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20 Cards in this Set
- Front
- Back
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Phenotypes
These directly observable characteristics are called phenotypes. |
An individual's directly observable physical and behavioral characteristics, which are determined by both genetic and environmental factors.
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Genotype
They depend in part on the individual's genotype- the complex blend of genetic information that determines our species and influences all our unique characteristics. |
An individual's makeup. Distinguished from phenotype.
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Chromosomes
Within every cell is a control or center, or nucleus, that contains rodlike structures call chromosomes. |
Rodlike structures in the cell nucleus that store and transmit genetic information.
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Deoxyribonucleic Acid or DNA
Chromosomes are made up of deoxyribonucleic acid, or DNA. |
Long, double-stranded molecules that make up chromosomes.
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Mitosis
A unique feature of DNA is that it can duplicate itself through a process called mitosis. |
The process of cell duplication, in which each new cell receives an exact copy of the original chromosomes.
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Gametes
New individuals are created when two special cells call gametes, or sex cells combine. |
Sex cells, or sperm and ova, which contain half as many chromosomes as regular body cells.
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Zygote
When sperm and ovum unite at fertilization, the resulting cell, called a zygote. |
The newly fertilized cell formed by the union of sperm and ovum of conception.
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Crossing over
A special event call crossing over occurs, in which chromosomes next to each other break at one or more points along their length and exchange segments, so that genes from one are replaced by genes from another. |
During meiosis, the exchange of genes between chromosomes next to each other.
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Meiosis
Gametes are formed through a cell division process, called meiosis, which halves the number of chromosomes normally present in body cells. |
The process of cell division through which gametes are formed and in which the number of chromosomes in each cell is halved.
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Autosomes
The 22 matching pairs of chromosomes, which geneticists number from longest (1) to shortest (22). These are called autosomes. |
The 22 matching chromosome pairs in each human cell.
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Allele
Each form of a gene is called an allele. |
Each of two or more forms of a gene located at the same place on the chromosomes.
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Homozygous
If the alleles from both parents are alike, the child is homozygous and display the inherited trait. |
Having two identical alleles at the same place on a pair of chromosomes. Distinguished from heterozygous.
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Heterozygous
If the alleles differ, then the child is heterozygous, and relationships between the alleles determine the phenotype. |
Having two different alleles at the same place on a pair of chromosomes. Distinguished from homozygous.
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Carrier
Therefore, they are called carriers, of the the trait. |
A heterozygous individual who can pass a recessive trait to his or her offspring.
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Modifier genes
This is due to action of modifier genes, which enhance or dilute the effects of other genes. |
Genes that enhance or dilute the effects of other genes.
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Incomplete dominance
Instead, we incomplete dominance, a pattern, of inheritance in which both alleles are expressed in the phenotype, resulting in a combined trait, or one that intermediate between the two. |
A pattern off inheritance in which both alleles are expressed in the phenotype, resulting in a combined trait, or one that is intermediate between the two.
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X-linked inheritance
But when a harmful allele is carried on the X chromosome, X-linked inheritance applies. |
A pattern of inheritance in which a recessive gene is carried on the X-chromosome, so that males are more likely that females to be affected.
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Genomic imprinting
In genomic imprinting, alleles are imprinted, or chemically marked, so that one pair member is activated, regardless of its makeup. |
A pattern of inheritance in which alleles are imprinted, or chemically, marked, in such a way that one pair member is activated, regardless of its makeup.
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Mutation
The answer is mutation, a sudden but permanent change in a segment of DNA. |
A sudden but permanent change in a segment of DNA.
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Polygenic inheritance
These traits are due to polygenic inheritance, in which many genes determine the characteristic in question. |
A pattern of inheritance in which many genes determine a characteristic that varies on a continuum among people.
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