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MBG 2040 Lecture Notes - Lecture 1: Mendelian Inheritance, Dihybrid Cross, Null Allele

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School
University of Guelph
Department
Molecular Biology and Genetics
Course
MBG 2040
Professor
Krassimir Joseph Yankulov

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Document Summary

Both alleles of the same gene: genotype confers phenotype, genes are located on chromosomes, genetic information is transferred from dna to rna to protein, not always true. One of two or more alternative forms of a gene (can have 1, 2, 10 alleles of one gene) Set of alleles possessed by an individual organism. An individual organism possessing two different alleles at a locus. An individual organism possessing two of the same alleles at a locus. D and d are the two alleles of. F2: two heterozygous produce 3 tall and 1 dwarf the same gene trait (trait d size of the plant) Results in a close 3:1 ratio always, never get 3:1 exactly. The two traits are completely independent: each parental homozygote produces one kind of gamete, the f1 heterozygotes produce four kinds of gametes in equal proportions, self-fertilization of the f1 heterozygotes yields four phenotypes in a 9:3:3:1 ratio. Alleles are completely independent carriers of genetic information.

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Related Questions

Canaries: Green (wild-type) Pied phenotype Yellow type

Canaries are popular pets and easy to breed in captivity. Additionally, they display great phenotypic diversity, which allows you to do some interesting genetic investigations with them.

When you take a canary from a true-breeding green strain and cross it with a canary from a true-breeding yellow strain, all offspring display the pied phenotype. Based on this you suspect that this color variation is inherited by a gene with a co-dominant inheritance pattern (showing both phenotypic traits in hybrid phenotypes).

You decide to test this hypothesis. To do so, you take pairs of your hybrid F1 individuals (of pied phenotype), and cross them to produce an F2 generation.

After many dozens of crosses and hundreds of offspring, you arrive at the peculiar ratio of:

3/16 green : 6/16 pied : 7/16 yellow

Which of the following hypotheses are consistent with these data? (Note that not all of these hypotheses are mutually exclusive. Assume that the two genes are independently assorting)

Hint: This problem is very hard to work from the given ratios to what is happening genetically. It is easier to "work backwards" and start with each choice below, and see if you can obtain all or important aspects of the results of your cross when making the assumption that the answer choice is correct.

Select all that apply:

Select one or more:

a. At least one of the genes involved is sex linked.

b. One gene controls production of darker pigment (melanin which appears green when mixed with yellow). A second gene acts as a patterning gene with one allele causing expression and the other non-expression of melanin and when in the heterozygous condition each allele controls melanin expression on different parts of the body so long as the bird's genotype of the first gene allows for the production of melanin.

c. this is a single-gene trait with co-dominance

d. one of the two genes involved displays complete dominance, while the other displays co-dominance.

e. the genes involved are epistatically interacting

f. more than one gene is involved

Expression vectors inprokaryotes do not make functional eukaryotic gene products inbacteria very well because

Answer Not sure which one ?!

· the codon sequence for prokaryotes is differentthan the codon sequence in eukaryotes

· there are no disulfide bridges formed in proteinsnormally made in prokaryotes

· prokaryotic expression vectors cannot translateeukarytic sequences

· eukaryotic genes have introns, and prokaryotesdon't

· eukaryotic genes have exons and prokaryotesdon't


I create a knockout mouseusing the agouti/black fur system \. When I cross the agoutioffspring of the originally engineered mouse, I find a ratio of 2agouti mice to 1 black furred mouse. What is the bestexplanation?

Answer not sure which one?!

· The gene knocked out was recessive.

· The gene knocked out was dominant.

· The gene knocked out was a lethalgene.

· The knockput was integrated into a random spot,and did not knockput the original gene.

A restriction enzyme cuts DNAand leaves the following end

xxCTGCA
xxG

Which of the following could be the sequence of the correspondingend of the other end of the cut DNA?

Answer

· xxG
xxCTGCA

· xxC
xxGTGCA

· xxCCGAT
xxG

· xxGGCTA
xxC


An SNP always occurs dueto

Answer

· a one base-pair change.

· a three base-pair change.

· a single restriction site change.

· a single amino acid change.

· None of these.


I PCR out a mutated gene in apatient with Lisenbee chorea (the inability to dance in acoordinated fashion) and I compare it to another patient with thatsame disease phenotype. One subject had a mutation on chromosome 4,and the other subject couldn't rock it because of a mutation onchromosome 5. This is an exampe of

Answer

· pleitropy

· locus heterogeneity

· allelic heterogeneity

· dominant negative mutation

· penetrance

In his experiments, Mendelnoted that when two traits are involved in a genetic cross, theyare inherited independently of each other. Though Mendel didn'tknow about chromosomes, this still holds true (mostly)because

Answer

· genes on the same chromosome are often mixedthrough meiotic crossover during the formation ofgametes.

· variant alleles of the same gene do not interferewith the phenotypic expression of the gentoype in different geneticloci.

· most higher organisms are diploid, making only twoalleles available for every genetic locus, and there is a 50/50chance of geting either allele from a single parent.

· expression of phenotypes can vary from thegenotypes because of encironmantal influences.

· chromosomes often recombine

Anticipation is caused by amutation that increases in expressivity over subsequentgenerations.

Answer

· True

· False

Question 44

I have a genotype that shouldproduce a specific phenotype, but some of the individuals with thegenotype do not demonstrate any evidence of the phenotype. I wouldconsider this an example of

Answer

· allelic heterogeneity.

· locus heterogeneity.

· penetrance.

· expressitivity.

· sheer luck.

Question

Which of the following doesnot occur during the PCR reactions?

Answer

· Changes in the reaction temperature by athermocycler

· Denaturation at high temperatures

· Synthesis of oligonucleotide primers

· Extension of primers by DNA polymerase

· Annealing of oligonucleotide primers

Question

DNA markers, or variantnon-coding regions of DNA, are DNA polymorphisms that are usefulfor genetic mapping.

Answer

· True

· False

A mosaic is an organismwith

Answer

· multiple genotypes within one organism

· multiple alleles within one genotype

· more than one color of fur

· transgenes added to the zygote beforedevelopement

· a wt phenotype but a mutated genotype

Question

Genotype causesphenotype.

Answer

· No, gentoype just influences phenotype.

· Yes, genotype is the DNA sequence that createsphenotype.

Question

A true genetic chimera can becreated by

Answer

· mutating a gene early on in the development of anorganism resulting in different alleles being present in theadult

· multiple fertilized eggs or zygotes fusing to formone embryo

· adding a transgene to the genome of an organismduring fetal development only

· adding cells of a different species to an adultorganism

· adding a transgene to the genome of an animal atany stage in development

Question

The ABO blood group can bestbe explained by the concept of _______.

Answer

· dominant traits

· recessive traits

· allelic heterogeneity

· locus heterogeneity

· vampirism

If a loss of functionmutation creates a dominant phenotype, it may be becauseof

Answer

· haploinsufficiency

· penetrance

· expressivity

· allelic heterogeneity

· locus heterogeneity

Please select the best matchfor each.

Answer

· PCR: Technique used to generatecopies of a DNA fragment

· Southern blot : Screeningprocedure used to assay DNA fragments

· RFLPs : DNA fragments generatedby restriction enzymes that vary in length betweenindividuals

· Northern blot : Screeningprocedure used to assay mRNA fragments

· Electrophoresis Movement ofmacromolecules in an electrical field

Answer

A.

Screening procedure used toassay DNA fragments

B.

Movement ofmacromolecules in an electrical field

C.

Screening procedure used toassay mRNA fragments

D.

DNA fragments generated byrestriction enzymes that vary in length betweenindividuals

E.

Technique used to generatecopies of a DNA fragment

A gene mutates, and theprotein produced has a novel way of interacting with the cell, andcreates a new phenotype because of this new functionality. This iscalled

Answer

· pleitropy

· locus heterogeneity

· allelic heterogeneity

· dominant negative mutation

· gain of function dominant mutation

Question 62

Mutations in the somaticchromosomes may be inherited by the next generation.

Answer

· True

· False


A degenerate PCR primer withmany variant sequences must be used to make multiple copies of agene

Answer

· if only the protein sequence of the gene productis known to construct the primers

· if the DNA you are using is cDNA to constructthe primers

· if the DNA you are using is genomic DNA to becopied

· if the DNA you are trying to copy iscDNA

· if the vector is prokaryotic and the transformedcell is eukarytotic

Question

Please select the best matchfor each term.

Answer

· Restriction enzyme


· PCR C

· Plasmid

· YAC A

· Dideoxynucleotide

Answer

A.

Endonuclease isolated frombacteria

B.

Eukaryotic cloningvector

C.

Method for amplification ofDNA sequences

D.

Small circular fragment ofDNA

E.

Molecule used in DNAsequencing

Question

A couple goes on MauryPovitch, and the results are in: you are not the father. But noother man impregnated the female (granted, unlikely for a MauryPovitch guest, but work with me here) and he must be the father.DNA analysis claims otherwise, though the child definitely wasmom's (poor thing). What may be going on here?

Answer

· the child is parthenogenic because the motheractually impregnated herself like a shark, and the child's DNA isall mom's

· the child had a mutation that changed the genethat is used to trace paternity

· the child is a mosaic because he is actually a setof twins fused early during fetal development, and therefore camefrom 2 eggs and 2 sperm

· the dad may have germ-line mosaicism, meaning thatthe genotype of his sperm is different from his somaticgenotype

· mitochondrial DNA only comes from mom, so there isno way to tell whobthe baby's father is




If an organism’s diploid chromosome number is 18, how many different possible combinations of homologous chromosomes lining up during meiosis exist for the eggs or sperm produced by that organism?

A.

512

B.

9

C.

18

D.

128

E.

36

At the end of metaphase I, _______________ separate.

A.

sister chromatids

B.

germ cells

C.

homologous chromosomes

D.

haploid chromatids

E.

centrioles

Mendel observed that dominant traits

A.

are seen in all of the F1 hybrid pea plants in his experiments.

B.

are expressed in all plants.

C.

were absent in the F1 generation of pea plants that he used in his experiments.

D.

were the only traits seen in the F2 generation of pea plants in his experiments.

E.

are only expressed in hybrids.

Cytokinesis in plant cells differs from cytokinesis in animal cells because

A.

there is no difference.

B.

in plant cells, the cell plate must also divide into two parts.

C.

the contractile protein, actin, is important only in plant cells.

D.

plant cells have a rigid cell wall.

E.

a contractile ring forms only in plant cells.

Sickle cell anemia is an example of what type of inheritance?

A.

complete dominance

B.

incomplete dominance

C.

codominance

D.

multiple alleles

E.

recessive dominance

Which of the following statements is true:

A.

The dominant allele is masked in homozygous dominant individuals.

B.

With recessive genetic disorders, if both parents are carriers, the offspring will all be affected.

C.

In carriers, the recessive allele causes an intermediate phenotype.

D.

In recessive genetic disorders, the mother and/or father of an affected individual must also be affected.

E.

With dominant genetic disorders, the mother and/or father of an affected individual must also be affected.

Skin cancers typically develop in the

A.

upper layers of the epidermis.

B.

lower layers of the dermis.

C.

subcutaneous layer.

D.

lower layers of the epidermis.

E.

upper layers of the dermis.

Duchenne muscular dystrophy (MD) is inherited from an X-linked recessive allele. What is the probability that a son with Duchenne MD inherited this disease from his biological father?

A.

1/2

B.

0

C.

1/16

D.

1/4

E.

1/8

The genetic makeup of a particular trait in an individual is its

A.

genotype.

B.

heterozygosity.

C.

phenotype.

D.

filial.

E.

dominance.

What structure holds the sister chromatids to the spindle fibers?

A.

chromatin

B.

kinetochore

C.

MPF

D.

centromere

E.

cyclin

If you view a cell in which the genetic material is beginning to be visible as separate bodies, and the nucleus has disappeared from view, you may surmise that the cells is in

A.

telophase.

B.

anaphase.

C.

interphase.

D.

metaphase.

E.

prophase.

Gregor Mendel was successful in his analysis of the genetics of pea plants because

A.

he examined and analyzed both the F1 and F2 generations.

B.

he studied the parental plants to determine their differences.

C.

he decided to only look at his results in an objective manner.

D.

he studied a trait that had a strange inheritance pattern.

E.

pea plants have genetics different from other organisms.

Tall corn plants (T) are dominant to dwarf plants (tt). Solid green leaves (G) are dominant to leaves with a white tip (gg). A cross between two corn plants yielded the following phenotypes: 51 tall plants with a white tip on their leaves; 43 dwarf plants with solid leaves; 48 dwarf plants with white tips on their leaves; 45 tall plants with solid leaves. What are the genotypes of the parents that produced these plants?

A.

None of the above

B.

TtGg x Ttgg

C.

ttGG x TTgg

D.

TtGg x TtGg

E.

TtGg x ttgg

In humans, a gene that has been identified as causing a type of skin cancer is the

A.

superwoman echidna.

B.

mutant superman.

C.

sonic hedgehog.

D.

mutant mole rat.

E.

superhero aardvark.

The segregation principle states that in sexually reproducing diploid organisms the two copies of each gene

A.

segregate from each other during meiosis.

B.

must always be the same allele.

C.

separate from each other during mitosis.

D.

will both wind up in either the sperm or egg.

E.

move together as a unit during meiosis.

In what phases is the genetic material in the cell correctly referred to as chromatids?

A.

metaphase and telophase

B.

anaphase and metaphase

C.

interphase and telophase

D.

interphase and prophase

E.

metaphase and prophase

Consider two traits for an organism, determined by two genes, each of which is governed by at least two alleles. In the case of a dihybrid individual, the gametes formed will be of either the parental type or the recombinant type. Recombinant type gametes are formed because of

A.

the principle of dihybrids.

B.

multiple alleles.

C.

heterozygosity.

D.

incomplete dominance.

E.

independent assortment.

An allele is

A.

an alternate form of a gene.

B.

always recessive.

C.

the main factor determining a trait.

D.

always one of a pair.

E.

the dominant form of a gene.

After the DNA is replicated, and it condenses in prophase, two identical rods of DNA are seen. These are

A.

spindle fibers.

B.

kinetochores.

C.

chromatids.

D.

chromatin.

E.

centromeres.

Special cells found in the gonads that give rise to gametes upon division are called

A.

egg cells.

B.

somatic cells.

C.

germ cells.

D.

stem cells.

E.

basal cells.