ch 10 Meiosis
ch 11 mendelian patterns of inheritance
the type of cell division that produces the sexcells or gametes.
what happens to cells in meiosis
a diploid cell undergoes two sets of divisions to produce up to four haploid cell. Fertilization, which involves the joining of male and female gametes, restores the diploid number of chromosomes.
difference between process of meiosis and mitosis
Meiosis is the process by which sex cells or gametes are formed, while mitosis is the process by which all other cells of the body divide.
difference in cell division between meiosis and mitosis
During meiosis a diploid cell divides to form up to four haploid cells; during mitosis a diploid cell divides to form two genetically identical diploid cells.
difference in series of division
Meiosis involves two series of divisions each of which has a prophase, metaphase, anaphase, and telophase; while mitosis involves one series of divisions.
difference in prophase I
During prophase I of meiosis the four sister chromatids formed from the original pair of homologous chromosomes remain connected to form a tetrad; whereas in mitosis each pair of sister chromatids migrates to the metaphase plate independently of one another. *Crossing-over of genetic information occurs when the sister chromatids are in the tetrad state. This increases genetic variability in the resulting cells.
difference in goals
The goal of meiosis is to produce genetically different cells that have half the number of chromosomes as the original cell; while the goal of mitosis is to produce two cells that are genetically identical to the parent cell.
science of heredity.
who discovered genetics, in what year, using what plants?
the mid-1800's an Austrian monk named Gregor Mendel first discovered the basic principles of genetics working with pea plants.
3 ways pea plants facilitated his discovery
1. Pea plants self-pollinate in nature. Thus, Mendel could carefully control which pea plats were to be cross-fertilized.
2. Pea plants are easy to grow, produce many offspring (peas), and have a short life span. Thus, a great deal of genetic information can be collected quickly over a number of generations.
3. The pea characteristics (phenotypes) that he chose to study in were easy to observe and distinguish (tall or short plants, green or yellow peas).
the parental generation; the first breeding that takes place.
the "first filial" generation; the offspring resulting from the parental cross. Subsequent generations may be labeled F2, F3 ...
varieties that when crossed produce offspring identical to the parents.
offspring resulting from the cross of two different varieties.
a genetic cross that tracks the inheritance of a single trait.
a genetic cross that tracks the inheritance oftwo different traits.
a portion of a chromosome that codes for a particular trait. There are many genes on a single chromosome.
alternative forms of a particular gene that can affect the expression of a trait in different ways.
dominant alleles will be expressed as a certain trait even if only one member of a homologous pair is dominant.
recessive alleles require both members of the homologous pair to be recessive before they will be expressed as a certain trait.
a pair of identical alleles; may be homozygous dominant (AA) or homozygous recessive (aa).
a pair of alleles in which one is dominant and the other recessive (Aa).
the type of alleles in a certain pair (AA, aa,Aa).
the expressed trait; the effect that a particular pair of alleles will have.
Law of Dominance and Recession
certain alleles (dominant) can mask or hide the effect of other alleles (recessive) when they occur in pairs. Dominant alleles will be expressed when only one is present in a gene pair, while recessive alleles are expressed only when they occur in pairs.
Law of Segregation
gene pairs separate (segregate) during gamete formation (meiosis); fertilization restores the gene pair.
Law of Independent Assortment
each pair of alleles separates independently during gamete formation (meiosis).
a genetic cross that tracks a single trait.
an individual with an unknown genotype for a particular trait is crossed with a homozygous recessive individual
a genetic cross that tracks two traits.
a situation where two different alleles occurring in a pair are both expressed to some degree. This results in offspring that have intermediate phenotypes compared to the parents. For instance, a red flower crossed with a white flower produces pink-flowered offspring.
a situation where two different alleles occurring in a pair are both expressed. This results in both traits appearing in the offspring. For instance, with human blood groups an AB genotype will result in the presence of both the "A" protein and the "B" protein appearing on the red blood cell membrane.
one gene affects many traits. An example would be the mutant sickle cell gene which in the homozygous condition may cause anemia, physical weakness, spleen damage, pain, fever, rheumatism, and kidney failure.
polygenic inheritance -
a single trait is caused by many genes. An example would be human skin color, which is determined by three sets of genes that are inherited separately.
linked genes -
occur on the same chromosome, and are often inherited together.
genes affecting these traits occur on the same chromosome that determines the sex of the organism.Therefore, these traits often appear more often in one sex than the other. Examples of sex-linked traits in humans would be hemophilia and color-blindness.
the genetic makeup of the organism.
a method of organizing the chromosomes in a cell with respect to their appearance, number, and size.
the failure of chromosomes to separate properly during meiosis.
can be used to track genetic information over several generations.
recessive disorders in humans
1. cystic fibrosis
2. sickle cell anemia
4. phenylketonuria (PKU)
5. Tay-Sachs disease
dominant disorders in humans
2. Huntington's disease
3. Alzheimer's disease
sex linked disorders in humans
chromosomal abnormalities in humans
1. Down's Syndrome (Trisomy-21)
2. Turner syndrome (XO) manly woman
3. Metafemale (XXX)
4. Klinefelter's syndrome (XXY) underdeveloped male