Biology

IN the Watson-Crick model of a double helix, the steps of the spiral staircase are composed of what?

Nitrogen bases

If a woman heterozygous for color-blindness marries a normal man how many sons are expected to show color blindness?

1/2

When was DNA discovered?

1953

in incomplete dominance, genotypes can be expected to appear in a ratio of what?

1:2:1

The second generation phenotypes resulting from the cross of true-breeding monohybrid pollination will display a ratio of what?

1:3

The nucleus of each cell in the human body contains how many chromosome from each parent?

23

What is the chromosome number of a human female?

44 + XX

What is the chromosome number of a human male?

44 + XY

How many combinations of genotypes are possible for the coat coloration of rabbits which is governed by three alleles?

6

IN considering the cross of YyRr and YyRr, the phenotype ratios of F2 generation will be what?

9:3:3:1

What are the nitrogen base pairs in the DNA molecule?

Adenine and thymine, and cytosine and guanine

Different forms of a given gene are known as what?

Alleles

A person with Klinefelter's syndrome possesses what?

An extra X chromosome

Within a set of human chromosome, 22 pairs are called what?

Autosomes

Why didn't Charles Edward, the grandson of Queen Victoria, receive hemophilia from his father Leopold?

Because the disease is not the Y chromosome and Helena did not have the trait

A pedigree chart can show a trait that is what?

Both dominant and a mutation

How is the sex of the offspring determined?

By the combination of the sex chromosomes of the male and female

Differences among blood groups result from what?

Chemical differences on the red blood cell

Down's syndrome involves a what?

Chromosomal abnormality

What are genes composed of?

DNA

Mendel's principle of segregation implies that the two members of an allelic pair of genes are what?

Distributed to separate gametes

Fertilization produces what in the offspring?

Double the haploid number of chromosomes

The Y chromosome in human males appears to be what?

Genetically almost inactive

Genes that carry contrasting inheritance factors are called what?

Heterozygotes

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

Heterozygous for the gene

In a dihybrid cross, the F2 will have nine genotypes, but only four phenotypes because what?

Heterozygous genes cause the dominant traits of mask the recessive traits

The complete genetic code of an organism is present where?

In the nucleus of all somatic cells

As a result of nondisjunction, a female gamete may contain what?

No sex chromosomes or two

The ratio of the offspring of 9:3:3:1 is for the what?

Phenotype

What cross will yield four phenotypes in the 1:1:1:1 ratio?

RrYy x rryy

Traits determined by recessive genes located on the X chromosome are said to be what traits?

Sex-linked

Genes act by directing the formation of what?

Specific enzymes

Radiation damage has hereditary effects if it altars what?

The DNA in gametes

What is meant by homologous chromosomes?

The gene's alleles are found in matched chromosome pairs

Nitrogen bases are found on the DNA twisted ladder as what?

The rungs

How can a mutation be inherited?

Through gamete reproduction and fertilization or 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 what?

Thymine

All ova contain sex chromosomes corresponding to what?

X

The human chromosome apparently lacking in gene influence is what chromosome?

Y chromosome

Do all members of each species have the same number of chromosomes?

Yes

Linkage refers to genes for different traits being what?

Located on the same chromosome

Segregation and independent assortment of genetic material occurs during what?

Meiosis

Sex cells are produced in a process called what?

Meiosis