Biology unit 5

What would be a female bleeder's genotype? (Let XB stand for the normal condition for clotting and Xb stand for the recessive hemophilia allele.)

XbXb

Mark the genotypes which express hemophilia.

XbY, XbXb

The human chromosome apparently lacking in gene influence is the:

Y chromosome

Nitrogen bases are found on the DNA twisted ladder:

as the rungs

Why didn't Charles and Alexander, the grandsons of Queen Victoria receive hemophilia from their father Leopold?

because the disease is not on the "Y" chromosome and Helena did not have the trait

Why would it be wise for a woman carrying the hemophilia gene to keep her son from being circumcised?

because the probability of hemophilia would be 1:2

Why didn't the two sons of Queen Victoria (Alfred and Arthur) display hemophilia? (refer to pedigree chart)

because they did not receive the recessive gene (Xb) from their mother.

Mutations can be caused by:

both

A pedigree chart can show a trait that is:

both dominant and a mutation

Differences among blood groups result from:

chemical differences on the red blood cell

Choose from the following list of diseases those that are sex-linked.

color blindness, muscular dystrophy, rolling eyeballs, diabetes, nonfunctional sweat gland, certain deafness, white forelock, night blindness

The large number of potential gene ______ make it unlikely that any two people will be identical.

combinations

The factors that are responsible for the ABO blood type, or the Rh, are located on the surface of the _______.

erythrocyte

Mental illness may be the result of:

heredity and enviroment

When the alleles of a gene pair are expressed differently, but neither is dominant to the other, they are called _______ dominant.

incomplete

Two of the risk factors for Down's syndrome include which of the following?

increased age of female, infectious hepatitis

Some scientists believe that sickle-cell anemia is a beneficial mutation because it:

increases resistance to malaria

In the Watson-Crick model of a double helix, the "steps" of the "spiral staircase" are composed of:

nitrogen bases

Failure of homologous chromosomes to separate during meiosis is called ______.

nondisjunction

An XXY or an XO person can occur when the female has _______, producing an egg with two XX or no _____ chromosomes. The male produces the normal sperm of X or Y.

nondisjunction, X

Nutrition affects development of the physical brain therefore:

nutrition is related to intelligence

If a woman heterozygous for color-blindness marries a normal man:

one-half of the sons are expected to show color blindness

Represented by word descriptions, such as black and short-haired:

phenotype only

The Rh __________ condition occurs in most of the world population.

positive

The condition of the Rh factor is called _________ when present and ________ when absent.

positive, negative

The traits for blood type and Rh are the result of the presence or absence of particular _______ on the erythrocytes.

proteins

Sex-linked inheritance refers to ______ hereditary alleles usually being passed on the __________ chromosome.

recessive, X

In the ABO series, the gene for blood type O is _________, while A and B are ________ genes, and AB is _________.

recessive, dominant, codominant

The X and Y chromosomes are:

sex chromosomes

Traits determined by recessive genes located on the X chromosome are said to be ____________________ traits.

sex-linked

What is true about the heterozygous sickle-cell (HbA HbS) condition?

sickle-cell anemia is expressed under conditions of oxygen deficiency

Why do identical twins have the same set of genes?

they were born of one fertilized ovum

How can a mutation be inherited?

through gamete reproduction and fertilization, through meiosis and fertilization

Biochemists have found that though the amount of any given base found in DNA varies considerably from one species to another, the amount of adenine is always equal to the amount of:

thymine

The blood type trait is controlled by more than two alleles for a given gene and therefore is called multiple alleles.

true

The genotype of the person with normal red blood cells in all environmental conditions is ______.

HbA HbA

The genotype of persons with the sickle-cell trait, but often not exhibiting sickle-cell, is _______.

HbA HbS

A person whose blood tests show neither protein A nor protein B present has blood type:

O

What genotype produces a baritone voice?

SA

The Talmud permitted a father with hemophilia to have his son circumcised. Would this preclude all possible problems?

yes-if the mother is not a possible carrier

The hemoglobin of sickle cell anemia:

differs from the normal protein by one amino acid

A given gene has two allelic forms. An organism possesses this gene is said to be:

heterozygous for the gene

A TT genotype is said to be

homozygous

The complete genetic code of an organism is present:

in the nucleus of all somatic cells

The blood type AB is an example of _______ dominance.

incomplete

Which problems are associated with sickle-cell anemia?

oxygen respiration, blood circulation

Genes act by directing the formation of:

specific enzymes

When using data from population genetics research:

the sample must have a high probability of representing the population

n a large population, approximately 65 percent are tasters and 35 percent are nontasters. Does the class compare favorably to the general population?

yes

Each member of a class sampled a piece of PTC testing paper. Thirty people sampled the chemical. Twenty persons were tasters. How many had heterozygous genes?

0-20

Each member of a class sampled a piece of PTC testing paper. Thirty people sampled the chemical. Twenty persons were tasters. How many had homozygous recessive genes?

10

Each member of a class sampled a piece of PTC testing paper. Thirty people sampled the chemical. Twenty persons were tasters. How many had homozygous genes?

10-30

Down's syndrome is a condition where an extra chromosome is produced on the _____ chromosome.

21st

A normal human body contains:

23 pairs of chromosomes, 46 total chromosomes

Given that black is dominant over brown and that a pure-bred black mouse is mated to a pure-bred brown mouse, the offspring can be expected to be _____.

All black

The extra chromosome which produces down's syndrome is:

An autosome

A person with Klinefelter's syndrome possesses:

An extra X chromosome

A pedigree is not helpful to a counselor in predicting the probability of a recessive gene being present and the chances for an offspring to receive the gene and express the trait.

False

Hemophilia is a condition where the blood clotting action is dangerously high.

False

In considering sex-linked inheritance, both sexes are equally susceptible to the manifestation of the trait.

False

In sex-linked inheritance, females are most susceptible because they have only one X chromosome. Therefore, whichever gene is present, be it dominant or recessive, it is expressed. The male has two X chromosomes, and in order to be expressed, both genes must be recessive.

False

Intelligence is not related to heredity.

False

Sex determination is an example of environmental factors influencing the phenotype.

False

A couple who is extremely intelligent can give birth to a child who is below average intelligence.

True

A female can be susceptible to expressing hemophilia.

True

In general, the "Y" sex chromosome does not appear to exert as much genetic influence as the "X" chromosome.

True

The presence of tight ligaments in the thumb is a recessive trait.

True

Choose from the following list the three genotypes the parents must have in order for a daughter to have XbXb ?

XBXb, XbXb, XbY

DNA was discovered in:

1953

In incomplete dominance, genotypes can be expected to appear in a ratio of _____.

1:2:1

Genes are composed of:

DNA

A family pedigree is a chart of various patterns that shows a general trend.

False

When does nondisjunction occur which affects inheritance?

Meiosis

Radiation damage has hereditary effects if it:

alters the DNA in gametes

Down's syndrome involves a:

chromosomal abnormality

Sex cells are produced in a process called _______.

meiosis

If gene A is masked by its allele, gene B, gene A is

recessive

Hemophilia, red-green color blindness, and the white-eyed trait in fruit flies are

sex-linked disorders