Question 1

An individual who is homozygous dominant for a trait can be symbolized
A)AA.
B)Aa.
C)aa.
D)none of the above.

Accepted Answer

An individual who is homozygous dominant for a trait has two copies of the dominant allele, which is represented by the same letter. In this case, the letter is A. The homozygous dominant genotype is therefore symbolized as AA.

Question 2

Identical alleles are said to be
A)homozygous.
B)heterozygous.
C)recessive.
D)dominant.

Accepted Answer

Homozygous refers to having two identical alleles for a particular gene.

Question 3

A gene is
A)a DNA sequence that contains the information for producing one type of protein.
B)a structure that contains chromosomes.
C)an amino acid sequence that contains the information for producing a particular DNA sequence.
D)the collection of all of the protein-encoding DNA sequences on a particular chromosome.

Accepted Answer

A gene is a section of DNA that contains the genetic information for producing a particular protein. The process of gene expression involves the transcription of the DNA sequence into mRNA, which is then translated into the amino acid sequence of the protein. Therefore, a gene is responsible for specifying the sequence of amino acids in a protein, and ultimately determines its structure and function. Choices B, C, and D are incorrect because they do not accurately describe the nature or function of a gene.

Question 4

The phenotypes and genotypes that result from a cross of Aa and aa (A = normal pigmentation and a = albinism)are
A)phenotypes-all normal;genotypes-50% heterozygous and 50% homozygous recessive.
B)phenotypes-all albino;genotypes-all homozygous recessive.
C)phenotypes-50% normal and 50% albino;genotypes-50% heterozygous and 50% homozygous recessive.
D)phenotypes-all albino;genotypes-50% heterozygous and 50% homozygous recessive.

Accepted Answer

The cross between Aa and aa produces offspring with a genotype of Aa and aa in a ratio of 1:1. Aa individuals are heterozygous for the gene and express the dominant trait, normal pigmentation. aa individuals are homozygous recessive and express the recessive trait, albinism. Therefore, the offspring will have a 50% chance of inheriting the dominant A allele and exhibiting normal pigmentation (phenotype: normal) and a 50% chance of inheriting the recessive a allele and exhibiting albinism (phenotype: albino). The genotypic ratio of the offspring will be 50% Aa heterozygotes and 50% aa homozygous recessive individuals.

Question 5

The genotypes and phenotypes that result from a cross of AA and Aa (A = normal pigmentation and a = albinism)are
A)phenotypes-all normal;genotypes-50% homozygous dominant and 50% heterozygous.
B)phenotypes-50% normal and 50% albino;genotypes-all heterozygous.
C)phenotypes-75% norma and 25% albino;genotypes-75% heterozygous and 25% homozygous.
D)phenotypes-all albino;genotypes-50% heterozygous and 50% homozygous recessive.

Accepted Answer

This cross involves a homozygous dominant parent (AA) and a heterozygous parent (Aa). The possible gametes of the AA parent are all A, and the possible gametes of the Aa parent are A and a. The Punnett square for this cross will show that all offspring will have at least one A allele, resulting in normal pigmentation. The genotypes will be 50% AA (homozygous dominant) and 50% Aa (heterozygous), as each parent can only contribute one allele to each offspring.

Question 6

A person normally has two alleles of a gene because
A)DNA only comes in two forms.
B)one allele of a gene is carried on each of two homologous chromosomes.
C)there isn't enough DNA to accommodate more than this.
D)all genes come in only two varieties.

Accepted Answer

Homologous chromosomes come in pairs, with one chromosome from each parent, and each chromosome carries one allele of a specific gene. Therefore, an individual has two alleles of a gene, one on each homologous chromosome.

Question 7

A gene typically has many alleles because
A)humans have many traits.
B)a chromosome has many genes.
C)a DNA sequence can vary in many ways.
D)a protein sequence can vary in many ways.

Accepted Answer

A gene can have many alleles because the DNA sequence of a gene can vary in many ways, such as point mutations, insertions, deletions, and rearrangements. These variations can result in different forms of the gene, or alleles, that code for different versions of the protein product. Having many alleles allows for diversity in the population and provides the potential for natural selection to act upon.

Question 8

The term "exome" refers to
A)the parts of the genome that determine sex.
B)the protein-encoding parts of the genome.
C)the parts of the genome that lie exteriorly along the chromosomes.
D)the set of RNAs made in a particular cell type under specific conditions.

Accepted Answer

The term "exome" refers to the protein-encoding parts of the genome, which makes up only about 1-2% of the entire genome. This is because these regions are transcribed into messenger RNA (mRNA), which is subsequently translated into proteins, the functional molecules that carry out most of the cell's activities. Therefore, studying the exome is a way to focus on the regions of the genome that have the most direct impact on cellular function and human disease.

Question 9

The two types of information needed to predict the inheritance pattern of a trait are
A)the way genes are distributed in meiosis and the way that they come together when sperm joins egg.
B)the health of the mother and the father.
C)the way mitosis distributes the alleles of a gene and whether those alleles are dominant or recessive.
D)the age at which the trait appears and how it affects males or females.

Accepted Answer

In order to predict the inheritance pattern of a trait, one needs to understand both how the genes are distributed during meiosis and how they come together when sperm and egg fuse. This involves knowledge of concepts such as dominance and recessiveness, as well as the laws of segregation and independent assortment. The health of the parents or the age of onset of the trait are not necessarily relevant to predicting inheritance patterns. The way mitosis distributes alleles is also not relevant, as mitosis does not involve the formation of gametes and therefore does not affect inheritance patterns.

Question 10

The two general types of chromosomes are
A)autosomes and allosomes.
B)sex chromosomes and allosomes.
C)sex chromosomes and autosomes.
D)X and Y chromosomes.

Accepted Answer

Sex chromosomes determine an individual's biological sex, while autosomes carry genetic information for all other traits except sex determination. Therefore, the two general types of chromosomes are sex chromosomes and autosomes. Option A and B contain incorrect terminology, and option D is not comprehensive enough to cover all chromosomes.

Question 11

The origin of the 46 chromosomes in a human zygote is
A)all from the sperm cell.
B)half from DNA and half from RNA.
C)half from the sperm and half from the egg.
D)all from the egg.

Accepted Answer

The 46 chromosomes in a human zygote come from the fusion of a sperm and an egg cell during fertilization. Each gamete (sperm or egg) carries 23 chromosomes, so when they combine, the resulting zygote has a total of 46 chromosomes. Therefore, half of the chromosomes come from the sperm and half come from the egg.

Question 12

Genetics is the study of
A)sperm and eggs.
B)the effect of the environment on health.
C)inheritance of characteristics.
D)DNA.

Accepted Answer

Genetics is the study of inheritance of characteristics, which is the passing down of traits from parents to offspring through their genes. While sperm and eggs and DNA are involved in genetics, they are not the entire focus of the field. The effect of the environment on health is not directly related to genetics, although it may influence how genetic traits are expressed.

Question 13

The human genome consists of
A)DNA,most of which encodes protein.
B)DNA,most of which does not encode protein.
C)protein,most of which encodes DNA.
D)protein,most of which does not encode DNA.

Accepted Answer

The human genome consists of DNA, but only a small portion of it actually codes for proteins. The rest of the DNA has regulatory, structural, or unknown functions. Therefore, option B is the best choice.

Question 14

An allele that is not expressed in the heterozygous condition is
A)recessive.
B)dominant.
C)autosomal.
D)codominant.

Accepted Answer

An allele that is not expressed in the heterozygous condition is a recessive allele. This means that the individual would need to inherit two copies of the recessive allele in order for it to be expressed. The dominant allele is always expressed in the heterozygous condition, while codominant alleles are both expressed. Autosomal refers to genes located on chromosomes that do not determine sex.

Question 15

Different alleles of the same gene are said to be
A)homozygous.
B)heterozygous.
C)recessive.
D)dominant.

Accepted Answer

Different alleles of the same gene are said to be heterozygous when there are two different versions (alleles) of a gene present in an individual's DNA.

Question 16

An allele that masks the effect of another is
A)homozygous.
B)heterozygous.
C)recessive.
D)dominant.

Accepted Answer

An allele that masks the effect of another allele is dominant. When a dominant allele is present, it will always be expressed and will mask the effect of any recessive allele present.

Question 17

The processes that pass genetic information from generation to generation are
A)mitosis and fertilization.
B)meiosis and fertilization.
C)mitosis and meiosis.
D)interactions of DNA and the environment.

Accepted Answer

Meiosis produces haploid cells that combine during fertilization to create a new individual with a unique set of genes. Mitosis is a process for cell division, but does not pass genetic information from generation to generation. DNA interactions with the environment can affect gene expression and may cause mutations, but this is not a process for passing genetic information to offspring.

Question 18

A karyotype is
A)a diagram that represents family relationships.
B)a size-ordered chart of chromosomes.
C)a genome sequence.
D)a website that lists genes and the proteins they encode.

Accepted Answer

A karyotype is a size-ordered chart of chromosomes, usually represented in pairs, that allows for the identification of any chromosomal abnormalities or irregularities. It can be used to diagnose genetic disorders, determine the sex of an individual, and assess the risk of passing on certain genetic conditions.

Question 19

The genotypes and phenotypes that result from the cross of Aa and Aa (A = normal pigmentation and a = albinism)are
A)phenotypes-75% normal and 25% albino;genotypes-25% homozygous dominant and 50% heterozygous and 25% homozygous recessive.
B)phenotypes-50% normal and 50% albino;genotypes-all homozygous recessive.
C)phenotypes-50% normal and 50% albino;genotypes-50% homozygous recessive and 50% homozygous dominant.
D)phenotypes-25% normal and 75% albino;genotypes-25% homozygous dominant and 50% heterozygous and 25% homozygous recessive.

Accepted Answer

The Punnett square for the cross of Aa and Aa would be:

|   | A |   |
|---|---|---|
| a | Aa| Aa|
| a | Aa| Aa|

From this square, we can see that the offspring would have a 75% chance of having normal pigmentation (A_) and a 25% chance of being albino (aa). The genotypes of the offspring would be 25% AA, 50% Aa, and 25% aa. Therefore, the best choice is A.

Question 20

How alike are our genomes?
A)About 10%
B)About 25%
C)About 75%
D)Nearly 100%

Accepted Answer

Human genomes are nearly 99.9% identical to each other, meaning the correct answer is that they are nearly 100% alike. This small fraction of difference accounts for the vast diversity among individuals.

Quiz 24: Genetics and Genomics

An individual who is homozygous dominant for a trait can be symbolized

Identical alleles are said to be

A gene is

The phenotypes and genotypes that result from a cross of Aa and aa (A = normal pigmentation and a = albinism) are

The genotypes and phenotypes that result from a cross of AA and Aa (A = normal pigmentation and a = albinism) are

A person normally has two alleles of a gene because

A gene typically has many alleles because

The term "exome" refers to

The two types of information needed to predict the inheritance pattern of a trait are

The two general types of chromosomes are

The origin of the 46 chromosomes in a human zygote is

Genetics is the study of

The human genome consists of

An allele that is not expressed in the heterozygous condition is

Different alleles of the same gene are said to be

An allele that masks the effect of another is

The processes that pass genetic information from generation to generation are

A karyotype is

The genotypes and phenotypes that result from the cross of Aa and Aa (A = normal pigmentation and a = albinism) are

How alike are our genomes?