Genetics Final exam

An experiment was conducted with Drosophila flies carrying recessive white-eye and yellow-body alleles. The white and yellow genes are on the X-chromosome. The parental (P0) individuals were homozygous white-eye, normal body female and red-eye, yellow-body male. F1 females had a wild-type phenotype and F1 males had normal bodies and white eyes. F1 individuals were then mated. What phenotypes are expected in the F2 generation? Please select all that apply.

-100% of females have a normal body -there are very few wild-type males

AUU, AUC, and AUA all encode isoleucine, but AUA is used only ~10% of the time. Why is this thought to be the case?

-A and G are both purines -A and G are both pyrimindines

Ascomycete fungi are valuable models for studying recombination. Which of the following are advantages of these systems? Please select all that apply.

-Haploid progeny can be analyzed directly -The four products of meiosis remain together -test crossing is not always needed

Genetic analysis in model organisms such as Drosophila cannot easily be replicated in humans. Which of the following factors are true of Drosophila but not humans? Please select all that apply.

-Short generation times -large numbers of offspring

Which of the following are necessary characteristics of balancer chromosomes? Please select all that apply.

-Suppression of crossing over -Easily distinguished heterozyotes

Which of the following statements about double-crossovers are true? Please select all that apply.

-The chance of double crossovers occurring between two loci increases with the distance between the loci -double crossovers result in the estimated map distance between two loci being underestimated

With a few exceptions, the genetic code is universal. What are the implications of this? Please select all that apply.

-all living organisms -finite genetic differences -a gene from one organism

Position-specific weight matrix tables show relatively few substitutions for cysteine and tryptophan compared with other proteins. Which of the following are possible explanations for this? Please select all that apply.

-cysteine and tryptophan are more likely to have essential roles -cystenine and tryptophan have unusual structures - the codons

Which of the following are characteristics of translation initiation? Please select all that apply.

-first codon is for methionine - tRNA used for initiation

Attenuation is involved in the regulation of tryptophan production in E. coli. Which factors are involved in the tryptophan attenuation mechanism?

-hairpin -transcription termination -translation

Why are regions between genes (intergenic regions) often chosen as mapping markers in genome-wide association studies? Please select all that apply.

-intergenic regions are usually not under postivie or negative selection - polymorphism frequency in intergenic regions is usually unaffected by the health of individuals

Syntenic blocks are sections of chromosomes that have remained largely intact during evolution. For example, human chromosome 4 corresponds to syntenic blocks on mouse chromosomes 3, 5, and 8. Which of the following statements about synteny are true? Please select all that apply.

-the ancestor of humans and mouse probably had similar syntenic blocks to those currently seen in mouse and human -X chromosomes are largely syntenic between placental mammals

Which of the following statements about genetic and physical maps are true? Please select all that apply.

-the order of genes is the same in physical and genetic maps -a physical map shows the location of genes on the DNA molecule

what is BLOSUM matrix used for? select all.

-to assess the probability - to show the probability

which of the following statements abot transcription translation are true? select all.

-translation in bacteria -rRNA is involved in translation -mRNA is transported out of nucleus

In an experiment, you have a tall plant that produces round peas. Tall and round are dominant and the plant is heterozygous for both traits. The plant is then self-fertilized. What is the probability that a single offspring plant is tall and has wrinkled peas? Express your answer as a decimal.

0.1875

Double-strand breaks (DSB) are needed for crossing-over to occur in meiosis. In a pair of homologous chromosomes, how many chromatids require a DSB in order for crossing over to occur?

1

A cross between tall plants (Tt genotype) and short plants (tt genotype) produced 6 offspring. What is the probability that all 6 offspring are tall? 1/2

1/64

What does 10 centMorgans (cM) represent?

10% recombination between two genes on the same chromosome

A cross between Aa and aa produced four offspring. What is the chance that at least one of the offspring had the recessive phenotype?

15/16

events of translation in order

1= tRNA is charged 2= tRNA interacts 3= peptide bond forms 4= tRNA leaves

In an experiment, two homologous chromosomes with alleles as shown below (original homologous chromosomes) underwent meiosis and to product four chromosomes (resultant chromosomes). How many crossovers appear to have occurred during meiosis?

2

There are 4 different bases and 64 possible codons in the genome, 20 different amino acids, and a large but variable number of tRNA genes (400-500 in mammals). How many aminoacyl synthetase genes are there?

20

Fill in the blank. In a cross between parents with the genotypes A/a;B/b and a/a;b/b, where the A and B loci are unlinked, __% of the offspring will have a phenotype that differs from the phenotype of both parents.

50

The maximum map distance that can be observed in a cross concerning two loci is ___ map units.

50

How many offspring plants from a cross between R_ (round peas) and rr (wrinkled peas) genotypes would need to be examined to be confident at the 1% level that the R_ plant is actually RR?

7

A tall plant with purple flowers with genotype TtPp was self-fertilized. There were 8 offspring. What is the chance that at least one of the plants was short?

90%

A cross between two true-breeding strains (P0 generation) with genotypes A/A;b/b and a/a;B/B results in an F1 genotype of A/a;B/b. If this is test-crossed to a/a;b/b, which of the following offspring have parental phenotypes?

A/a;b/b a/a:B/b

[A] on [B], which is held within a tunnel in the [C], base-pairs with [D] on tRNA. The 5' of the anticodon corresponds to the [E] of the codon and the 3' of the anticodon correspond to the [F] of the codon.

A= a codon B= mRNA C= ribosome D= an anticodon E= 3' F= 5'

match the site in the ribosome to its function

A= charged tRNA enters B= tRNA holds C= uncharged tRNA leaves

In developing Drosophila embryos, [A] mRNA is evenly distributed through the embryo whereas [B] mRNA is confined to the posterior pole. Nanos protein binds to hunchback mRNA and represses its transcription. This produces a gradient of Nanos protein in the embryo, with more at the [C] end, and a corresponding gradient of Hunchback protein, with more at the [D] end.

A= hunchback B= nanos C= posterior D= anterior

Match the points on the bacterial growth curve with their descriptions.

A= no cell division B= cells doubling C=nutrients D= cell death

Tryptophan is an essential amino acid. Wild-type E. coli can synthesize their own tryptophan and are called [A]. Mutants that cannot synthesize an essential nutrient like tryptophan are called [B]. Transcription of the genes for tryptophan synthesis is not [C]: i.e., the genes are transcribed only when needed. Transcription is therefore [D]. When tryptophan is [E], the repressor [F] and transcription of the tryptophan mRNA proceeds. When tryptophan is [G], the repressor [H] and transcription is prevented.

A= prototrophs B=auxotrops C=constitutive D= repressible E= absent F= does not bind G= presnt H= bind to DNA

What does linkage disequilibrium refer to?

Association of phenotypes

Physical (top) and genetic (bottom) maps are shown for C. elegans chromosome I.

B C(longest) A(shortest)

Match the type of DNA sequence variation with its name

CNV= changes in the number of copies of a small sequences SNP= changes at one nucleotide Private polymorphism= changes occuring only in a small number of related individuals Indel= Additions or deletions of pieces of DNA

Fill in the blank. Ploidy refers to the number of sets of chromosomes found in an organism. Most multicellular organisms are _____

Diploid

Match the genetic notations to their definitions: a. strains used to initiate a mating experiment_____ b. offspring of the initial mating cross______ c. dominant allele_____ d. wild-type allele____

F1; R; PO; +

Which phase of the cell cycle has two copies of the genome in the cell for the entire phase?

G2

This question relates to Mendel's breeding experiments with peas. Mendel crossed a true-breeding smooth pea plant with a true-breeding wrinkled pea plant. Mendel then crossed the offspring to each other. Which statements are true about the offspring of the second cross? Please select all that apply.

Half the offspring had a genotype with 1 recessive and 1 dominant allele. the Offspring of cross 2 had a 3:1 smooth:wrinkled ratio.

This question relates to Mendel's breeding experiments with peas. A true breeding plant producing smooth peas was crossed with a true-breeding plant producing wrinkled peas (cross 1). The offspring of cross 1 all produced smooth peas. The offspring of cross 1 were then crossed with the wrinkled-pea parent (cross 2). Which of the statements about the cross outcomes are true? Please select all that apply.

Half the offspring of cross 2 had smooth peas. All the offspring of cross 1 had the same genotype. The wrinkled allele is recessive.

What term describes a situation where two functional alleles are required for proper biological function

Haplo-insufficient

Iron response proteins (IRPs) are involved in regulating iron levels in the cell through translational regulation. Which of the following statements regarding IRP regulation is untrue?

IRP binding prevents transferrin translaion

What is the term used for the first individual identified in a family to be affected by a phenotype?

Proband

A series of crosses to test whether two genes in Drosophila flies are sex-linked and on the same chromosome, and which alleles are dominant, are described below. Match each conclusion with the piece of evidence supporting it.

There are no phenotypic differences between males and females in the F1 generation= the two genes are autosomal All F1 flies have normal wings= Normal wings Offspring...= The two genes are on the same chromosome

What term is used for a variety that passes a trait onto all its offspring when crossed to a similar variety?

True-Breeding

what is an evolutionarily accepted mutation?

a mutation that does not have adverse impact on the function of a protein

Match the missing words in the following phrase. Genes are [A] if they are on the same chromosome and are [B] if they are on different chromosomes. Genes that are on different chromosomes segregate [C] at meiosis whereas genes on the same chromosome are more frequently inherited [D].

a- linked b-unlinked c-independently d-together

Which characteristics are true of complex traits? Please select all that apply. a. Complex traits exhibit continuous variation b. complex traits are the result of expression of multiple genes c. genes underlying complex traits are inherited in a con-Mendelian fashion d. complex traits are true-breeding

a. complex traits exhibit continuous variation b. complex traits are the result of expression of multiple genes

Match the missing words in the following phrase. In [A]-Wide Association Studies, researchers identify lots of [B] with ([C]) and without ([D]) a [E]. Genomes are compared and any [F] that are consistently associated with the trait are identified.

a= genome b= individuals c= affected d= unaffected e= phenotype f= sequences

Match the missing words in the following phrase. Genomes in [A] could be mapped even though, unlike [B], they do not undergo meiotic [C]. Genes can be transferred between bacteria by [D] and bacterial genomes can be mapped according to [E]. Currently, bacterial genomes are almost always mapped by assessing the [F].

a= prokaryotes b= eukaryotes c= recombination d= conjugation e= time of entry f= sequence

The genotype of an organism with a dominant phenotype but unknown genotype can be inferred using a test cross. What genotype should a plant A_ be crossed to in a test cross?

aa

which of the following is not a post-translational modification?

addition of a 5' cap

A Drosophila parent fly heterozygous for alleles for black body, dumpy wings, and purple eyes was test-crossed to a fly that was homozygous recessive for all three genes. The genes are all on the same chromosome. The offspring had the following phenotypes in the following numbers:

b+p+d+ bpd

Fill in the blank. The biochemical process of breaking down a complex molecule into its simpler components is termed _____

catabolism

microtubules attach to the ____ and originate from the ______

centromere; centrosome

Match the missing words in the following phrase. [A] separate during meiosis I and [B] separate during meiosis II. Mitosis is more similar to [C] than to [D].

chromosomes; chromatids; meiosis II; meiosis I

Tryptophan is involved in transcriptional regulation of the tryptophan-encoding genes. It does this by binding to the tryptophan repressor. Tryptophan is therefore a ________

corepressor

Which structure that forms during meiosis leads directly to the formation of recombinant chromosomes?

crossover

put these terms in order: DNA replication, centrosome separation, aster formation, chromosome separation

dna replication, centrosome separation, aster formation, chromosome separation

True or false? Biochemically similar amino acids are likely to have similar codons. This reduces the chance that a mutation will cause an amino acid to be substituted with a different amino acid.

false

True or false? For a locus to be classed as polymorphic, the second most common polymorphism must be found at least 10% of the time.

false

True or false? If recombination rate is high, then a particular combination of alleles is likely to be transferred to the next generation intact.

false

True or false? In a cross between two heterozygotes, the ratio of genotypes is the same as the ratio of phenotypes

false

True or false? The kinetochore consists of proteins attached to the centromere of the chromosome.

false

True or false? The physical outcome - or trait - that results from gene expression is a genotype.

false

True or false? The role of checkpoints in the cell cycle is to accelerate the transitions between different phases of the cycle.

false

True or false? When genes are on the same chromosome, the alleles on one of the two homologous chromosomes are considered to be in trans.

false

true or false? the majority of genes in mammals encode proteins

false

fill in the blank. Descent from a common ancestor is defined as___

homology

The On-line Mendelian Inheritance in Man (OMIM) database is an important resource for human genetics. Most of the content in OMIM relates to monogenic diseases. Which of the following conditions are not generally thought to be monogenic? Please select all that apply.

hypertension Type 2 diabetes

During which stage of translation is translational regulation most likely to occur?

initiation

which of the following is the critical regulatory stage for the majority of genes?

initiation of transcription

Which of the statements about inheritance of rare traits in pedigrees are true?

it is assumed that unrelated individuals who join an affected family do not carry the genes

Fill in the blank. _____ enzymes carry out post-translational phosphorylation of peptides.

kinase

Which of the following phases are in mitosis? Please select all that apply.

metaphase, anaphase, telophase, prophase

alpha tubulin

minus end

Which of the following statements about meiosis and mitosis are true? Please select all that apply.

mitosis involves one round of DNA replication; mitosis involves one round of chromosome/ chromatid separation

where do repressor proteins bind?

operator sequence

as ____ consists of multiple genes that are transcribed as a single transcript

operon

beta tubulin

plus end

What molecular genetics term is used for making a connection between the gene as it relates to a phenotype and the gene in terms of its DNA sequence?

positional cloning

Match the levels of protein structure to their descriptions.

primary= peptide amino secondary= regional folding tertiary= three-dimensional quaternary= combination

A Drosophila fly heterozygous for alleles for black body, dumpy wings, and purple eyes was test-crossed to a fly that was homozygous recessive for all three genes. The genes are all on the same chromosome. The offspring had the following phenotypes in the following numbers:

purple-black-dumpy

what is chromosome pairing?

recognition and coming together of homologous chromosomes

Chromosomes align at the metaphase plate before separating at anaphase. Which of the following factors keep chromosomes together at metaphase? Please select all that apply.

securin, cohesin

The regulation that determines the anterior and posterior ends of a developing Drosophila embryo is primarily ______

spatial

which is not true of translation termination?

stop codons bind to special tRNA molecules

Fill in the blank. If two or more independent events produce the same result, the probability that either will occur is the ____ of their probabilities.

sum or total

what is the term used for a mutation that overcomes the effect of another mutation?

suppressor mutation

Which of the statements about the synaptonemal complex (SC) are false? Please select all that apply.

the synaptonemal complex forms between chromosomes in meiosis and mitosis; The width of the SC differs between organisms; Central element proteins of the SC are evolutionarily conserved

Which of the following characteristics do genes need to possess? Please select all that apply.

they must be expressed and heritable

What are cytological maps used for?

to examine changes in chromosomal structure

True or false? Genes that are located close together on a homologous chromosome are more likely to be inherited together than genes that are further apart.

true

True or false? Mendel's Law of Segregation refers to the fact that the two alleles for a gene in a diploid organism separate during gamete formation and each gamete receives only one of these alleles.

true

True or false? Two genes can be syntenic and unlinked.

true

true or false? the majrity of polypeptides are post-translationally modified

true

What is a tetrad?

two pairs of sister chromatids

Fill in the blank. Position 3 in the codon is the least likely to influence which amino acid is encoded and has the weakest base-pair interaction; i.e., the position can _______

wobble

Alleles for hairy body, curled wings, and glass eyes are on the same Drosophila chromosome. There are 23.5 map units between hairy and curled and 13 map units between curled and glass. One percent of offspring from a test cross had double crossovers. Was crossover interference observed?

yes. Interference is 67%