BIO156: Lesson 9 (9.5, Chapter 10)

If a colorblind woman marries a colorblind man, the chances of any daughter being of normal vision is 0%25%50%less than 25%It is impossible to tell, as the grandparents' genotype have to be figured into the problem.

0% (wrong said 25)

If a woman is a carrier for the color blind recessive allele and her husband's color vision is normal what are their chances that their daughter will be color blind? 100%, because one of the parents has the gene.50%, because the mother is a carrier.25%, because the mother carries the recessive allele.0%, because the mother is not affected.0%, because the father is normal

0%, because the father is normal

Parents who do not have cystic fibrosis (recessive) produce a child who has cystic fibrosis. What are the chances that each child born to this couple will have cystic fibrosis? 100%75%25%0%All of the choices are correct.

25%

Two parents are both carriers for an autosomal recessive disease. What is the probability that the will have a child is also a carrier? 0%25 %33%50%.75%.

50% (wrong said 25%)

In a pedigree chart, which is correct? Circles = males; squares = females.A line between a circle and a square represents a mating.A carrier with a normal phenotype is represented by a black circle or square.Offspring are represented by triangles.Only dominant traits are represented.

A line between a circle and a square represents a mating.

pedigrees

Chart that marks the appearance of a phenotype through generations of a family tree. A pedigree is constructed in a standard way, with individuals represented as polygons and relationships between them as lines Males are represented as squares; females, as circles. A filled-in polygon indicates an individual with the trait being studied. A marriage (or mating) is signified by a line connecting parents. Any offspring of the match are connected to the marriage by a perpendicular line, and every generation appears in a row designated by a roman numeral (I, II, III, and so on). A pedigree allows geneticists to estimate the probability that a phenotype will reappear in future generations. A genetic disorder causes medical problems; a genetic abnormality is a rare but harmless trait.

Solve the following multiple allele problem: Susan, a mother with Type B blood, has a child with Type O blood. She claims that Craig, who has Type A blood, is the father. He claims that he cannot possibly be the father. Further blood tests ordered by the judge reveal that Craig is AA. The judge rules that Susan is right and Craig must pay child support.Craig is right and doesn't have to pay child support.Susan cannot be the real mother of the child; there must have been an error made at the hospital.It is impossible to reach a decision based on the limited data available.

Craig is right and doesn't have to pay child support.

Dr. Smith's parents have normal hearing. However, Dr. Smith has an inherited form of deafness. Deafness is a recessive trait that is associated with the abnormal allele d. The normal allele at this locus, associated with normal hearing, is D. Dr. Smith's parents could have which of the following genotypes? DD and dddd and ddDd and DdDD and DDNone of the choices are correct.

Dd and Dd

epistasis

Form of polygenic inheritance in which the effect of an allele on a trait masks the effect of a different gene. Note that epistasis is not the same as dominance, which describes a relationship between alleles of the same gene.

multiple allele system

Gene for which three or more alleles persist in a population at relatively high frequency.

In the gene arrangement ABCDEFG breaks and a segment repositions itself so that the segment now reads ABEDCFG, what specific kind of mutation has occurred? DeletionTranslocationInversionNondisjunctionReciprocal mutation

Inversion

Sickle-cell anemia is a trait that is seen with equal frequency in males and females. Two people who do not have symptoms of the disease might have offspring that do, at an approximate frequency of one in four. What can you conclude about how this disorder is inherited? It is inherited as an autosomal dominant disorder.It is inherited as an autosomal recessive disorder.It is inherited as an X-linked dominant disorder.It is inherited as an X-linked recessive disorder.You cannot conclude anything about its pattern of inheritance.

It is inherited as an autosomal recessive disorder.

10.1 Study card

Like most other human traits, skin color has a genetic basis. Minor differences in the alleles that govern melanin production and the deposition of melanosomes affect skin color. Skin color differences probably evolved as a balance between vitamin production and protection against harmful UV radiation.

9.5 note

Mendel studied traits with distinct forms arising from alleles that have a clear dominant-recessive relationship. Other, more complex relationships between alleles and traits are more common.

genetic abnormalities

Note that a rare or uncommon version of a trait, such as having six fingers on a hand, or a web between two toes, not inherently life-threatening, and how you view them is a matter of opinion. By contrast, a genetic disorder sooner or later causes medical problems that may be quite severe. have multiple symptoms (a syndrome) that may vary among affected individuals. A few genetic disorders are governed by single genes inherited in a Mendelian fashion. Most human traits are polygenic, and some have environmental contributions.

Incomplete Dominance in Heterozygous (Pink) Snapdragons.

One allele (R) encodes an enzyme that makes a red pigment. The enzyme encoded by a mutated allele (r) cannot make any pigment. Plants homozygous for the R allele (RR) make a lot of red pigment, so they have red flowers. Plants homozygous for the r allele (rr) make no pigment, so their flowers are white. Heterozygous plants (Rr) make only enough red pigment to tint their flowers pink (Figure 9.10). A cross between two heterozygous plants yields red-, pink-, and white-flowered offspring in a 1:2:1 ratio.

incomplete dominance

One allele is not fully dominant over another, so the heterozygous phenotype is an intermediate blend between the two homozygous phenotypes. the phenotype of heterozygous individuals is an intermediate blend of the two homozygous phenotypes.

polygenic inheritance

Pattern of inheritance in which the form of a single trait is collectively determined by alleles of several genes. two or more genes affect the same trait Hundreds of genes may be involved, with each gene making a small contribution to the phenotype. With polygenic inheritance, multiple genes collectively influence the form of one trait. Epistasis is an example.

universal donors

People with type O blood are called universal donors because they can donate blood to anyone. However, because their body is unfamiliar with the carbohydrates made by people with type A or B blood, they can receive type O blood only. People with type AB blood can receive a transfusion of any blood type, so they are called universal recipients.

Which of the following is the common inheritance pattern when one gene influences multiple traits? PleiotropyPolygenic InheritanceDominanceIncomplete DominanceCodominance

Pleiotropy

pleiotropic

Refers to a gene that affects multiple traits. so mutations that affect its expression or its product affect all of the traits

ABO gene

The ABO gene encodes an enzyme that modifies a carbohydrate on the surface of human red blood cells. Two alleles of the gene, A and B, encode slightly different versions of the enzyme, which in turn modify the carbohydrate differently. A third allele, O, has a mutation that causes a frameshift The protein encoded by this allele has no enzymatic activity, so the carbohydrate remains unmodified. The alleles you carry for the ABO gene determine the form of the carbohydrate on your red blood cells, so they are the basis of your ABO blood type. Alleles A and B are codominant when paired. If your genotype is AB, then you have both versions of the carbohydrate, and your blood type is AB. The O allele is recessive when paired with either the A or B allele. If your genotype is AA or AO, your blood type is A. If your genotype is BB or BO, it is type B. If you are OO, it is type O

codominance

The full and separate phenotypic effects of two alleles are apparent in heterozygous individuals. traits associated with two alleles are fully and equally apparent in heterozygous individuals; neither allele is dominant or recessive. Codominant alleles have full and separate effects, so the heterozygous phenotype comprises both homozygous phenotypes. heterozygous individuals have both homozygous phenotypes. Codominance may occur in multiple allele systems such as the one underlying ABO blood type.

A colorblind woman mates with a man who is not colorblind. All of the sons and none of the daughters are colorblind. What is the best explanation of this result? The gene for color vision is linked to the X chromosome.The gene for color vision is codominant with the gene for sex determination.The gene for color vision is linked to the Y chromosome.The gene for color vision is incompletely dominant to the gene for sex determination.The gene for color vision is completely dominant to the gene for sex determination.

The gene for color vision is linked to the X chromosome.

An Example of Epistasis.

The product of the TYRP1 gene helps make the brown melanin. A dominant allele (B) of this gene results in a higher production of brown melanin than the recessive allele (b). The product of the MC1R gene affects the type of melanin produced. A dominant allele (E) of this gene triggers production of the brown melanin; its recessive partner (e) has a mutation that results in production of the reddish form. Dogs homozygous for the e allele are yellow because they make only the reddish melanin.

A man has hemophilia, but his parents do not. Using H for normal and h for hemophilia, give the genotype of his father, mother, and himself in that order. Hh, Hh, hhXHY, hh, XHYXHY, XHXh, XhYXhY, XHXH, XhYXHY, XhY, Xhy

XHY, XHXh, XhY

Could a man with blood type A father a child with blood type B? No, only males with type B or AB can have children with type B blood.Yes, if his genotype was AO and the mother had type B or AB blood.Yes, blood type is the result of the environment.No, children will always have the same blood type as their fathers.Yes, crossing over recombines all possible blood-group genes during gamete formation.

Yes, if his genotype was AO and the mother had type B or AB blood.

Which of the following is a genetic disorder? a. Cystic fibrosis b. Albinism c. Red hair d. Polydactyly

a. Cystic fibrosis

What causes Down syndrome? the lack of pigment productionan extra chromosome 21the presence of two different codominant allelesinability to produce normal connective tissuethe environment interacting with the genotype

an extra chromosome 21

A chicken with black feathers is mated with a chicken with white feathers. Each offspring has both white and black feathers. This is an example of incomplete dominance. a. True b. False

b. False

A person who has type AB blood illustrates the principle of co-dominance.incomplete dominance.blending inheritance.polygenic inheritance.regressive absorption.

co-dominance.

The expression of both alleles for a trait in a heterozygous individual illustrates incomplete dominance.co-dominance.pleiotropy.polygenic inheritance.blending inheritance.

co-dominance.

A man with blood type A marries a woman with blood type B. They have a daughter with blood type O. The man accuses the woman of infidelity because the child matches neither his nor his wife's blood type. Is he correct? a. Yes, the children should only be type AB. b. Yes, even if the man is heterozygous for A, then the children should be either type AB or type B. c. Yes, even if the wife is heterozygous for B, then the children should be either type AB or type A. d. No, if the man was heterozygous for A and his wife was heterozygous for B, then the children could be types A, B, AB, and O.

d. No, if the man was heterozygous for A and his wife was heterozygous for B, then the children could be types A, B, AB, and O.

Which refers to the loss of a portion of a chromosome? inversiontranslocationdeletionduplicationnondisjunction

deletion

Which refers to the addition of an extra segment of a chromosome? inversiontranslocationdeletionduplicationnondisjunction

duplication

A carrier of a genetic disorder who does not show symptoms is most likely to be __________ to transmit it to offspring. heterozygous for the trait and ableheterozygous for the trait and unablehomozygous for the trait and ablehomozygous for the trait and unableNone of the choices are correct.

heterozygous for the trait and able

Imagine that beak color in a finch species is controlled by a single gene. You mate a finch homozygous for orange (pigmented) beak with a finch homozygous for ivory (unpigmented) beak and get numerous offspring, all of which have a pale, ivory-orange beak. This pattern of color expression is most likely to be an example of incomplete dominance.co-dominance.pleiotropy.polygenic inheritance.crossing over.

incomplete dominance.

Nondisjunction occurs when a portion of a chromosome breaks off and is lost.chromosomes replicate too many times.two chromosomes fuse into one.members of a chromosome pair fail to separate.an entire pair of chromosomes is lost during meiosis I.

members of a chromosome pair fail to separate.

An abnormal number of chromosomes could result during meiosis because of ____. recombinationcarriernondisjunctioninversiontranslocation

nondisjunction

How many sex chromosomes are in an egg or a sperm? onetwo2346It varies from individual to individual.

one

What is the normal complement of sex chromosomes in a human male? two X chromosomestwo Y chromosomestwo X chromosomes and one Y chromosomeone X chromosome and one Y chromosomeone Y chromosome

one X chromosome and one Y chromosome

When you trace the occurrence of a specific characteristic through your past ancestry, you are constructing a family ______________. genetic probability chartincidence of occurrencegenotype referencepedigreemeiotic history

pedigree

Which of the following terms refers to the situation where a single phenotypic characteristic is determined by the additive effects of two or more genes? incomplete dominance.co-dominance.pleiotropy.polygenic inheritance.blending inheritance.

polygenic inheritance.

Many genetic disorders of humans are caused by multiple alleles.recessive alleles.drinking during pregnancy.a mutation that occurs in the egg, sperm, or zygote that gives rise to the affected individual.interactions with others who have the disease.

recessive alleles.

A recessive disorder is a genetic disorder _______. with two functioning alleles.that will express itself in the presence of two defective allelesthat involves changes in chromosomal numberthat will express itself in the presence of one functioning allelethat is the result of a change in chromosome structure

that will express itself in the presence of two defective alleles

Recessive X-linked traits are more likely to be expressed in a male than a female because males are haploid.the male's SRY gene doubles the chances that sex-linked genes are expressed.the male's phenotype results entirely from his single X-linked gene.More than one of the choices is correct.None of the choices are correct.

the male's phenotype results entirely from his single X-linked gene.

Which refers to the movement of a piece of one chromosome to another nonhomologous chromosome? inversiontranslocationdeletionduplicationnondisjunction

translocation

Analysis of a pedigree can reveal whether a single-gene disorder is associated with a dominant or recessive allele, and whether the allele is on an autosome or a sex chromosome.

true