child will be XO and have Turner syndrome.

A couple has a son with XYY syndrome, a condition in which an extra copy of the Y chromosome is present. This condition also results from nondisjunction. During which meiotic division, and in which parent, could nondisjunction have occurred to produce a child with this condition? Select all that apply.

Meiosis II in the father The key to solving this problem is to realize that the child got two Y chromosomes. Both of those Y chromosomes had to have come from the father, as the mother has no Y chromosomes. In order to get two Y chromosomes, nondisjunction would have to have occurred in meiosis II - identical Y sister chromatids migrated together into one cell. During meiosis II, sister chromatids should separate. If nondisjunction occurs, both sister chromatids migrate into same daughter cell, instead of different daughter cells. If this happens in the father, either two identical copies of the X chromosome end up in one cell, with no sex chromosome in the other cell - or as in this case two identical copies of the Y chromosome end up in one cell, with no sex chromosome in the other cell. If the sperm containing two copies of the Y chromosome fertilizes an egg containing an X chromosome, the child will be XYY.

Cat breeders are aware that kittens expressing the X-linked calico coat pattern and tortoiseshell pattern are almost invariably females. Which one of the following statements supports this conclusion?

Since females normally have two X chromosomes, random X inactivation during development of a heterozygous female will create a mottled pattern. Normal males are not mottled, because they only have one X chromosome and therefore can only express one of the two potential X-linked alleles.

Which of the following statements about Barr bodies is true?

They ensure that males and females have equal "doses" of the genes on the X chromosome.

In Drosophila, sex is determined by a balance between the number of haploid sets of autosomes and the number of ________.

X chromosomes

The role of sex chromosomes - via studies of sex-chromosome anomolies

X contains genetic info essential for both sexes - at least one X is required 2. Male-determining gene is located on Y (see Klinefelter syndrome) 3. The absence of Y yields female 4. Genes required for fertility are on X and Y- females need at least two Xs to be fertile 5. Additional X chromosomes are detrimental

mcclung

male grasshopper=heterochromosome female = 1 more chromosome than males

henking

male insects- strong body in nuclei= x body

The phenomenon in which one crossover decreases the likelihood of crossovers in nearby regions is called ________.

positive interference

heterogametic sex

the sex that produces two different gametes

In an interrupted mating experiment, the purpose of plating cells on a selective medium is _______.

to ensure that only recombinant genotypes are recovered

t or f A position effect occurs when a gene's expression is altered by virtue of a change in its position. One might expect position effects to occur with inversions and translocations.

true

All of the following events occur during normal meiosis except _______.

two haploid gametes fuse to form a diploid cell. Fusion of haploid gametes occurs after meiosis.

How can duplications arise?

uneven crossing over during meiotic prophase. Synapsis of homologs and unequal crossing over of chromatids during meiosis I can produce one chromatid with a duplication and one with a deletion.

A genomic condition that may be responsible for some forms of fragile-X syndrome, as well as Huntington disease, involves ________.

various lengths of trinucleotide repeats.