Chapter 23-Heredity: The Continuity of Life Flashcards
What is the transmission of characteristics from parent to offspring by means of genes?
Heredity
Heredity is the transmission of characteristics from parent to offspring by means of ______________, units of genetic information, in the chromosomes of the cells.
Genes
As the number of cells increase in the human body, certain cells are called out to become specialized components of tissues and organs in a process called:
Differentiation
What kind of cell in humans (also called a body cell) has 46 chromosomes?
Somatic cell
What term refers to the egg and sperm of the human parents which each contain only 23 chromosomes?
Gametes
In what specially designed type of cell division do the egg and sperm originate in which occurs in the ovaries of females and the testes of males?
Meiosis
When an egg and a sperm unite in the process of fertilization, the result is a single fertilized egg cell known as a:
Zygote
A sperm cell contains half the usual number of chromosomes; what is this set known as?
Haploid set
Since the sperm cell contains half the usual number of chromosomes and the egg cell contains half, the zygote contains the complete number of chromosomes, known as what kind of set?
Diploid
Because the number of chromosomes is reduced by one half in meiosis, it is often called:
Reduction division
What are the two successive stages that meiosis occurs in?
First and second meiotic division
In the first meiotic division of meiosis, homologous chromosomes pair up in a process called _________________, in which an exchange of genetic information takes place between paired homologous chromosomes.
Synapsis
Little was known about heredity until the mid-19th century when an Austrian monk named ________________ began working with pea plants in his small monastery garden in what is now the Czech Republic, and is called the father of genetics.
Gregor Mendel
What is the scientific study of heredity?
Genetics
In modern genetics, different forms of a gene for a particular trait, such as various seed colors, are called:
Alleles
If an organism has two identical alleles for the same trait, it is said to be:
Homozygous
If an organism has one allele different from the other, it is said to be:
Heterozygous
What shows up in the offspring even if an allele for a different trait is also present?
Dominant traits
Dominant traits show up in the offspring even if an allele for a different trait is also present. This fact is known as the:
Law of dominance
The trait which does not show up when the dominant allele is present is known as the:
Recessive trait
We can use what to represent the dominant allele for round seeds?
R
We can use what to represent the recessive allele for wrinkled seeds?
r
The letters used to refer to different plants (Rr, rr, RR) describe the _______________ of an individual, which is the actual combination of alleles inherited for a particular trait.
Genotype
What is the outcome or expression of the genes in the physical appearance of the individual?
Phenotype
Mendel used the term ___________ to describe an organism with two different alleles for a particular trait.
Hybrid
What law states that alleles for each trait segregate or separate randomly during the formation of gametes?
Law of segregation
What was the mixing or blending of traits in these plants called?
Codominance
What is an organism that is heterozygous for two traits called?
Dihybrid
Scientists now know that many traits of an organism, such as the seed color and the seed shape in peas, are inherited independently of each other according to what law? In other words, the segregation of one gene does not influence the segregation of another.
Law of independent assortment
If two genes are located close to each other, both traits may be inherited together and not be sorted independently. This is known as _________________, and the genes are said to be linked.
Linkage
When several genes are linked together, they are known collectively as a:
Linkage group
What are the chromosomes which determine an organism’s sex?
Sex chromosomes
Thomas Hunt Morgan demonstrated that not only were white eyes recessive to red eyes, but that the trait was ________________ because it was located in the X chromosome.
Sex-linked
What is the extent which a certain gene exists in a population?
Gene frequency
What is one of the most common hereditary diseases among children in the United States, and is caused by a recessive gene?
Cystic fibrosis
Receiving a CF gene from only one parent makes the child a:
Carrier
What happens when both alleles for a trait are equally expressed in a heterozygous individual?
Codominance
A person suffering from what disease is H^2H^2 and makes only abnormal hemoglobin molecules; the abnormal hemoglobin causes the red blood cells to become sickle-shaped under certain conditions?
Sickle-cell anemia
If a normal person marries a person with sickle-cell anemia, their children must be heterozygous. Because neither gene is dominant, both express themselves. This is called:
Sickle-cell trait
What occurs when there are more than two different alleles of a gene for a particular trait?
Multiple allele inheritance
Recent advances in genetics have demonstrated that most genes influence not just one trait but several seemingly unrelated traits. This is known as:
Pleiotropy
What involves traits controlled by many different pairs of genes? Thus, instead of one pair of genes controlling an expression, many pairs are involved.
Polygenic inheritance
Some people have advocated the practice of ___________________, an attempt to improve the human race through the control of hereditary factors.
Eugenics
