Genetics exam 1

In the genetic code, how many nucleotides are necessary to specify one amino acid?

3

Assume a tautomeric shift occurred, which was followed by two rounds of DNA replication. If the mutation is not repaired, the result would be an

AT to GC mutation in one of the four daughter molecules.

In trinucleotide repeat expansion disorders, when the expansion occurs in the coding sequence of the gene, the repeat sequence is usually

CAG

Adenine, thymine, guanine and cytosine are nitrogen-containing bases found in

DNA

the largest macromolecule found in living cells

DNA

what is the genetic material of all living organisms composed of?

DNA

Which is the best description of the particulate theory of inheritance?

Genes are inherited as discrete units that remain unchanged from generation to generation.

What is translation?

The synthesis of a polypeptide based on the sequence of mRNA

What is gene expression?

The use of a gene sequence to affect the characteristics of a cell or organism.

A trinucleotide repeat expansion commonly occurs via the formation of

a hairpin that interferes with DNA replication.

characteristic of an organism

a trait

The genetic code directs the order of ______ within a polypeptide based on the sequence of nucleotides within a DNA molecule.

amino acids

The covalent bond between deoxyribose and a purine base is rather unstable and can undergo a spontaneous reaction with water. The breaking of the bond releases the base, and leaves a(n) _____ site in the DNA.

apurinic

Mutations that affect the phenotype only under certain circumstances are called

conditional mutations

Which of these bases is most readily deaminated?

cytosine

breaking of chemical bonds during the degradation of small molecules (i.e. amino acids and glucose) provides _____ to drive cellular processes

energy

A position effect can alter gene expression in cases when the gene is moved from a less condensed, or ______ chromosome, where it is active, to a very highly condensed, or ______ chromosome, where its expression may be turned off.

euchromatic; heterochromatic

The process of using a gene sequence to affect the characteristics of cells and organisms is called gene ______.

expression

unit of heredity (intricate molecular units that manifest themselves as critical contributors to cell structure and function)

gene

The two main mechanisms used to repair DNA double-strand breaks are ____ recombination repair and ______ end joining.

homologous; non homologous

For a tautomeric shift to cause a mutation, it must occur

immediately prior to DNA replication

The mutation rate is commonly expressed as the number of new mutations

in a given gene per cell generation.

What is the main function of a cell's genetic material?

it encodes proteins

Examples of trinucleotide repeat expansion (TRNE) disorders include _____ muscular dystrophy and ____ X syndrome.

myotonic; fragile

A DNA molecule is a linear sequence of subunits called

nucleotides

Changes to DNA structure caused by reactive oxygen species are termed ______ DNA damage

oxidative

An imbalance between the production of reactive oxygen species and an organism's ability to break them down is known as

oxidative stress

DNA stores information in the _____ of it bases

sequence

Bacteria possess

several different DNA repair systems.

The fact that genetic determinants are inherited as discrete units that are unchanged when passed from generation to generation is best explained by

the particulate theory of inheritance.

Mutations in the 5'-UTR or 3'-UTR of an mRNA molecule are most likely to affect what?

the stability of mRNA, the mRNA's ability to be translated

In trinucleotide repeat expansion diseases, the phenomenon of anticipation varies based on the gender of the transmitting parent, suggesting that

there are differences in expansion in oogenesis vs. spermatogenesis.

What is a genetic cross?

The breeding of two individuals and the analysis of their offspring

What can cause a frameshift mutation?

addition or deletion of nucleotides

Escherichia coli

bacterium

Which of these are used by cells to limit the harmful effects of reactive oxygen species?

catalase, vitamin c, superoxide dismutase

Which of the following methods would best be applied to determine if the observed phenotypic ratios of a two-factor cross fit the expected ratios by Mendelian inheritance?

chi square test

In living cells, DNA is found in large structures called ______, which are contained in the nucleus of a eukaryotic cell.

chromosomes

What structures in a cell contain DNA?

chromosomes

The rare enol form of thymine pairs with the

common keto form of guanine.

Silent mutations are possible because the genetic code is

degenerate

The removal of a purine (adenine or guanine) from DNA is called

depurination

Cells can prevent the buildup of reactive oxygen species by using enzymes such catalase and superoxide ____

dismutase

Proteins associated with trinucleotide repeat expansion disorders typically contain long tracts of the amino acid

glutamine

When a protein-encoding gene is transcribed, the RNA molecule that is produced is referred to as ______ RNA (mRNA).

messenger

base substitutions for which an amino acid change does result

missense mutations

A DNA sequence is transcribed in to RNA, which is translated into protein.

molecular level

In a DNA molecule, information is contained in the sequence of

nitrogenous bases

A silent mutation is a mutation that results in

no change to the amino acid sequence of the polypeptide.

Which term refers to the imbalance between an organism's production of ROS and the ability to break them down?

oxidative stress

Guanine is commonly

oxidized to 8-oxoguanine.

Reactive oxygen species (ROS) are

products of oxygen metabolism in all aerobic organisms.

Products of oxygen metabolism, such as hydrogen peroxide, superoxide, and hydroxyl radical, are collectively called ______ species.

reactive oxygen

Mutations in eukaryotic genes that change the ______ recognition sequences may affect the order and/or number of exons contained in the mature mRNA.

splice

Errors in DNA replication are examples of ______ mutations, while mutations caused by ultraviolet light are ______ mutations.

spontaneous; induced

at the molecular level, ____ is a segment of DNA that has information to produce a functional product (i.e. polypeptide) and influences one or more traits of an organism

a gene

The common stable form of guanine and thymine is the ______ form.

keto

A gamete has only one copy of each gene. Which of Mendel's laws defines this fact?

law of segregation

The rare imino form of cytosine pairs with the common amino form of

adenine

The amino form is the common stable form of which bases?

adenine & cytosine

The function of a protein in a cell affects the structure and function of the cell.

cellular level

a linear sequence of amino acids that folds into units that constitute proteins

polypeptide

functional product of most genes

polypeptide

Chromosomes that differ between males and females are called

sex chromosomes

Saccharomyces cerevisiae

yeast

subunits of DNA

nucelotides

The base cytosine is deaminated to produce the base

uracil

Arabidopsis thaliana

flowering plant

What type of RNA contains the information required to synthesize a protein?

mRNA

nucleic acids, proteins, and carbohydrates form _____ that are composed of many repeating units of smaller building blocks

macromolecules

How many total linkage groups does a cell from a human male contain?

25

What is the name of the process that involves crossing-over during meiosis, generating a new combination of alleles?

Genetic recombination

How do alleles differ from one another?

They have slightly different DNA sequences.

When can DNA damage happen that affects the phenotype of an individual?

before/during mitosis

The lateral movement of a Holliday junction is called

branch migration

According to the Holliday model, a Holliday junction can migrate laterally through a process called ________. The swapping of DNA strands during this process may produce a ________ region in DNA that contains base mismatches.

branch migration; heteroduplex

The product of the dominant mutant allele is expressed in cells where it is not normally active, leading to a change in phenotype.

gain-of-function mutation

A situation in which one allele is changed to the allele found on the homologous chromosome is called

gene conversion

Select alternative names for genetic mapping

gene mapping; chromosome mapping

When traditional gene mapping approaches cannot be used, what type of approaches can be used to map genes?

molecular

Because bacterial cells contain one large circular chromosome, all genes within that chromosome are

syntenic

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

syntenic

A temporary change in base structure due to movement of hydrogen atoms is called a(n)

tautomeric shift

Bases which exist in keto and enol or amino and imino forms are best described as

tautomers

All of the following events occur during prometaphase except: - the spindle fibers "capture" chromosomes (Rationale: Spindle fibers that happen to make contact with a kinetochore will be connected with that chromosome.) - the nuclear envelope completely breaks down - the mitotic spindle is completely formed - the chromosomes become visible with the light microscope

the chromosomes become visible with the light microscope (this occurs during prophase)

According to Morgan's fly experiment, crossing over was more likely to occur if

two genes were far apart on the X chromosome.

Differences in inherited traits among individuals within a population are referred to as genetic

variation

Trinucleotide repeat expansions are repeated sequences of three bases

which increase generation after generation.

In trinucleotide repeat expansion diseases, the phenomenon of anticipation can vary depending on

which parent the allele was inherited from.

How many map units apart do two genes have to be to follow the law of independent assortment?

50 mu

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

8 (2^3)

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

what is a species?

A group of organisms that maintains a distinctive set of attributes

For Mendel's pea plants, the tall phenotype is determined by a dominant allele and the dwarf phenotype is determined by a recessive allele. In the first or F1 generation, what is the outcome of a cross between true-breeding tall and true-breeding dwarf plants?

All of the offspring will be tall.

Genetic anticipation refers to what phenomenon?

An increase in severity of the symptoms as a disease is passed through future generations

What is a model organism?

An organism that is studied so that researchers can determine broadly applicable scientific principles

which are involved in crossing over?

Breakage of non-sister chromatids at analogous locations, Alignment of a pair of homologous chromosomes, Exchange of corresponding chromosome segments

In recombination, the process that synthesizes small stretches of DNA to replace those removed by strand degradation is called

DNA gap repair synthesis.

Which model of recombination includes the formation of a D loop and the resolution of two Holliday junctions?

Double-strand break model

1. A double-strand break occurs on one chromosome 2. A small region of DNA near the double-strand break is degraded 3. A single-stranded DNA segment invades the intact double helix of the homologous chromosome 4. Strand displacement results in formation of a D-loop 5. DNA gap repaid synthesis fills in missing DNA 6. Two Holliday junctions are produced and then resolved

Double-strand break model of homologous recombination in the correct order.

True or false: Geneticists only study the transmission of one character at a time in a given genetic cross.

False (geneticists often study two or more characters in a genetic cross)

In Morgan's cross between a female with a gray body, red eyes, and long wings and a male with a yellow body, white eyes, and miniature wings, what are the two categories with the lowest anticipated offspring?

Gray body, white eyes, long wings; Yellow body, red eyes, miniature wings

Branch migration is the lateral movement of a(n)

Holliday junction

During homologous recombination, after DNA is nicked, the strands invade opposite helices and base pair with complementary strands. The strands are then linked covalently to form a structure called a(n)

Holliday junction

Homologous chromosomes in which non-sister chromatids are covalently linked to one another. This structure is called a(n)

Holliday junction

The first proposal for a set of steps at the molecular level that lead to homologous recombination is called the

Holliday model

1. A nick occurs at identical sites in one strand of each of the two homologous chromatids 2. Single strands of DNA invade the opposite helices 3. A junction is formed between the invading DNA and the existing DNA of the chromatid 4. Branch migration occurs as the junction between DNA of different helices moves laterally 5. The Holliday junction is resolved by the breakage and rejoining of two DNA strands to produce two separate chromosomes

Holliday model of homologous recombination in the correct order.

Which recombination processes occur in bacterial cells?

Homologous recombination of replicated regions during DNA replication; Exchange of segments between identical copies of the bacterial chromosome within the same cell

The figure shows two sets of chromosomes after homologous recombination according to the double-strand break model. Which set consists of chromosomes that show no recombination for the alleles but do have a heteroduplex region?

Left set

How many genes does a typical human chromosome contain?

Many hundreds

heterozygote has a phenotype that is more beneficial than the phenotypes of either homozygote

Overdominance

Rank the phases of mitosis in order, starting with the earliest at the top.

PPMAT (prophase, prometaphase, metaphase, anaphase, telophase)

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

Which of the following events occurs during metaphase of mitosis?

Pairs of sister chromatids become organized in a single row

Which of the following represents the sequence of phases during mitosis?

Prophase — prometaphase — metaphase — anaphase — telophase

Two sets of chromosomes after homologous recombination according to the double-strand break model. Which set consists of chromosomes that show both recombination for the alleles and a heteroduplex region?

Right set

Which of the following events occurs during anaphase of mitosis?

Sister chromatids separate from each other and head to opposite poles

Select the experiments/calculations that are included in using a three-factor cross to map genes.

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

Select the benefits of genetic mapping.

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

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 fewer recombinant offspring than nonrecombinant offspring.

When geneticists learned that chromosomes contained genetic material, why did they think there may be a conflict between the law of independent assortment and the behavior of chromosomes during meiosis?

There are many more genes than chromosomes.

For Mendel's pea plants, the tall phenotype is determined by a dominant allele and the dwarf phenotype is determined by a recessive allele. Suppose there is a cross between true-breeding tall and true-breeding dwarf plants. What is the expected outcome in the second or F2 generation when F1 plants are crossed to each other?

Three-fourths of the offspring will be tall and one-fourth of the offspring will be dwarf.

two sets of chromosomes after the resolution phase of homologous recombination. Which set consists of chromosomes that show no recombination for the alleles but do have a heteroduplex region?

Top set

True or false: Alternative methods of gene mapping allow genes to be mapped in species with long generation times or without experimental crosses.

True

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

True

In contrast to the Holliday model, which other mechanisms for initiating recombination have been observed in experimental results?

Two breaks occur, one in each DNA strand of the same chromatid; A single nick occurs in one DNA strand

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 need to add in double crossovers.

A cell with at least one copy of a wild-type allele will typically produce

a functional version of the protein specified by this allele.

A testcross is a cross between

a heterozygote and a recessive homozygote

This diagram represents a cell that has an original diploid number (2n) of six chromosomes. The cell is shown in which phase of cell division?

anaphase of mitosis

Distance on a chromosome is generally measured in (chose all correct answers)

centimorgans; map units

Which of the following are genomic alterations that may induce genetic variation?

changes in chromosome number; gene mutations; changes in chromosome structure

A _______ is sometimes called a ______ because it contains a group of genes that are physically linked together.

chromosome; linkage group

A crossover is unlikely to occur in the region between two genes when they are

close together

pattern in which both alleles are expressed in the heterozygote without blending

codominance

What is the name of the process in diploid eukaryotic species where homologous chromosomes exchange pieces with each other?

crossing over

Which process involves the exchange of corresponding segments of a homologous chromosome pair?

crossing over

Homologous recombination that produces a new combination of alleles occurs through

crossover between homologous chromosomes during meiosis.

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

distance

The product of the dominant mutant allele interacts with the product of the normal allele causing an altered phenotype.

dominant-negative mutation

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 recombinant

Experimental results support which model(s) for initiating recombination during meiosis and DNA repair?

double-strand break model

In the resolution phase of recombination,

either recombinant or non-recombinant chromosomes will be produced, depending on which DNA strands are involved in the cutting and rejoining.

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

A double crossover between two genes could involve ________ ,_______ , or ________ chromatids.

four; three; two

The result of a two-factor cross depends on whether the ____ are linked together on the same _____

gene; chromosome

The functional units of a chromosome are called

genes

The transmission of ____ that are close to each other on the same chromosome violates the law of _______

genes; independent assortment

Most genes contain the information to direct the synthesis of a polypeptide. The order of amino acids in the polypeptide is specified according to the ______ code.

genetic

The linear arrangement of genes on chromosome is depicted on a _________

genetic linkage map

When more than one wild-type allele occurs in a population, the phenomenon is called

genetic polymorphism

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

genetic; chromosome

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

genetic; long

describes the combination of alleles an individual has.

genotype

small organic molecules such as ________ are produced by the linkage of atoms via chemical bonds

glucose and amino acids

The dominant mutant allele loses its function so that a heterozygous individual shows an abnormal phenotype or disease phenotype.

haploinsufficiency

A region in double-stranded DNA that contains base mismatches due to the swapping of DNA strands during homologous recombination is called a(n)

heteroduplex

In a testcross to determine recombination frequency in Drosophila, the female is always the

heterozygote

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

heterozygous

A bacterial cell can contain more than one copy of its chromosome. These extra copies are identical to the original chromosome. The genetic exchange that occurs between these chromosomal copies is called

homologous recombination

The Holliday model outlines the molecular steps that occur during the process of

homologous recombination

Which process leads to a new combination of alleles in the chromosomal products?

homologous recombination during meiosis

pattern producing an intermediate phenotype in the heterozygote

incomplete dominance

Morgan explained his data by suggesting that if two genes are far apart from each other, crossing-over

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

the two fundamental laws of inheritance discovered by Mendel

law of independent assortment, law of segregation

Which law states that two copies of a gene separate from each other during transmission from parent to offspring?

law of segregation

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

locus

Compared to two-factor testcrosses, three-factor testcrosses can provide additional information about ______

map distance and gene order

One __________ equals 1% recombinant offspring in a testcross.

map unit

A known locus within a genetic ______ may help molecular geneticists to clone the _______

map; gene

Chromosomes line up in the middle of the cell

metaphase

During _______ of mitosis, chromosomes are aligned along the equatorial plate, or the center of the cell.

metaphase

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

nonrecombinant

in a testcross, a phenotype or arrangement of alleles on a chromosome that occurs in the offspring but is not found in the parental generation.

nonrecombinant

During prophase of mitosis, the nuclear membrane breaks down into small vesicles, the ________ becomes less visible, and the mitotic ______ begins to form.

nucleolus; spindles

- microtubules forming mitotic spindle - sister chromatids become condensed - nucleolus becomes less visible - nuclear membrane begins to dissociate into small vesicles

occurs during prophase

Gene conversion is a phenomenon in which

one allele of a gene is changed to the allele found on the homologous chromosome.

A(n) ______ mutation refers to a mutation in which just one base is changed within the DNA sequence.

point

The field of genetics that focuses on the relationship of genetic variation to an organism's environment is called

population genetics

The expression of an intact gene may be altered when it is moved to a new location. This is due to a(n)

position effect

During ______, pairs of sister chromatids become attached to kinetochore microtubules which emanate from opposite poles of the cell.

prometaphase

Chromosomes become visable, nuclear envelop dissolves, spindle forms

prophase

Crossing over occurs during ______ of meiosis I

prophase

Which type of allele is likely to be responsible for an inherited human disease when the symptoms are due to a decrease in the production of a specific protein?

recessive mutant allele

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; map

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

recombination

The chromosomes in two haploid cells in the lower portion of this picture show ______ as a result of crossing over.

recombination

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

recombination; distance

A heteroduplex is a(n)

region of double-stranded DNA that contains base mismatches.

New cells or organisms are produced via the biological process termed ______.

reproduction

The biological process by which new cells or new organisms are produced is known as

reproduction

Breakage and rejoining of DNA strands to produce separate chromosomes at the end of recombination is called

resolution

The process of separating two chromosomes that were joined by a Holliday junction is called

resolution

DNA gap repair synthesis

restores the stretches of DNA removed by strand degradation at the initiation of recombination.

Traditional genetic mapping approaches are feasible in

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

A mutation that does not change the amino acid sequence of a polypeptide is known as a(n) _____ mutation.

silent

follows a strict dominant/recessive relationship

simple mendelian inheritance

Homologous recombination between genetically identical sister chromatids is called

sister chromatid exchange

Homologous recombination that does not produce a new combination of alleles is called

sister chromatid exchange

Trinucleotide repeats can form hairpins due to

slipped mispairing during DNA replication.

Crossing over does not occur during _______ formation in Drosophila.

sperm

A change of one base for another is described as a base ______ mutation.

substitution

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

testcross; heterozygous

A locus is

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

The transmission pattern of two or more characters is affected by

their linkage on a chromosome.

In the genetic code, there are 64 codons consisting of ______ nucleotide(s) each that specify the 20 different amino acids. (Your answer will be a number).

three

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

three-factor cross

Which of the following bases is produced by the deamination of 5-methylcytosine?

thymine

What are the four nitrogen-containing bases found in the nucleotides that make up DNA?

thymine, cytosine, guanine, adenine

When a gene is expressed, its DNA sequence is ______ into RNA, which is then ______ to produce a polypeptide.

transcripted; translated

The synthesis of a polypeptide based on the nucleotide sequence of a messenger RNA molecule is called

translation

The inheritance of genes and the way that genes influence traits is the focus of ______ genetics.

transmission

Which field of genetics focuses on how genes are passed on from parents to offspring?

transmission genetics

purines and pyrimidines are interchanges in this type of mutation

transverison

The oxidized form of guanine, 8-oxoguanine, can produce a

transversion mutations

In the general population, 1/150 people are carriers for the allele for Tay-Sachs disease. A child with the disease is born to healthy parents who are unaware of their carrier status. The allele that prevents the disease in the parents is a ______ allele and the one that causes the disease is a ______ allele.

wild-type; mutant

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?

xzy