Tay Sachs disease results in non-functioning enzymes. Phenotypically, carriers of this disease appear normal and can maintain daily functions. Enzymatically, carriers of Tay Sachs disease have a total enzymatic activity of 50% where those without the trait have 100% and those with the trait have 0%. Molecularly, there is an equal amount of diseased cells as normal cells in the body of a carrier. What type of dominance is displayed in these levels respectively?

Phenotype - complete, enzyme - incomplete, molecular - codominance

When you cross two heterozygous black dogs you would expect a ratio of ¾ black : ¼ white in their offspring. However, you find that you get a ratio of ⅔ black : ⅓ white, with equal numbers of males and females in both groups. What genetic inheritance pattern can explain these results?

The allele for black coats is dominantly lethal

Hereditary hemochromatosis (HH) is a genetic condition that causes "iron overload." Patients with severe forms of the disease must donate blood regularly to remove excess iron from their bloodstreams. Clinically, it is difficult to determine which HH patients will actually develop increased iron levels and the adverse symptoms associated with the disorder. Which type of inheritance pattern describes the inability to predict whether an individual with the HH allele will develop the disorder based on his or her genotype?

incomplete penetrance

Marfan syndrome is an autosomal dominant disorder associated with a mutation in collagen and resulting in skeletal, optical, and cardiovascular abnormalities. Each person with a dominant mutant allele expresses at least one of the symptoms, with varying degrees of severity. This is an example of

variable expressivity

Porphyria is an inherited or acquired disorder of the heme biosynthetic pathway that leads to the accumulation of the porphyrins (or their chemical precursors). Inherited cases of porphyria are manifested with a combination of seemingly unrelated symptoms, including mental disturbances and hallucinations, constipation, vomiting, muscle weakness, pain, and seizures. Which genetic term best describes this type of mutation?

pleiotropy

A scientist studying deer notices that the gene for antler production is on chromosome 2. However, antler production is ONLY found in males. This is an example of a

sex limited trait

In humans, male pattern baldness is dominant in males and recessive in females. The genotype for male pattern baldness also presents differently in each sex. If the gene for this is located on chromosome 17, this is an example of a

sex influenced traits

Red-Green color blindness is located on the X chromosome. This is an example of a

sex linked trait

In sweet pea, red flower color is controlled by two genes involved in the anthocyanin pathway, A and B. Both genes are required for expression, so that a recessive pair of alleles at either locus would result in a pink phenotype. If an AaBb plant were allowed to self-cross and you got only red and pink flowers, what dihybrid ratio would you expect in the offspring?

9:7

What type of gene interaction is present in a 9:7 ratio?

Complementary gene interaction

In sweet pea, red flower color is controlled by two genes involved in the anthocyanin pathway, A and B. Both genes are required for expression, so that a recessive pair of alleles at either locus would result in a pink phenotype. If an AaBb plant were allowed to self-cross and you got only red and pink flowers, what dihybrid ratio would you expect in the offspring?

12 white : 3 yellow : 1 green

In corn, you find that two different genes (R and B) both make purple pigment in the stalk of the plant. Thus, only when both alleles are mutated (rrbb) would the corn stalk be green instead of purple. When you cross two heterozygotes, you find a ratio of 15:1 of plants with purple stalks to plants with green stalks. What type of genetic interaction is this?

duplicate gene interaction

Mutation of several different genes can result in albinism. Suppose two parents both have albinism, but they have a child with normal pigmentation. What is the possible genetic explanation for this result?

Genetic complementation

Achondroplasia is an autosomal dominant lethal mutation. Two people with achondroplasia are expecting a child. What are the chances that their child does NOT have achondroplasia?

1/3

Given that black coats (B) are dominant to brown coats (b) and the pigmentation gene E is recessively epistatic to the gene for coat color, such that when a lab is ee it will be yellow, solve the following problem. A brown lab undergoes a test cross. The offspring from the cross are half brown labs and half yellow labs. What were the parent genotypes?

bbEe x bbee

In peas, green is completely dominant to yellow. A homozygous dominant (GG) green pea crossed with a homozygous recessive (gg) yellow pea. However, only 60% of the offspring are green as expected and the other 40% are yellow. Why is this?

incomplete penetrance

Sex linked traits are located on the sex chromosomes

false

Which of the following is an example of complementation?

True In a two gene cross, the two parents both show the mutant phenotype but all of the F1 generation shows the wild type

What is Pleiotropy?

One gene causes several DISTINCT phenotypes

What is Polygenic Inheritance?

Multiple genes combine to produce one phenotype

What is Variable Expressivity?

one genotype produces different phenotypes that exist on a spectrum

What is Incomplete penetrance?

Occurs when a percent of the population's genotype do not produce the expected phenotype for a trait

In which of these situations would you NOT use FISH analysis?

to visualize single nucleotide changes in DNA

Genetic Linkage is in direct opposition to Mendel's Law of Independent Assortment

true

Which r value below would represent the two closest genes on a chromosome?

1%

If two genes are not syntenic, which theta value and lod score combination is most likely?

0.5 and -10

A parental generation AABB x aabb crosses to make an F1 generation of AaBb. You preform a test cross to determine if there is any genetic linkage. You have 1000 offspring. 230 are Aabb, 245 are aaBb, 260 are AaBb, and 265 are aabb. Is there likely to be genetic linkage?

no

What is the recombination frequency in the above problem?

47.5%

Map units in linkage mapping correlate with a specific number of base pairs

false

Changes in a restriction enzyme site can be used as polymorphic markers?

true

What are these markers called in the above question?

RFLP

What genetic markers can be inherited together to form a haplotype?

SNPs

Which of these is NOT an indicator for referral to genetic counseling

exposure to carcinogens as an adult

Om is observing a genome sequence in a chromosome and notices it contains a paracentric inversion. If the original genetic sequence of the chromosome is UGO*TTHIS, what would be an example of this type of mutation? (* is the centromere)

UGO*TIHTS

Janeen notices that a chromosome contains a mutation but is not sure which kind. If the original genetic sequence of the chromosome is GENE*TICS and the mutated sequence is GEIT*ENCS, what type of mutation has occurred?

Pericentric inversion

Which of the following is NOT true about the nucleosome?

It contains 8 types of core histone proteins

Chromatin condensation plays a role in regulating gene expression

true

In a telocentric chromosome, what structure is missing?

the p arm

A gene is transcribed often during the life of a cell, and its region of the chromosome lightly stains with G-banding. What type of chromatin is this?

euchromatin

What types of gametes result from each type (meiosis I and meiosis II) of meiotic nondisjunction?

Meiosis I nondisjunction results in four normal diploid cells, whereas meiosis II nondisjunction results in four aneuploid cells.

Which of the following human genetic disorders is an example of a terminal chromosome deletion?

Cri-du-chat syndrome

Which type of chromosomal mutation can result in two normal chromosomes, one deletion chromosome, and one translocation chromosome?

unbalanced translocation

A gamete has experienced a chromosomal mutation, and the offspring exhibit a reduction in chromosome number but no loss of gene segments. Which type of chromosomal mutation has likely occurred?

Robertstonian translocation

In a given cell, the DNA shows a defect in the linker DNA, but the nucleosome structure is intact. Which histone protein has likely been mutated to cause this type of structural change?

H1

What gives chromosomes their shape?

non histone scaffolding proteins

Which mode of inheritance results in both alleles being detected equally in the heterozygous phenotype?

codominance

A mutation results in an enzyme that is partially active compared to the wild-type allele. This type of "leaky" mutation is classified as

hypomorphic

A mutation results in a gene product with a novel function that is not normally found in wild-type organisms. This type of mutation is known as

neomorphic

What type of allele is often detected as a distortion in segregation ratios, where one class of expected progeny is missing?

lethal allele

Many oncogenes result from mutations that cause excessive expression of a protein in cells where it is normally not expressed or is expressed at inappropriate times during development. This type of mutation can be described as

hypermorphic

Which mode of inheritance results in the phenotype of a heterozygote being indistinguishable from that of an organism homozygous for the dominant allele?

complete dominance

Which mode of inheritance produces heterozygotes with phenotypes that differ from either homozygote and might appear to be a blending of the two phenotypes?

incomplete dominance

A metabolic reaction requires 40 units of enzymatic activity to proceed. If a dominant allele D can generate 40 units of enzyme and a mutant allele d" generates 20 units of enzyme, what can be said of the dominant wild-type allele?

D is haplosufficient.

Loss-of-function mutations more likely to be recessive.

true

The four different human blood types are caused by how many different alleles?

three

People with the dominant mutant polydactyly allele can have extra digits on one or both of their hands. What is the genetic explanation for this observation?

variable expressivity

Most people with the dominant mutant polydactyly allele have extra digits but at least 25% have the normal number of digits. What is the genetic explanation for this observation?

incomplete penetrance

Gene interactions in which an allele of one gene modifies or prevents expression of alleles of another gene is known as

epistasis

King George III of England and other members of the royal family were afflicted with a series of strange, seemingly unrelated symptoms including abdominal pain, rapid pulse, convulsions, and insanity. It has been determined that he likely suffered from porphyria, caused by a mutation in a single allele. What is the genetic term describing the alteration of multiple, distinct traits of an organism by a mutation in a single gene?

pleiotropy

You are looking at the color of feathers in ducks and find that yellow ducks (Y) are dominant to green ducks (y). However, a second gene, H, controls whether the color will be expressed in the feathers. If the duck is hh, the duck will always be white, because the pigment does not go into feathers. What ratio of phenotypes would you expect following a dihybrid cross?

9:3:4

The alleles of linked genes tend to

segregate together during gamete production

What is the highest possible frequency of recombination between linked genes that can be generated by any type of crossover event?

50%

Which of the following will result in modifications to the expected Mendelian ratios?

Gene interaction, Incomplete dominance, Incomplete penetrance, Epistasis

Sex-limited traits are caused by genes that are on sex chromosomes.

false

For a gene with multiple alleles, what is the maximum number of alleles a diploid organism may have?

two

The alleles of linked genes tend to

segregate together during gamete production

Syntenic genes can assort independently when

they are far apart on a chromosome and crossing over occurs frequently between the genes

Genetic linkage leads to the production of a significantly greater than expected number of gametes containing chromosomes with

parental combinations of alleles

What is the highest possible frequency of recombination between linked genes that can be generated by any type of crossover event?

50%

Recombination frequency differs between males and females. Which sex has a higher rate of recombination, heterogametic (males) or homogametic (females)?

homogametic (females)

The 9:6:1 ratio seen in the dihybrid cross of summer squash indicates what genetic relationship between the two genes controlling fruit shape?

dominant gene interaction

A chromosome with a different combination of alleles than parental that is created by crossing over between homologous chromosomes is termed

recombinant chromosome

Alleles of linked genes usually segregate together during meiosis. When they don't, it is because crossing over has occurred between them.

true

5% recombination is equal to ________ map unit(s) (m.u.) or centimorgan(s) (cM) of distance between linked genes.

5

Instead of creating a gene map along a chromosome, ________ is a method of analysis that detects and locates the genes that, as a group, influence form or appearance.

genome-wide association studies (GWAS)

Which type of chromosome has no p arms?

telocentric

A region of a chromosome spanning the centromere is broken and reattached in the reverse direction. This is an example of which type of chromosomal defect?

pericentric inversion

The specific array of alleles making up a set of linked genes on a single chromosome is called a haplotype

true

Instead of creating a gene map along a chromosome, genome wide association studies (GWAS) is a method of analysis that detects and locates the genes that, as a group, influence form or appearance.

true

During gametogenesis, what percentage of gametes would be aneuploid if the nondisjunction event occurs during meiosis I?

100%

What is used to map genes in deleted chromosome regions by a method known as deletion mapping. It is a genetic phenomenon that occurs when a normally recessive allele is "unmasked" and expressed in the phenotype because the dominant allele on the homologous chromosome has been deleted.

Pseudodominance

Chromosomal translocation involves chromosome breakage and reattachment of the broken segment to a homologous chromosome.

false

What technique would you use to detect a target sequence in an intact chromosome using a labeled molecular probe?

fluorescent in situ hybridization (FISH)

Which of the following is FALSE regarding organization in an interphase nucleus?

Each chromosome occupies exactly the same region in all nuclei within an organism.

When nondisjunction occurs early in embryogenesis rather than gametogenesis, what would you expect in the resulting karyotype?

mosaicism