SmartBook Chapter 4

What are the functions of a pedigree?

-They are used as starting points for identifying and describing, or annotating, a gene from the human genome sequence. -They are used to help families identify the risk of transmitting an inherited illness.

Rank the steps involved in solving a problem based on the inheritance of a single-gene trait. Start with the first step at the top.

1.List all possible genotypes and phenotypes for the trait 2.Determine the genotypes of the individuals in the first generation 3.Derive the possible alleles in geametes each individual produces 4.Calculate ratiosfor the f1 generation 5.Calculate ratios for the F2 generation

Huntington disease is inherited in an autosomal dominant manner. Through genetic testing, Joseph has learned that he inherited Huntington disease from his mother who suffers from the illness. There is no history of Huntington disease in Joseph's father's family. What is the probability that Joseph will pass the dominant allele for Huntington disease to his children?

50%

How many boxes are present in a Punnett square for three genes?

64

The phenotypic ratio expected in a typical dihybrid cross is _____.

9:3:3:1

Which of the following crosses is expected to yield a phenotypic ratio of 9:3:3:1?

AaBb x AaBb

This individual is affected by a disorder called

Albinism

In general, Mendel's laws can be used to predict which of the following in crosses involving single-gene traits?

Both genotypes and phenotypes

The wild type allele is always dominant.

False= the wild type allele may be recessive or dominant.

In _____, researchers compare the DNA sequence of the exome of an individual who has unexplained symptoms or traits to the DNA sequences of the exomes of relatives.

Family exome analysis.

The combination of alleles for a gene in an individual constitutes a(n)

Genotype

An individual with two identical alleles for a gene is ___ for that gene.

Homozygous

Identify an autosomal dominant disease_____

Huntington disease

Which of the following statements best describes the wild type allele?

It may be dominant or recessive

Which of the following statements about an organism's appearance is true?

It reveals its alleles some of the time.

A recessive trait is said to arise from a "__" because the recessive allele usually prevents the production or activity of the normal protein.

Loss of function

A single gene named OCA2 confers eye color by controlling __synthesis.

Melanin

The color of the iris is due to pigments called

Melanin

Mendel's experiment is called a _____ cross because it follows one trait and the self-crossed plants are hybrids.

Monohybrid

A phenotype is a variant of a gene's expression that arises when the gene undergoes a change.

Mutant

A change in a gene is called a _____.

Mutation

P1 F1 F2

P1 First generation or the parental generation F1 First filial generation F2 Second filial generation

A(n)___ in genetics differs from a family tree in genealogy in that it indicates diseases or traits as well as relationships and ancestry. It may also indicate molecular data and test results.

Pedigree

An application of _____ theory called the product rule can predict the chance that parents with known genotypes can produce offspring of a particular genotype.

Probability

The __rule states that the chance that two independent events will both occur equals the product of the chances that either event will occur alone.

Product

A diagram that follows the transmission of alleles and shows the expected genotypic and phenotypic ratios is known as a(n)

Punnett square

In the context of Mendel's experiments, the masked trait is _____.

Recessive

When a child is born with a syndrome not previously observed and both parents are unaffected, it is possible that both parents are carriers for _______mutations in the same gene for a condition that has not yet been identified or that a new _________ mutation arose spontaneously in the sick child, in a sperm or an oocyte.

Recessive Dominant

Which genotypes were produced among the progeny when Mendel self-crossed the F1 plants with the Tt genotype?

TT, tt, and Tt

Consider a clinical scenario where a child has a syndrome not seen before, and both parents are unaffected. What are the results possible in a family exome analysis?

The affected child inherited recessive mutations from both parents. The affected child has a "new mutation."

Which of the following are characteristics of autosomal dominant traits?

The trait can appear in either sex The trait typically does not skip generations

Which of the following are characteristics of autosomal recessive inheritance?

The trait typically skips generations The trait can appear in either sex.

A monogenic disease is caused by ______.

a mutation in a single gene

Which of the following designations best represents a compound heterozygote?

a1a2 = two different recessive alleles for the same gene.

A(n) _____ disease affects both sexes and usually appears in every generation.

autosomal dominant

A homozygous recessive individual is always used in a test cross because it is the only genotype that _____.

can be identified by its phenotype

Identify how the genotype of a homozygous recessive individual is represented

dd

A cross that involves two genes and traits and where the self-crossed plants are hybrids is known as a(n)

dihybrid

One dominant and one recessive allele in an individual indicates a _____.

heterozygote

Mendel's second law is the law of _____.

independent assortment

A human disease caused by a mutation in a single gene is called _____

monogenic

Mendel conducted many monohybrid crosses including one between short and tall plants. The F2 progeny of that cross were in the ratio of _____.

one-quarter short to three-quarters tall plants

Charts called _____ display family relationships and depict which relatives have specific phenotypes and, sometimes, genotypes.

pedigrees

The earliest pedigrees were strictly genealogical, not indicating traits.

true

A true-breeding tall plant is crossed to a true-breeding dwarf plant. The offspring in the F1 generation are all tall plants. The F1 generation is then crossed to yield a F2 generation. What is the genotypic ratio of the F2 generation? (Let T be the allele for the tall trait and t be the allele for the dwarf trait.

1TT: 2Tt: 1tt

A true-breeding tall plant is crossed to a true-breeding dwarf plant. The offspring in the F1 generation are all tall plants. The F1 generation is then crossed to yield a F2 generation. What is the phenotypic ratio of the F2 generation?

3 tall: 1 dwarf.

A recessive allele of the OCA2 gene confers blue eye color and a dominant allele confers _____ eye color.

Brown= recessive= blue eyes and dominant would be brown if the OCAgene that controls melanin is missing it abolished control over the OCA

How would the genotype of a homozygous dominant individual be represented?

DD

Dark brown/black->______ Red-yellow->_________

Dark brown/black->Eumelanin Red-yellow->Pheomelanin

A(n) _____ describes an outward expression of an allele combination. .phenotype

Dd

Identify the traits that Mendel studied in the pea plant.

Flower position Seed form Pod form Seed coat color

An individual with two different alleles is _____—what Mendel called "non-true-breeding" or "hybrid."

Heterozygous

For which of the following patterns of inheritance must individuals have a homozygous genotype in order to show the trait?

autosomal recessive

The compartments of a Punnett square typically represent how genes in gametes ______.

join if they are on different chromosomes

The two factors—equal allele distribution into gametes and random combinations of gametes—underlie Mendel's _____.

law of segregation

An individual with two different recessive alleles for the same gene is termed a(n)

Compound heterozygous

An offspring's genotype depends on the parents' genotypes, which may not be obvious from their phenotypes. This statement best describes ______ probability.

Conditional

_____ is a situation in which an autosomal recessive condition is more likely to recur.

Consanguinity

Which of the following is a true statement about dominant disorders?

Dominant mutations that harm health early in life make people who have the allele either too ill or incapable of surviving long enough to reproduce.

Suppose exome sequencing shows that a child has a new (de novo) mutation not carried by either parent. Which type of inheritance pattern does this mutation show?.

Dominant.

The law of independent assortment states that for two genes on different chromosomes, the inheritance of one gene _____.

does not influence the chance of inheriting the other gene

Huntington disease is autosomal ____, which means that each child of an affected individual need inherit only one copy of the mutant gene to develop the disease.

dominant

In the context of Mendel's experiments, one trait that masks another is _____.

dominant

True or false: An organism's appearance always reveals its alleles.

false

When analyzing genetic crosses, the first generation is designated as the parental generation, and the second generation is the ____generation.

filial

A Punnett square for genes has 256 boxes

four

An individual with two dominant alleles is _____.

homozygous dominant

For a gene, if both alleles are recessive, an individual is _____.

homozygous recessive

Mendel crossed plants with one trait variant with the alternate and produced _____, which are offspring that inherit a different gene variant from each parent.

hybrids

Albinism results from the absence of an enzyme necessary to manufacture the pigment

melanin

A cross that involves a single trait and where the self-crossed plants are hybrids is known as a(n) _____cross

monohybrid

Two genes are said to independently assort because they are _____.

packaged into gametes at random

Hybrids hide one expression of a trait that reappears when hybrids are self-crossed because _____.

paired sets of elementen separate as gametes form, and when gametes join at fertilization, the elementen combine anew

A loss-of-function mutation is typically ______ and results in a deficit or absence of the gene's protein product.

recessive

Disease-causing recessive alleles ______.

remain in populations because healthy heterozygotes pass them to future generations

Mendel's idea that elementen separate in the gametes is called the law of ____

segregation

Gregor mendel studied the transmission of ____ traits in the pea plant.

seven

Crossing an individual of unknown genotype with a homozygous recessive individual is called a _____.

test cross

In conditional probability, an offspring's genotype depends on ______.

the parents' genotypes, which may not be obvious from their phenotypes

In the context of consanguinity, the risk of having a child with a particular autosomal recessive condition is higher because the related parents may carry _____.

the same alleles inherited from an ancestor that they have in common

Mendel performed his experiments with plants that had been cultivated over many generations to ensure that they always "bred true," producing _____.

the same expression of a trait

Two genes on the same chromosome can appear to assort independently if ______.

they are located very far apart from each other

The earliest pedigrees were strictly genealogical, not indicating traits

true

In a monohybrid cross, the F2 generation was in the ratio where _____.

two-thirds of the progeny exhibiting dominant trait were non-true-breeding, and one-third were true-breeding