PCB Exam 1

All EXCEPT which of the following factors were crucial to the success of Gregor Mendel's experiments?

A) He chose traits that were not greatly influenced by the environment.

B) He kept detailed quantitative records.

C) He observed only one or very few traits in any given experiment.

D) He always allowed all pea plants to self-fertilize, avoiding contamination from other individuals.

D) He always allowed all pea plants to self-fertilize, avoiding contamination from other individuals.

Which two genotypes in an individual would be expressed as the same phenotype in a diploid organism?

A) homozygous dominant and heterozygous

B) homozygous recessive and heterozygous

C) homozygous dominant and homozygous recessive

A) homozygous dominant and heterozygous

The offspring of the P1 generation is known as the _______ generation.

F1

Mendel's unit factors in pairs are most accurately known to be _______.

two alleles on paternal and maternal homologs

Which of the following statements is an example of independent assortment?

A) A diploid individual passes only one copy of a gene on to her offspring.

B) A tall pea plant is no more or less likely to have round seeds than a dwarf pea plant.

C) Some genetic traits are more likely to be inherited than others.

D) A pea plant may have one unit factor for violet flowers and one unit factor for white flowers.

B) A tall pea plant is no more or less likely to have round seeds than a dwarf pea plant.

Which of the following statements is true regarding a trihybrid cross between two true-breeding homozygous individuals with contrasting phenotypes?

A) The most frequent F2 phenotypic class is recessive for all three traits.

B) The F2 generation has 4 different phenotypes.

C) The laws of probability cannot be used in crosses with three or more traits.

D) The least frequent F2 phenotypic class is recessive for all three traits.

D) The least frequent F2 phenotypic class is recessive for all three traits.

In a trihybrid cross between two true-breeding homozygous individuals with contrasting phenotypes, what is the probability of an F2 phenotype being triply recessive?

1/64

How did Mendel's work support the chromosomal theory of inheritance?

The behavior of chromosomes during meiosis, as observed under a microscope, correlated with Mendel's principles of inheritance.

How do chrmosomes segregate during meiosis?

Independently and randomly

Mendel's work supported the idea that the genetic information was carried on

chromosomes

What is the expression of the binomial theorem?

(a+b)n=1

Chi-square analysis can help us to decide whether _______.

our observations of an event differ from our expectations

What information can be obtained from a human pedigree?

how a gene is inherited

Gain-of-function mutations may affect regulation of __________ of the gene in question.

transcription

What symbol indicated a wild type allele?

+

+ indicates a wild type allele, whether?

or not it is a dominant or recessive to a mutant allele

Define Codominance

Both phenotypes are expressed in heterozygotes

Define Incomplete Dominance

The heterozygotes shows a phenotype that is intermediate between the two homozygotes

In both codominance and incomplete dominance, the heterozygote shows a phenotype that is ____ from either homozygote

distinct

Why can multiple alleles only be studied in populations?

Any individual diploid organism can have, at most, two different alleles at a single locus.

Define multiple allelism

involves three or more alleles

No single diploid organism can have all the alleles in a ________ system

multiple allele

Which of the following statements is always true when mutations occur in genes whose products are essential to an organism's survival?

A) A homozygote for a recessive lethal allele will not survive.

B) One normal copy of the gene will allow survival.

C) Reversion of the mutation must occur for the organism to survive.

D) The heterozygote always has a normal phenotype.

A) A homozygote for a recessive lethal allele will not survive.

Which term describes the phenomenon that occurs when the expression of one gene pair masks the expression of another gene pair?

epistasis (9:3:4, 9:7, always add up to 16)

Complementation analysis is used to determine _______.

whether two mutations that produce the same phenotype reside in the same or different genes

A gene in which the heterozygous condition is displayed differently in males and females is referred to as _______.

sex-fluenced

Pattern baldness is expressed in _________ males, but not in _________ females.

heterozygous, heterozygous

Some genes and mutations vary in their phenotypic expression depending on the sex of the parent from whom the gene is inherited. This phenomenon is known as _______.

imprinting

Phenomenon whereby the phenotypic expression of a gene is determined by the sex of the parent from whom it is inherited.

imprinting

Which of the following reflects the genotype of an individual in the phenotype?

A) position effect

B) incomplete penetrance

C) variable expressivity

D) complete dominance

D) complete dominance

Represents all of the genes located on the same chromosome

A linkage group

Genes located on the same chromosome will show evidence?

of linkage to each other

When Morgan carried out crosses involving two X-linked genes in Drosophila, he sometimes observed new phenotypes that were not present in the parents. What did Morgan propose from these observations?

The points of overlap between synapsed homologous chromosomes, called chiasmata, were points of genetic exchange.

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.

When analyzing three genes that reside on the same chromosome, the expected frequency of double-crossover events can be determined by multiplying the frequency of single crossovers between each pair of genes. What would cause the number of observed double-crossover events to be less than the expected value?

positive interference

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

Multiple crossovers are more common.

Lod scores are used to predict what?

gene linkage

Lod stands for

log of odds favoring linkage

Somatic cell hybridization analysis can be used to _______.

assign human genes to the chromosomes on which they reside

Which of the following DNA markers cannot be used for mapping?

A) microsatellites

B) Chiasmata

C) SNPs

D) RFLPs

B)Chiasmata

Mark points where crossing over occurred between homologous chromosomes.

chiasmata

In which of the following does crossing over NOT occur? A) sister chromatids

B) haploid organisms with a transitory diploid stage

C) cells undergoing mitosis

Crossing over occurs in all of these choices

Genetic cross over has been in observed in?

Every type of dividing cell

Why didn't Mendel find linkage in his studies?

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

What limits bacterial growth within a culture of medium?

nutrients and oxygen

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.

Which of the following statements about conjugation is true?

A) One strand of DNA from an F+ cell integrates into the chromosome of an F- cell, and the other strand is degraded.

B) DNA is transferred from an F+ cell to an F- cell.

C) Only competent cells can undergo conjugation.

D) The F factor is an element that is found in the chromosome of an F+ cell.

B) DNA is transferred from an F+ cell to an F- cell.

True or false. RecA is the only protein required for bacterial recombination.

FALSE

Mutations in recA diminish genetic recombination in bacteria by ______ fold

1000.0

Mutations in recBCD diminish genetic recombination by _____ fold

100.0

Which of the following statements about cotransformation is true?

A) Nonlinked genes are passed simultaneously from one cell to another.

B) The F factor plus a few chromosomal genes are passed from one cell to another.

C) Two bacterial cells within a culture are transformed by the same bacteriophage.

D) A bacterial cell receives two adjacent genes on a single piece of DNA from the medium.

D) A bacterial cell receives two adjacent genes on a single piece of DNA from the medium.

An episome is _______.

a plasmid that may exist separately or be integrated into the main chromosome

The F factor is an example of an ______

episome

All EXCEPT which of the following statements about bacteriophages are true?

A) They use the metabolic machinery of a bacterial cell to produce more copies of themselves

B) They can pick up bacterial genes during the process of infecting a bacterial cell.

C) They are viruses.

D) Within their heads, they can pack the main chromosome from one cell and transfer it to another.

D) Within their heads, they can pack the main chromosome from one cell and transfer it to another.

What is transduction?

virus-mediated bacterial recombination

What does intergenic mapping involve?

mapping genes by observing recombination between two different virus genomes

What is the value of the rII locus in mapping the Phage T4 genome?

Mutants at this locus produced distinctive plaques when plated on E. coli strain B. These distinctive plaques allowed identification of the rII mutants.

Chromosomes other than the sex chromosomes. In humans there are 22 pairs.

Autosomes

Pre-Mendelian: The idea that an organism or organ arises through the sequential appearance and development of new structures

Epigenesis

A short, highly polymorphic DNA sequence of 1-4 base pairs, widely distrubuted in the genome, that are used as molecular markers in a variety of methods. Also called simple sequence repeats (SSRs)

Microsatellites

A form of cell division producing two progeny cells identical genetically to the progenitor cell--that is, the production of two cells from one, each having the same chromosome complement as the parent cell

Mitosis

In human genetics, a diagram showing the ancestral relationships and transmission of genetic traits over several generations in a family

Pedigree

Change in expression of a gene associated with a change in the genes location within the genome

Position effect

An individual who is the focus of a genetic study leading to the construction of a pedigree tracking the inheritance of a genetically determined trait of interest. Formerly known as propositus.

Proband

A trait that is expressed in only one sex even though the trait may not be X-linked

Sex-limited inheritance

Pre-Mendelian Idea: Sex cells contain a miniature adult called a homunculus that just grows up during development

Preformation

Pre-Mendelian: An organism's traits are determined by averaging the parents traints

Blending

A group of identical individuals that always produce offspring of the same phenotype when mated with each other.

True Breeding Strain

A discrete inherited factor

Gene

Mendels Laws of Segregation

1) Two copies of a gene segregate equally during gamete formation.

2) During fertilization, gametes unite at random

The law of segregation is based on?

The behavior of chromosomes

Genes are located on

Chromosomes

Every organism has a species-specific number of chromosomes, designated as _____

n

Number of human chromosomes (n)

23.0

Meiosis: G1 Phase

Chromosomes have not yet replicated

Meiosis: S Phase

Chromosomes replicate

After replication. Chromosomes exist as _______, and each _______ consists of two identical ________.

dyads; dyads; chromatids

The chromatids are joined at their _________.

centromeres

Mitosis starts with a single diploid cell and ends with

two diploid cells

Mitosis has

only one cell division

Meiosis starts with a single diploid cell and ends with

four haploid cells

Meiosis involves how many cell divisions

two

Meiosis 1: Chromosomes condense; Homologous chromosomes undergo synapsis

Prophase 1

In Prophase 1, a pair of duplicated homologous chromosomes are know as

tetrad

The close pairing of homologous chromosome dyads with each other

synapsis

The close pairing of homologous chromosome dyads with each other

crossing over

Meiosis 1: Tetrads align at equator of cell after Prophase 1

Metaphase 1

Meiosis 1: Homologous chromosome dyads separate and move toward opposite poles after Metaphase 1

Anaphase 1

Meiosis 1: Nuclear membranes reform, and cytokinesis follows to make two daughter cells

Telophase

Meiosis 2: In each daughter cell, chromosomes prepare for a second round of divison

Prophase 2

Meiosis 2: Chromosome dyads move to the cell equators

Metaphase 2

Meiosis 2: Chromatids separate and move to opposite poles of each cell

Anaphase 2

Meiosis 2: Chromosomes start to decondense and nuclear envelope reforms

Telophase 2

Meiosis 2: Daughter cells physically sperate

Cytokinesis

RNA is ______ stranded

single

RNA replaces thymine (T) with

Uracil (U)

Traits which vary across an unbroken range of values.

Continuous

Traits which show two or more distinct and separate forms

Discontinuous (discrete) traits

Of Mendel's traits of study, only _____ haven been characterized molecularly

3.0

Mendels postulates: Genetic characters are controlled by _______ existing in pairs in individual organisms

unit factors