genetics ch.7

In distinguishing between linkage and independent assortment, the chi-square equation calculates the sum of (O-E)2/E2 for each class. (O-E)/E for each class. (O-E)/E2 for each class. (O-E)2/E for each class.

(O-E)2/E for each class.

In the Creighton and McClintock experiments, the genotype of Parent B was cc Wxwx. This parent could make ____ types of gametes.

2

How many total linkage groups does a cell from a human male contain? 24 46 (A human male has 22 autosomal linkage groups, an X linkage group, a Y linkage group, and a mitochondrial genome linkage group.) 25 23

25

How many map units apart do two genes have to be to follow the law of independent assortment? 100 mu (If the calculation shows that the genes are 100 mu apart, this means that only recombinant offspring were produced, a highly unlikely scenario. Parental combinations would represent at least 50% of the offspring if the genes are on separate chromosomes or far apart on the same chromosome.) 50 mu (Although two genes can be on the same chromosome and more than 50 mu apart, a test cross yields a maximum of 50% recombinant offspring due to multiple crossovers. When two genes are more than 50 mu apart, they follow the law of independent assortment in a test cross.) 1,000 mu (A value of 1000 mu cannot be observed in a test cross. Although two genes can be on the same chromosome and more than 50 mu apart, a test cross yields a maximum of 50% recombinant offspring due to multiple crossovers. When two genes are more than 50 mu apart, they follow the law of independent assortment in a test cross.) 5 mu

50 mu

In a three-factor cross, how many possible phenotypic combinations of offspring are there? 6 4 8 2

8

When considering two genes on a fly chromosome, if a fly cross yields 63 recombinant offspring out of 656 total offspring, what is the distance between the two genes in question? 9.6 map units 10.4 map units 41328 map units

9.6 map units

Based on Mendel's law of independent assortment, what phenotypic ratio should the offspring of a two-factor cross between two individuals heterozygous for two genes show?. 12:3:1 1:1:1:1 9:3:3:1 7:4:4:3

9:3:3:1

*Figure 7.6 Crossing over between a normal and abnormal chromosome 9 in corn* The corn chromosome 9 used in experiments by Creighton and McClintock, and shown here, had which unusual structural features? A deleted region in the center of the chromosome A knob at one end of the chromosome A knob consisting of a translocation of a piece of chromosome 8 A knob in the center of the chromosome A translocation of piece of chromosome 8

A knob at one end of the chromosome A translocation of piece of chromosome 8

The genes studied in the Creighton and McClintock corn crosses were the C gene and the Wx gene. The C allele leads to colored kernels, and the recessive c allele leads to uncolored kernels. The Wx allele results in starchy endosperm, and the recessive wx allele results in waxy endosperm. Match each genotype to its phenotype below. C C Wx wx c c Wx Wx C c wx wx c c wx wx colored starchy uncolored starchy uncolored waxy colored waxy

C C Wx wx -> colored starchy c c Wx Wx -> uncolored starchy C c wx wx -> colored waxy c c wx wx -> uncolored waxy

Select the experiments/calculations that are included in using a three-factor cross to map genes. Chi square analysis Calculation of map distance Cross of two true-breeding fly strains Testcross

Calculation of map distance Cross of two true-breeding fly strains Testcross

Select alternative names for genetic mapping. Chromosome mapping Gene mapping Independent assortment Test crossing

Chromosome mapping Gene mapping

Place in order from first to last these steps for using a three-factor cross to map genes. Collect data for the F2 generation calculate the map distance between pairs of genes cross two true-breeding strains that differ with regard to three alleles construct the map perform a testcross by mating F1 female heterozygous to male flies homozygous recessive for all three alleles

Cross two true-breeding strains that differ with regard to three alleles Perform a testcross by mating F1 female heterozygous to male flies homozygous recessive for all three alleles Collect data for the F2 generation Calculate the map distance between pairs of genes Cross two true-breeding strains that differ with regard to three alleles Construct the map

What is the name of the process in diploid eukaryotic species where homologous chromosomes exchange pieces with each other? Testcross Interference Crossing-over Independent assortment

Crossing-over

What can affect the outcome of a cross, causing scientists to reject the independent assortment hypothesis, even though it may be correct? Decreased viability of particular phenotypes A homozygous mother Incorrect map locations of genes (Inaccuracies in gene map locations will not affect the observed phenotypic ratios among the offspring.)

Decreased viability of particular phenotypes

If the genes in Morgan's three factor crosses were all located together on the X chromosome, why did some of the F2 generation display new combinations of traits? Due to recombination between X chromosomes Due to mutation Due to experimental mistakes Due to recombination between X and Y chromosomes

Due to recombination between X chromosomes

A diploid cell has a pair of homologous chromosomes. One chromosome has the alleles FGH and the other chromosome has the alleles fgh. The cell undergoes meiosis. Select alleles found in the nonrecombinant haploid cells. FGH FGh Fgh FgH fgh fGh fgH fGH

FGH fgh

True or false: Crossing-over can only occur during meiosis. True (Crossing over occurs much less frequently in mitosis than meiosis, but it does happen on rare occasion) False

False

True or false: Geneticists only study the transmission of one character at a time in a given genetic cross. True (Geneticists often study two or more characters in a genetic cross.) False

False

Select the benefits of genetic mapping. A genetic map allows scientists to understand what genes are expressed within different cell types within a species. Information on a genetic map can be used to diagnose inherited human diseases. The genetic map helps scientists understand the complexity and genetic organization of a species. Genetic maps can help us understand the evolutionary relationship between species.

Information on a genetic map can be used to diagnose inherited human diseases. The genetic map helps scientists understand the complexity and genetic organization of a species. Genetic maps can help us understand the evolutionary relationship between species.

How many genes does a typical human chromosome contain? Less than one hundred Tens of thousands Many hundreds Several million (A typical chromosome is expected to contain many hundred or perhaps a few thousand different genes.)

Many hundreds

A diploid cell has a pair of homologous chromosomes. One chromosome has the alleles Pq and the other chromosome has the alleles pQ. The cell undergoes meiosis. Select the recombinant cells below. PQ pQ pq Pq

PQ pq

In a testcross, if the genes in question are linked, how does the number of recombinant offspring relate to the number of nonrecombinant offspring? There are more recombinant offspring than nonrecombinant offspring. (Separation of chromosomes without recombination is more frequent than recombination between linked genes.) There are fewer recombinant offspring than nonrecombinant offspring. There are equal numbers of recombinant and nonrecombinant offspring.

There are fewer recombinant offspring than nonrecombinant offspring.

True or false: Three-factor crosses can yield additional information about map distance and gene order as compared to two-factor crosses. True False (Three-factor crosses provide additional information about map distance and gene order.)

True

Morgan studied the X-linked pattern of inheritance by crossing female fruit flies that had yellow bodies (yy), white eyes (ww), and miniature wings (mm) to wild type males. The wild type alleles are written as y+(gray body), w+(red eyes), and m+(long wings). What was the phenotype of the F1 males? XywmY (This is a genotype, not a phenotype.) Yellow bodies, white eyes, and miniature wings Xy+w+m+Y Gray body, red eyes, and long wings (The wild-type alleles for these three genes are y+ (gray body), w+ (red eyes), and m+ (long wings).)

Yellow bodies, white eyes, and miniature wings

You carry out a three point cross for genes a, b, and c, and calculate your map distances. You are confused to find that when you add the distance between a-b to the distance between b-c, the number is larger than your calculated distance from a-c. Why? You've made a math error. You need to add in double crossovers. There must have been a mutation.

You need to add in double crossovers.

A testcross is a cross between two dominant homozygotes. two heterozygotes. a heterozygote and a recessive homozygote. two recessive homozygotes. a heterozygote and a dominant homozygote.

a heterozygote and a recessive homozygote.

To conduct a chi square analysis to discriminate between linkage and independent assortment in a cross, a scientist needs map locations for each gene in question. a hypothesis. the expected number of offspring based on a Punnett square. the observed number of offspring.

a hypothesis. the expected number of offspring based on a Punnett square. the observed number of offspring.

Creighton and McClintock discovered that crossovers produce recombinant chromosomes through an exchange of chromosomal segments between non-homologous chromosomes. (Crossing over occurs between homologous chromosomes.) mutation. an exchange of chromosomal segments between homologous chromosomes. an exchange of chromosomal segments between different species.

an exchange of chromosomal segments between homologous chromosomes.

Traditional genetic mapping approaches are feasible in humans. certain animal species. several plant species. insects such as Drosophila.

certain animal species. several plant species. insects such as Drosophila.

A ___ ____ test is used to distinguish between linkage and independent assortment.

chi square

The first direct evidence that genes are physically located on the same ____came from the studies of Thomas Hunt _____, who studied the inheritance pattern of characters following an ______-linked pattern of inheritance.

chromosome and Morgan and X

A i___ s sometimes called a ____ ____ because it contains a group of genes that are physically linked together. Listen to the complete question

chromosome and linkage and group

A crossover is unlikely to occur in the region between two genes when they are homologous. far apart. (As Morgan's experiments suggested, crossing over is more likely to occur if the genes on the same chromosome are farther apart.) close together. at the same locus.

close together.

A gene for corn kernel ___ resides near the knobbed end of corn chromosome 9, whereas a gene that affects the texture of the kernel ____ resides near the translocated piece of chromosome 8.

color and endosperm

*Figure 7.1 An experiment of Bateson and Punnett with sweet peas, showing that independent assortment does not always occur.* These results from a sweet pea cross by Bateson and Punnett show a significant variation between the observed and expected numbers of each phenotype. This is because the genes for flower ___ and ___ shape are found on the same _____

color and pollen and chromosome

*Figure 7.4 Morgan's explanation for nonrecombinant and recombinant offspring.* For Morgan's fly crosses, considering the genes shown on the F1 female's X chromosomes, this picture depicts ______. crossing over and recombinant offspring no crossing over and recombinant offspring no crossing over and nonrecombinant offspring crossing over and nonrecombinant offspring

crossing over and recombinant offspring

Genetic mapping is based on estimating the distance between linked genes based on the likelihood that a ____ will occur between them.

crossover

Morgan proposed that the likelihood of crossing-over depends on the ____ between two genes.

distance

In a three-factor cross, ____ crossovers are incorporated into map distance by multiplying their number by 2 and adding this number to the previous value ____ of offspring in the equation for map distance.

double and recombinant

McClintock and Creighton hypothesized that a crossover between a normal chromosome 9 and a knobbed, translocated chromosome 9 would produce a recombinant chromosome that had ______. either a knob or a translocation but not both a knob both a knob and a translocation (One of the parental chromosomes has both a knob and a translocation.) a translocation

either a knob or a translocation but not both

When performing a chi-square test to distinguish between linkage and independent assortment in a two-factor cross, a scientist must take into account the observed and ___ values for each of the four phenotypes in the cross.

expected

An experiment that studies the transmission of three different characters in a genetic cross is called a three-____ ____

factor cross

Compared to two-factor testcrosses, three-factor testcrosses can provide additional information about whether the parental flies are homozygous or heterozygous for the genes of interest. (Two-factor testcrosses are used to distinguish between homozygous and heterozygous individuals.) gene order. map distance.

gene order. map distance.

The functional units of a chromosome are called

genes

The purpose of _____ mapping is to determine the linear order and the distance between genes on the same ____

genetic and chromsome

Traditional ____ mapping approaches can be difficult due to ____ generation times or the inability to carry out experimental crosses.

genetic and long

*Figure 7.7 A simplified genetic linkage map of Drosophila melanogaster.* This picture shows a ______. genetic library testcross genetic linkage map chi square analysis

genetic linkage map

The linear arrangement of genes on a chromosome is depicted on a____ ____ map.

genetic linkage map

In a testcross to determine recombination frequency in Drosophila, the female is always the recessive homozygote. heterozygote. dominant homozygote.

heterozygote.

In a three-factor cross, the goal of the first step is to obtain F1 individuals that are ____ for all three genes.

heterozygous

In conducting a chi square analysis of a two factor cross, if the chi square value is ____ , we reject the null hypothesis that the genes assort independently, and accept that the genes are linked.

high

Statistical analysis cannot prove that a/an ____ is true.

hypothesis

Mendel's law of ___ ____suggests that a two-factor cross between two individuals heterozygous for two genes should yield a 9:3:3:1 phenotypic ratio among the offspring.

independent assortment

Morgan explained his data by suggesting that if two genes are far apart from each other, crossing-over is less likely to occur than between two genes that are closer together. will occur with the same frequency as between two genes that are closer together. is more likely to occur than between two genes that are closer together.

is more likely to occur than between two genes that are closer together.

A ___ and a ____on corn chromosome 9 proved instrumental in showing that crossing over can result in genetic recombination, in experiments by Creighton and McClintock.

knob and translocation

When conducting a chi square analysis to determine if genes in a two factor cross are linked or independently assorted, scientists begin with the hypothesis that the genes are not ____

linked

The site where a gene is found on a particular chromosome is called its ___

locus

In conducting a chi square analysis of a two factor cross, if the chi square value is ____, we cannot reject the null hypothesis, and we infer that the genes assort _____

low and independent

To construct a genetic _____ with data from a three-factor cross, you first use ____ the between the genes that are closest together.

map and distance

A known locus within a genetic ____ may help molecular geneticists to clone the ____.

map and gene

One ___ ____ equals 1% recombinant offspring in a testcross. Listen to the complete question

map unit

Distance on a chromosome is generally measured in (chose all correct answers) centimeters. map units. centiMorgans. recombinant units. mapMorgans.

map units. centiMorgans.

Crossing-over during ______ occurs much less frequently than crossing-over during ______. meiosis; mitosis (Crossing over during meiosis is fairly common. Crossing over during mitosis is much less common.) mitosis; meiosis

mitosis; meiosis

If ____ recombination occurs at an early stage of embryonic development, the adult organism may have a patch of tissue with characteristics different from the rest of the organism.

mitotic

You discover a dog that has a patch of white hair on its side and is completely black otherwise. The patch may be the result of ______. a double crossover meiotic recombination mitotic recombination a testcross

mitotic recombination

Stern proposed that twin spots were a result of mitotic recombination in the adult organism. meiotic recombination. mitotic recombination during embryonic development.

mitotic recombination during embryonic development.

*Figure 7.4 Morgan's explanation for nonrecombinant and recombinant offspring.* For Morgan's fly crosses, considering the genes shown, this picture depicts no crossing over and recombinant offspring (Offspring will only be recombinant if crossing over occurred.) crossing over and recombinant offspring no crossing over and nonrecombinant offspring crossing over and nonrecombinant offspring (Crossing over implies that there was an exchange of DNA between chromosomes. The chromosomes inherited by the F2 generation are parental types because there is no observed recombination.)

no crossing over and nonrecombinant offspring

When two genes are linked, offspring tend to inherit the ______ pattern of alleles more often than the ______ pattern of alleles. recombinant; non-recombinant (Inheritance of the non-recombinant (parental) pattern is most frequent.) non-recombinant; recombinant

non-recombinant; recombinant

In a three-factor cross involving linked genes, the ______ phenotype occurs most frequently. recombinant (In crosses involving linked genes, the nonrecombinant phenotype occur most frequently in the offspring.) nonrecombinant

nonrecombinant

Offspring that display the same combination of alleles that were found in the chromosomes of their parents are called ______ offspring. nonrecombinant recombinant

nonrecombinant

Offspring that display the same combination of alleles that were found in the chromosomes of their parents are called ______ offspring.. recombinant nonrecombinant

nonrecombinant

To perform chi square analysis for gene linkage, we start with a ____ ____ that there is no difference between observed values and those expected based on the law of independent assortment.

null hypothesis

Crossing over occurs during ______ of meiosis I. metaphase anaphase prophase telophase

prophase

From first to last, order the steps in applying the chi square test to distinguish between linkage and independent assortment. Interpret the calculated chi square value apply the chi square formula, using the data for observed and expected value propose a hypothesis based on the hypothesis, calculate the expected value of each of the four phenotypes

propose a hypothesis based on the hypothesis, calculate the expected value of each of the four phenotypes apply the chi square formula, using the data for observed and expected value Interpret the calculated chi square value

Offspring that display combinations of traits that are different from those of either parent are called ____

recombinant

The number of ____ offspring divided by the total number of offspring multiplied by 100 equals the genetic ______ distance.

recombinant and map

The fraction of ____ in a testcross gives an idea of the physical ____ between two genes on the same chromosome.

recombination and distance

Results from the experiments by McClintock and Creighton supported the view that genetic ___ involves a physical exchange between ____ chromosomes.

recombination and homologous

In using the chi square test to distinguish between linkage and independent assortment in Morgan's fly crosses, we anticipate that the chi square analysis will allow us to ______ the independent assortment hypothesis in favor of a linkage hypothesis. reject accept (The hypothesis allows us to calculate expected values. Because the data seems to to conflict with the hypothesis, we anticipate to reject the independent assortment hypothesis in favor of the linkage hypothesis.)

reject

Morgan hypothesized that the genes for body color, eye color, and wing length are all located on the ___ _____, suggesting that they will most likely be inherited together. However, crossing over allows some recombinant patterns of alleles to be displayed in the F2 generation.

same chromosome

Crossing over does not occur during ____ formation in Drosophila.

sperm

Because bacterial cells contain one large circular chromosome, all genes within that chromosome are. non-homologous. syntenic. homologous. (Homologous chromosomes are generally located at the same loci, and code for the same trait, but they are on two separate chromosomes.) recombinant.

syntenic

In humans, the genes for fibroblast growth factor receptor 1 and lipoprotein lipase are both on chromosome 8. Therefore these genes are recombinant. independently assorted. homologous. syntenic.

syntenic.

The goal of a ____ is to determine the frequency with which a doubly ___ parent produces recombinant gamete types.

testcross and heterozygous

In developing a hypothesis to explain Morgan's fly data, we assume that one of the four phenotypes will be lethal. the alleles in question follow the law of independent assortment. the two traits in question are actually controlled by the same gene. the four phenotypes produced by his crosses are equally viable.

the alleles in question follow the law of independent assortment. the four phenotypes produced by his crosses are equally viable.

The null hypothesis for chi square analysis of a two factor cross states that the genes in question are linked. (The null hypothesis assumes that there is no real difference between observed and expected values. The expected values would be based on outcomes predicted by Mendel's principles.) the genes in question are the same. the genes in question are not linked.

the genes in question are not linked.

A locus is the chromosome on which a gene is found. the distance between genes on a genetic map. the site where a particular gene is found on a chromosome. only applicable to linked genes.

the site where a particular gene is found on a chromosome.

The first step in using a three-factor cross to map genes is to cross two _____-breeding lines of flies that differ with regard to alleles at three gene loci.

true

In experiments with Drosophila, Curt Stern observed places in which two adjacent regions of a fly's body were phenotypically different from each other and their surroundings. These places are called ____ ____

twin spot

A double crossover between two genes could involve___, ____ , ____, or chromatids.

two, three and four

You are studying three genes, x, y, and z. You have calculated that the distance from x to z is 3 map units, the distance from y to z is 7 map units and the distance from x to y is 10 map units. What is the correct order of the genes? yxz xyz xzy

xzy