Molgen 4500: Module 1 (AU17)

In the following cross, what proportion of individuals will have the Bombay phenotype? AB Hh x AB Hh

1/4

In the cross AaBbCc x AaBbCc, what is the probability of producing the genotype aaBBCC?

1/64

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

In the G0 stage of the cell cycle, which of the following is true:

the cell exits the cell cycle, non dividing stage outside of the cell cycle

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a). Two parents with normal pigmentation have an albino child. What is the probability that their next three children will be albino?

(¼) (¼) (¼) = 1/64

In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be genotypically AABBCCdd?

1/256

If a couple with Sickle cell disease genotypes Ss and Ss mate, and have a child with the disease, what is the chance that the next child has the disease as well?

0.25

In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be genotypically AAbbCCdd?

1/256

In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be phenotypically recessive?

1/256

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of G2 and the end of metaphase?

16 and 16

With incomplete dominance, a likely ratio resulting from a monohybrid cross would be:

1:2:1

What types of phenotypic ratios are likely to occur in crosses when dealing with a single gene pair where all the genotypic combinations are of equal variability?

1:2:1, 3:1

Mitosis ends with ________, while meiosis ends with _______

2 diploid cells; 4 haploid cells

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

If a typical somatic cell has 64 chromosomes, how many chromosomes are expected in each gamete of that organism?

32

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 present in the cell during metaphase I of meiosis?

42

In the G1 of the cell cycle, the genus Oompa Lumpa has aa DNA content © 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 picograms

The ant, Myrmecia pilosula, is particularly interesting because it carries all its genetic information in a single pair of chromosomes. In other words 2n=2. (Males are haploid and have just one chromosome.) For the purposes of this question, assume that a G1 somatic cell nucleus in a female Myrmecia pilosula contains 2 picograms of DNA. How much DNA would be expected in a Metaphase I cell of a female?

5 picograms

An organism has a haploid number of 6. How many possible assortments of chromosomes are possible based on the independent assortment of the chromosome?

64

A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percentage of their remaining offspring would be expected to have normal pigmentation?

75%

In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be phenotypically ABCD?

81/256

Typical ratios resulting from epistatic interactions in dihybrid crosses would be?

9:3:4, 9:7

A. What is the relative gene order based on the results from this three point mapping cross: B. What is recombination distance between B and D locus? a B d 404 A b D 395 A B d 210 a b D 195 a B D 15 A b d 19 a b d 154 A B D 139

A D B or B D A (small letter fine) Recombination distance A to D: 21.35 cM (21 or 22) by doing (15 + 19 + 154 + 139) /(1531) x 100

The fruit fly has a 2n chromosome number of 8. Assuming that a somatic G2 nucleus contains about 8.0 picograms of DNA, how many picograms of nuclear DNA would you expect in A) Mitotic metaphase B) A primary oocyte(metaphase) C) A secondary oocyte(metaphase) D) A first polar body (metaphase)

A) 8 B) 8 C) 4 D) 4

A couple has one girl and is expecting more children. What is the probability that the next child will be a boy? After several years and several births, this couple now has 4 daughters and is expecting a fifth. What is the probability that this child will be a boy? What is the likelihood that the next three children will also be girls?

A. 50% B. 50% C. ½ x ½ x ½ = ⅛

Which of the following parental genotypes will produce on heterozygous F1 offspring?

AA x aa

Assume that a black guinea pig crossed with an albino guinea pig produced 5 black offspring. When the albino was crossed with a second black one, 4 black and 3 albino offspring were produced. What genetic explanation would apply to these data?

Albino= recessive, black= dominant

A form of a gene that has 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

Genes come in different versions called:

Alleles

What inheritance is suggested by each description? Extensive pedigree analysis on a characteristic shows all 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, ¼ of the children are affected

Autosomal recessive

A chromosome with a centromere at the very end is called

Telometric

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?

Color-blind woman

Interactions among the human ABO blood type alleles involve___and___

Complete dominance Codominance

What does the term consanguinity mean in the context of pedigree analysis, and what is the relevance?

Consanguinity is the mating between closely related individuals, and the relevance is that it increases the chance of homozygous recessive progenies. Consanguinity occurs when two related individuals mate and produce an offspring. This is shown in a pedigree by two lines ( = ) connecting the two to each other. This is potentially dangerous because there will be less genetic variation in their offspring so their offspring will have an increased risk of getting a disease if prevalent in the parents family. Also an increased change of homozygous recessive progenies.

During interphase of the cell cycle

DNA content essentially doubles

During interphase of the cell cycle,

DNA content essentially doubles

What are two similarities and two differences between mitosis and meiosis?

Differences: Mitosis occurs in somatic (nonsex) cells; Meiosis occurs in sex cells that produce gametes Meiosis involves chromosome pairing (of homologous chromosomes); Mitosis does not Mitosis produces nonsex cells; Meiosis produces gametes Mitosis produces cells of the same ploidy; Meiosis produces haploid cells from diploid cells Meiosis has two consecutive divisions; Mitosis has one Mitosis produces two daughter cells; meiosis produces four daughter cells Mitosis produces identical daughter cells; Meiosis produces four different daughter cells Similarities Both involve the separation of replicated chromosomes during cell division Both are processes to ensure that daughter cells in cell division receive a complete set of chromosomes DNA replication must occur first Cytokinesis usually occurs at the end of each

Describe the differences between dominance, codominance, and incomplete dominance

Dominance is the condition in which one allele of a gene pair completely masks or inhibits phenotypic expression of the other allele. Codominance is the condition in which the complete expression of both alleles of a given gene pair is observed example would be AB blood type, both the A allele and B allele are equally expressed, that is the expression if neither allele influences the expression of the other. Incomplete dominance is the condition in which one allele only partially inhibits the expression of the other allele in the phenotype. Example is pink flowers, when red flowers which contain the dominant red allele are mated with white recessive flowers the offspring can be heterozygous with a pink phenotype.

Which are the abnormalities involving abnormal numbers of autosome chromosome?

Down Syndrome

Name the single individual whose work in the mid-1800s contributed to our understanding of the particulate nature of inheritance as well as the basic genetic transmission patterns. With what organisms did this person work?

Gregor Mendel, Pisum sativum

Males with an X-linked gene are said to be _____

Hemizygous

Codominant alleles are expressed in individuals that are _____

Heterozygous

What are homologous chromosomes?

Homologous chromosomes may have different alleles, but carry the same genes.

Describe the differences between meiosis I and meiosis II

In meiosis I, sister chromatids do not separate during anaphase I. In meiosis II they do separate in anaphase II. Meiosis I produces two cells, meiosis II produces four cells. In meiosis I, the number of chromosomes decreases from 2n to n, while in meiosis II, the number of chromosomes stays the same (n to n). In meiosis I, homologous chromosomes separate in anaphase I while in meiosis II, sister chromatids separate in anaphase II. In meiosis I, the cohesin holding the sister chromatids together is protected by a protein so the chromatids don't separate while in meiosis II, cohesin is broken down and the sister chromatids separate. The end product of meiosis I is 2 haploid cells, while the end product of meiosis II is 4 diploid cells.

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 more easily visualized

What conditions are likely to apply if the progeny from the cross AaBb X AaBb appear in the 9:3:3:1 ration? Options: Independent assortment, linked genes, no gene interaction, codominance, complete dominance

Independent assortment, no gene interaction, complete dominance

"The occurrence of partial expressivity and incomplete penetrance demonstrates that gene expression can be influenced by biological or environmental context." Explain this statement and give examples to support it.

Individuals with identical genotypes can exhibit different degrees of given phenotypes based on their sex, stress levels, lifestyle, nutritional status, and so forth. An individual's genotype defines genetic potential; the expression of genetic potential can vary greatly depending on other factors that determine the overall context of gene expression. For example, men and women with the same genotype for pattern baldness exhibit very different phenotypes due to the biological context (i.e male or female) the genotype exhibits in. The high relative level of testosterone produced in men provides a biological context whereby the genotype for baldness can be more fully expressed.

During the cell cycle, chromosomal replication occurs in:

Interphase

Where on the chromosome are the microtubules attached?

Kinectochore

What is the relative gene order based on the results from this three point mapping cross below. What is the recombination distance between genes A and B? a B f 404 A b F 395 A B f 13 a b F 17 a B F 150 A b f 191 a b f 154 A B F 139

Least amount of: ABf, abG (double crossing over events) Most amount of: aBF, AbF (parental combinations) A: BAf (A/a allele in the center) B: 22 map units/centimorgans (13+17+154+139)/(total number of offspring=.22 → 22% → 22 centimorgans

Assume that you analyze a cross involving two genes that you suspect may be located at opposite poles of a large chromosome. Will recombination mapping likely help allow you to answer the question if the two genes are indeed linked or not?

Likely not. Given the provided information (opposite pole of a large chromosome), there is a good chance that the recombination frequency may approach 50%. At this point it is not possible to use recombination frequency to determine linkage

Crossing over can change the...

Linkage of particular variants of two or more different genes on the same chromosome

Often, a mutation in a gene results in a reduction or loss of the product of that gene. The term given for this type of mutation is:

Loss of function or null (in the case of complete loss)

Homologous chromosomes move toward opposite poles of the dividing cell during

Meiosis I

Crossing over (genetic recombination) occurs in

Meiosis I Prophase

A situation where there are more than two alternative forms of a given gene would be called

Multiple alleles

What are non-sister chromatids?

Non-sister chromatids are chromatids from different but homologous chromosomes.

What are three characteristics of an autosomal dominant trait observed in a pedigree analysis?

Number of males=number of females, affected have affected parents, individuals with affected parents have 50% chance of being affected, does not skip generations

The Chi-square test involves a statistical comparison between measured (observed) and predicted (expected) values. One generally determines degrees of freedom as:

One less than the number of classes being compared

A human with XX can have a male phenotype if one of the X chromosomes carries a ____

SRY region

Hemizygosity would most likely be associated with which of the following?

Sex-linked inheritance

What are sister chromatids?

Sister chromatids are duplicates and (except for errors in replication) are identical in sequence.

Human blood types are an example of codominance because:

The A and B alleles both express equality in individuals with both alleles

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

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generations 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.

The difference between the homogametic sex and the heterogametic sex is that?

The heterogametic sex determines the gender of the offspring.

Name one characteristic of X-linkage that is often used to identify X-linked genes in pedigree analysis

The phenotype largely or exclusively affects males, criss-cross pattern of inheritance where all songs exhibit mutant mother phenotype

How do incomplete penetrance and variable expressivity differ?

Variable expressivity occurs when a trait is expressed differently in individuals with the same genotype. Incomplete penetrance is when the genotype of a trait is not phenotypically expressed like it usually is. Variable expressivity can occur due to environmental differences between individuals, such as a mouse with normal ears in Africa and a mouse with curled ears in Greenland. Incomplete penetrance can occur in traits such as polydactyly where some individuals who have the trait will express normal phenotypes with normal numbers of fingers and toes and others with the same trait will express variable numbers of fingers and toes. When using the term penetrance, think of populations. Another example of variable expressivity is male pattern baldness.

Which modes of inheritance are influenced by the sex of the individual?

Which modes of inheritance are influenced by the sex of the individual?

In a healthy male, how many sperm cells would be expected to be formed from (a) 400 primary spermatocytes? (b) 400 secondary spermatocytes?

a) 1600 b)800

An allele is

an alternative form of a gene

If an organism is diploid and a certain gene found in the organism has 18 known alleles (variants), than any given organism of that species can/must have which of the following?

at most, 2 alleles for that gene

The attachment point on the chromosome for spindle microtubules is the?

centromere or kinetochore

In order to determine if mutations from different organisms that exhibit the same phenotype are allelic, which test would you perform?

complementation test

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 the following circumstance:

complete linkage

A condition in which one gene pair masks the expression of a nonallelic gene pair is called

epistasis

Ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. What is the woman's genotype?

heterozygous

Assume that a cross is made between AaBb and aabb plants and that all the offspring are either AaBb, aaBb, Aabb, or aabb. These results are consistent with the following circumstance:

independent assortment

Two and three factor testcross can both be used to___ and___

map gene loci and determine genotype

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

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

What are three characteristics of an autosomal recessive trait that are observed in pedigree analysis?

number of males = number of females, most affected usually produce unaffected, most affected have unaffected parents, individuals with an affected sibling have a 25% chance of being affected, trait may skip generations

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 the autosome

The fundamental Mendelian process that involves the separation of contrasting genetic elements at the same locus would be called

segregation

Which is the smallest unit containing the entire human genome?

one human somatic cell

The DNA of a eukaryotic chromosome is:

one long double helix

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? What is the genotype of the parent with green seeds?

ppYy only Ppyy

Cytokinesis is

the formation of two new cells at the end of mitosis in both plants and animals

Extensive pedigree analysis on a characteristic shows 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 What mode of inheritance is suggested?

x-linked recessive