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
